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Insects provide key pollination services in most terrestrial biomes, but this service depends on a multistep interaction between insect and plant. An insect needs to visit a flower, receive pollen from the anthers, move to another conspecific flower, and finally deposit the pollen on a receptive stigma. Each of these steps may be affected by climate change, and focusing on only one of them (e.g., flower visitation) may miss important signals of change in service provision. In this study, we combine data on visitation, pollen transport, and single-visit pollen deposition to estimate functional outcomes in the high Arctic plant-pollinator network of Zackenberg, Northeast Greenland, a model system for global warming-associated impacts in pollination services. Over two decades of rapid climate warming, we sampled the network repeatedly: in 1996, 1997, 2010, 2011, and 2016. Although the flowering plant and insect communities and their interactions varied substantially between years, as expected based on highly variable Arctic weather, there was no detectable directional change in either the structure of flower-visitor networks or estimated pollen deposition. For flower-visitor networks compiled over a single week, species phenologies caused major within-year variation in network structure despite consistency across years. Weekly networks for the middle of the flowering season emerged as especially important because most pollination service can be expected to be provided by these large, highly nested networks. Our findings suggest that pollination ecosystem service in the high Arctic is remarkably resilient. This resilience may reflect the plasticity of Arctic biota as an adaptation to extreme and unpredictable weather. However, most pollination service was contributed by relatively few fly taxa (Diptera: Spilogona sanctipauli and Drymeia segnis [Muscidae] and species of Rhamphomyia [Empididae]). If these key pollinators are negatively affected by climate change, network structure and the pollination service that depends on it would be seriously compromised.

Tropical forests, which harbor high levels of biodiversity, are being lost at an alarming speed. Madagascar, a biodiversity hotspot, has lost more than half of its original forest cover. Most of the remaining forests are small fragments of primary and secondary forest with differing degrees of human impact. These forests, as well as coffee and fruit plantations, may be important in supporting the forest-dependent biodiversity in Madagascar but this has been little studied. In Madagascar, dung beetles, which offer important ecosystem services, are largely restricted to forests. We examined the ability of fragmented and degraded forests to support dung beetle diversity, compared to the large areas of primary forest in eastern Madagascar. We found a general trend of a reduction of species with a loss of forest connectivity. In contrast, a higher level of forest disturbance was associated with higher species diversity. In several sites of low-quality forest as many or more species were found as in less disturbed and primary forests. The average size of dung beetles was smaller in the lower quality localities than in the primary forests. These findings suggest that many forest dung beetles in Madagascar are better adapted to forest disturbance than earlier expected, although they require some level of connectivity to surrounding forest. in Malagasy is available with online material.

Summary A crucial step in the use of DNA markers for biodiversity surveys is the assignment of Linnaean taxonomies (species, genus, etc.) to sequence reads. This allows the use of all the information known based on the taxonomic names. Taxonomic placement of DNA barcoding sequences is inherently probabilistic because DNA sequences contain errors, because there is natural variation among sequences within a species, and because reference data bases are incomplete and can have false annotations. However, most existing bioinformatics methods for taxonomic placement either exclude uncertainty, or quantify it using metrics other than probability. In this paper we evaluate the performance of the recently proposed probabilistic taxonomic placement method PROTAX by applying it to both annotated reference sequence data as well as to unknown environmental data. Our four case studies include contrasting taxonomic groups (fungi, bacteria, mammals and insects), variation in the length and quality of the barcoding sequences (from individually Sanger-sequenced sequences to short Illumina reads), variation in the structures and sizes of the taxonomies (800–130 000 species) and variation in the completeness of the reference data bases (representing 15–100% of known species). Our results demonstrate that PROTAX yields essentially unbiased probabilities of taxonomic placement, which means its quantification of species identification uncertainty is reliable. As expected, the accuracy of taxonomic placement increases with increasing coverage of taxonomic and reference sequence data bases, and with increasing ratio of genetic variation among taxonomic levels over within taxonomic levels. We conclude that reliable species-level identification from environmental samples is still challenging and that neglecting identification uncertainty can lead to spurious inference. A key aim for future research is the completion of taxonomic and reference sequence data bases and making these two types of data compatible.

15 pages; International audience; How food webs are structured has major implications for their stability and dynamics. While poorly studied to date, arctic food webs are commonly assumed to be simple in structure, with few links per species. If this is the case, then different parts of the web may be weakly connected to each other, with populations and species united by only a low number of links. We provide the first highly resolved description of trophic link structure for a large part of a high-arctic food web. For this purpose, we apply a combination of recent techniques to describing the links between three predator guilds (insectivorous birds, spiders, and lepidopteran parasitoids) and their two dominant prey orders (Diptera and Lepidoptera). The resultant web shows a dense link structure and no compartmentalization or modularity across the three predator guilds. Thus, both individual predators and predator guilds tap heavily into the prey community of each other, offering versatile scope for indirect interactions across different parts of the web. The current description of a first but single arctic web may serve as a benchmark toward which to gauge future webs resolved by similar techniques. Targeting an unusual breadth of predator guilds, and relying on techniques with a high resolution, it suggests that species in this web are closely connected. Thus, our findings call for similar explorations of link structure across multiple guilds in both arctic and other webs. From an applied perspective, our description of an arctic web suggests new avenues for understanding how arctic food webs are built and function and of how they respond to current climate change. It suggests that to comprehend the community-level consequences of rapid arctic warming, we should turn from analyses of populations, population pairs, and isolated predator-prey interactions to considering the full set of interacting species.

In the High Arctic, the species richness of spiders is typically low, but abundances can be very high. Thus, how the few spider species occurring in the region choose their prey, and what prey taxa they focus on, may significantly affect the community structure of arctic arthropods. Here we estimate the ecological imprint of adult spiders of three large-bodied species coexisting in Northeast Greenland: the morphologically similar crab spiders Xysticus deichmanni and X. labradorensis (Thomisidae) and the wolf spider Pardosa glacialis (Lycosidae). To describe an important part of these spiders’ diet in detail, we amplified and sequenced DNA from prey remains in their guts, selectively focusing on two of the most abundant prey orders in the area (Diptera and Lepidoptera). By comparing the resultant sequences to a reference library including most taxa encountered in the region, we assigned the prey to species. Among the spider taxa occurring in the region, the wolf spider Pardosa glacialis is dominant in terms of both biomass and density. All three spider species proved to be wide generalists, with no detectable differences in prey choice among either the two crab spiders, or among these crab spiders and the wolf spider. This lack of dietary differentiation among species may be caused by the limited prey availability in the Arctic, forcing the predators to both generalism and opportunism. Given the substantial abundance of spiders and the lack of other predatory arthropods in the region, the opportunistic prey choice observed implies that these High-Arctic spider species have the potential for inflicting a strong influence on their prey community.

A crucial step in the use of DNA markers for biodiversity surveys is the assignment of Linnaean taxonomies (species, genus, etc.) to sequence reads. This allows the use of all the information known based on the taxonomic names. Taxonomic placement of DNA barcoding sequences is inherently probabilistic because DNA sequences contain errors, because there is natural variation among sequences within a species, and because reference databases are incomplete and can have false annotations. However, most existing bioinformatics methods for taxonomic placement either exclude uncertainty, or quantify it using metrics other than probability.In this paper we evaluate the performance of a recently proposed probabilistic taxonomic placement method PROTAX by applying it to both annotated reference sequence data as well as unknown environmental data. Our four case studies include contrasting taxonomic groups (fungi, bacteria, mammals, and insects), variation in the length and quality of the barcoding sequences (from individually Sanger-sequenced sequences to short Illumina reads), variation in the structures and sizes of the taxonomies (from 800 to 130 000 species), and variation in the completeness of the reference databases (representing 15% to 100% of the species).Our results demonstrate that PROTAX yields essentially unbiased assessment of probabilities of taxonomic placement, and thus that its quantification of species identification uncertainty is reliable. As expected, the accuracy of taxonomic placement increases with increasing coverage of taxonomic and reference sequence databases, and with increasing ratio of genetic variation among taxonomic levels over within taxonomic levels.Our results show that reliable species-level identification from environmental samples is still challenging, and thus neglecting identification uncertainty can lead to spurious inference. A key aim for future research is the completion and pruning of taxonomic and reference sequence databases, and making these two types of data compatible.

How networks of ecological interactions are structured has a major impact on their functioning. However, accurately resolving both the nodes of the webs and the links between them is fraught with difficulties. We ask whether the new resolution conferred by molecular information changes perceptions of network structure. To probe a network of antagonistic interactions in the High Arctic, we use two complementary sources of molecular data: parasitoid DNA sequenced from the tissues of their hosts and host DNA sequenced from the gut of adult parasitoids. The information added by molecular analysis radically changes the properties of interaction structure. Overall, three times as many interaction types were revealed by combining molecular information from parasitoids and hosts with rearing data, versus rearing data alone. At the species level, our results alter the perceived host specificity of parasitoids, the parasitoid load of host species, and the web-wide role of predators with a cryptic lifestyle. As the northernmost network of host-parasitoid interactions quantified, our data point exerts high leverage on global comparisons of food web structure. However, how we view its structure will depend on what information we use: compared with variation among networks quantified at other sites, the properties of our web vary as much or much more depending on the techniques used to reconstruct it. We thus urge ecologists to combine multiple pieces of evidence in assessing the structure of interaction webs, and suggest that current perceptions of interaction structure may be strongly affected by the methods used to construct them.

Madagascar, the world's fourth largest island, has a long history of isolation (160 million years) and a wide range of climates and ecosystems which have in turn resulted in high levels of endemism across different taxonomic levels. Although Madagascar has a rich dung beetle fauna that belongs to various tribes only three species of the Scarabaeini are found there, namely Scarabaeus viettei, S. radama and S. sevoistra. These three species are superficially quite distinctive and have, consequently, had a variable taxonomic history since the first one was described in 1896. The morphological differences between these species resulted in them being placed in different genera at different times. However, currently, based on cladistic analyses, they are all classified in the genus Scarabaeus. In this study, two of the species, S. viettei and S. radama, were included in a phylogenetic analysis based on two mitochondrial gene regions — cytochrome oxidase I (COI) and 16S rRNA — and a 247 morphological and behavioural dataset of 23 members of the Scarabaeinae. A Bayesian phylogram supports the monophyly of the genus Scarabaeus, with the two species from Madagascar appearing sister to three species of Scarabaeus from south-west Africa. Estimated times of divergence based on published mutation rates of 0.012 and 0.0075 for COI indicate that a shared African/Madagascan origin occurred around 15.18 or 24.15 million years ago, respectively. is study is another example in support of Madagascan fauna having an African origin with colonisation having occurred via dispersal as opposed to ancient vicariant events.

The wet tropical forests in Madagascar have endemic dung beetles that have radiated for tens of millions of years using a limited range of resources produced by the species-poor mammalian fauna. Beetles were trapped in two wet-forest localities over 4 years (6407 trap nights, 18,869 individuals). More limited data for six other local communities were used to check the generality of the results. Local communities are relatively species poor (around 30 species) in comparison with wet-forest-inhabiting dung beetle communities elsewhere in the tropics (typically 50 or more species). The species belong to only two tribes, Canthonini and Helictopleurina (Oniticellini), which have evolved, exceptionally for dung beetle tribes, completely nocturnal versus diurnal diel activities, respectively. Patterns in the elevational occurrence, body size and resource use suggest that interspecific competition restricts the numbers of locally coexisting species exploiting the limited range of resources that are available. On the other hand, regional turnover in the species composition is exceptionally high due to a large number of species with small geographical ranges, yielding a very large total fauna of dung beetles in Madagascar (>250 species). Apart from exceptionally low local (alpha) diversity and high beta diversity, the Malagasy dung beetle communities are ecologically distinctive from comparable communities in other tropical regions in having high numerical dominance of the most abundant species, small average body size and low degree of resource specialization.

Many taxa, including dung beetles, exhibit small-scale microendemism in Madagascar, which has contributed to the high level of species' diversity on the island. Species in the genus Nanos are numerically dominant in the dung beetle communities in rainforests in eastern Madagascar, but typically just one species occurs in any one locality. The two northern species, N. clypeatus and N. dubitatus, cannot be distinguished by either a mitochondrial or a nuclear genetic marker (cytochrome oxidase subunit I and internal transcription spacer 2). One population of the southern N. viettei is genetically highly divergent, although morphologically indistinguishable. Genetic data indicate that introgression occurred from N. dubitatus to N. viettei 1–2 Mya, and these species may continue to hybridize. Complex genetic patterns have mostly evolved within the last 2 Myr. During this time, the glacial cycles in the northern hemisphere were reflected in the oscillating climatic conditions in Africa, which repeatedly fragmented and re-united the rainforests in eastern Madagascar, possibly leading to the observed complex phylogeographical patterns in Nanos. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 96, 942–955.

Dung beetle species belonging to the worldwide tribe Canthonini (Scarabaeidae) and occurring in Madagascar are all endemic to that island. The Malagasy Canthonini form three lineages, one of which is the group Longitarsi that includes five genera. The phylogenetic relationships of Malagasy Canthonini are not fully resolved and only few species of Longitarsi have been included in previous studies. Here we infer the phylogenetic relationships within the Longitarsi group using molecular data and together with morphological examination revise the systematics of the group. The five genera of the Longitarsi group form one monophyletic clade and thus we suggest the synonymization of the younger genera Sikorantus, Phacosomoides, Madaphacosoma and Aleiantus; with the oldest genus belonging to this clade Epactoides. We describe two new species: Epactoides jounii sp. n and Epactoides mangabeensis sp. n. Most of the species of Longitarsi inhabit the eastern rainforests, with very low local species diversity and highly restricted geographical ranges. In the group Longitarsi four species are wingless. The loss of wings has evolved at least twice, at high altitude along the mountain range.

The endemic dung beetle subtribe Helictopleurina has 65 species mostly in wet forests in eastern Madagascar. There are no extant native ungulates in Madagascar, but three Helictopleurus species have shifted to the introduced cattle dung in open habitats in the past 1500 years. Helictopleurus neoamplicollis and Helictopleurus marsyas exhibit very limited cytochrome oxidase subunit 1 haplotype diversity and a single haplotype is present across Madagascar, suggesting that these species shifted to cattle dung in a small region followed by rapid range expansion. In contrast, patterns of molecular diversity in Helictopleurus quadripunctatus indicate a gradual diet shift across most of southern Madagascar, consistent with somewhat broader diet in this species. The three cattle dung-using Helictopleurus species have significantly greater geographical ranges than the forest-dwelling species, apparently because the shift to the currently very abundant new resource relaxed interspecific competition that hinders range expansion in the forest species.

DNA sequences offer powerful tools for describing the members and interactions of natural communities. In this study, we establish the to-date most comprehensive library of DNA barcodes for a terrestrial site, including all known macroscopic animals and vascular plants of an intensively studied area of the High Arctic, the Zackenberg Valley in Northeast Greenland. To demonstrate its utility, we apply the library to identify nearly 20 000 arthropod individuals from two Malaise traps, each operated for two summers. Drawing on this material, we estimate the coverage of previous morphology-based species inventories, derive a snapshot of faunal turnover in space and time and describe the abundance and phenology of species in the rapidly changing arctic environment. Overall, 403 terrestrial animal and 160 vascular plant species were recorded by morphology-based techniques. DNA barcodes (CO1) offered high resolution in discriminating among the local animal taxa, with 92% of morphologically distinguishable taxa assigned to unique Barcode Index Numbers (BINs) and 93% to monophyletic clusters. For vascular plants, resolution was lower, with 54% of species forming monophyletic clusters based on barcode regions rbcLa and ITS2. Malaise catches revealed 122 BINs not detected by previous sampling and DNA barcoding. The insect community was dominated by a few highly abundant taxa. Even closely related taxa differed in phenology, emphasizing the need for species-level resolution when describing ongoing shifts in arctic communities and ecosystems. The DNA barcode library now established for Zackenberg offers new scope for such explorations, and for the detailed dissection of interspecific interactions throughout the community.

Madagascar has an exceptionally large fauna of more than 250 species of endemic dung beetles. Based on molecular phylogenies, the species descend from eight independent overseas colonisations, of which four have given rise to big radiations. Here, we analyse the tribe Canthonini with three parallel radiations following the respective colonisations at 64–44 Mya (Arachnodes–Epilissus, 101 species), 30–19 Mya (Epactoides, 37 species), and 24–15 Mya (Apotolamprus–Nanos, 61 species). All three radiations have taken place in forests, but there are also substantial differences between them. The oldest radiation exhibits the greatest ecological diversification, including monophyletic groups of primate and cattle dung specialists and multiple shifts to arboreal foraging. Analysis of pairs of sister species suggests allopatric speciation in the oldest and the youngest, apparently non-adaptive, radiations, whereas in Epactoides closely related species have diverged ecologically and have largely overlapping geographical ranges, suggestive of adaptive radiation in parapatry or regional sympatry.

Adaptive radiations of mammals have contributed to the exceptionally high levels of biodiversity and endemism in Madagascar. Here we examine the evolutionary history of the endemic dung beetle tribe Helictopleurini (Scarabaeidae) and its relationship to the widely distributed Oniticellini and Onthophagini. Helictopleurini species are dependent on mammals for their resources. We date the single origin of the tribe at 37 to 23 MY ago, indicating overseas colonization of Madagascar. The main radiation occurred concurrently with the main radiations of lemurs. The ancestors of Helictopleurini are inferred to have been coprophagous species inhabiting open habitats. Subsequent evolution has involved a shift into forests, changes in resource use to a more generalized diet, and changes in body size. Four species of the extant 65 species have shifted to use the dung of the recently introduced cattle in open habitats, allowing these species to greatly expand their geographical ranges. ispartof: Molecular phylogenetics and evolution vol:47 issue:3 pages:1076-89 ispartof: location:United States status: published