Fifty million years of beetle evolution along the Antarctic Polar Front

Infrequent Long-Range Dispersal and Evolution of a Top Terrestrial Arthropod Predator in the Sub-Antarctic

AbstractThe sub-Antarctic terrestrial ecosystems survive on isolated oceanic islands in the path of circumpolar currents and winds that have raged for more than 30 million years and are shaped by climatic cycles that surpass the tolerance limits of many species. Surprisingly little is known about how these ecosystems assembled their native terrestrial fauna and how such processes have changed over time. Here, we demonstrate the patterns and timing of colonization and speciation in the largest and dominant arthropod predators in the eastern sub-Antarctic: spiders of the genus Myro. Our results indicate that this lineage originated from Australia before the Plio-Pleistocenic glacial cycles and underwent an adaptive radiation on the Crozet archipelago, from where one native species colonized multiple remote archipelagos via the Antarctic circumpolar current across thousands of kilometers. The results indicate limited natural connectivity between terrestrial macroinvertebrate faunas in the eastern sub-Antarctic and partial survival of repeated glaciations in the Plio-Pleistocene. Furthermore, our findings highlight that by integrating arthropod taxa from multiple continents, the climatically more stable volcanic Crozet archipelago played a critical role in the evolution and distribution of arthropod life in the sub-Antarctic.

Taxonomic review of weevils of the tribe Celeuthetini, mainly from Sundaland, Sulawesi and the Lesser Sunda Islands (Coleoptera, Curculionidae, Entiminae)

Type material of species belonging to the weevil tribe Celeuthetini Lacordaire, 1863 mainly from Sundaland, Sulawesi and the Lesser Sunda Islands was studied. Mitochondrial sequence data could be obtained for 27 old type specimens, providing important evidence on their systematic placement. Various taxonomic problems evident from molecular and morphological data are remedied. Nusasyntrophus Riedel gen. n., Parasyntrophus Riedel gen. n., and Apotomorhamphus geminus Riedel sp. n. are described. The following genera are junior synonyms of Piezonotus Schoenherr, 1834: Coptorhynchus Guérin-Méneville, 1841 (syn. n.), Picronotus Marshall, 1956 (syn. n.), Platyspartus Faust, 1897 (syn. n.). Colpomus Marshall, 1956 is a junior synonym of Enaptomias Faust, 1897 (syn. n.) and Aulacophrys Marshall, 1956 is a junior synonym of Apiezonotus Heller, 1941. Coptorhynchus ternatensis Guérin-Méneville, 1841 and Isomerinthus asper Pascoe, 1881 are transferred to Piezonotus Schoenherr, 1834: Piezonotus ternatensis (Guérin-Méneville, 1841) (comb.n.), Piezonotus asper (Pascoe, 1881) (comb.n.). New synonymies are proposed for the following species: Syntrophus carinicollis (Heller, 1914) = Syntrophus costicollis Marshall, 1956 (syn. n.); Syntrophus echinatus (Heller, 1900) = Syntrophus bipusulosus (Heller, 1940) (syn. n.). Apotomorrhamphus heteroglymmoides Günther, 1938 and A. femoratus Voss, 1940 are transferred to Heteroglymma Faust, 1897: Heteroglymma heteroglymmoides (Günther, 1938) comb.n., Heteroglymma femoratum (Voss, 1940) comb.n.; Heteroglymma bispinosa Heller, 1900 and Heteroglymma hoplocnemis Günther, 1938 are transferred to Atactoglymma Heller, 1900: A. bispinosum (Heller, 1900) comb. n., A. hoplocnemis (Günther, 1938) comb. n.; Heteroglymma carinuliferum Heller, 1914 is transferred to Javaulius Marshall, 1956: Javaulius carinulifer (Heller, 1914) comb.n.; Idiopsodes gitgitus (Heller, 1914), Idiopsodes radiatifrons (Heller, 1914), and Idiopsodes setosapex (Heller, 1914) are transferred to Parasyntrophus gen. n.: Parasyntrophus gitgitus (Heller, 1914) comb. n., P. radiatifrons (Heller, 1914) comb. n., P. setosapex (Heller, 1914) comb. n.; Phraotes nodifer Voss, 1940 is transferred to Bonthaina Heller: Bonthaina nodifera (Voss, 1940) comb. n. Piezonotus humeralis Heller, 1914 is transferred to Temnogastrus Marshall, 1956: Temnogastrus humeralis (Heller, 1914) comb. n.; Heteroglymma echinatum Heller, 1900 and Trigonops bipusulosa Heller, 1940 are transferred to Nusasyntrophus gen. n.: Nusasyntrophus echinatus (Heller, 1900) comb. n., Nusasyntrophus bipusulosus (Heller, 1940) comb. n. Nusasyntrophus echinatus virescens (Heller, 1914) and Tarunus wolterecki banggaiensis (Günther, 1938) are elevated to species status: N. virescens (Heller, 1914) stat. n., comb. n., Tarunus banggaiensis (Günther, 1938) stat. n. Apotomorrhamphus parcesetosus Voss, 1940 is resurrected from synonymy with A. splendens Faust, 1897. Bonthaina solitaria Heller, 1900 is designated type species of Bonthaina Heller, 1900. Lectotypes are designated for the following names: Apotomorhamphus sarasini Faust, Apotomorhamphus splendens Faust, 1897, Borneobius curvipes Marshall, 1956, Coptorrhynchus beccarii Pascoe, 1885, Coptorrhynchus wolterecki banggaiensis Günther, 1938, Coptorrhynchus wolterecki Günther, 1938, Heteroglymma bispinosum Heller, 1900, Heteroglymma carinicolle Heller, 1914, Heteroglymma carinuliferum Heller, 1914, Heteroglymma echinatum Heller, 1900, Heteroglymma echinatum virescens Heller, 1914, Heteroglymma setosum Marshall, 1925, Idiopsis gitgita Heller, 1914, Idiopsis radiatifrons Heller, 1914, Idiopsis setosapex Heller, 1914, Isomerinthus asper Pascoe, 1881, Javaulius rudis Marshall, 1956, Javaulius subvirens Marshall, 1956, Piezonotus suturalis Gyllenhal, 1834, Trigonops kombuisana Marshall, 1925, Trigonops renschi Heller, 1940, Trigonops tuberculata Faust, 1896, Piezonotus humeralis Heller, 1914, Piezonotus javanus Faust, 1896, Sphaeropterus gramineus Pascoe, 1881. Piezonotus suturalis Gyllenhal, 1834 is an endemic to the South Moluccas and its record for Java in the original description is erroneous. The genus Heteroglymma Faust, 1897 is redefined based on a ventral blunt tooth of the protibia. Some characters traditionally used for diagnosis of genera are briefly discussed. Apodemes attached to the body of the penis by flexible loops are discovered in the genera Apotomorhamphus Faust, 1897, Bonthaina Heller, 1900, and Nothes Marshall, 1956. A key to the genera of Celeuthetini from Sundaland, Sulawesi and the Lesser Sunda Islands is provided. Keys to the species are provided for the following genera: Apotomorhamphus Faust, 1897 (only species from Mt. Lompobattang), Bonthaina Heller, 1900, Javaulius Marshall, 1956, Nusasyntrophus gen. n., Parasyntrophus gen. n., Temnogastrus Marshall, 1956.

The genome of the invasive and broadly polyphagous Diaprepes root weevil, Diaprepes abbreviatus (Coleoptera), reveals an arsenal of putative polysaccharide-degrading enzymes

The Diaprepes root weevil (DRW), Diaprepes abbreviatus, is a broadly polyphagous invasive pest of agriculture in the southern United States and the Caribbean. Its genome was sequenced, assembled, and annotated to study genomic correlates of specialized plant-feeding and invasiveness and to facilitate the development of new methods for DRW control. The 1.69 Gb D. abbreviatus genome assembly was distributed across 653 contigs, with an N50 of 7.8 Mb and the largest contig of 62 Mb. Most of the genome was comprised of repetitive sequences, with 66.17% in transposable elements, 5.75% in macrosatellites, and 2.06% in microsatellites. Most expected orthologous genes were present and fully assembled, with 99.5% of BUSCO genes present and 1.5% duplicated. One hundred and nine contigs (27.19 Mb) were identified as putative fragments of the X and Y sex chromosomes, and homology assessment with other beetle X chromosomes indicated a possible sex chromosome turnover event. Genome annotation identified 18,412 genes, including 43 putative horizontally transferred (HT) loci. Notably, 258 genes were identified from gene families known to encode plant cell wall degrading enzymes and invertases, including carbohydrate esterases, polysaccharide lyases, and glycoside hydrolases (GH). GH genes were unusually numerous, with 239 putative genes representing 19 GH families. Interestingly, several other beetle species with large numbers of GH genes are (like D. abbreviatus) successful invasive pests of agriculture or forestry.

Integrated phylogenomic approaches in insect systematics

The increased accessibility of genomic and imaging methods, and the improved access to ecological, spatial, and other natural history-related data is allowing for insect systematics to grow and find answers to central evolutionary and taxonomic questions. Today, integrated studies in insect phylogenomics and systematics are combining natural history, behavior, developmental biology, morphology, fossils, geographic range data, and ecological interactions. This integration is contributing to the clarification of evolutionary relationships, and the recognition of the role played by these factors on the evolution of insects. Future work should continue to build on these advances, seeking to further increase open-access databasing and support for natural history research, as well as expand its analytical palettes.

Polar lake microbiomes have distinct evolutionary histories

Toward the poles, life on land is increasingly dominated by microorganisms, yet the evolutionary origin of polar microbiomes remains poorly understood. Here, we use metabarcoding of Arctic, sub-Antarctic, and Antarctic lacustrine benthic microbial communities to test the hypothesis that high-latitude microbiomes are recruited from a globally dispersing species pool through environmental selection. We demonstrate that taxonomic overlap between the regions is limited within most phyla, even at higher-order taxonomic levels, with unique deep-branching phylogenetic clades being present in each region. We show that local and regional taxon richness and net diversification rate of regionally restricted taxa differ substantially between polar regions in both microeukaryotic and bacterial biota. This suggests that long-term evolutionary divergence resulting from low interhemispheric dispersal and diversification in isolation has been a prominent process shaping present-day polar lake microbiomes. Our findings illuminate the distinctive biogeography of polar lake ecosystems and underscore that conservation efforts should include their unique microbiota.

Phylogenomics illuminates the phylogeny of flower weevils (Curculioninae) and reveals ten independent origins of brood-site pollination mutualism in true weevils

Weevils are an unusually species-rich group of phytophagous insects for which there is increasing evidence of frequent involvement in brood-site pollination. This study examines phylogenetic patterns in the emergence of brood-site pollination mutualism among one of the most speciose beetle groups, the flower weevils (subfamily Curculioninae). We analysed a novel phylogenomic dataset consisting of 214 nuclear loci for 202 weevil species, with a sampling that mainly includes flower weevils as well as representatives of all major lineages of true weevils (Curculionidae). Our phylogenomic analyses establish a uniquely comprehensive phylogenetic framework for Curculioninae and provide new insights into the relationships among lineages of true weevils. Based on this phylogeny, statistical reconstruction of ancestral character states revealed at least 10 independent origins of brood-site pollination in higher weevils through transitions from ancestral associations with reproductive structures in the larval stage. Broadly, our results illuminate the unexpected frequency with which true weevils-typically specialized phytophages and hence antagonists of plants-have evolved mutualistic interactions of ecological significance that are key to both weevil and plant evolutionary fitness and thus a component of their deeply intertwined macroevolutionary success.

Patterns of genetic differentiation imply distinct phylogeographic history of the mosquito species Anopheles messeae and Anopheles daciae in Eurasia

Detailed knowledge of phylogeography is important for control of mosquito species involved in the transmission of human infectious diseases. Anopheles messeae is a geographically widespread and genetically diverse dominant vector of malaria in Eurasia. A closely related species, An. daciae, was originally distinguished from An. messeae based on five nucleotide substitutions in its ribosomal DNA (rDNA). However, the patterns of phylogeographic history of these species in Eurasia remain poorly understood. Here, using internal transcribed spacer 2 (ITS2) of rDNA and karyotyping for the species identification we determined the composition of five Anopheles species in 28 locations in Eurasia. Based on the frequencies of 11 polymorphic chromosomal inversions used as genetic markers, a large-scale population genetics analysis was performed of 1932 mosquitoes identified as An. messeae, An. daciae and their hybrids. The largest genetic differences between the species were detected in the X sex chromosome suggesting a potential involvement of this chromosome in speciation. The frequencies of autosomal inversions in the same locations differed by 13%-45% between the species demonstrating a restricted gene flow between the species. Overall, An. messeae was identified as a diverse species with a more complex population structure than An. daciae. The clinal gradients in frequencies of chromosomal inversions were determined in both species implicating their possible involvement in climate adaptations. The frequencies of hybrids were low ~1% in northern Europe but high up to 50% in south-eastern populations. Thus, our study revealed critical differences in patterns of phylogeographic history between An. messeae and An. daciae in Eurasia. This knowledge will help to predict the potential of the malaria transmission in the northern territories of the continent.

Phylogenomics illuminates the evolution of orb webs, respiratory systems and the biogeographic history of the world's smallest orb-weaving spiders (Araneae, Araneoidea, Symphytognathoids)

The miniature orb weaving spiders (symphytognathoids) are a group of small spiders (< 2 mm), including the smallest adult spider Patu digua (0.37 mm in body length), that have been classified into five families. The species of one of its constituent lineages, the family Anapidae, build a remarkable diversity of webs (ranging from orbs to sheet webs and irregular tangles) and even include a webless kleptoparasitic species. Anapids are also exceptional because of the extraordinary diversity of their respiratory systems. The phylogenetic relationships of symphytognathoid families have been recalcitrant with different classes of data, such as, monophyletic with morphology and its concatenation with Sanger-based six markers, paraphyletic (including a paraphyletic Anapidae) with solely Sanger-based six markers, and polyphyletic with transcriptomes. In this study, we capitalized on a large taxonomic sampling of symphytognathoids, focusing on Anapidae, and using de novo sequenced ultraconserved elements (UCEs) combined with UCEs recovered from available transcriptomes and genomes. We evaluated the conflicting relationships using a variety of support metrics and topology tests. We found support for the phylogenetic hypothesis proposed using morphology to obtain the "symphytognathoids'' clade, Anterior Tracheal System (ANTS) Clade and monophyly of the family Anapidae. Anapidae can be divided into three major lineages, the Vichitra Clade (including Teutoniella, Holarchaea, Sofanapis and Acrobleps), the subfamily Micropholcommatinae and the Orb-weaving anapids (Owa) Clade. Biogeographic analyses reconstructed a hypothesis of multiple long-distance transoceanic dispersal events, potentially influenced by the Antarctic Circumpolar Current and West Wind Drift. In symphytognathoids, the ancestral anterior tracheal system transformed to book lungs four times and reduced book lungs five times. The posterior tracheal system was lost six times. The orb web structure was lost four times independently and transformed into sheet web once.

Survivors and colonizers: Contrasting biogeographic histories reconciled in the Antarctic freshwater copepod Boeckella poppei

Two main hypotheses have been proposed to explain the contemporary distribution of Antarctic terrestrial biota. We assess whether the current distribution of maritime Antarctic populations of the freshwater copepod Boeckella poppei is the result of (1) a post-Last Glacial Maximum (LGM) colonization, or whether (2) the species survived in regional glacial refugia throughout the LGM and earlier glaciations. Using 438 specimens from 34 different sampling sites across Southern South America, South Georgia, South Orkney Islands, South Shetland Islands, and the Antarctic Peninsula, we analyzed mitochondrial and nuclear sequences to uncover patterns of genetic diversity and population structure. We also performed median-joining haplotype network, phylogenetic reconstruction, and divergence time analyses. Finally, we evaluated past demographic changes and historical scenarios using the Approximate Bayesian Computation (ABC) method. Our data support the existence of two clades with different and contrasting biogeographic histories. The first clade has been present in maritime Antarctica since at least the mid-Pleistocene, with the South Orkney Islands the most likely refugial area. The second clade has a broader distribution including southern South America, South Georgia, South Shetland Islands, and the Antarctic Peninsula. The ABC method identified long-distance dispersal (LDD) colonization event(s) from southern South America to South Georgia and the maritime Antarctic after the LGM deglaciation, supporting more recent colonization of Antarctic locations. The current Antarctic and sub-Antarctic distribution of B. poppei is likely derived from two independent biogeographic events. The combination of both (1) post-LGM colonization from southern South America and (2) longer-term persistence in in situ regional refugia throughout glacial periods challenges current understanding of the biogeographic history of Antarctic freshwater biota. Re-colonization of ice-impacted Antarctic areas would have occurred following a LDD and Establishment model, pointing to the existence of possible post-dispersal barriers, despite widely assumed high passive dispersal capacity in freshwater invertebrates.

Emerging biological archives can reveal ecological and climatic change in Antarctica

Anthropogenic climate change is causing observable changes in Antarctica and the Southern Ocean including increased air and ocean temperatures, glacial melt leading to sea-level rise and a reduction in salinity, and changes to freshwater water availability on land. These changes impact local Antarctic ecosystems and the Earth's climate system. The Antarctic has experienced significant past environmental change, including cycles of glaciation over the Quaternary Period (the past ~2.6 million years). Understanding Antarctica's paleoecosystems, and the corresponding paleoenvironments and climates that have shaped them, provides insight into present day ecosystem change, and importantly, helps constrain model projections of future change. Biological archives such as extant moss beds and peat profiles, biological proxies in lake and marine sediments, vertebrate animal colonies, and extant terrestrial and benthic marine invertebrates, complement other Antarctic paleoclimate archives by recording the nature and rate of past ecological change, the paleoenvironmental drivers of that change, and constrain current ecosystem and climate models. These archives provide invaluable information about terrestrial ice-free areas, a key location for Antarctic biodiversity, and the continental margin which is important for understanding ice sheet dynamics. Recent significant advances in analytical techniques (e.g., genomics, biogeochemical analyses) have led to new applications and greater power in elucidating the environmental records contained within biological archives. Paleoecological and paleoclimate discoveries derived from biological archives, and integration with existing data from other paleoclimate data sources, will significantly expand our understanding of past, present, and future ecological change, alongside climate change, in a unique, globally significant region.

From monocots to dicots: host shifts in Afrotropical derelomine weevils shed light on the evolution of non-obligatory brood pollination mutualism

Weevils from the tribe Derelomini (Curculionidae: Curculioninae) are specialized brood pollinators engaged in mutualistic relationships with several angiosperm lineages. In brood pollination systems, reproductive plant tissues are used for the development of insect larval stages, whereas adult insects pollinate their plant hosts as a reward. The evolutionary history of derelomines in relationship to their hosts is poorly understood and potentially contrasts with other brood pollination systems, wherein a pollinator lineage is usually associated with a single host plant family. In the case of Afrotropical Derelomini, host records indicate a diverse host repertoire consisting of several families of monocot and dicot plants. In this study, we investigate their phylogenetic relationships, timing of diversification and evolution of host use. Our results suggest that derelomine lineages started their diversification ~40 Mya. Reconstructions of host use evolution support an ancestral association with the monocotyledonous palm family (Arecaceae), followed by several shifts towards other plant families in Afrotropical lineages, especially to dicotyledonous plants from the family Ebenaceae (on the genus Euclea L.). Some level of phylogenetic conservatism of host use is recovered for the lineages associated with either palms or Euclea. Multiple instances of sympatric weevil assemblages on the same plant are also unravelled, corresponding to either single or independent colonization events. Overall, the diversity of hosts colonized and the frequency of sympatric assemblages highlighted in non-obligatory plant–derelomine brood pollination systems contrast with what is generally expected from plant–insect brood pollination systems.

Extinction of austral diatoms in response to large-scale climate dynamics in Antarctica

Despite evidence for microbial endemism, an understanding of the impact of geological and paleoclimate events on the evolution of regional protist communities remains elusive. Here, we provide insights into the biogeographical history of Antarctic freshwater diatoms, using lacustrine fossils from mid-Miocene and Quaternary Antarctica, and dovetail this dataset with a global inventory of modern freshwater diatom communities. We reveal the existence of a diverse mid-Miocene diatom flora bearing similarities with several former Gondwanan landmasses. Miocene cooling and Plio-Pleistocene glaciations triggered multiple extinction waves, resulting in the selective depauperation of this flora. Although extinction dominated, in situ speciation and new colonizations ultimately shaped the species-poor, yet highly adapted and largely endemic, modern Antarctic diatom flora. Our results provide a more holistic view on the scale of biodiversity turnover in Neogene and Pleistocene Antarctica than the fragmentary perspective offered by macrofossils and underscore the sensitivity of lacustrine microbiota to large-scale climate perturbations.