Biogeographic survey of soil bacterial communities across Antarctica.

BACKGROUND: Antarctica and its unique biodiversity are increasingly at risk from the effects of global climate change and other human influences. A significant recent element underpinning strategies for Antarctic conservation has been the development of a system of Antarctic Conservation Biogeographic Regions (ACBRs). The datasets supporting this classification are, however, dominated by eukaryotic taxa, with contributions from the bacterial domain restricted to Actinomycetota and Cyanobacteriota. Nevertheless, the ice-free areas of the Antarctic continent and the sub-Antarctic islands are dominated in terms of diversity by bacteria. Our study aims to generate a comprehensive phylogenetic dataset of Antarctic bacteria with wide geographical coverage on the continent and sub-Antarctic islands, to investigate whether bacterial diversity and distribution is reflected in the current ACBRs. RESULTS: Soil bacterial diversity and community composition did not fully conform with the ACBR classification. Although 19% of the variability was explained by this classification, the largest differences in bacterial community composition were between the broader continental and maritime Antarctic regions, where a degree of structural overlapping within continental and maritime bacterial communities was apparent, not fully reflecting the division into separate ACBRs. Strong divergence in soil bacterial community composition was also apparent between the Antarctic/sub-Antarctic islands and the Antarctic mainland. Bacterial communities were partially shaped by bioclimatic conditions, with 28% of dominant genera showing habitat preferences connected to at least one of the bioclimatic variables included in our analyses. These genera were also reported as indicator taxa for the ACBRs. CONCLUSIONS: Overall, our data indicate that the current ACBR subdivision of the Antarctic continent does not fully reflect bacterial distribution and diversity in Antarctica. We observed considerable overlap in the structure of soil bacterial communities within the maritime Antarctic region and within the continental Antarctic region. Our results also suggest that bacterial communities might be impacted by regional climatic and other environmental changes. The dataset developed in this study provides a comprehensive baseline that will provide a valuable tool for biodiversity conservation efforts on the continent. Further studies are clearly required, and we emphasize the need for more extensive campaigns to systematically sample and characterize Antarctic and sub-Antarctic soil microbial communities. Video Abstract.

The presence of a guard vicariously drives split sex ratios in a facultatively social bee.

Split sex ratios provide broad insights into how reproductive strategies evolve, and historically have special relevance to the evolution of eusociality. Yet almost no attention has been directed to situations where split sex ratios may potentially decrease the payoffs for worker-like behaviour, increasing selective thresholds for eusociality. We examined sex ratios in a facultatively social colletid bee, Amphylaeus morosus. Sex ratios in this bee vary strongly with the presence of a nest guard and in a pattern that does not conform to assumptions of previous models in which split sex ratios facilitate altruism. While the production of daughters was constant across social and solitary nests, mothers produced more brood when a non-reproductive guard was present, but these extra brood were all male. This leads to split sex ratios, vicariously driven by guards that are unable to manipulate sex ratios in their favour. Importantly, if guarding becomes more common in a population this would lead to an excess of males and lower the genetic value of these extra males to guards, effectively putting a brake on selection for worker-like behaviour.

Location, location, location: survival of Antarctic biota requires the best real estate.

The origin of terrestrial biota in Antarctica has been debated since the discovery of springtails on the first historic voyages to the southern continent more than 120 years ago. A plausible explanation for the long-term persistence of life requiring ice-free land on continental Antarctica has, however, remained elusive. The default glacial eradication scenario has dominated because hypotheses to date have failed to provide a mechanism for their widespread survival on the continent, particularly through the Last Glacial Maximum when geological evidence demonstrates that the ice sheet was more extensive than present. Here, we provide support for the alternative nunatak refuge hypothesis-that ice-free terrain with sufficient relief above the ice sheet provided refuges and was a source for terrestrial biota found today. This hypothesis is supported here by an increased understanding from the combination of biological and geological evidence, and we outline a mechanism for these refuges during successive glacial maxima that also provides a source for coastal species. Our cross-disciplinary approach provides future directions to further test this hypothesis that will lead to new insights into the evolution of Antarctic landscapes and how they have shaped the biota through a changing climate.

The use of different 16S rRNA gene variable regions in biogeographical studies.

16S rRNA gene amplicon sequencing is routinely used in environmental surveys to identify microbial diversity and composition of the samples of interest. The dominant sequencing technology of the past decade (Illumina) is based on the sequencing of 16S rRNA hypervariable regions. Online sequence data repositories, which represent an invaluable resource for investigating microbial distributional patterns across spatial, environmental or temporal scales, contain amplicon datasets from diverse 16S rRNA gene variable regions. However, the utility of these sequence datasets is potentially reduced by the use of different 16S rRNA gene amplified regions. By comparing 10 Antarctic soil samples sequenced for five different 16S rRNA amplicons, we explore whether sequence data derived from diverse 16S rRNA variable regions can be validly used as a resource for biogeographical studies. Patterns of shared and unique taxa differed among samples as a result of variable taxonomic resolutions of the assessed 16S rRNA variable regions. However, our analyses also suggest that the use of multi-primer datasets for biogeographical studies of the domain Bacteria is a valid approach to explore bacterial biogeographical patterns due to the preservation of bacterial taxonomic and diversity patterns across different variable region datasets. We deem composite datasets useful for biogeographical studies.

Two new species of Western Australian Abantiades Herrich-Schffer (Lepidoptera: Hepialidae) and a description of the female of Abantiades paradoxa (Tindale).

Two new species, Abantiades concordia sp. nov. and Abantiades malleus sp. nov., are described from Australia. Both species were collected in the Eastern Goldfields subregion of the Coolgardie bioregion in Western Australia. Abantiades concordia sp. nov. is shown to be closely related to A. paradoxa (Tindale, 1932) by sequence similarity of the mtDNA (COI) gene. The female of A. paradoxa is also described here for the first time. Abantiades paradoxa and the new species A. concordia sp. nov. are morphologically similar with respect to the structure of their genitalia, sternite VIII, wing patterning and their antennae with bi-forked rami. Abantiades malleus sp. nov. is quite distinct by sequence similarity of the mtDNA (COI) gene, but related in a clade with A. marcidus Tindale,1932, A. albofasciatus (Swinhoe, 1892), and A. furva (Tindale,1932), the latter species once placed in the synonymised Bordaia Tindale, 1932. Discussion of similar species once grouped under the genus Bordaia and under the genus Trictena Meyrick, 1890 (both junior synonyms of Abantiades Herrich-Schffer, 1855) is also included.

Unparalleled mitochondrial heteroplasmy and Wolbachia co-infection in the non-model bee, Amphylaeus morosus.

Mitochondrial heteroplasmy is the occurrence of more than one type of mitochondrial DNA within a single individual. Although generally reported to occur in a small subset of individuals within a species, there are some instances of widespread heteroplasmy across entire populations. Amphylaeus morosus is an Australian native bee species in the diverse and cosmopolitan bee family Colletidae. This species has an extensive geographical range along the eastern Australian coast, from southern Queensland to western Victoria, covering approximately 2,000 km. Seventy individuals were collected from five localities across this geographical range and sequenced using Sanger sequencing for the mitochondrial cytochrome c oxidase subunit I (COI) gene. These data indicate that every individual had the same consistent heteroplasmic sites but no other nucleotide variation, suggesting two conserved and widespread heteroplasmic mitogenomes. Ion Torrent shotgun sequencing revealed that heteroplasmy occurred across multiple mitochondrial protein-coding genes and is unlikely explained by transposition of mitochondrial genes into the nuclear genome (NUMTs). DNA sequence data also demonstrated a consistent co-infection of Wolbachia across the A. morosus distribution with every individual infected with both bacterial strains. Our data are consistent with the presence of two mitogenomes within all individuals examined in this species and suggest a major divergence from standard patterns of mitochondrial inheritance. Because the host's mitogenome and the Wolbachia genome are genetically linked through maternal inheritance, we propose three possible hypotheses that could explain maintenance of the widespread and conserved co-occurring bacterial and mitochondrial genomes in this species.

A taxonomic revision of the tube-web spiders of the genus Ariadna (Araneae: Segestriidae) in Tasmania.

The genus Ariadna Audouin, 1826 is revised for Tasmania to include 13 species, ten of which are described as new: Ariadna abbreviata sp. nov., A. alta sp. nov., A. amabilia sp. nov., A. crypticola sp. nov., A. ferrogrisea sp. nov., A. fragilis sp. nov., A. gonzo sp. nov., A. muscosa Hickman, 1929, A. segmentata Simon, 1893, A. subnubilum sp. nov., A. thylacinus sp. nov. and A. tigrina sp. nov.. The species described in this manuscript exhibit high levels of sympatry.

Holocene population expansion of a tropical bee coincides with early human colonization of Fiji rather than climate change.

There is substantial debate about the relative roles of climate change and human activities on biodiversity and species demographies over the Holocene. In some cases, these two factors can be resolved using fossil data, but for many taxa such data are not available. Inferring historical demographies of taxa has become common, but the methodologies are mostly recent and their shortcomings often unexplored. The bee genus Homalictus is developing into a tractable model system for understanding how native bee populations in tropical islands have responded to past climate change. We greatly expand on previous studies using sequences of the mitochondrial gene COI from 474 specimens and between 171 and 3928 autosomal (DArTSeq) single nucleotide polymorphism loci from 19 specimens of the native Fijian bee, Homalictus fijiensis, to explore its historical demography using coalescent and mismatch analyses. We ask whether past changes in demography were human- or climate-driven, while considering analytical assumptions. We show that inferred changes in population sizes are too recent to be explained by past climate change. Instead we find that a dramatic increase in population size for the main island of Viti Levu coincides with increasing occupation by humans and their modification of the environment. We found no corresponding change in bee population size for another major island, Kadavu, where human populations and agricultural activities have been historically very low. Our analyses indicate that molecular approaches can be used to disentangle the impacts of humans and climate change on a major tropical pollinator and that stringent analytical approaches are required for reliable interpretation of results.

Two new endemic species of emAbantiades/em Herrich-Schäffer (Lepidoptera: Hepialidae) from Kangaroo Island, Australia.

Abantiades penneshawensis Moore Beaver sp. nov. and Abantiades rubrus Moore Beaver sp. nov. are described as new. Both species are endemic to Kangaroo Island, and although both are related to species that occur on the Australian mainland and other islands, they are distinguished from those sister and phenotypically similar species by morphology and mtDNA (COI) barcodes. These two new species raise the number of Abantiades species on Kangaroo Island to six, three being endemic, and 45 species in the genus for the whole of Australia. There are now 13 species of Hepialidae (one undescribed) known from Kangaroo Island and we discuss the potential effects of recent catastrophic fire on some distributions.

Molecular diversity and species delimitation in the family Gasteruptiidae (Hymenoptera: Evanioidea).

Gasteruptiidae Ashmead is an easily recognised family of wasps with ∼589 described species worldwide. Although well characterised by traditional taxonomy, multiple authors have commented on the extreme morphological uniformity of the group, making species-level identification difficult. This problem is enhanced by the lack of molecular data and molecular phylogenetic research for the group. We used 187 cytochrome c oxidase subunit I (COI) barcodes to explore the efficiency of sequence data to delimitate species in Gasteruptiidae. We undertook a graphical and discussion-based comparison of six methods for species delimitation, with the success of methods judged based on known species boundaries and morphology. Both distance-based (ABGD and jMOTU threshold analysis) and tree-based (GMYC and PTP) methods compared across multiple parameters recovered variable molecular operational taxonomic units (MOTUs), ranging from 55 to 123 MOTUs. Tree-based methods tended to split known morphological species less than distance-based methods, with the single-threshold GMYC method the most concordant with known morphospecies. Our results suggest that the incorporation of molecular species delimitation techniques provides a powerful tool to assist in the interpretation of species and help direct informed decisions with taxonomic uncertainty in the family.

Extreme genetic diversity among springtails (Collembola) in subterranean calcretes of arid Australia.

The subterranean islands hypothesis for calcretes of the Yilgarn region in Western Australia applies to many stygobitic (subterranean-aquatic) species that are "trapped" evolutionarily within isolated aquifers due to their aquatic lifestyles. In contrast, little is known about the distribution of terrestrial-subterranean invertebrates associated with the calcretes. We used subterranean Collembola from the Yilgarn calcretes to test the hypothesis that troglobitic species, those inhabiting the subterranean unsaturated (non-aquatic) zone of calcretes, are also restricted in their distribution and represent reciprocally monophyletic and endemic lineages. We used the barcoding fragment of the mtDNA cytochrome c oxidase subunit 1 (COI) gene from 183 individuals to reconstruct the phylogenetic history of the genus Pseudosinella Schäffer (Collembola, Lepidocyrtidae) from 10 calcretes in the Yilgarn. These calcretes represent less than 5% of the total possible calcretes in this region, yet we show that their diversity for subterranean Collembola comprises a minimum of 25 new species. Regionally, multiple levels of diversity exist in Pseudosinella, indicative of a complex evolutionary history for this genus in the Yilgarn. These species have probably been impacted by climatic oscillations, facilitating their dispersal across the landscape. The results represent a small proportion of the undiscovered diversity in Australia's arid zone.

Climate change and invasive species: a physiological performance comparison of invasive and endemic bees in Fiji.

Anthropogenic climate change and invasive species are two of the greatest threats to biodiversity, affecting the survival, fitness and distribution of many species around the globe. Invasive species are often expected to have broad thermal tolerance, be highly plastic, or have high adaptive potential when faced with novel environments. Tropical island ectotherms are expected to be vulnerable to climate change as they often have narrow thermal tolerance and limited plasticity. In Fiji, only one species of endemic bee, Homalictus fijiensis, is commonly found in the lowland regions, but two invasive bee species, Braunsapis puangensis and Ceratina dentipes, have recently been introduced into Fiji. These introduced species pollinate invasive plants and might compete with H. fijiensis and other native pollinators for resources. To test whether certain performance traits promote invasiveness of some species, and to determine which species are the most vulnerable to climate change, we compared the thermal tolerance, desiccation resistance, metabolic rate and seasonal performance adjustments of endemic and invasive bees in Fiji. The two invasive species tended to be more resistant to thermal and desiccation stress than H. fijiensis, while H. fijiensis had greater capacity to adjust their CTmax with season, and H. fijiensis females tended to have higher metabolic rates than B. puangensis females. These findings provide mixed support for current hypotheses for the functional basis of the success of invasive species; however, we expect the invasive bees in Fiji to be more resilient to climate change because of their increased thermal tolerance and desiccation resistance.

Four new species of Splendid Ghost Moths (Lepidoptera: Hepialidae: Aenetus) from Australia and Papua New Guinea.

Four new Aenetus Herrich-Schäffer species are described from northern Australasia; Aenetus simonseni sp. nov. from the top-end of the Northern Territory, Australia, A. maiasinus sp. nov. from the Kimberley region of Western Australia, A. trigonogrammus sp. nov. from south-eastern Queensland, Australia, and A. albadamanteum sp. nov. from eastern Papua New Guinea. Aenetus simonseni sp. nov. and A. maiasinus sp. nov. appear to belong to the tegulatus-group of species (sensu Grehan et al. 2018), A. trigonogrammus sp. nov. is part of the splendens-group of species (sensu Simonsen 2018), while A. albadamanteum sp. nov. shares morphological similarities with A. hampsoni (Joicey Noakes, 1914), A. crameri Viette, 1956, and A. toxopeusi Viette, 1956, from New Guinea, and A. cohici Viette, 1961 from New Caledonia. The four new species are illustrated and compared with superficially similar species in morphology and, for two species, molecular (mtDNA COI gene) sequences.

Description of two new Australian species of Abantiades Herrich-Schäffer (Lepidoptera: Hepialidae) and females of two further species with notes on their biogeography.

Abantiades cephalocorvus sp. nov. and Abantiades tembyi sp. nov. are described, along with the previously undescribed females of A. macropusinsulariae Simonsen, 2018 and A. pallida Simonsen, 2018. All of these species belong to a triforked Abantiades Herrich-Schäffer clade that is loosely centred around the Nullarbor and other arid regions of Australia. We explore DNA barcodes (mtDNA COI gene) from these and other Abantiades and discuss their significance for species recognition. The species distributions are entirely or largely allopatric and we discuss their origins from a widespread common ancestor that was likely distributed over inland and coastal regions in the mid- to late-Mesozoic before the onset of desertification. Notes on new distributional data for all of the known species in this clade are included.

Four new tri-forked species of the Australian genus Abantiades Herrich-Schäffer (Lepidoptera: Hepialidae) from the "dark obscura clade".

A distinct group of Abantiades Herrich-Schäffer species is here confirmed as a valid clade that we refer to as the "dark obscura clade" supported by morphological and mtDNA evidence. The clade is the sister group of A. obscura Simonsen of north-western Australia and comprises four new species: Abantiades centralia sp. nov., A. kayi sp. nov., A. zonatriticum sp. nov., and A. hutchinsoni sp. nov. These species together with A. obscura, are reciprocally allopatric and have a combined distribution spanning much of the western half of Australia and this distribution is consistent with their each differentiating locally from a widespread ancestor. The four new species raise the diversity of Abantiades to 42 species. [Zoobank urn:lsid:zoobank.org:pub:C05458D1-0D34-4432-8EC4-D031ED6B7BEF].

Three new ghost moths of the genus Oxycanus Walker, 1856 from Australia (Lepidoptera: Hepialidae).

Three new species of ghost moth, Oxycanus ephemerous sp. nov., O. flavoplumosus sp. nov., and O. petalous sp. nov. are described from South Australia, New South Wales, and south-west Western Australia, respectively. We illustrate these species and compare morphological and molecular (mtDNA COI gene) characters with similar Oxycanus Walker, 1856 species from Australia. Comparative images of Oxycanus subvaria (Walker, 1856), O. byrsa (Pfitzner, 1933), and O. determinata (Walker, 1856) are figured. The type material of the three new species are held in the Australian National Insect Collection, Canberra, the Western Australian Museum, Perth, and in the South Australian Museum, Adelaide. The type specimens of Oxycanus hildae Tindale, 1964 syn. n. were also examined and the taxon is here considered synonymous with O. subvaria. Concerns are raised about the conservation status of all three new species due to few or localised distribution records.

Radiation of tropical island bees and the role of phylogenetic niche conservatism as an important driver of biodiversity.

Island biogeography explores how biodiversity in island ecosystems arises and is maintained. The topographical complexity of islands can drive speciation by providing a diversity of niches that promote adaptive radiation and speciation. However, recent studies have argued that phylogenetic niche conservatism, combined with topographical complexity and climate change, could also promote speciation if populations are episodically fragmented into climate refugia that enable allopatric speciation. Adaptive radiation and phylogenetic niche conservatism therefore both predict that topographical complexity should encourage speciation, but they differ strongly in their inferred mechanisms. Using genetic (mitochondrial DNA (mtDNA) and single-nucleotide polymorphism (SNP)) and morphological data, we show high species diversity (22 species) in an endemic clade of Fijian Homalictus bees, with most species restricted to highlands and frequently exhibiting narrow geographical ranges. Our results indicate that elevational niches have been conserved across most speciation events, contradicting expectations from an adaptive radiation model but concordant with phylogenetic niche conservatism. Climate cycles, topographical complexity, and niche conservatism could interact to shape island biodiversity. We argue that phylogenetic niche conservatism is an important driver of tropical island bee biodiversity but that this phylogenetic inertia also leads to major extinction risks for tropical ectotherms under future warming climates.

Review of the bee genus Homalictus Cockerell (Hymenoptera: Halictidae) from Fiji with description of nine new species.

The genus Homalictus Cockerell has not been taxonomically reviewed in the Fijian archipelago for 40 years. Here we redescribe the four known species and describe nine new ones, bringing the number of endemic Homalictus in Fiji to 13 species. We provide identifications keys to all species. Most of the species diversity (11 species) have their distributions over 800 m asl (meters above sea level; highlands), and with only two species under 800 m asl (lowlands). We highlight the vulnerability of the highland-restricted species to a warming climate, and document the potential extinction of one highland species. The new species described here are H. atritergus sp. nov., H. concavus sp. nov., H. groomi sp. nov., H. kaicolo sp. nov., H. nadarivatu sp. nov., H. ostridorsum sp. nov., H. taveuni sp. nov. H. terminalis sp. nov. and H. tuiwawae sp. nov.. [Zoobank URL: urn:lsid:zoobank.org:act:71318BEC-40CD-470F-A1E7-0E1FD18A6459].

Estimating the biodiversity of terrestrial invertebrates on a forested island using DNA barcodes and metabarcoding data.

Invertebrates are a major component of terrestrial ecosystems, however, estimating their biodiversity is challenging. We compiled an inventory of invertebrate biodiversity along an elevation gradient on the temperate forested island of Hauturu, New Zealand, by DNA barcoding of specimens obtained from leaf litter samples and pitfall traps. We compared the barcodes and biodiversity estimates from this data set with those from a parallel DNA metabarcoding analysis of soil from the same locations, and with pre-existing sequences in reference databases, before exploring the use of combined data sets as a basis for estimating total invertebrate biodiversity. We obtained 1,282 28S and 1,610 COI barcodes from a total of 1,947 invertebrate specimens, which were clustered into 247 (28S) and 366 (COI) OTUs, of which ≤ 10% were represented in GenBank. Coleoptera were most abundant (730 sequenced specimens), followed by Hymenoptera, Diptera, Lepidoptera, and Amphipoda. The most abundant OTU from both the 28S (153 sequences) and COI (140 sequences) data sets was an undescribed beetle from the family Salpingidae. Based on the occurrences of COI OTUs along the elevation gradient, we estimated there are ~1,000 arthropod species (excluding mites) on Hauturu, including 770 insects, of which 344 are beetles. A DNA metabarcoding analysis of soil DNA from the same sites resulted in the identification of similar numbers of OTUs in most invertebrate groups compared with the DNA barcoding, but less than 10% of the DNA barcoding COI OTUs were also detected by the metabarcoding analysis of soil DNA. A mark-recapture analysis based on the overlap between these data sets estimated the presence of approximately 6,800 arthropod species (excluding mites) on the island, including ~3,900 insects. Estimates of New Zealand-wide biodiversity for selected arthropod groups based on matching of the COI DNA barcodes with pre-existing reference sequences suggested over 13,200 insect species are present, including 4,000 Coleoptera, 2,200 Diptera, and 2,700 Hymenoptera species, and 1,000 arachnid species (excluding mites). These results confirm that metabarcoding analyses of soil DNA tends to recover different components of terrestrial invertebrate biodiversity compared to traditional invertebrate sampling, but the combined methods provide a novel basis for estimating invertebrate biodiversity.

First record of Gasteruption Latreille (Hymenoptera: Evanioidea: Gasteruptiidae) from Fiji with the description of a new species.

A new Gasteruption Latreille species, G. tomanivi, is described from Viti Levu, Fiji. The new species is the first record of the genus for Fiji and can be distinguished from other Oceanian Gasteruption species by the length of the mesosoma and the large malar space compared with the length of the pedicel. DNA Barcode (mtDNA-COI) sequence is provided.