Search

Lehmann, H., Neiber, M. T., & Hausdorf, B. (2024) Caucasian/Pontic–Mediterranean disjunction and recolonization of Europe by Pomatias (Hyrcania) species (Caenogastropoda, Pomatiidae)—Zoologica Scripta, 00, 000‐000. We studied the phylogeny and phylogeography of Pomatias (Hyrcania) species (Caenogastropoda: Pomatiidae) to investigate refugia and the causes of disjunctions in Asia anterior and in southeastern Europe. There is a Caucasian/Pontic–Mediterranean disjunction between the ranges of the sister species P. rivularis from the Caucasus region, the Pontic Mountains and southeastern Europe and P. hyrcanus from the coastal region of the southern Caspian Sea in the north and that of P. glaucus along the Mediterranean coast in the south. The disjunct ranges of the Pomatias (Hyrcania) species are probably relics of a previously more continuous distribution across Anatolia. They became disjunct as a result of the successive aridification of the Anatolian Plateau, which intensified in the late Pliocene following the uplift of the Anatolian Plateau, as has also been shown for several other taxa. The mitochondrial and nuclear genetic diversity of P. rivularis, the most widespread Pomatias (Hyrcania) species, is highest in the populations from the southern Greater Caucasus and the adjacent eastern Pontic Mountains. The southern Greater Caucasus and the coastal regions along the Caspian Sea and the Eastern Mediterranean acted as refugia for the Pomatias (Hyrcania) species after the aridification of the Anatolian Plateau. The low genetic diversity of P. rivularis in Eastern Europe and Ciscaucasia suggests that Miocene and Pliocene fossils identified as P. rivularis from these areas cannot be attributed to this species, that the Pomatias (Hyrcania) populations became extinct there by the Pleistocene, and that P. rivularis recolonized these areas later, probably only in the Holocene. [ABSTRACT FROM AUTHOR]

Hausdorf, B., Xu, J., BAMBERGER, S. (2024) Repeated colonization of the Northern Limestone Alps from the Southern Limestone Alps by the rock‐dwelling snail species Cochlostoma henricae—Zoologica Scripta, 00, 000–000. The evolution of biogeographic disjunctions in the Southern and Northern Limestone Alps has been studied only in a few taxa. Cochlostoma henricae (Strobel, 1851) is a land snail species restricted to limestone rocks showing such disjunctions. We studied the phylogeny and population structure of this species using genomic ddRAD data to better understand the differentiation of the species in the Southern Alps and the origin of the isolated occurrences in the Northern Limestone Alps. Phylogenetic and population‐genetic analyses of the ddRAD data revealed a subdivision of the C. henricae populations into a western cluster and an eastern cluster. These clusters were probably separated by glaciers that extended from the Piave Valley to the margin of the Alps. Such a longitudinal subdivision is a common pattern of several species in the Southern Limestone Alps. However, the boundaries between western and eastern population groups differ between taxa. Cochlostoma henricae colonized the Northern Limestone Alps at least twice. The population from Breitenwang in Tyrol originated from the western group, whereas the occurrences in the Salzkammergut are from the eastern group. These and similar disjunctions of several other land snails show that even species with limited dispersal abilities could cross the Alps repeatedly by passive long‐distance dispersal events. A subdivision of C. henricae into three subspecies, proposed based on shell characters, does not correspond to its population‐genetic structure. Instead, the eastern and western population groups represent distinct evolutionary units. [ABSTRACT FROM AUTHOR]

Aim: Various species distributed in the Alps have their disjunct occurrences in the Carpathians. Fossil evidence for some woodland snails of Alpine distribution suggests that they colonized the Carpathians during the Holocene forest optimum or later. Here, we focus on disjunct Carpathian populations of the rock‐dwelling alpine snail Pyramidula saxatilis. As it occupies very stable habitats, that is, high‐elevation limestone rocks, one can assume its potential survival in Carpathian refugia over the glacial period(s). For comparison, the more widespread and warm‐climate P. pusilla is analysed. Location: Europe. Taxon: Pyramidula saxatilis and P. pusilla. Methods: We analysed the genetic diversity of P. saxatilis and P. pusilla populations across their entire ranges using mitochondrial DNA and nuclear DNA markers. Seven fossil mollusc successions from the area where P. saxatilis occurs in the Carpathians were analysed and dated using the radiocarbon method. Habitat suitability models of both species were calculated for selected time periods since the Last Glacial Maximum. Results: All Carpathian P. saxatilis populations were genetically homogeneous and similar to those from the Eastern Alps. In P. pusilla, we found a genetically distinct lineage in the southern Western Carpathians. Both species were found in three fossil profiles since the Middle Holocene, and in one already in the Late Glacial. Habitat suitability models suggested the fluctuations of suitable conditions in the Carpathians driven by summer precipitation, especially for P. saxatilis. Main Conclusions: Our results suggest that the Carpathian populations of P. saxatilis represent a post‐LGM colonization from the Eastern Alps triggered by climatic changes, mainly by the increase in summer precipitation during the Late Glacial interstadials and Middle Holocene. The evidence for P. pusilla is similar, but also suggests rare long‐term survival in the Carpathian microrefugia. The palaeoecological evidence indicates a possible threat to high‐elevation species from future fluctuations in precipitation regimes. [ABSTRACT FROM AUTHOR]

Aim: Island biological communities are considered to comprise non‐random assemblages from surrounding source pools, but whether they converge towards predictable structural properties remains unclear. Here, we (i) test whether insular communities of land snails converge towards similar functional and/or taxonomic properties and (ii) evaluate whether island functional diversity is determined by island biogeographical characteristics such as area and distance to the pool as well as human‐related variables. Location: Sixty‐six continental Aegean islands. Taxon: Land snails. Methods: We compiled a database of two morphological traits with functional significance (shell height and width) for 163 island species and 1529 species from the major species pools. We quantified inter‐specific morphological dissimilarity between pairs of islands (turnover), using a modified index of the mean nearest taxon distance. We tested for functional and taxonomic convergence using null models and assessing whether overall mean turnover among islands and pairwise island‐by‐island turnover were lower than expected by chance. We performed multiple regression analyses to test whether functional diversity metrics scale with island biogeographical characteristics and human‐related variables. Results: Our analyses provide strong evidence that communities of land snails across the Aegean islands converge towards non‐random functional properties and taxonomic structure. At the island level, a wide range of different shell shapes is observed, indicating greater functional richness than expected by chance. Regression analyses showed that island area is the only efficient predictor of functional diversity, indicating that available ecological/resource space is of central importance in driving the assembly of different shell shapes. Main Conclusions: Our findings, consistent with previous studies of other taxa from oceanic islands, highlight that island species communities are not randomly assembled and display convergence in their functional and taxonomic composition. Integrating functional diversity metrics within biogeographic analyses has the potential to further our understanding of island biodiversity patterns. [ABSTRACT FROM AUTHOR]

Intrashell oxygen isotope (δ18Os) analyses of terrestrial snails have been carried out over two decades. However, the intraspecies/interspecies differences are not yet well understood. Here, we conducted a high‐resolution intrashell δ18Os study on 43 shells from Cathaica fasciola and Bradybaena ravida, and 1449 δ18Os data were obtained. These large amounts of data demonstrate the reproducibility of intrashell δ18Os. Our results suggest that C. fasciola and B. ravida have similar growing seasons mainly from March to October in the studied region. The ecological habits of the two species could explain the distinctive variations in their δ18Os sequences. Therefore, our study may interpret the discrepancy between the studies of land snail species and the stable/clumped isotopes of their shells. Moreover, the calculated average growth rate is ∼290 μm/day (from 250 to 330 μm/day) for nonadult C. fasciola. Thus, the use of snail shells for reconstructing high‐resolution terrestrial climate changes is promising. Plain Language Summary: Land snails are sensitive to climatic and environmental changes. Therefore, the oxygen isotopic composition of snail shells (δ18Os) has often been used to study environmental changes. Researchers started to collect multiple samples from a single shell for δ18Os analyses about two decades ago. However, it is still unclear whether high‐resolution intrashell δ18Os results are repeatable and whether the influences of different individuals/species may exist. To address these issues, we collected 43 snail shells from Cathaica fasciola and Bradybaena ravida. In total, 1449 δ18Os data were obtained. The large amount of data showing similar variations in the intrashell δ18Os from different shells demonstrates the repeatability. Accordingly, our data suggest that the two species have similar growing seasons, mainly from March to October, although their ecological habits are different. In addition, the ecological habits of these two species could explain the subtle differences in their δ18Os. Taken together, our study could resolve the discrepancy between previous work on land snail species and stable/clumped isotopes. Furthermore, the estimated average growth rate is ∼290 μm/day (from 250 to 330 μm/day) for nonadult C. fasciola. Overall, snail shells are promising records for exploring high‐resolution terrestrial climate changes in the future. Key Points: The intrashell δ18Os of land snails is reproducible, which mainly records the δ18O of precipitationCathaica fasciola and Bradybaena ravida have different ecological habits but similar growing seasonEcological habits could explain the discrepancy between studies of land snail species and stable/clumped isotopes [ABSTRACT FROM AUTHOR]

Mucus is applied to substrates as snails move and when they rest. Beyond the use of mucus in movement and adhesion, the wide array of chemicals in mucus allows for supplemental use in communication. This communication is apparent in trail‐following behavior. This study addresses the potential communication via mucus in selecting resting sites in a laboratory assay. In a series of six experiments, individuals of Cornu aspersum (which often rest on above‐ground surfaces) were placed into lidded plastic containers with three or four sections swabbed with water (the control) or mucus, which included the test snail's own mucus, mucus from conspecifics from the same or a different container holding snails from the same lab colony, or from a different colony, and mucus from three additional snail species. The resting location was recorded on the following day. In two additional experiments, the facultative predator Rumina decollata was tested against conspecific and other snails' mucus. Individuals of C. aspersum preferentially rested in areas with the mucus of familiar conspecifics over mucus of unfamiliar conspecifics, a behavior that may contribute to homing and aggregation behaviors. There was evidence that juveniles may be less selective than adults. The mucus of only one of the three other species was avoided by individuals of C. aspersum. Unlike individuals of C. aspersum, individuals of the predator R. decollata avoided the mucus of conspecifics, which may be associated with less need for mate‐finding in this self‐fertilizing species. Individuals of R. decollata did not select among potential prey species. [ABSTRACT FROM AUTHOR]

There have been five Mass Extinction events in the history of Earth's biodiversity, all caused by dramatic but natural phenomena. It has been claimed that the Sixth Mass Extinction may be underway, this time caused entirely by humans. Although considerable evidence indicates that there is a biodiversity crisis of increasing extinctions and plummeting abundances, some do not accept that this amounts to a Sixth Mass Extinction. Often, they use the IUCN Red List to support their stance, arguing that the rate of species loss does not differ from the background rate. However, the Red List is heavily biased: almost all birds and mammals but only a minute fraction of invertebrates have been evaluated against conservation criteria. Incorporating estimates of the true number of invertebrate extinctions leads to the conclusion that the rate vastly exceeds the background rate and that we may indeed be witnessing the start of the Sixth Mass Extinction. As an example, we focus on molluscs, the second largest phylum in numbers of known species, and, extrapolating boldly, estimate that, since around AD 1500, possibly as many as 7.5–13% (150,000–260,000) of all ~2 million known species have already gone extinct, orders of magnitude greater than the 882 (0.04%) on the Red List. We review differences in extinction rates according to realms: marine species face significant threats but, although previous mass extinctions were largely defined by marine invertebrates, there is no evidence that the marine biota has reached the same crisis as the non‐marine biota. Island species have suffered far greater rates than continental ones. Plants face similar conservation biases as do invertebrates, although there are hints they may have suffered lower extinction rates. There are also those who do not deny an extinction crisis but accept it as a new trajectory of evolution, because humans are part of the natural world; some even embrace it, with a desire to manipulate it for human benefit. We take issue with these stances. Humans are the only species able to manipulate the Earth on a grand scale, and they have allowed the current crisis to happen. Despite multiple conservation initiatives at various levels, most are not species oriented (certain charismatic vertebrates excepted) and specific actions to protect every living species individually are simply unfeasible because of the tyranny of numbers. As systematic biologists, we encourage the nurturing of the innate human appreciation of biodiversity, but we reaffirm the message that the biodiversity that makes our world so fascinating, beautiful and functional is vanishing unnoticed at an unprecedented rate. In the face of a mounting crisis, scientists must adopt the practices of preventive archaeology, and collect and document as many species as possible before they disappear. All this depends on reviving the venerable study of natural history and taxonomy. Denying the crisis, simply accepting it and doing nothing, or even embracing it for the ostensible benefit of humanity, are not appropriate options and pave the way for the Earth to continue on its sad trajectory towards a Sixth Mass Extinction. [ABSTRACT FROM AUTHOR]

BACKGROUND: The white garden snail, Theba pisana, is distributed worldwide and is a serious molluscan pest of different crops. Emamectin benzoate (EMB) 'an avermectin derivative' is a novel biorational agent and highly effective pesticide. This study focused on the lethal and in vivo sublethal toxic effect of EMB on the energy reserves (glycogen, lipids and proteins), total energy reserves and activities of glutathione S‐transferase (GST), γ‐glutamyl transferase (γ‐GT), lactate dehydrogenase (LDH), aspartate aminotransferase (AST) and alanine aminotransferase (ALT) in the hepatopancreas of T. pisana for up to 7 days of exposure. RESULTS: The median lethal dose (LD50) at 48 h of EMB treatment was 5.34 μg g−1 body weight (b.w.). Sublethal doses of 1.07 and 3.20 μg g−1 b.w. (i.e., 20% and 60% of the LD50) led to significant dose‐ and time‐dependent decreases in glycogen and lipids; these doses increased the total protein level. Overall, the tested sublethal doses significantly decreased the total energy reserves. Moreover, GST and γ‐GT activities were elevated, whereas the activities of AST and ALT were inhibited in the exposed snails. A decrease in LDH activity after 1 and 3 days of exposure and an increase after 7 days of exposure were seen in snails treated with EMB. CONCLUSION: EMB exerted lethal toxicity on T. pisana and consequently caused changes in energy reserve levels and enzyme activities in the animal. © 2022 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

Mountain regions are centers of biodiversity endemism at a global scale but the role of arid‐zone mountain ranges in shaping biodiversity patterns is poorly understood. Focusing on three guilds of taxa from a desert upland refugium in Australia, we sought to determine: (a) the relative extent to which climate, terrain or geological substrate predict endemism, and (b) whether patterns of endemism are complimentary across broad taxonomic guilds. We mapped regional endemism for plants, land snails, and vertebrates using combined Species Distribution Models (SDMs) for all endemic taxa (n = 82). We then modelled predictors of endemism using Generalised Additive Models (GAMs) and geology, terrain, and climate variables. We tested for the presence of inter‐ and intraguild hotspots of endemism. Many individual plant and land snail taxa were tightly linked with geology, corresponding to small distributions. Conversely, most vertebrate taxa were not constrained to specific geological substrates and occurred over larger areas. However, across all three guilds climate was the strongest predictor of regional endemism, particularly for plants wherein discrete hotspots of endemism were buffered from extreme summer temperatures. Land snail and vertebrate endemism peaked in areas with highest precipitation in the driest times of the year. Hotspots of endemism within each guild poorly predicted endemism in other guilds. We found an overarching signal that climatic gradients play a dominant role in the persistence of endemic taxa in an arid‐zone mountain range system. An association with higher rainfall and cooler temperatures indicates that continuing trends toward hotter and drier climates may lead to range contractions in this, and potentially other, arid‐zone mountain biotas. Contrasting patterns of endemism across guilds highlight the need to couple comprehensive regional planning for the protection of climate refugia, with targeted management of more localized and habitat specialist taxa. [ABSTRACT FROM AUTHOR]

In the present study, we performed gastropod analyses on loess–palaeosol sequences from northeast Armenia (Southern Caucasia) covering at least three glacial–interglacial cycles. The elaborated ecostratigraphy shows significant patterns of species composition related to the succession of pedocomplexes and loess, respectively. Pedocomplexes included species that can be associated with high‐grass to forest‐steppe biomes, indicating increased humidity for these sections compared to the loess layers. In contrast, loess layers that relate to glacial periods are associated with gastropod species of semidesert environments with shrub‐ and shortgrass‐steppes, indicating semiarid to arid conditions. Furthermore, the loess deposits do not show any evidence for cold‐adapted gastropod species. Therefore, we suggest that average July temperatures in the study area were above 10 °C, even during periods of loess deposition. Consequently, we propose that the limiting factor for tree growth during glacial periods was aridity, rather than temperature. In addition, we observe environmental differences between the various glacial times, with our results indicating a trend towards steadily increasing aridity in Southern Caucasia across the Middle to Late Pleistocene. [ABSTRACT FROM AUTHOR]

Calcium (Ca) is an essential element for many animal species, especially for land snails with shell structures. The availability of Ca imposes constraints on their growth and survival as well as their density and distribution. However, little is known about how they obtain Ca in a natural environment. For example, many species of land snails feed on lichens, but lichens have Ca in the form of calcium oxalate, making it difficult for animals to utilize. Therefore, we predicted that lichens or a representative food source of land snails is not necessarily a major source of Ca, and there may be another source for shell development. The strontium isotope ratio (87Sr/86Sr) is a useful index for estimating the source of Ca. With this technique, we estimated Ca sources of an arboreal land snail, Euhadra brandtii sapporo, and tested the hypothesis described above. The data for the 87Sr/86Sr ratio show that E. brandtii sapporo did not obtain Ca from lichens and moss in tree canopies, although the data for the δ15N and δ13C show that the species' main food source may be lichens and moss. We also conducted the isotope analysis of Ezohelix gainesi as a reference, which inhabits the forest floor. The data of δ15N and δ13C show E. gainesi may feed mainly on litter. The 87Sr/86Sr ratio was markedly different from that of arboreal E. brandtii sapporo, and this ground‐dwelling snail likely obtains Ca from ground litter or soil. Our results indicate that Ca sources are different between arboreal and ground‐dwelling land snails, and the former obtains Ca through something other than its major food sources, perhaps from stemflow and precipitation. Differences in the two species indicate that land snails utilize different Ca sources depending on their habitats. [ABSTRACT FROM AUTHOR]

We studied the door‐snail genus Alopia in the Southern Carpathians in Romania to better understand non‐adaptive radiations and the processes that determine their course. Alopia in the Bucegi Mountains offers the opportunity to study all stages of a radiation within a few kilometres. The species (as defined by the differential fitness species concept) in the most advanced stage of the radiation differs from other species in the genitalia and co‐occurs with other species. The least advanced stages are genetically differentiated clusters of populations that are geographically separated from other clusters but are not yet morphologically differentiated. Differentiation does not increase with a constant rate as shown by a lineage that was separated early in the evolution of the genus but fused with other taxa upon secondary contact. Since non‐adaptive radiation cannot be accelerated by divergent natural selection beyond the slow pace of speciation that is possible by genetic drift alone, sexual selection plays a crucial role in non‐adaptive radiations. This is supported by the differences in the genitalia found in the most advanced stage of the speciation which indicate that the speciation process was accelerated by a co‐evolutionary arms race resulting in the elongation of spermatophore‐producing and spermatophore‐receiving organs. Another process that facilitates non‐adaptive radiation is long‐distance dispersal that results in geographically isolated populations that can differentiate without gene flow and that have a higher likelihood of speciation due to the founder event. Several taxa that were considered distinct species until now, but fuse upon contact should better be classified as subspecies of a polytypic species. [ABSTRACT FROM AUTHOR]

Stable isotopes of land snail fossil shell carbonates (δ13Cshell and δ18Oshell) provide the opportunity to decipher paleodietary and paleoenvironmental changes. However, the environmental meanings of δ13Cshell and δ18Oshell remain elusive especially in the monsoonal climate region. To elucidate this, δ13Cshell and δ18Oshell of the two most common land snails in China, Cathaica and Bradybaena, were analyzed in this study. Results show that Bradybaena has a wider distribution than Cathaica and provides considerable potential for use in paleoenvironmental reconstruction. In addition, δ13Cshell of Bradybaena increases with altitude and temperature, decreases with mean annual precipitation, and reflects the isotopic signal of C3 plants. In contrast, Cathaica δ13Cshell documents a C3/C4 mixing signal and exhibits only a strong altitude effect. δ18Oshell of Bradybaena decreases with mean annual precipitation in the Indian monsoon and westerlies regions but increases with mean annual temperature in the East Asian monsoon region; as a strong correlation exists between the two variables, they could thus potentially be used to reconstruct paleotemperatures. However, uncertainties should be recognized due to the complexity of the land‐snails' ecophysiological responses to environmental changes. Cathaica has slightly lower δ18Oshell than Bradybaena, which suggests that the two land snails have different ecophysiological traits, and the δ18Oshell of Cathaica follows mean annual temperature in northeast China. This study lays a ground for explaining land snail stable isotopes in paleorecord in China and reasserts the importance of different ecophysiological traits of land snails in paleoclimatic research. Key Points: Stable isotopes and snail shell‐dimension studies suggest Bradybaena and Cathaica have different ecophysiological traitsδ13Cshell is a tracer of dietary vegetation and can be used to monitor rainfall in the region dominated by C3 plantsδ18Oshell of Bradybaena rises with temperature in East Asia monsoon region but declines with rainfall in Indian monsoon and westerlies areas [ABSTRACT FROM AUTHOR]

Among the questions surrounding the biogeographical history of the Chilean biota, none has gathered more interest than the origin of the Fray Jorge (FJ) forest relict and its biota. Inserted in a semi‐desert area, this forest enclave exists due to the existence of a very particular microclimate in this region. The age of the disjunction and the historical relationship between the FJ biota with the remaining components of South America are explained by two distinct, competing hypotheses: the first suggests that it would have become isolated during the climatic changes of the Paleogene/Neogene, while the second suggests that the isolation is a product of Quaternary glaciations. To discriminate between these competing hypotheses, we used DNA sequence phylogeny methods and molecular genetic dating to the study of a genus of land snails (Plectostylus) that occurs in the FJ relict and throughout Chile. The phylogeny shows a clear distinction between forest and arid clades, and each of these clades is formed by many geographically circumscribed populations. The FJ fragment snails form a clade that is sister to all other forest clades. The separation between the Fray Jorge clade and the other forest clades dates back to the Paleogene/Neogene. Our data suggest that the FJ forest is a relict from the forests that occupied that landscape during the Paleogene/Neogene and retreated due to the aridification of the region. We also observe that the current taxonomy of the Plectostylus genus must be re‐evaluated. The Fray Jorge (FJ) forest relict is a wet temperate forest inserted in a xerophile matrix (the Atacama desert, the driest desert in the world) and separated from other similar temperate forests by thousands of km. We performed a phylogeographic analyses of the snail genus Plectostyus to disentangle the origin and timing of the FJ relict. Our tree shows that FJ is sister to all other forest clades. Our molecular clock analysis shows that FJ became isolated in the Paeogene/Neogene. [ABSTRACT FROM AUTHOR]

Aim: To quantify the influence of past archipelago configuration on present‐day insular biodiversity patterns, and to compare the role of long‐lasting archipelago configurations over the Pleistocene to configurations of short duration such as at the Last Glacial Maximum (LGM) and the present‐day. Location: 53 volcanic oceanic islands from 12 archipelagos worldwide—Azores, Canary Islands, Cook Islands, Galápagos, Gulf of Guinea, Hawaii, Madeira, Mascarenes, Pitcairn, Revillagigedo, Samoan Islands and Tristan da Cunha. Time period: The last 800 kyr, representing the nine most recent glacial–interglacial cycles. Major taxa studied: Land snails and angiosperms. Methods: Species richness data for land snails and angiosperms were compiled from existing literature and species checklists. We reconstructed archipelago configurations at the following sea levels: the present‐day high interglacial sea level, the intermediate sea levels that are representative of the Pleistocene and the low sea levels of the LGM. We fitted two alternative linear mixed models for each archipelago configuration using the number of single‐island endemic, multiple‐island endemic and (non‐endemic) native species as a response. Model performance was assessed based on the goodness‐of‐fit of the full model, the variance explained by archipelago configuration and model parsimony. Results: Single‐island endemic richness in both taxonomic groups was best explained by intermediate palaeo‐configuration (positively by area change, and negatively by palaeo‐connectedness), whereas non‐endemic native species richness was poorly explained by palaeo‐configuration. Single‐island endemic richness was better explained by intermediate archipelago configurations than by the archipelago configurations of the LGM or present‐day. Main conclusions: Archipelago configurations at intermediate sea levels—which are representative of the Pleistocene—have left a stronger imprint on single‐island endemic richness patterns on volcanic oceanic islands than extreme archipelago configurations that persisted for only a few thousand years (such as the LGM). In understanding ecological and evolutionary dynamics of insular biota it is essential to consider longer‐lasting environmental conditions, rather than extreme situations alone. [ABSTRACT FROM AUTHOR]

The entry of secondary invaders into, or their expansion within, native communities is contingent on the changes wrought by other (primary) invaders. When primary invaders have altered more than one property of the recipient community, standard descriptive and modeling approaches only provide a best guess of the mechanism permitting the secondary invasion. In rainforest on Christmas Island, we conducted a manipulative field experiment to determine the mechanism of invasion success for a community of land snails dominated by non-native species. The invasion of rainforest by the yellow crazy ant ( Anoplolepis gracilipes) has facilitated these land snails, either by creating enemy-free space and/or increased habitat and resources (in the form of leaf litter) through the removal of the native omnivorous-detritivorous red land crab ( Gecarcoidea natalis). We manipulated predator densities (high and low) and leaf litter (high and low) in replicated blocks of four treatment combinations at two sites. Over the course of one wet season (five months), we found that plots with high leaf litter biomass contained significantly more snails than those with low biomass, regardless of whether those plots had high or low predation pressure, at both the site where land crabs have always been abundant, and at the site where they have been absent for many years prior to the experiment. Each site was dominated by small snail species (<2 mm length), and through handling size and predation experiments we demonstrated that red crabs tend not to handle and eat snails of that size. These results suggest that secondary invasion by this community of non-native land snails is facilitated most strongly by habitat and resource augmentation, an indirect consequence of red land crab removal, and that the creation of enemy-free space is not important. By using a full-factorial experimental approach, we have confidently determined-rather than inferred-the mechanism by which primary invaders indirectly facilitate a community of secondary invaders. [ABSTRACT FROM AUTHOR]

Land snails are an important component of biodiversity but the information regarding the factors that influence their distribution is very incomplete or anecdotal in most geographic areas. In this article our aim was to uncover environmental factors that influence the distribution and diversity of a Gastropoda community in a Mediterranean Reserve (Collserola Natural Park, Barcelona). Fieldwork was conducted from 2001 to 2003, and we systematically sampled all 1 km UTM squares throughout the park by randomly selecting at least one 200 m plot within each square. We used a community-based approach to analyse the relationships between 61 Gastropod species distributions and environmental predictors by means of Redundancy Analysis (RDA). Our results highlighted that the land snail community was affected by the environmental predictors (even for short gradients), but their influence was low according to the explained variance (30 %). Climate and habitat predictors were more important than the spatial variables in determining the community composition and diversity. 48 out of 61 (78.7 %) land snail species showed significant responses to the environmental gradients with an association of specialist species with particular habitat types. Collserola is a reserve surrounded by urbanised areas and affected by multiple anthropogenic threats mostly related to habitat transformation. The high degree of specialisation within the Gastropoda community suggests that the restoration of heterogeneous landscapes would be useful to conserve and restore terrestrial mollusc diversity in Collserola. This study can help stakeholders to make decisions related to landscape planning and habitat transformation. [ABSTRACT FROM AUTHOR]

Aim We investigated the location of Pleistocene mountain refugia in the European Southern Alps based on distribution data for four endemic land snail taxa and tested the hypothesis that the subdivision of species into endemic subspecies may be attributed to the same vicariance events. Location The European Southern Alps between Lago di Como and Lago di Garda in Italy. Methods We compiled distributional data for four land snail species ( Cochlostoma porroi, Clausilia brembina, Clausilia whateliana and Charpentieria itala), which are subdivided into endemic subspecies in the study region, and investigated to what extent their distribution areas are congruent and correspond to regions that remained unglaciated during the glacials. To examine also whether their phylogeographic patterns are concordant, as would be expected if the subdivision of the species was caused by the same vicariance events, we reconstructed the phylogenetic relationships between the subspecies of the four species using 16S rDNA sequences and amplified fragment length polymorphism (AFLP) data. Results The endemic subspecies were found to be concentrated in mountain regions that remained unglaciated during the glacials, consistent with these regions acting as Pleistocene refugia for these snails. Although the Oglio glacier did not equally affect the differentiation of the investigated species, the repeated contractions of their ranges into these refugia resulted in similar patterns of colonization and differentiation. Main conclusions Climate change such as the recurrent glaciations during the Pleistocene can result in similar distribution and colonization patterns, but the patterns in different species and their evolutionary trajectories are rarely completely identical because of their different histories, the randomness of dispersal, and small differences in ecology or dispersal capability. [ABSTRACT FROM AUTHOR]

Land-use intensification is increasing dramatically in production systems world-wide. Livestock production is an important component of production land use, and increases in livestock densities have had a wide range of negative consequences. The off-site effects of livestock grazing and trampling on native vegetation adjacent to pastoral land have received less attention than on-farm effects. Moreover, where significant ecological effects of livestock spillover have been identified, the mechanistic determinants of these effects have not typically been investigated., Here, we tested the mechanistic drivers of livestock trampling effects on land snail communities in forest remnants using simulated trampling under field conditions. We used a factorial combination of leaf-litter manipulation and trampling treatments to partition different causal drivers of livestock impacts on land snail communities and related them to five environmental variables that are altered by livestock., We show that even very low frequency trampling caused severe changes to land snail communities. Land snail density, even under the lowest trampling frequency, declined by an average of 42 individuals m−2 and land snail species richness decreased by an average of 10 species per plot compared with control plots., The underlying drivers of changes in land snail communities varied, but were primarily linked to leaf-litter mass, rather than soil compaction., Synthesis and applications. Overall, these results suggest that even minimal disturbance by livestock has large effects on land snail communities, but the underlying drivers of these effects require further investigation in longer duration and more intensive studies. Our results provide strong support for livestock exclusion as an important management tool for native forest remnants embedded within production landscapes. [ABSTRACT FROM AUTHOR]

The distribution of additive vs. non-additive genetic variation in natural populations represents a central topic of research in evolutionary/organismal biology. For evolutionary physiologists, functional or whole-animal performance traits ('physiological traits') are frequently studied assuming they are heritable and variable in populations., Physiological traits of evolutionary relevance are those functional capacities measured at the whole-organism level, with a potential impact on fitness. They can be classified as capacities (or performances) or costs, the former being directly correlated with fitness and the latter being inversely correlated with fitness (usually assumed as constraints)., In spite of their obvious adaptive significance, the additive genetic variation in physiological traits, and its relative contribution to phenotypic variance (or narrow-sense heritability) in comparison with maternal, dominance or epistatic variance, is known only for a few groups such as insects and mammals., In this study, we assessed the additive and maternal/non-additive genetic variation in a suite of physiological and morphological traits in populations of the land snail Cornu aspersum., Except for dehydration rate ( h2 = 0·32 ± 0·15), egg mass ( h2 = 0·82 ± 0·30) and hatchling mass ( h2 = 1·01 ± 0·31; population = fixed effect), we found very low additive genetic variation. Large non-additive/maternal effects were found in all traits. Cage effects did not change the results, indicating low contribution of common environmental variance to our results. No differences were found between the phenotypic and non-additive genetic variance/covariance matrices., Even though we compared populations across 1300 km in a common garden set-up, our results suggest an absence of physiological as well as morphological differentiation in these populations., These results contrast with previous analyses in the original distributional range of this species, which found high additive genetic variation in morphological traits. These are intriguing results demanding further quantitative genetic studies in the original distributional range of this species as well as the history of colonization of this invasive species. [ABSTRACT FROM AUTHOR]

To forecast the responses of species to future climate change, an understanding of the ability of species to adapt to long-term shifts in temperature is crucial. We present a review on evolutionary adaptation and phenotypic plasticity of temperature- related traits in terrestrial invertebrates. The evidence for adaptive evolution in melanization is good, but we caution that genetic determination needs to be tested in each individual species, and complex genetic correlations may exist. For phenological traits allochronic data sets provide powerful means to track climate- induced changes; however, rarely are responses deconstructed into evolutionary and plastic responses. Laboratory studies suggest climate change responses in these traits will be driven by both. For stress resistance, the evidence for shifts in traits is poor. Studies leaning heavily on Drosophila have demonstrated potential limits to evolutionary responses in desiccation and heat resistance. Quantifying the capacity for these species to respond plastically and extending this work to other taxa will be an important next step. We also note that, although not strictly speaking a species trait, the response of endosymbionts to heat stress requires further study. Finally, while clearly genetic, and possibly adaptive, the anonymous nature of latitudinal shifts in clines of genetic markers in Drosophila prevents further interpretation. [ABSTRACT FROM AUTHOR]

ABSTRACT The land snail Sphincterochila candidissima from archeological records in Villena (SE Spain) was studied isotopically to estimate the Younger Dryas (YD)-early Holocene transition in the western Mediterranean. Live-collected individuals exhibited body (−21.8 ± 1.6‰) and shell (−5.8 ± 1.4‰) δ13C values typical of a C3 plant diet, probably combined with carbonate ingestion. Calculations of a carbon flux balance-mixing model suggest that living specimens experienced similar metabolic rates, with comparable ratio of input and output fluxes of bicarbonate from the snail hemolymph. All fossil shells showed comparable δ13C values among each other, but values were ∼2‰ higher than living specimens. This may be explained by higher water stress at the YD-Holocene transition or by the Suess effect. Shell δ18O values averaged +1.3 ± 0.8‰ for living individuals, −0.5 ± 0.8‰ for Holocene (8.4-10.2 cal ka BP) specimens and +0.4 ± 0.6‰ for YD (12.0-12.4 cal ka BP) snails. An oxygen flux balance-mixing model suggests that YD shells precipitated during relative humidity (RH) values of ∼79-82%, after which RH increased gradually reaching maximum values of ∼87-88% at ∼8.4-8.6 cal ka BP and, from there, RH eventually declined to present values of ∼82%. Comparisons with other snail data suggest that the xerophilous Sphincterochila records different environmental signatures fro other contemporaneous taxa. [ABSTRACT FROM AUTHOR]

Hybrid zones are regions where genetically distinct populations meet, mate and produce offspring. In such zones, genetically less compatible gene combinations are usually generated, resulting in reduced fitness, and hybrid zones are often maintained because of continuous removal of unfit genotypes, balanced by gene flow into the zone from the parental populations (and are then referred to as 'tension zones'). Tension zones often display unexpectedly high frequencies of gene variants that are rare outside the zone. Previous work has shown that this 'rare allele phenomenon' is not the result of intragenic recombination or increased mutation rates. Further understanding of the population genetics of the phenomenon requires an approach in which both the numbers of individuals and the numbers of loci is increased. Here, we report an approach using a combination of Illumina next-generation sequencing and mass spectrophotometer genotyping to identify markers that may be used for genome-wide investigations of the rare allele phenomenon. We test this approach on a hybrid zone in the land snail Albinaria hippolyti from Greece. [ABSTRACT FROM AUTHOR]

The lively debate about speciation currently focuses on the relative importance of factors driving population differentiation. While many studies are increasingly producing results on the importance of selection, little is known about the interaction between drift and selection. Moreover, there is still little knowledge on the spatial-temporal scales at which speciation occurs, that is, arrangement of habitat patches, abruptness of habitat transitions, climate and habitat changes interacting with selective forces. To investigate these questions, we quantified variation on a fine geographical scale analysing morphological (shell) and genetic data sets coupled with environmental data in the land snail Murella muralis, endemic to the Mediterranean island of Sicily. Analysis of a fragment of the mitochondrial DNA cytochrome oxidase I gene ( COI) and eight nuclear microsatellite loci showed that genetic variation is highly structured at a very fine spatial scale by local palaeogeographical events and historical population dynamics. Molecular clock estimates, calibrated here specifically for Tyrrhenian land snails, provided a framework of palaeogeographical events responsible for the observed geographical variations and migration routes. Finally, we showed for the first time well-documented lines of evidence of selection in the past, which explains divergence of land snail shell shapes. We suggest that time and palaeogeographical history acted as constraints in the progress along the ecological speciation continuum. Our study shows that testing for correlation among palaeogeography, morphology and genetic data on a fine geographical scale provides information fundamental for a detailed understanding of ecological speciation processes. [ABSTRACT FROM AUTHOR]

Aim We collate and analyse data for land snail diversity and endemism, as a means of testing the explanatory power of the general dynamic model of oceanic island biogeography ( GDM): a theoretical model linking trends in species immigration, speciation and extinction to a generalized island ontogeny. Location Eight oceanic archipelagos: Azores, Canaries, Hawaii, Galápagos, Madeira, Samoa, Society, Tristan da Cunha. Methods Using data obtained from literature sources we examined the power of the GDM through its derivative ATT2 model (i.e. diversity metric = b1 + b2Area + b3Time + b4Time2), in comparison with all the possible simpler models, e.g. including only area or time. The diversity metrics considered were the number of (1) native species, (2) archipelagic endemic species, and (3) single-island endemic species. Models were evaluated using both log-transformed and untransformed diversity data by means of linear mixed effect models. For Hawaii and the Canaries, responses of different major taxonomic groups were also analysed separately. Results The ATT2 model was always included within the group of best models and, in many cases, was the single-best model and was particularly successful in fitting the log-transformed diversity metrics. In four archipelagos, a hump-shaped relationship with time (island age) is apparent, while the other four archipelagos show a general increase of species richness with island age. In Hawaii and the Canaries outcomes vary between different taxonomic groups. Main conclusions The GDM is an intentionally simplified representation of environmental and diversity dynamics on oceanic islands, which predicts a simple positive relationship between diversity and island area combined with a humped response to time. We find broad support for the applicability of this model, especially when a full range of island developmental stages is present. However, our results also show that the varied mechanisms of island origins and the differing responses of major taxa should be taken into consideration when interpreting diversity metrics in terms of the GDM. This heterogeneity is reflected in the fact that no single model outperforms all the other models for all datasets analysed. [ABSTRACT FROM AUTHOR]

Two groups of subspecies of the door snail Charpentieria itala are distributed in a mosaic pattern in the Southern Alps. Some subspecies that morphologically resemble Charpentieria stenzii occur at exposed rocks at higher altitudes, whereas other subspecies live on more humid rocks at lower altitudes. This pattern can be explained by two alternative hypotheses. Either the stenzii-like or 'stenzioid' subspecies have a common origin and represent relicts of an early colonization wave that survived the ice ages in isolated mountain refuges within the Alps, or the geographically isolated stenzioid subspecies evolved through parallel adaptation of C. itala populations to life on exposed rocks. In this study, the first hypothesis could be supported by several lines of evidence. Analyses of amplified fragment length polymorphisms (AFLP) data indicated a common origin of the stenzioid subspecies of the Bergamasque Prealps and of the stenzioid subspecies of the Brescia and Garda Prealps, whereas an outlier analysis detected only few AFLP markers that might be under selection. High 16S rDNA distances between subspecies suggest that the divergence of the subspecies predates at least most of the glacials. The occurrences of the stenzioid subspecies are concentrated in mountain areas that were not glaciated during the Last Glacial Maximum. The genetic differentiation and the isolated distribution areas of the stenzioid subspecies indicate that they survived in five separate mountain refuges in the Bergamasque, Brescia and Garda Prealps. In addition, the clustering of the Charpentieria itala latestriata populations from different valleys indicates a low-altitude refuge. [ABSTRACT FROM AUTHOR]

Aim It is generally believed that communities of small organisms, or those with small propagules, are structured mainly by local niche-based processes, and less by dispersal limitation. Conversely, weaker environmental and stronger spatial structure, indicating dispersal limitation, are expected to occur more frequently in communities of large organisms. However, this hypothesis has rarely been tested by comparing spatial and environmental effects across groups of organisms of different size (or with different size of propagules) sampled at the same set of sites. Here, we test it in urban environments. Location Thirty-two cities in 10 countries of Central Europe and Benelux. Methods We compared effects of spatial location and climate on species composition of different groups of organisms sampled in corresponding types of urban habitats. The studied groups were: (1) subaerial cyanobacteria and algae, (2) vascular plants, (3) land snails; and subgroups of vascular plants with different life form and dispersal mode, namely: (4) herbs, (5) animal-dispersed trees and shrubs, and (6) wind-dispersed trees and shrubs. Data were analysed by variation partitioning based on redundancy analysis (RDA) with principal coordinates of neighbour matrices (PCNM). Eighteen PCNM eigenvectors (expressing spatial effects) and mean annual temperature, July-January temperature difference and annual precipitation sum (expressing environmental effects) were used as explanatory variables. Results Pure effects of climate on species composition, indicating niche-based processes, were not significant for any group or subgroup of the studied organisms. In contrast, pure effects of space, indicating dispersal limitation, were significant for all groups and subgroups except herbs. Surprisingly, the community of cyanobacteria/algae possessed much stronger spatial structure independent of climate than communities of larger organisms, although cyanobacteria/algae had the lowest beta diversity among the studied cities. Main conclusions We hypothesize that the community of subaerial cyanobacteria/algae is structured by natural processes which involve dispersal limitation, whereas communities of urban plants and snails are influenced by human-assisted dispersal of their propagules between cities, which results in weaker dispersal limitation. Our study indicates that dispersal vectors can be more important for community structure than size of organisms or of their propagules. [ABSTRACT FROM AUTHOR]

lthough land snail communities could be a good indicator of soil quality and landscape structure impact, they are seldom analysed in an urban context, probably because of the lack of interest in this ecosystem and because no fast and reliable method of inter-site comparison seems to exist. The classical method of removing large quantities of soil leads to degradations unsuitable in urban gardens and involves time-consuming sorting. For the purpose of ecological comparisons, we analysed different methods to assess land snail communities in urban parks in order to set up a simplified strategy. Snail communities were sampled in three parks within the city of Paris (France) using (1) quadrat method (litter and soil removed over a given area, snails sorted later in the laboratory), (2) visual search in situ (hand-picking snails in the leaf litter), (3) wooden boards placed on the ground and regularly checked, and (4) pitfall traps, usually used for insect sampling. Our results suggest that the wooden board and pitfall trap did not yield enough data to determine community structure and that visual search was not sufficient to sample all dominant species, especially the smallest ones. In order to allow for replication of samples, we suggest a mixed strategy suitable for ecological comparisons, combining visual searches of five 0.5 m areas (15 min for each area) and litter and soil sampling on two 0.0625 m quadrats. [ABSTRACT FROM AUTHOR]

The influence of non-native species on native ecosystems is not predicted easily when interspecific interactions are complex. Species removal can result in unexpected and undesired changes to other ecosystem components. I examined whether invasive non-native species may both harm and provide refugia for endangered native species. The invasive non-native plant Casuarina stricta has damaged the native flora and caused decline of the snail fauna on the Ogasawara Islands, Japan. On Anijima in 2006 and 2009, I examined endemic land snails in the genus Ogasawarana. I compared the density of live specimens and frequency of predation scars (from black rats[Rattus rattus] ) on empty shells in native vegetation and Casuarina forests. The density of land snails was greater in native vegetation than in Casuarina forests in 2006. Nevertheless, radical declines in the density of land snails occurred in native vegetation since 2006 in association with increasing predation by black rats. In contrast, abundance of Ogasawarana did not decline in the Casuarina forest, where shells with predation scars from rats were rare. As a result, the density of snails was greater in the Casuarina forest than in native vegetation. Removal of Casuarina was associated with an increased proportion of shells with predation scars from rats and a decrease in the density of Ogasawarana. The thick and dense litter of Casuarina appears to provide refugia for native land snails by protecting them from predation by rats; thus, eradication of rats should precede eradication of Casuarina. Adaptive strategies, particularly those that consider the removal order of non-native species, are crucial to minimizing the unintended effects of eradication on native species. In addition, my results suggested that in some cases a given non-native species can be used to mitigate the impacts of other non-native species on native species. [ABSTRACT FROM AUTHOR]

Aim The main aims of the study were: (1) to investigate the effect of fragment age in relation to other patch- and landscape-scale measures of forest fragmentation, and (2) to assess the relative importance of fragmentation, habitat degradation (i.e. degradation caused by selective logging and past shifting cultivation) and putative pre-existing species turnover in structuring current land-snail assemblages. Location South-western Sri Lanka. Methods The land-snail fauna was sampled using standardized belt transects. Fifty-seven transects were sampled in 21 lowland rain forest fragments ( c. 1–33,000 ha). The spatial arrangement of fragments in the study area was explicitly considered in an effort to take into account the non-random nature of fragmentation and degradation and the possibility that current species composition may reflect patterns of species turnover that existed prior to fragmentation. The data set of 57 land-snail species and 28 environmental and spatial variables was analysed using canonical correspondence analysis and partial canonical correspondence analysis. Results Fragment age, mean shape complexity (i.e. a landscape-scale measure of shape complexity), altitude, and the spatial variables x (longitude), y (latitude) and y2 explained significant variation in land-snail species composition. None of the three nominal variables quantifying habitat degradation was significantly correlated with variation in species composition. The independent effects of fragment age and mean shape complexity were similar. The combined effect of the spatial variables alone was larger than the independent effects of fragment age, mean shape complexity or altitude, but was of the same order of magnitude. The total variation explained by the spatial variables was comparable to the total non-spatial variation accounted for by fragment age, mean shape complexity and altitude. Main conclusions Fragment age was found to be one of only two key determinants (the other was shape complexity at the landscape scale) driving fragmentation-related changes in community composition. The influence of pre-fragmentation patterns of species turnover on assemblage structure can be stronger than the effects of fragmentation measures, such as age, and may override the effects of forest degradation. Thus, strong patterns of pre-existing turnover may potentially confound interpretation of the effects of forest fragmentation and degradation. [ABSTRACT FROM AUTHOR]

Aim Using New Zealand land snails as a case study, we evaluated recent spatial modelling approaches for the analysis of diversity in species-rich invertebrate groups. Applications and prospects for improved conservation assessment were investigated. Location New Zealand. Methods The study used a spatially extensive and taxonomically comprehensive, plot-based dataset on community structure in New Zealand land snails. Generalized regression analysis and spatial prediction (GRASP) was used to model and predict species richness as a function of environmental variables (including aspects of climate, soils and vegetation). Generalized dissimilarity modelling (GDM) was used to model turnover in species composition in relation to environmental and geographical distances, and to assess community similarity and the representativeness of the reserve network. Results Observed land snail richness in 20 × 20 m plots ranged from 1 to 74 (mean 17.5). The GRASP model explained a modest 27% of the variation in richness. The GDM model explained 57% of the variation in species turnover and indicated approximately equal amounts related to environmental (Cody’s beta diversity) and geographical distance (Cody’s gamma diversity). Temperature and moisture were the most important environmental variables. Results indicate that snail distributions are not only sorted by environment but are also strongly influenced by historical effects consistent with those expected of poorly dispersing taxa that have persisted in refugia during past climatic change. The GDM model enabled spatial classifications of snail communities, highlighting diverse communities in heterogeneous regions, such as the South Island mountains, and also enabled continuous depictions of community similarity and adequacy of New Zealand’s protected natural areas network. Main conclusions The GRASP and GDM analyses allowed us to model and depict spatial patterns of diversity in land snail communities involving 845 species, and produce community classifications and estimates of community similarity. These tools advance conservation assessment in species-rich groups, but require further conceptual and methodological development. [ABSTRACT FROM AUTHOR]

Aim We investigated whether the biogeographical patterns expected if the East African fauna was affected by cycles of contraction to refugia and expansion of ranges, as has been previously hypothesized, can be found in the land snail fauna of rain forests in Uganda. Location The Albertine Rift region and the Lake Victoria forest belt in Uganda. Methods Snails and slugs were sampled in 60 plots in 13 rain forests, and small species were extracted from 5-L leaf litter samples. Relative species richness was calculated by rarefaction. The influence of putative determinants of species richness was examined by bivariate correlation and multiple regression. Clustering and nestedness were tested by Monte Carlo simulations with a null model that considers the range size distribution, the species richness distribution of the forests, and the spatial autocorrelation of the occurrences of each species. Biotic elements were determined by model-based Gaussian clustering. Results A total of 169 land snail species were recorded from 13 Ugandan rain forests. Relative species richness increases with rainfall and altitude, and decreases with evaporation and distance from the putative East Congolian refugia. Mean annual rainfall and distance from the putative East Congolian refugia were included in the best multiple regression model. The distribution areas of the Ugandan land snails are significantly clustered. Two montane, two lowland and a northern biotic element were found. The mean range extension increases with increasing distance from the putative East Congolian refugia. Moreover, the ranges of the Ugandan land snails are significantly nested. The centre of the sets of nested subsets is in the Virunga Mountains, close to the putative East Congolian refugia. Main conclusions The decrease of diversity with increasing distance from the putative East Congolian refugia, the clustering and nestedness of ranges, and the range size increase with increasing distance from the refugia indicate that the East African land snail fauna was affected by cycles of contraction to refugia and expansion of ranges. The significant clustering and nestedness cannot be explained by current environmental conditions. Given the environmental history, it can be supposed that the lowland elements expanded post-glacially, whereas the ranges of the montane species are probably currently contracting. [ABSTRACT FROM AUTHOR]

1. Modified habitats have a profound impact on the biota of fragmented tropical forests. We investigated the structure of land-snail assemblages in Sri Lankan lowland rainforest and village home gardens, a habitat of the surrounding matrix of modified habitats. We focused on four questions, (i) How do the land-snail faunas of lowland rainforest and home gardens differ and can forest species persist in gardens? (ii) Can environmental variables such as altitude, canopy density and soil pH explain significant variation in species composition independent of the effects of habitat type? (iii) What is the extent of geographical species turnover? (iv) How valuable are the two habitats for the conservation of native land snails? 2. Sixty-nine standardized belt transects were sampled in 21 rainforest fragments and 12 gardens. Data were analysed using canonical and partial canonical correspondence analysis. 3. Land-snail species composition varied significantly between gardens and forest. Lowland rainforest was dominated by native snails, many of which were restricted to forest. Gardens contained a distinct component of exotic and native synanthropic snails, as well as many native forest species. Altitude, canopy density and soil pH explained significant variation in species composition independent of the effects of habitat type but were closely correlated with variation in species composition between gardens and forest. Longitude and latitude explained significant variation in species composition across both gardens and forest. 4. Synthesis and applications. Most rainforest snails were restricted to forest. This, together with the high level of geographical turnover and the scale of forest fragmentation, emphasizes the need to conserve all remaining rainforest cover. A substantial number of widespread and localized forest land-snail species can survive in gardens. Home gardens therefore offer great potential for restoring and increasing forest cover and connectivity. [ABSTRACT FROM AUTHOR]

Aim To unravel the reasons why a group of islands of 800 km2 area should support over 200 extant land snail species. Location The temperate Atlantic Madeiran archipelago. Methods Distributional surveys and model testing. Results Repeated volcanic events have changed the topography of the islands and created periodic further isolates. There has been climatic fluctuation and varying sea level. Individual locations are not species-rich, but there is replacement from one subregion to another. Evidence of competitive interactions is lacking. Main conclusions High diversity results from the fortuitous coincidence of rates of geological and climatic change and isolation on the one hand, and migration and genetic divergence on the other. Hubbell’s neutral model of biodiversity explains species richness if a factor is added describing structural instability or periodicity, here called the geodetic rate. This geodetic, biological interaction can explain why some archipelagos are species-rich. [ABSTRACT FROM AUTHOR]

Introduced predators have become major threats to native animal species in oceanic islands. A number of studies have shown that alien predators have caused serious extinctions of island endemics. However, little attention has been paid to the evolutionary impacts of alien predators on native species. The present study shows that predation by black rats, Rattus rattus, has resulted in ecological and morphological changes in the land snail Mandarina anijimana from the island of Anijima in the Ogasawara archipelago. The frequency of empty predated shells has increased over the past 17–19 years in southern areas of the island. The shells of these snails were found to be significantly higher, smaller and darker in the survey in 2006 than in the survey in 1987–1989 performed in central and southern parts of Anijima, where predation by Rattus was serious. M. anijimana were formerly restricted to shallow broad-leaved litter, whereas they are currently found in deep palm litter, where predation pressure from Rattus may be lower. This suggests that increased predation pressure by Rattus has changed the habitat use of M. anijimana. The close association between shell morphology and habitat use of Mandarina species suggests that the habitat shift induced by the predation of Rattus has caused these changes in the shell morphology of M. anijimana over a period of 17–19 years. [ABSTRACT FROM AUTHOR]

Aim To investigate the importance of vicariance in shaping land snail faunas. Location Three data sets of Mediterranean land snails were analysed: Helicoidea of the Iberian Peninsula and the complete land snail faunas of the central and eastern Aegean Islands and of Israel and Palestine. Methods The vicariance model predicts a clustering of species ranges. We tested for clustering of species ranges with a Monte Carlo simulation. For this simulation we used a null model that generates range data sets in such a way that their range size distribution, their species richness distribution and the spatial autocorrelation of the ranges approximate the parameters in the real data set. Biotic elements (clusters of species ranges) were delimited with model-based Gaussian clustering. A second prediction of the vicariance model is that closely related species belong to different biotic elements. This was tested with a chi-squared test. Results The distribution areas of the Iberian Helicoidea and the Israeli/Palestinian land snails are significantly clustered. The same is true for Israeli/Palestinian land snail species belonging to groups with geographically restricted species. However, the clustering is not significant in the complete central and eastern Aegean land snail data set, the Iberian Helicoidea species, and the central and eastern Aegean land snails belonging to groups with geographically restricted species. Contrary to the prediction of the vicariance model, closely related Iberian Helicoidea species and Israeli/Palestinian land snails belong significantly more often to the same biotic element than expected by chance. The null hypothesis that closely related species are homogeneously distributed across biotic elements cannot be rejected only for the data set that includes the Israeli/Palestinian land snails belonging to groups with geographically restricted species. Main conclusions The patterns found in the central and eastern Aegean land snail and the Iberian Helicoidea data sets do not correspond with the predictions of the vicariance model. This indicates that speciation modes other than vicariance were frequent, or that the distribution areas of many species in these faunas were largely modified by extensive post-speciation dispersal and/or regional extinction. Hardly any possible vicariance events that might have contributed to the origin of the observed biotic elements in the Israeli/Palestinian land snail fauna could be identified. On the contrary, the biotic elements of the Israeli/Palestinian land snail fauna correspond with ecological factors. Vicariance has had only a limited influence on current biogeographical patterns in Mediterranean land snails. [ABSTRACT FROM AUTHOR]

Aim The aim of this paper is to evaluate the combined effects of geographical distance and environmental distance on patterns of species similarity (similarity in species composition between sites), and to identify factors affecting the rate of decay in species similarity with each type of distance. Location Israel. Methods Data on species composition of land snails and land birds were recorded in 27 sites of 1 × 1 km scattered across a rainfall gradient in Israel. Matrices of similarity in species composition between all pairs of sites were computed and analysed with respect to corresponding matrices of geographical distance and rainfall distance (defined as the difference in mean annual rainfall between sites, and used as a measure of environmental distance). Mantel tests were applied to determine the correlation between species similarity and each type of distance. Factors affecting the decay in species similarity were investigated by comparing different subsets of the data using randomization tests. Results Both rainfall distance and geographical distance had negative effects on species similarity. The effect of rainfall distance was statistically significant even after controlling for differences in geographical distance, and vice versa. The per-unit effect of rainfall distance on species similarity decreased with increasing geographical distance, indicating that the two types of distances interacted in determining the similarity in species composition. Snails showed a higher rate of decay in species similarity with geographical distance than birds, and large snails showed a higher rate of decay than small snails, which are better passive dispersers. The per-unit effects of both rainfall distance and geographical distance on species similarity were higher in the desert region than in the Mediterranean region. Analyses focusing on a grain size of 10 × 10 m showed a lower similarity in species composition and a lower rate of decay in species similarity with rainfall distance than analyses carried out at a grain size of 1 × 1 km. Main conclusions Patterns of similarity in species composition are influenced by the combined effects of environmental variation, the position of the area along environmental gradients, the dispersal properties of the component species, and the scale (both spatial extent and grain size) at which the patterns are examined. [ABSTRACT FROM AUTHOR]

Vicariance biogeography emerged several decades ago from the fusion of cladistics and plate tectonics, and quickly came to dominate historical biogeography. The field has since been largely constrained by the notion that only processes of vicariance and not dispersal offer testable patterns and refutable hypotheses, dispersal being a random process essentially adding only noise to a vicariant system. A consequence of this thinking seems to have been a focus on the biogeography of continents and continental islands, considering the biogeography of oceanic islands less worthy of scientific attention because, being dependent on stochastic dispersal, it was uninteresting. However, the importance of dispersal is increasingly being recognized, and here we stress its fundamental role in the generation of biodiversity on oceanic islands that have been created in situ, never connected to larger land masses. Historical dispersal patterns resulting in modern distributions, once considered unknowable, are now being revealed in many plant and animal taxa, in large part through the analysis of polymorphic molecular markers. We emphasize the profound evolutionary insights that oceanic island biodiversity has provided, and the fact that, although small in area, oceanic islands harbour disproportionately high biodiversity and numbers of endemic taxa. We further stress the importance of continuing research on mechanisms generating oceanic island biodiversity, especially detection of general, non-random patterns of dispersal, and hence the need to acknowledge oceanic dispersal as significant and worthy of research. [ABSTRACT FROM AUTHOR]

In a review of recent challenges in conservation planning, Ferrier (2002) proposed the incorporation of models of similarity in species composition as a means for prioritizing areas for biodiversity conservation. A key assumption of this approach is that estimates of compositional similarity derived from models of similarity in species composition can be used as effective surrogates for real similarity data. We used data on snail distribution in Israel to test this assumption. We used two types of models to analyze patterns of similarity in species composition: one based on presence/absence data and the second based on abundance data. Both models accounted for large amounts of the observed variation in compositional similarity. Variation-partitioning analysis indicated that a considerable amount of the variation in compositional similarity could be separated into “pure” geographical versus “pure” environmental components, indicating that reserve selection procedures should take into account spatial considerations in determining priorities for conservation. The relative effects of geographical versus environmental factors varied between the two types of models, indicating that different indices of similarity should be used if one wishes to represent species composition per se or ecological communities including their relative species abundances. A comparison of distribution patterns of land snails and land birds in a subset of the study sites revealed a high degree of congruence in compositional similarity between the two groups. Moreover, compositional similarity in snails was a better predictor of compositional similarity in birds compared with all environmental and geographical distances taken together. Models calibrated based on data collected in small plots explained a considerable amount of the variation observed at larger scales, suggesting that sampling efforts required for conservation planning might be lower (and thus, more feasible) than assumed previously. Models of similarity in species composition may serve as an important tool for conservation planning. [ABSTRACT FROM AUTHOR]

Aim To test the performance of the choros model in an archipelago using two measures of environmental heterogeneity. The choros model is a simple, easy-to-use mathematical relationship which approaches species richness as a combined function of area and environmental heterogeneity. Location The archipelago of Skyros in the central Aegean Sea (Greece). Methods We surveyed land snails on 12 islands of the archipelago. We informed the choros model with habitat data based on natural history information from the land snail species assemblage. We contrast this with habitat information taken from traditional vegetation classification to study the behaviour of choros with different measures of environmental heterogeneity. R2 values and Akaike's information criterion (AIC) were used to compare the choros model and the Arrhenius species–area model. Path analysis was used to evaluate the variance in species richness explained by area and habitat diversity. Results Forty-two land snail species were recorded, living in 33 different habitat types. The choros model with habitat types had more explanatory power than the classic species–area model and the choros model using vegetation types. This was true for all islands of the archipelago, as well as for the small islands alone. Combined effects of area and habitat diversity primarily explain species richness in the archipelago, but there is a decline when only small islands are considered. The effects of area are very low both for all the islands of the archipelago, and for the small islands alone. The variance explained by habitat diversity is low for the island group as a whole, but significantly increases for the small islands. Main conclusions The choros model is effective in describing species-richness patterns of land snails in the Skyros Archipelago, incorporating ecologically relevant information on habitat occupancy and area. The choros model is more effective in explaining richness patterns on small islands. When using traditional vegetation types, the choros model performs worse than the classic species–area relationship, indicating that use of proxies for habitat diversity may be problematic. The slopes for choros and Arrhenius models both assert that, for land snails, the Skyros Archipelago is a portion of a larger biogeographical province. The choros model, informed by ecologically relevant habitat measures, in conjunction with path analysis points to the importance of habitat diversity in island species richness. [ABSTRACT FROM AUTHOR]

The slowly dispersing Greek land snail species Isabellaria ( Carinigera) pharsalica ( ) can be readily distinguished from related species of the subgenus Carinigera on biogeographical grounds, i.e. by a separation of nearly 200 km. Nevertheless, I. pharsalica shows overlap in shell morphology with Isabellaria ( Carinigera) buresi (A. J. Wagner, 1927). The aim of this paper is to study the interrelationships and phylogeography of I. pharsalica and selected I. buresi subspecies, in order to reconcile these apparently contradictory observations. Northern Greece, Macedonia, Serbia and southern Bulgaria. Mitochondrial COI genealogical interrelationships were studied for specimens of I. pharsalica, selected I. buresi subspecies and other related Isabellaria species. COI sequences of I. pharsalica constitute a clade nested among sequences of I. buresi from north-eastern Greece and adjacent Bulgaria. The genetic divergence among the I. pharsalica sequences is remarkably low compared to the divergence among the I. buresi sequences. I. pharsalica descended from specimens of I. buresi that dispersed into Thessaly, and it should therefore be classified as a subspecies within I. buresi . This find is in line with the conchological similarities between I. buresi pharsalica and other I. buresi subspecies. Given the low vagility of the snails in question and the c. 200-km separation by land and sea between the ranges of I. buresi pharsalica and the combined range of the other I. buresi subspecies, passive dispersal of the I. pharsalica ancestors is most likely. Since the inferred area of origin of these hypothetical ancestors of I. buresi pharsalica nearly coincides with an ancient marble quarry, human-aided dispersal during marble transport offers a possible explanation for I. buresi pharsalica's erratic distribution. [ABSTRACT FROM AUTHOR]

We investigated the short-term effects of forest clearcutting on land snails (terrestrial gastropods) in 15 forest stands along small streams in Sweden. Two different silvicultural treatments were applied at each site: clearcutting across the stream channel and buffer strips 10 m wide on each side of the stream. Additionally, we studied 10 reference sites in unlogged riparian forests along similar-sized streams. All sites were studied before logging and then 2.5 years after logging. After clearcutting the number of individuals in a 0.5-m2 sample from each site decreased on average from 107 to 87, and the mean number of species per sample decreased from 9.9 to 7.7. Most species were negatively affected, but there were also clear differences in sensitivity. There were correlations between species survival and ground moisture. At the wettest clearcut sites with an almost intact bryophyte cover, the land snails were unaffected by clearcutting. This result suggests that wet or moist forest floors can serve as refugia even at very small spatial scales (e.g., shallow hollows, crevices). If this is an important mechanism, the spatial distribution of small habitats could be important for the long-term survival of the snail fauna or other small, dispersal-limited organisms at clearcut sites. In the buffer strips, the number of individuals decreased but not the number of species, indicating that buffer-strip retention is a good practice for protecting land snails in riparian forests. The varying effectiveness of the buffer strip could partly be explained by the proportion of the remaining basal area, emphasizing that buffer strips could be even more effective if efforts are made to avoid heavy damage by windthrows. [ABSTRACT FROM AUTHOR]

ABSTRACT Aim To investigate latitudinal and altitudinal patterns in body size variation among north-west European land snail species, as well as factors influencing such patterns. Location Latitudinal patterns were investigated in north-west Europe from the British Isles and France in the west to Finland, Poland, Slovakia and Hungary in the east and from Norway in the north to France (with the exception of the Mediterranean part of the country), Switzerland, Austria and Hungary in the south. Altitudinal patterns were examined in the Alps in Austria and Switzerland. Methods Data on latitudinal ranges of 366 north-west European land snail species, on altitudinal ranges of 175 species from Austria and 150 species from Switzerland, and on their body sizes were used to test for the presence of interspecific latitudinal or altitudinal body size patterns. Four methods, Stevens’ method, the midpoint method, the across-species method, and a phylogenetically controlled analysis (CAIC) were applied. Results As a result of the predominance of some small bodied clades at higher latitudes and some large bodied clades at lower latitudes, body size of north-west European land snails decreases significantly with increasing latitude. However, little of the body size variation across species is explained by latitude and the phylogenetically controlled analysis showed that the decrease of body size with increasing latitude is not a result of repeated and independent evolution of an association between body size and latitude in many clades. There is no significant correlation between body size of land snail species and altitude in the Alps although a negative correlation of body size and altitude is frequent within species. Main conclusion If phylogenetic effects are controlled for, neither latitudinal nor altitudinal patterns in body size could be found. Bergmann's rule, which predicts a positive correlation between body size of species and latitude, could not be confirmed for north-west European land snails. [ABSTRACT FROM AUTHOR]

Abstract A high level of geographical variation at an exceptionally fine scale was detected in the mitochondrial 16S ribosomal RNA genes of a land snail species Euhadra quaesita from the Kanto region of Japan. In total, 50 haplotypes were detected from 27 populations, with most sample sites possessing private alleles. In some individual populations the different haplotypes do not fall as a monophyletic group, so that some of the haplotypes are phylogenetically distant, differing from each other by > 10%. In contrast, phylogenetically similar haplotypes were found in separate sites at long distances from their main distribution. Together, these findings strongly suggest that contraction and expansion of populations has occurred repeatedly in the past. The subsequent expansion of populations and migration from different areas may have mixed distant populations. This repetition of isolation and mixing has resulted in an exceptionally fine scale of geographical variation, and the accumulation of high genetic diversity within and between populations of this species. [ABSTRACT FROM AUTHOR]

Summary Aim We examined the species-area relation of Aegean land snails, comparing different models to describe the relation. By examining those factors other than area that may also affect species richness, we tested whether the Aegean land snail fauna was more influenced by equilibrial migration and colonization processes, or rather is conservative and relictual. Location The Aegean archipelago (Greece). Methods Sixty-five islands were examined. Data were taken from own collections and from literature sources. Multiple regression analysis was used to test the null hypothesis of no relationship between species richness and island area, elevation, distance to the next larger island, and the presence and extent of calcareous substrate. Results The single most important factor determining land snail species number was area. While colonization-extinction dynamics have frequently been cited to explain this result, this conclusion was not tenable in this study as it was contradicted by species number not being related to the islands’ distances to neighbouring larger islands, after accounting for other factors affecting species number. We also found that habitat diversity affected species richness even after accounting for the effects of area: both increased elevation and greater extent of calcareous substrate on islands resulted in higher species number. This effect was most likely due to the fact that particular ecological conditions increased the probability that particular species could survive on an island. We compared the utility of the power and extreme-value function models of the species-area relation and found that both gave substantially the same results. However, fitting the power function model using nonlinear regression was of questionable utility. Main conclusions We conclude that the snail fauna of the Aegean is relictual, not equilibrial. The unusually high number of land snail species found on Crete is consistent with this conclusion. Crete is... [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate vertical migration behaviors in two species of hygrophilous micro‐snails, Vertigo moulinsiana and Vertigo angustior, in relation to the time of the year (spring and summer) at two sites that differ in ground water level (periodically inundated site and non‐inundated site). The study shows different patterns of vertical migrations in the studied species. Vertigo angustior demonstrated a strong affinity to the litter layer (a weak tendency for vertical movements), independent of the time of year and site studied. By contrast, V. moulinsiana showed a clear tendency for vertical migrations, which differed depending on the time of year and site. These differences may be related to the spatial segregation of microhabitats used by these two species at the sites studied and to differences in the ability to resist inundation. Vertigo angustior is associated with microhabitats which are not subjected to prolonged inundation and tolerates a brief submersion. The periodic character of vertical migrations may suggest the effect of endogenous factors related to reproduction in V. moulinsiana. Some plasticity of this behavior in relation to habitat conditions demonstrated by this species may be an adaptation to live in unpredictably flooded environments. [ABSTRACT FROM AUTHOR]

Abstract This study sought to investigate land-snail diversity, abundance and distribution in Arabuko Sokoke forest. Sampling was done using standard timed direct search and litter sample methods. In total, 25 species and 1263 specimens were recorded. The 25 species rank Arabuko Sokoke forest as the second richest coastal forest in land snails in East Africa. The 25 species, however, are not uniformly distributed across the forest. The majority of the snails were localized with low levels of abundance. Eight species were restricted to one forest type, whereas those shared among forest types tended to concentrate in one forest type. Only five species, Gulella radius, Gulella foveolata, Gonaxis kibweziensis, Pseudoglessula biovini and Opeas gracilis, were widespread. The highest snail diversity was recorded in the mixed forest, implying that special conservation of this habitat is necessary for retention of the broadest molluscan diversity. The observation that some species rare in the mixed forest were recorded in excess from Brachystegia and Cynometra forest, further suggests that conservation of the entire A. Sokoke forest is critical for efficient molluscan conservation. Species recorded in low levels of abundance are probably declining and investigation on the snails' ecology to understand factors that influence the snails' diversity is recommended. [ABSTRACT FROM AUTHOR]