Search

The morphology of leaves is shaped by both historical and current selection acting on constrained developmental systems. For this reason, the phylogenetic signal of these characters is usually overlooked. Methodology. We investigate morphology of the leaflets of all genera of the Zamiaceae using multiple microscopical techniques to test whether leaf characters present a phylogenetic signal and whether they are useful to define clades at a suprageneric level. Pivotal results. Our investigation shows that most genera are quite uniform in their leaflet anatomy, with the largest genera (Zamia, Encephalartos) presenting the highest degree of variation. Using both Bayesian and parsimony methods on two different molecular scaffolds, we are able to show that leaflet anatomy has a strong phylogenetic signal in the Zamiaceae and that many clades retrieved by molecular analyses present potential synapomorphies in their leaflet anatomy. Particularly, the placement of Stangeria in a clade with Zamia and Microcycas is supported by the presence of both an adaxial and an abaxial girder sclerenchyma and the absence of sclerified hypodermis. The placement of Stangeria as sister to Bowenia, on the other hand, is not supported by our analysis. Instead, our results put into question the homology of the similar guard cell morphology in the two genera. Conclusions. We show that leaflet anatomy has a substantial amount of phylogenetic signal in the Zamiaceae, supporting relationships that are not supported by general morphology. Therefore, anatomical investigation represents a promising avenue for plant systematists.

Aquatic invaders often cause severe declines of native amphibian populations, either through competition, predation and/or alterations of the habitat. Such situation has raised additional concerns for the persistence of endemic species exhibiting rare and alternative phenotypes. Here, we experimentally assessed the impact of the invasive mosquitofish (Gambusia holbrooki) on adult newts (Lissotriton graecus) exhibiting paedomorphosis, the retention of larval traits such as gills, making them fully aquatic. Mosquitofish had a negative impact on paedomorphic newts by inducing both behavioral and phenotypic changes. Paedomorphic newts exhibited avoidance behavior and higher metamorphosis rates in the presence of fish. Both female and male newts responded by decreasing mobility and foraging activity. Females stopped investing in egg-laying in presence of fish and males metamorphosed earlier than females. Hence, our results show that mosquitofish introductions, particularly in areas with populations exhibiting paedomorphosis, might have detrimental consequences on the preservation of alternative developmental pathways. Both behavioral and phenotypic effects should be assessed to understand the impacts of introduced species.

Beetles are the most species-rich animal radiation and are among the historically most intensively studied insect groups. Consequently, the vast majority of their higher-level taxa had already been described about a century ago. In the 21st century, thus far, only three beetle families have been described de novo based on newly collected material. Here, we report the discovery of a completely new lineage of soft-bodied neotenic beetles from the Brazilian Atlantic rainforest, which is one of the most diverse and also most endangered biomes on the planet. We identified three species in two genera, which differ in morphology of all life stages and exhibit different degrees of neoteny in females. We provide a formal description of this lineage for which we propose the new family Jurasaidae. Molecular phylogeny recovered Jurasaidae within the basal grade in Elateroidea, sister to the well-sclerotized rare click beetles, Cerophytidae. This placement is supported by several larval characters including the modified mouthparts. The discovery of a new beetle family, which is due to the limited dispersal capability and cryptic lifestyle of its wingless females bound to long-term stable habitats, highlights the importance of the Brazilian Atlantic rainforest as a top priority area for nature conservation.

A rapid phenotype deviation is a common population response to atypical environmental conditions in aquatic animals. However, the implications for adaptive specialisation, stochastic segregation and ancestral traits fixation in the stress‐induced phenotype transformation are not clear. Here, we cross‐analyse the populations of commonly fluvial Dolly Varden charr Salvelinus malma multiply locked in small lakes (

Simple Summary Jurasaidae are small neotenic beetles which were only recently discovered in the Brazilian Atlantic Forest biodiversity hotspot. They have a limited dispersal propensity due to their larviform wingless females. Only adult males are capable of flight. So far, only three species classified in two genera are known. Here, we report the discovery of two new species together with a morphologically and geographically interesting population of one already described species. Our discovery is important not only for understanding the diversity of the group but also from a biogeographic point of view. For the first time, we report here the discovery of a jurasaid species from the relatively dry transitional zone between the Atlantic Forest and the Caatinga biomes. Considering our recent findings as well as the minute body size and cryptic lifestyle of Jurasaidae, we expect many more species will be discovered in the future from the Atlantic Forest and possibly also other surrounding ecoregions. Our study should motivate colleagues not only to perform field research in the eastern part of South America but also to pay special attention to yet undetermined materials deposited in local institutions, laboratories and collections. Abstract Jurasaidae are a family of neotenic elateroid beetles which was described recently from the Brazilian Atlantic Forest biodiversity hotspot based on three species in two genera. All life stages live in the soil, including the larviform females, and only adult males are able to fly. Here, we report the discovery of two new species, Jurasai miraculum sp. nov. and J. vanini sp. nov., and a new, morphologically remarkable population of J. digitusdei Rosa et al., 2020. Our discovery sheds further light on the diversity and biogeography of the group. Most species of Jurasaidae are known from the rainforest remnants of the Atlantic Forest, but here for the first time we report a jurasaid species from the relatively drier Atlantic Forest/Caatinga transitional zone. Considering our recent findings, minute body size and cryptic lifestyle of all jurasaids, together with potentially high numbers of yet undescribed species of this family from the Atlantic Forest and possibly also other surrounding ecoregions, we call for both field research in potentially suitable localities as well as for a detailed investigation of a massive amount of already collected but still unprocessed materials deposited in a number of Brazilian institutes, laboratories and collections.

Observations on the ontogeny and diversity of salamanders provided some of the earliest evidence that shifts in developmental trajectories have made a substantial contribution to the evolution of animal forms. Since the dawn of evo-devo there have been major advances in understanding developmental mechanisms, phylogenetic relationships, evolutionary models, and an appreciation for the impact of ecology on patterns of development (eco-evo-devo). Molecular phylogenetic analyses have converged on strong support for the majority of branches in the Salamander Tree of Life, which includes 764 described species. Ancestral reconstructions reveal repeated transitions between life cycle modes and ecologies. The salamander fossil record is scant, but key Mesozoic species support the antiquity of life cycle transitions in some families. Colonization of diverse habitats has promoted phenotypic diversification and sometimes convergence when similar environments have been independently invaded. However, unrelated lineages may follow different developmental pathways to arrive at convergent phenotypes. This article summarizes ecological and endocrine based causes of life cycle transitions in salamanders, as well as consequences to body size, genome size, and skeletal structure. Salamanders offer a rich source of comparisons for understanding how the evolution of developmental patterns has led to phenotypic diversification following shifts to new adaptive zones. This article is protected by copyright. All rights reserved.

Eusocial insects exhibit reproductive division of labor, in which only a part of colony members differentiates into reproductives. In termite colonies, the division of labors is performed among multiple types of individuals (i.e., castes), such as reproductives, workers, and soldiers to organize their society. Caste differentiation occurs according to extrinsic factors, such as social interactions, leading to developmental modifications during postembryonic development, and consequently, the caste ratio in a colony is appropriately coordinated. In particular, when the current reproductives die or become senescent, some immature individuals molt into supplementary reproductives, also known as “neotenics,” that take over the reproductive task in their natal colony. Neotenics exhibit variety of larval features, such as winglessness, and thus, immature individuals are suggested to differentiate by a partial release from arrested development, particularly in the reproductive organs. These neotenic features, which have long been assumed to develop via heterochronic regulation, provide us opportunities to understand the developmental mechanisms and evolutionary origin of the novel caste. This article overviews the accumulated data on the physiological and developmental mechanisms that regulate the neotenic differentiation in termites. Furthermore, the evolutionary trajectories leading to neotenic differentiation are discussed, namely the acquisition of a regulatory mechanism that enable the partial release from a developmentally arrested state.

All students of xylem structure-function relations need to be familiar with the work of Sherwin Carlquist. He studies xylem through the lens of the comparative method, which uses the appearance of similar anatomical features under similar conditions of natural selection to infer function. "Function" in biology implies adaptation; maximally supported adaptation inferences require experimental and comparative xylem scientists to work with one another. Engaging with comparative inferences of xylem function will, more likely sooner rather than later, bring one to the work of Sherwin Carlquist. To mark his 90th birthday, I highlight just a few examples of his extraordinarily perceptive and general comparative insights. One is "Carlquist's Law", the pervasive tendency for vessels to be solitary when background cells are conductive. I cover his pioneering of "ecological" wood anatomy, viewing xylem variation as reflecting the effects of selection across climate and habit variation. Another is the embolism vulnerability-conduit diameter relationship, one of the most widely invoked structure-function relationships in xylem biology. I discuss the inferential richness within the notion of Carlquistian paedomorphosis, including detailed functional inferences regarding ray cell orientation. My final example comes from his very recent work offering the first satisfactory hypothesis accounting for the geographical and histological distribution of scalariform perforation plates as an adaptation, including "Carlquist's Ratchet", why scalariform plates are adaptive but do not re-evolve once lost. This extraordinarily rich production over six decades is filled with comparative inferences that should keep students of xylem function busy testing for decades to come.

International audience; Metamorphosis is widespread across the animal kingdom and induces fundamental changes in the morphology, habitat and resources used by an organism during its lifetime. Metamorphic species are likely to experience more dynamic selective pres- sures through ontogeny compared with species with single-phase life cycles, which may drive divergent evolutionary dynamics. Here, we reconstruct the cranial evolution of the salamander using geometric morphometric data from 148 species spanning the order’s full phylogenetic, developmental and ecological diversity. We demonstrate that life cycle influences cranial shape diversity and rate of evolution. Shifts in the rate of cranial evolution are consistently associated with transitions from bipha- sic to either direct-developing or paedomorphic life cycle strategies. Direct-developers exhibit the slowest rates of evolution and the lowest disparity, and paedomorphic species the highest. Species undergoing complete metamorphosis (biphasic and direct-developing) exhibit greater cranial modularity (evolutionary independence among regions) than do paedomorphic species, which undergo differential metamorphosis. Biphasic and direct-developing species also display elevated disparity relative to the evolutionary rate for bones associated with feeding, whereas this is not the case for paedomorphic species. Metamorphosis has profoundly influenced salamander cranial evolution, requiring greater autonomy of cranial elements and facilitating the rapid evolution of regions that are remodelled through ontogeny. Rather than compounding functional con- straints on variation, metamorphosis seems to have promoted the morphological evolution of salamanders over 180 million years, which may explain the ubiquity of this complex life cycle strategy across disparate organisms.

Beetles are the most species-rich animal radiation and are among the historically most intensively studied insect groups. Consequently, the vast majority of their higher-level taxa had already been described about a century ago. In the 21st century, thus far, only three beetle families have been described de novo based on newly collected material. Here, we report the discovery of a completely new lineage of soft-bodied neotenic beetles from the Brazilian Atlantic rainforest, which is one of the most diverse and also most endangered biomes on the planet. We identified three species in two genera, which differ in morphology of all life stages and exhibit different degrees of neoteny in females. We provide a formal description of this lineage for which we propose the new family Jurasaidae. Molecular phylogeny recovered Jurasaidae within the basal grade in Elateroidea, sister to the well-sclerotized rare click beetles, Cerophytidae. This placement is supported by several larval characters including the modified mouthparts. The discovery of a new beetle family, which is due to the limited dispersal capability and cryptic lifestyle of its wingless females bound to long-term stable habitats, highlights the importance of the Brazilian Atlantic rainforest as a top priority area for nature conservation.

Background and Aims: Evolutionary change in developmental trajectories (heterochrony) is a major mechanism of adaptation in plants and animals. However, there are few detailed studies of the variation in the timing of developmental events among wild populations. We here aimed to identify the climatic drivers and measure selection shaping a genetic-based developmental cline among populations of an endemic tree species complex on the island of Tasmania. Methods: Seed lots from 38 native provenances encompassing the clinal transition from the heteroblastic Eucalyptus tenuiramis to the homoblastic Eucalyptus risdonii were grown in a common-garden field trial in southern Tasmania for 20 years. We used 27 climatic variables to model the provenance variation in vegetative juvenility as assessed at age 5 years. A phenotypic selection analysis was used to measure the fitness consequences of variation in vegetative juvenility based on its impact on the survival and reproductive capacity of survivors at age 20 years. Key Results: Significant provenance divergence in vegetative juvenility was shown to be associated with home-site aridity, with the retention of juvenile foliage increasing with increasing aridity. Our results indicated that climate change may lead to different directions of selection across the geographic range of the complex, and in our mesic field site demonstrated that total directional selection within phenotypically variable provenances was in favour of reduced vegetative juvenility. Conclusions: We provide evidence that heteroblasty is adaptive and argue that, in assessing the impacts of rapid global change, developmental plasticity and heterochrony are underappreciated processes which can contribute to populations of long-lived organisms, such as trees, persisting and ultimately adapting to environmental change.

Background Amphibians are animals strongly dependent on environmental conditions, like temperature, water accessibility, and the trophic state of the reservoirs. Thus, they can be used in modern palaeoenvironmental analysis, reflecting ecological condition of the biotope. Methods To analyse the observed diversity in the temnospondyl Metoposaurus krasiejowensis from Late Triassic deposits in Krasiejów (Opole Voivodeship, Poland), the characteristics of the ornamentation (such as grooves, ridges, tubercules) of 25 clavicles and 13 skulls were observed on macro- and microscales, including the use of a scanning electron microscope for high magnification. The different ornamentation patterns found in these bones have been used for taxonomical and ecological studies of inter- vs. intraspecific variation. Results Two distinct types of ornamentation (fine, regular and sparse, or coarse, irregular and dense) were found, indicating either taxonomical, ecological, individual, or ontogenetic variation, or sexual dimorphism in M. krasiejowensis. Discussion Analogies with modern Anura and Urodela, along to previous studies on temnospondyls amphibians and the geology of the Krasiejów site suggest that the differences found are rather intraspecific and may suggest ecological adaptations. Sexual dimorphism and ontogeny cannot be undoubtedly excluded, but ecological variation between populations of different environments or facultative neoteny (paedomorphism) in part of the population (with types of ornamentations being adaptations to a more aquatic or a more terrestrial lifestyle) are the most plausible explanations.

Why humans have large brains with higher cognitive abilities is a question long asked by scientists. However, much remains unknown, especially the underlying genetic mechanisms. With the use of a transgenic monkey model, we showed that human-specific sequence changes of a key brain development gene (primary microcephaly1, MCPH1) could result in detectable molecular and cognitive changes resembling human neoteny, a notable characteristic developed during human evolution.

In termite species with asexual queen succession (AQS), parthenogenetically produced immatures mostly differentiate into secondary queens, called "neotenics." In order to elucidate the ontogenetic origin of neotenics in Cavitermes tuberosus (Termitidae: Termitinae), a neotropical termite with AQS, we investigated developmental pathways of offspring according to their sex and genetic origin using both morphometric and genetic tools. The caste system of C. tuberosus follows the classical pathway of Termitidae. After the first larval instar, there is a bifurcation between two developmental lines. The apterous line is composed of a second larval instar, several worker instars, presoldiers, and soldiers. Workers display a consistent male bias and soldiers are female-only. The nymphal line is composed of five nymphal instars and the imago stage. We highlight that neotenic queens derive from third and fourth instar nymphs displaying peculiar morphological traits, here termed "aspirants," most of which are produced by parthenogenesis. Aspirants are present in all nests and perform worker tasks while waiting for the queen's death to differentiate into neotenic queens. Aspirants can successfully be used to demonstrate the occurrence of parthenogenesis in termite species whose reproductive cores are difficult to access.

Plethodontid salamanders exhibit biphasic, larval form paedomorphic, and direct developing life cycles. This diversity of developmental strategies exceeds that of any other family of terrestrial vertebrate. Here we compare patterns of larval development among the three divergent lineages of biphasic plethodontids and other salamanders. We discuss how patterns of life-cycle evolution and larval ecology might have produced a wide array of larval life histories. Compared with many other salamanders, most larval plethodontids have relatively slow growth rates and sometimes exceptionally long larval periods (up to 60 mo). Recent phylogenetic analyses of life-cycle evolution indicate that ancestral plethodontids were likely direct developers. If true, then biphasic and paedomorphic lineages might have been independently derived through different developmental mechanisms. Furthermore, biphasic plethodontids largely colonized stream habitats, which tend to have lower productivity than seasonally ephemeral ponds. Consistent with this, plethodontid larvae grow very slowly, and metamorphic timing does not appear to be strongly affected by growth history. On the basis of this, we speculate that feeding schedules and stress hormones might play a comparatively reduced role in governing the timing of metamorphosis of stream-dwelling salamanders, particularly plethodontids.

Metazoans display a tremendous diversity of developmental patterns, including complex life cycles composed of morphologically disparate stages. In this regard, the evolution of life cycle complexity promotes phenotypic diversity. However, correlations between life cycle stages can constrain the evolution of some structures and functions. Despite the potential macroevolutionary consequences, few studies have tested the impacts of life cycle evolution on broad-scale patterns of trait diversification. Here we show that larval and adult salamanders with a simple, aquatic-only (paedomorphic) life cycle had an increased rate of vertebral column and body form diversification compared to lineages with a complex, aquatic-terrestrial (biphasic) life cycle. These differences in life cycle complexity explain the variations in vertebral number and adult body form better than larval ecology. In addition, we found that lineages with a simple terrestrial-only (direct developing) life cycle also had a higher rate of adult body form evolution than biphasic lineages, but still 10-fold lower than aquatic-only lineages. Our analyses demonstrate that prominent shifts in phenotypic evolution can follow long-term transitions in life cycle complexity, which may reflect underlying stage-dependent constraints.

Summary 1.Neotropical Bromeliaceae occupy an exceptional diversity of habitats. The five principal functional types, which are defined by innovations such as Crassulacean acid metabolism (CAM), epiphytism, the tank growth-form and neoteny, display distinct ecological water-use strategies. 2.The contribution of putative drought resistance traits to the ecological differentiation of functional types has not previously been assessed, despite growing interest in the importance of these traits in other plant groups. 3.We formulated a set of hypotheses to be tested through a major survey of 376 bromeliad species (over 10% of the entire family) representing different functional types and ecologies. We quantified four drought resistance traits: osmotic potential at full turgor (πo), saturated water content (SWC), water mass per unit area (WMA), and dry leaf mass per unit area (LMA). For a subset of 308 species, relationships between drought resistance traits and species bioclimatic envelopes were also analysed. 4.SWC, WMA, and LMA were closely inter-correlated, and there was weaker coordination with πo, but the four traits differed significantly between functional types. Species of different functional types occupied distinct areas of bioclimatic space, and the relationships mapping drought resistance trait values into bioclimatic space also varied between functional types. 5.We conclude that divergences in drought resistance trait values form an integral part of the evolution of functional type distinctiveness and climatic niche differentiation in this megadiverse tropical plant family. 6.This study demonstrates how rapid, taxonomically-extensive quantification of plant functional traits can provide important insights into the evolution of ecological diversity. This article is protected by copyright. All rights reserved.

Tetrapod limbs are serially homologous structures that represent a particularly interesting model for studies on morphological integration, i.e. the tendency of developmental systems to produce correlated variation. In newts, limbs develop at an early larval stage and grow continuously, including after the habitat transition from water to land following metamorphosis. However, aquatic and terrestrial environments impose different constraints and locomotor modes that could affect patterns of morphological integration and evolvability. We hypothesize that this would be the case for alternative heterochronic morphs in newts, i.e. aquatic paedomorphs that keep gills at the adult stage and adult metamorphs that are able to disperse on land. To this end, we analyzed patterns and strengths of correlations between homologous skeletal elements of the fore- and hindlimbs as well as among skeletal elements within limbs in both phenotypes in the alpine newt, Ichthyosaura alpestris. Our results showed that metamorphs and paedomorphs had similar, general patterns of limb integration. Partial correlations between homologous limb elements and within limb elements were higher in paedomorphs when compared to metamorphs. A decrease in partial correlation between homologous limb elements in metamorphs is accompanied with a higher evolvability of the terrestrial morph. All these results indicate that environmental demands shaped the patterns of morphological integration of alpine newt limbs and that the observed diversity in correlation structure could be related to a qualitative difference in the modes of locomotion between the morphs.

Insights into the ecology and natural history of the neotenic salamander, Eurycea tonkawae, are provided from eight years of capture-recapture data from 10,041 captures of 7,315 individuals at 16 sites. Eurycea tonkawae exhibits seasonal reproduction, with peak gravidity occurring in the fall and winter. Size frequency data indicated recruitment occurred in the spring and summer. Open-population capture-recapture models revealed a similar seasonal pattern at two of three sites, while recruitment was dependent on flow at the third site. Females can reach sexual maturity within one year, and oviposition likely takes place below ground. The asymptotic body length of 1,290 individuals was estimated as 31.73 mm (at ca. two years of age), although there was substantial heterogeneity among growth trajectories. Longevity was approximately eight years, and the median age for a recaptured adult was 2.3 years. Abundance estimated from closed-population and robust-design capture-recapture models varied widely within and among sites (range 41–834), although, surprisingly, dramatic changes in abundance were not observed following prolonged dry periods. Seasonal migration patterns of second-year and older adults may help explain lower ratios of large individuals and higher temporary emigration during the latter half of the year, but further study is required. Low numbers of captures and recaptures precluded the use of open-population models to estimate demographic parameters at several sites; therefore, closed-population (or robust-design) methods are generally recommended. Based on observations of their life history and population demographics, E. tonkawae seems well adapted to conditions where spring flow is variable and surface habitat periodically goes dry.

In cooperative societies such as those of ants, honey bees, and termites, the number of reproductives is often regulated by social interactions. In many termite species, helper individuals (i.e., larvae or workers) can potentially differentiate into a “neotenic” reproductive caste in the absence of reproductives. In some termite species, multiple neotenics coexist within a nest, often with female-biased sex ratios. However, although the presence of female neotenics can suppress neotenic differentiation of female workers, it is largely unknown how male neotenics affect the differentiation of female neotenics. Here, we show that male and female neotenics regulate the neotenic differentiation in a sex-specific manner in the damp-wood termite Hodotermopsis sjostedti, whose colonies are often headed by multiple male and female neotenics in the field. Our rearing experiments showed that the presence of female neotenics suppressed differentiation of female neotenics from fourth- to seventh-larvae, i.e., pseudergates (called as “workers” in this study), whereas male neotenics promoted the differentiation of female neotenics. Moreover, the results of rearing experiments that restricted physical contact between neotenics and workers suggested that these effects were not mediated by volatile chemicals, but rather by direct contact. We found that the male neotenics were frequently groomed by female workers, suggesting that these interactions promote the differentiation of female neotenics. Our results represent an empirical evidence that the neotenic differentiation from female and male workers is regulated by direct physical contact with the preexisting neotenics.

Aim Spelerpini is a major radiation in the Plethodontidae, the largest family of salamanders. Seventy-five percent of its species richness occurs in Eurycea, one of its six genera. We hypothesized that this was the result of the transgression of the Western Interior Seaway that provided ecological opportunity via ancestral range expansion into novel geographical regions, leading to an adaptive radiation. Location Eastern North America. Methods We sampled all but one species and two subspecies of extant Spelerpini, including several putative species, for four genes using maximum likelihood and Bayesian inference approaches to generate a comprehensive, robust phylogeny. We used five fossil calibrations to generate a chronogram, a likelihood framework to estimate the ancestral ranges/splits of all nodes on the phylogeny, and a Bayesian inference method to estimate diversification rate shifts putting the evolution of this group into a historical biogeographical context. Results A well-resolved, strongly supported phylogeny of the Spelerpini was recovered. Eurycea is among the oldest genera within the Spelerpini, originating c. 42 Ma with an ancestor occurring in four of five physiographical regions, each corresponding to a major Eurycea lineage. There is strong support for a rate shift in the Edwards Plateau neotenic Eurycea. Main conclusions A pattern of niche lability was found in the Spelerpini, as opposed to a pattern of niche conservatism found in other major radiations of plethodontids in eastern North America. The genus Eurycea dispersed widely into novel regions experiencing ecological opportunity as the Western Interior Seaway transgressed. This represents the first fossil calibrated and the most thoroughly sampled phylogeny of the group to date.

BackgroundBody shape can be both a consequence and cause of a species' evolution and ecology. There are many examples of phenotypes associated with specific ecological niches, likely as a result of specific selective regimes. A classic example of this is the phenotypic change associated with colonization of caves, including body and limb elongation. However, studies explicitly testing for differences in body shape between cave-dwelling and non-cave-dwelling lineages have been limited and so the role of the cave environment in determining morphological characteristics is still not completely understood. Here we examine variation in body shape among 405 individuals representing 20 species in the salamander genus Eurycea (Plethodontidae) and select outgroups exhibiting great diversity in morphology, ecological niche, and life history.ResultsAfter analyzing morphometric data in a phylogenetic context using phylogenetic MANOVA and examination of the phylomorphospace, we found significant differences in body shape among cave-dwelling and non-cave-dwelling species and between aquatic and terrestrial species. Notably, limb elongation and reduced body and tail size characterized cave-dwelling species. Terrestrial species also exhibited elongation of the limbs and digits. We also observed differences in shape variance among paedomorphic and biphasic species. Our results suggest that the functional limitations imposed by habitat and life history played a key role in the evolution of body shape in this group in the context of their phylogenetic history.

The European cave salamander Proteus anguinus is a charismatic amphibian endemic to the concealed and inaccessible subterranean waters of the Dinaric Karst. Despite its exceptional conservation importance not much is known about its ecology and interactions with the groundwater microbiome. The cutaneous microbiota of amphibians is an important driver of metabolic capabilities and immunity, and thus a key factor in their wellbeing and survival. We used high-throughput 16S rRNA gene sequencing based on seven variable regions to examine the bacteriome of the skin of five distinct evolutionary lineages of P. anguinus and in their groundwater environment. The skin bacteriomes turned out to be strongly filtered subsamples of the environmental microbial community. The resident microbiota of the analyzed individuals was dominated by five bacterial taxa. Despite an indicated functional redundancy, the cutaneous bacteriome of P. anguinus presumably provides protection against invading microbes by occupying the niche, and thus could serve as an indicator of health status. Besides conservation implications for P. anguinus, our results provide a baseline for future studies on other endangered neotenic salamanders.

A large number of specimens (1563) of a new Florarctus species were collected in a single intertidal sample from the Ionian Sea, Italy. The postembryonic development of the new species was studied with emphasis on external morphology and functional anatomy. The new Florarctus species was recognized as having two distinct larval stages, during which the anus is formed and the gonads mature prior to the development of a gonopore. The larval stages are followed by one adult stage in females and two adult stages in males. Cuticular structures change in morphology during postembryonic development, so that they exhibit a juvenile and an adult appearance. The accelerated growth in gonadal development could be the result of paedomorphosis, which was observed in the tendency of adult males of the new Florarctus species to maintain juvenile character conditions.

The ontogenetic changes of the maxillula in Loxoconcha noharai Le and Tsukagoshi, 2014 from the second instar (A-7) through to the adult are described. The general development and number of setae on the maxillula of L. noharai are the same as L. japonica Ishizaki, 1968 from the second (A-7) to the fourth instars (A-5), but differences in these characters are found between the two species in and after the fifth instar (A-4). The number of setae on the endites and endopodite of the maxillula of L. noharai reaches a maximum in the pre-adult stage A-1, whereas in other species, it continuously increases throughout all ontogenetic stages. The maxillula of L. noharai bears fewer setae and claws throughout ontogeny compared with other species in different superfamilies. This tendency reflects possible paedomorphic evolution in L. noharai. In addition, the new species Loxoconcha yoshidai sp. nov., from the Okinawa Islands, southern Japan, is described herein. The distribution pattern of pore systems below the eye tubercle, which is used to divide the genus Loxoconcha into groups, shows that this new species has an unstable intermediate state between Groups B and C.

Morphological differentiation in skull shape in small toothed whales is sometimes explained as driven by differences in ontogeny or adaptation to a benthic or pelagic habitat. To test these hypotheses, the comparison was made, using two-dimensional geometric morphometry, between neighbouring populations of harbour porpoises from the north-eastern Black Sea and the adjoining Sea of Azov, from the same genetically isolated subspecies, both known for their extreme paedomorphosis in body and skull development but differing in seasonal habitats (very shallow waters vs open sea). There were major differences between populations in the following traits: in Azov animals, rostrum was slightly shorter and more deflected downwards; premaxillary eminences shifted backward and facial region proportionally longer; more concave facial fossa and higher vertex; lower, downward-facing foramen magnum. Meanwhile, each of the populations followed its own ontogenetic trajectory. Therefore, differences in skull shape between populations were primarily directed by habitat. Shape differences were less discriminating than size; they might involve both echolocation and feeding mechanisms and could be associated with suction feeding. These adaptations were characterized by mixed allometric patterns including both paedomorphosis and peramorphosis in their ontogeny. Shallow habitat was found to be critical in forming specific adaptations even for animals migrating between different habitat types.

New growth rate estimates for nine species from three genera of New Zealand Crassatellidae (Mollusca: Bivalvia), combined with existing morphometric ontogenetic descriptions, allow identification of heterochronic processes in the evolution of these genera. Both paedomorphosis (progenesis and neoteny) and peramorphosis (hypermorphosis and acceleration) have occurred within the clade. Overall, morphological variability and response to environmental pressure in this nonsiphonate group is restricted by the interplay of anatomical and life habit constraints. Stability in the substrate, predator avoidance, sluggish burrowing speed, and inability to escape by deep burial are suggested as key drivers of, or constraints on, morphological change. Two groups of shell characters are identified: heavy, armored “anchors” and elongate “snorkels,” which combine juvenile and adult traits in shells of different sizes and ages, produced by heterochronic variation in developmental timing. Anchors and snorkels both represent different “solutions” to the problems of life as a nonsiphonate, infaunal bivalve.

Facultative or obligate paedomorphosis has evolved several times in Mexican populations of the salamander genus Ambystoma, leading to increased genetic divergence among populations with alternate life histories and contributing to population divergence in this species complex. In the present study, we surveyed the genetic diversity of Ambystoma populations in lakes of the Cuenca Oriental, a high elevation closed drainage basin that encompasses permanent crater lakes harbouring salamander populations. We genotyped individuals from five populations aiming to better understand population dynamics and the evolution of paedomorphosis in this system. Specifically, we tested the hypotheses that the evolution of paedomorphosis in Ambystoma taylori resulted in reduced genetic exchange with populations of Ambystoma velasci in neighbouring lakes. Second, we tested whether the populations in brackish lakes of the Cuenca Oriental, Lake Atexcac, and Lake Alchichica show restricted gene flow across the basin, possibly as a result of local adaptation to those microhabitats. Using various indices of population genetic diversity, Bayesian assignment, and approximate Bayesian computation methods, we show that genetic exchange between brackish lakes and freshwater lakes is negligible, despite continued gene flow among freshwater lakes. We show that the first divergence among populations occurred between Alchichica and the remaining populations and that the evolution of paedomorphosis in A. taylori was likely favoured by local adaptation to saline conditions, thus increasing its genetic isolation. An apparently similar process appears to be in progress independently in lake Atexcac, showing that local adaptation may play an important role in population isolation and, ultimately, in speciation.

The highest potencies of regeneration in tailed amphibians in comparison with the abilities of organ and tissue restoration in other vertebrates represent the goal of longstanding and intense studies. Accumulated information can half-open some mysteries of cellular and molecular fundamentals of regeneration in Urodela, but it does not explain the maintenance of regenerative abilities in mature, adult animals. The information summarized in the review suggests that the paedomorphosis inherent in this animal group determines the keeping of the juvenile state on all levels of organization—from organismic to molecular. This, in turn, permits and eases initiation and development of regenerative responses to trauma, right up to the epimorphic regeneration of whole organs. As an example, we have traced paedomorphosis-associated cellular and molecular specificities of urodelean eye and brain tissues, which could possibly play a permissive role in their complete regeneration.

In recent years, many molecular endocrine mechanisms that regulate tissue morphogenesis have been detailed in laboratory amphibian models. However, most of these pathways have not been examined across more closely related species to understand how deviations in endocrine pathways may have contributed to amphibian diversification. The timing of metamorphosis and maturation vary extensively across plethodontid salamanders (including direct developing, biphasic, and paedomorphic species), making them an ideal system for analyzing the evolution of endocrine mechanisms in a phylogenetic context. Recent phylogenetic-based reconstructions concluded that ancestral plethodontids were likely direct developers, and free-living larval periods were independently derived multiple times within this family. Furthermore, within one clade (Spelerpini) there have been multiple independent transitions from biphasic (metamorphic) to paedomorphic developmental modes. This inspires the question: What endocrine/developmental mec...

Fish introduction is one of the main causes of amphibian decline worldwide. It affects particularly rare aquatic phenotypes such as paedomorphs, which retain gills during the adult stage. In this context, we determined whether small wetlands, such as pools surrounding fished and fishless lakes, could sustain paedomorphic and metamorphic newts. To this end, we surveyed lakes known historically to sustain Alpine newts Ichthyosaura alpestris as well as 35 nearby pools. On the basis of the published records, the only known population exhibiting paedomorphosis in the Swiss Alps was found to be extirpated by salmonid introductions. However, the metamorphs persisted in peripheral pools, paedomorphosis was discovered at a new locality, and overwintering larvae were still present in one of the lakes. These results show the importance of conserving varied aquatic habitats such as pools in mountainous environments where the main resources can become unsuitable for amphibians because of fish introductions. Pools may also function as reservoirs in maintaining newt populations until programs to remove fish from lakes can be carried out. It is not known if paedomorphs could reappear after fish removal. However, the combined resilience of amphibians after fish removal and the genetic basis for paedomorphosis highlighted in other taxa by previous studies suggest that there is the potential to maintain this intraspecific case of diversity even after its disappearance.

Climatic variations during the Quaternary period had a considerable impact on landscapes and habitat fragmentation (rivers) in North Africa. These historical events can have significant consequences on the genetic structure of the populations. Indeed, geographically separated and genetically isolated populations tend to differentiate themselves through time, eventually becoming distinct lineages, allowing new species to emerge in later generations. The aim of the present study is to use genetic and morphological techniques to evaluate the major role of the Saalian glaciation (Middle Quaternary) in the establishment of the geographic space and in the evolution of the intraspecific genetic diversity, by tracing the demographic history of barbels belonging to the Luciobarbus pallaryi (Cyprinidae) species in the Guir Basin (Algeria). In this context, two populations, from two distinct and isolated sites, were studied. Analysis of the cytochrome b (cyt b) mitochondrial markers and of the "D-loop" control region has shown that the "upstream" and "downstream" Guir populations are genetically differentiated. The molecular analyses suggest that the upstream population was disconnected from this hydrographic system during the Saalian glaciation period of the Quaternary. Subsequently, it was isolated in the foggaras underground waters in the Great Western Erg, at approximately 320 000 years BP, creating, through a bottleneck effect, a new allopatric lineage referred to as "Adrar". Conversely, the high genetic diversity in the upstream Guir (Bechar) population suggests that the stock is globally in expansion. These barbels (n=52) were also examined with meristic, morphometric, osteological, and biological features. These data also reveal a complete discrimination between the two populations, with a remarkable and distinctive behavioural adaptation for the Adrar specimens: neoteny.

The temporal partitioning hypothesis suggests that the evolution of different diel activity rhythms in animals might facilitate the coexistence between prey and predators. However, the temporal shift of habitat use induced by predation has rarely been observed. The study of such a mechanism is particularly relevant for introduced species because it might explain how native species can persist or decline in response to the presence of alien species. The introduction of fish into ponds inhabited by amphibians has severe consequences for their occurrence and abundance. Fish particularly affect an alternative newt phenotype, the paedomorph, which does not undergo metamorphosis and maintains larval traits such as gills at the adult stage. In a laboratory design, we assessed the diel patterns of habitat use in the 2 distinct morphological phenotypes of palmate newt (Lissotriton helveticus) in the presence or absence of goldfish (Carassius auratus). Both newt phenotypes avoided a risky habitat more in the presence than in the absence of fish. This habitat shift was more pronounced during the daytime (i.e., when the risk could be considered higher for the newts) than during nighttime. However, in contrast to metamorphs, paedomorphs showed less adaptive changes according to temporal risk and remained in their shelter for most of the time. Temporal and habitat partitioning at the diel scale between native and alien species might promote their coexistence, but diel change can also imply a cost in the overall reduction of the time allocated to essential activities, showing that species interactions remain complex.

While termite neotenic reproductives, when present, are usually few and confined within the deepest parts of the colony, in Prorhinotermes species they are often abundant and may accompany soldiers and pseudergates during foraging trips. This suggests that such neotenics may act as dispersers, provided they are capable of founding new colonial units without help from pseudergates. Experiments on P. canalifrons showed that, although most isolated pairs of neotenics quickly died, groups of 12 neotenics were able to reconstitute a complete colony, with a typical caste composition, after 16 months. No down regulation of the number of neotenics occurred. We conclude that the specialization of pseudergates and neotenics towards specific roles is low in Prorhinotermes, compared with other termites. This is consistent with the alleged plesiomorphic caste and life history patterns encountered in this genus. A high propensity for the selfish differentiation of self-sufficient neotenics from little-specialized pseudergates in Prorhinotermes can be understood as an adaptation to very unstable habitats.

Evolutionary fixed physical underdevelopment of mature and reproducing organisms, the paedomorphosis, was considered by I.I. Schmalhausen as a result of natural selection for maximum economy of energy expenses in ontogeny. Deep-sea paedomorphic brachiopod taxa have thin semitransparent shells composed of flattened fibers and simplified (underdeveloped) lophophores similar to that of young specimens of closely related shallow-water species and genera. Paedomorphic features of juvenile underdevelopment up to complete disappearance of the brachial skeleton are characteristic of brachiopods dwelling not only at great depths, but also in tidal pools, shallow-water underwater caves, and bottom sreas under conditions of strong currents. Deep-sea paedomorphosis is also known in marine sponges (Porifera), solitary corals (Scleractinia), sipunculids, priapulids, nudibranchs, and sea spiders (Pycnogonida).

Comparison of metamorphosis of skull and hyobranchial system in two species of neotenic salamanders reveals two different types of neoteny. Ambystoma talpoideum is completely neotenic owing to delayed metamorphosis. Notophthalmus viridescens exhibits limited neoteny as a result of incomplete metamorphosis. Morphological details of neoteny are compared to life history in both species in order to discuss the ecological morphology of the two neotenic strategies. Comparisons to Taricha granulosa, Triturus vulgaris, and Ambystoma gracile indicate that these two strategies are widely employed and may represent familial patterns.

We assessed the subsistence-related variation of the human gut microbiome at a fine resolution for two of the main dimensions of microbiome variation, age and geography. For this, we investigated the fecal microbiome and metabolome in rural Bassa and urbanized individuals from Nigeria, including infants, and compared data with worldwide populations practicing varying subsistence. Our data highlight specific microbiome traits that are progressively lost with urbanization, such as the dominance of pristine fiber degraders and the low inter-individual variation. For the Bassa, this last feature is the result of their subsistence-related practices favoring microbial dispersal, such as their extensive environmental contact and the usage of untreated waters from the Usuma River. The high degree of microbial dispersal observed in the Bassa meta-community nullifies the differences between infant and adult intestinal ecosystems, suggesting that the infant-type microbiome in Western populations could be the result of microbiome-associated neotenic traits favored by urbanization. Ayeni et al. characterize the fecal microbiome and metabolome of rural Bassa and urban individuals from Nigeria, including infants. Their findings stress the loss of ancient signatures along with urbanization and support distinct trajectories of development of the intestinal ecosystem in early life, depending on human subsistence.

Body mass is rarely recorded in amphibians, and other body measurements (e.g. snout to vent length, SVL) are generally collected instead. However, length measurements, when used as proxies of body mass in comparative analyses, are problematic if different taxa and morphotypes are included. We developed allometric relationships to derive body mass from SVL measurements. We fitted phylogenetic generalized least square models for frogs (Anura) and salamanders (Caudata) and for several families separately. We tested whether allometric relationships differed between species with different habitat preferences and between morphs in salamanders. Models were fitted with SVL-mass measurements for 88 frog and 42 salamander species. We assessed the predictive performance of the models by cross-validation. Overall, the models showed high explained variance and low forecasting errors. Models differed among semi-aquatic, terrestrial and arboreal frogs, and between paedomorphic and non-paedomorphic salamanders. Body mass estimates derived from our models allow for comparability of studies on multiple taxa and can be used for testing theories built upon evolutionary and ecological processes which are directly related to body mass.

Biological features of six groups of stream resident Dolly Varden Salvelinus malma from the Kamchatka water courses with a different habitat conditions have been studied. Stream form over the entire peninsula is characterized by a low rate of growth and a similar exterior against the background of paedomorphic morphological reduction. The lifespan in different streams varies from 5 to 9 years, the number of spawning cycles varies from 1 to 4, and fecundity varies from 85 to 470 eggs. In populations of chars with eggs smaller than 3.5 mm, retardation of the formation and differentiation of bony structures in postembryogenesis has been observed. In the water courses exposed to the long-term natural volcanogenic pollution aberrations of development, high fluctuating asymmetry, and increased dispersion of morphometric traits of chars were revealed. The most specialized population that in the majority of its biological characteristics is closely related to Dolly Varden of the southern Kurils was found in the thermal water course of southwestern extremity of the peninsula.

We investigated the phylogeography and speciation of Drilus in the Mediterranean, with focus on the Aegean and especially Crete. Altogether 12 species were sequenced for two fragments of the cytochrome c oxidase subunit I gene (cox1-3 ' and cox1-5 ' mtDNA) and provided 1381 nucleotides. Both fragments were analysed under the maximum likelihood criterion and Bayesian inference separately and concatenated as a single dataset. The Drilus species from the Peloponnese, the Ionian islands and Crete did not form a monophylum. Drilus sp. E from the Peloponnese and Zakynthos was sister to D. mauritanicus Lucas from Spain in most cases. The remaining Greek Drilus species formed a robustly supported clade in all analyses; however, the species from Crete do not seem to be monophyletic. Estimating species divergences using BEAST, we found out that the key dates in the west Aegean Drilus phylogeography appeared to be the Tortonian Crete-Peloponnese separation (12-9 Mya), the desiccation of the Mediterranean basin during the Messinian Salinity Crisis (5.96-5.33 Mya), and the repeated fragmentation of Crete during the Pliocene and Pleistocene. Within the Drilus lineages, we obtained a substitution rate estimate of 2.75% divergence per million years, which is in excellent agreement with previous studies. A Generalized Mixed Yule Coalescent (GMYC) analysis suggested the presence of six Drilus species in Crete (seven species in total, since the DNA sequences were not available for D. creticus Pic); however, we formally identified and (re)described only four which can be morphologically defined: D. creticus, D. longulus Kiesenwetter, D. horasfakionus sp. nov. and D. baenai sp. nov. These species are endemic to Crete and surrounding islets. Their diagnostic characters are illustrated and an identification key to males of these species is provided. The intraspecific variability, distribution and ecology of all species are discussed and suggestions for further research are given.[GRAPHICS]

A rare diminutive belemnite, Pumiliobelus n. gen., is described based on the new species P. haigi and P. tumidus from the upper Gearle Siltstone (Cenomanian) of the Carnarvon Basin, Western Australia. No smaller belemnites than these species are known. That they are based on adult specimens rather than juveniles is supported by a large sample, some 80 specimens, of P. haigi which collectively show a proportional range in size typical of belemnite species in general, a group in which juveniles are conspicuously lacking in the fossil record. Rostral morphology places Pumiliobelus in the Dimitobelidae, a distinctively Austral family of Aptian–Maastrichtian age, which became progressively restricted to high latitudes through the late Cretaceous. Each species of Pumiliobelus is known from a single locality where it co-occurs with the long-ranging (Albian–Cenomanian) Dimitobelus diptychus Whitehouse of widespread distribution at mid to high latitudes in the Southern Hemisphere. Dwarfism in the Dimitobelidae, as expressed by Pumiliobelus, is considered to reflect adaptive evolution to engage opportunistic life strategies that favored small body size and rapid population turnover. The rare occurrence of dwarf Dimitobelidae indicates that such strategies were limited in both geographic range and duration. Dwarfism expressed by Pumiliobelus may relate to paedomorphosis induced by rising seawater temperatures in the mid Cretaceous.

One of the most interesting heterochronic processes in the European newt (genus Triturus) is paedomorphosis, a phenomenon of attaining reproductive maturity while retaining larval features. However, paedomorphosis seems to be rare in the crested newt (Triturus cristatus superspecies). In the locality Vrba, near the town of Tuzi (Montenegro), Dr Georg Dzukic found paedomorphic Macedonian crested newt (Triturus macedonicus). In this paper, new evidence for this heterochronic process in the crested newt from Montenegro is reported. Ministry of Education and Science of the Republic of Serbia {[}173043]

In contrast to most other North American fireflies that use flash dialogs for courtship, males of Phausis reticulata Say (Coleoptera: Lampyridae) (Fender 1966), often called blue ghost fireflies, glow as they fly slowly over the forest floor searching for flightless, neotenic females that are likewise bioluminescent. Recently, these Blue Ghost firefly displays have become increasingly popular as ecotourist attractions. Nevertheless, surprisingly little work has been done on P. reticulata courtship and mating behavior, and little is known of female oviposition patterns. Extensive field observations were conducted at 2 locations in Tennessee USA, leading to the description of new categories of male mate-searching search behaviors and nightly display activities. Spectrophotometric measures of bioluminescence were similar in both sexes (λ max = 552 nm). There was a 3-fold variation in female body size, and size was correlated to the number of dorsal photic organs (3 to 9). Field experiments suggested...

The types of symmetry that are characteristic for the class Holothuroidea and reflect different stages in the evolution of this group of echinoderms and the role of paedomorphosis in its origin are analyzed. A hypothesis is proposed to explain the distinctive structure of the water vessel (ambulacral) system of sea cucumbers and the origin of the class Holothuroidea. The development of holothurians was interrupted at the stage of five primary tentacles. It resulted in changing of the mode of metamorphosis. The catastrophic metamorphosis became evol.: the body of an adult organism became to develop based on the body of larva, and the larval tissues were partly included in the body of an adult holothurian. The body of holothurian larva became partially included in the body of adult organism. This process resulted in the modification of the place and way of radial complex organs origination and development and strengthening of the heterochrony processes. All this led to the formation of the holothurian body plan. Data presented support the homology between the radial ambulacral canals of sea cucumbers and other Eleutherozoa.

The neotenic click-beetle genus Selasia Laporte, 1838 is distributed mainly in the tropical Africa, and only a few species are known from the Palaearctic and Oriental regions. Herein, I describe and figure two new Palaearctic species: Selasia nigrobrunnea sp. nov. from the western Nepal, and Selasia sabatinellii sp. nov. from Pakistan. Both species are compared with their Palaearctic congeners, and an updated identification key to Selasia species from the Palaearctic region is provided.