Biogeographic Structure Research Articles

The composition, structure, and distribution of benthic ostracod fauna (Ostracoda, Myodocopa) in Antarctic waters

The benthic fauna of ostracods of the order Myodocopida of Antarctic waters is characterized by high diversity, relative species abundance, and a complicated taxonomic and ecological structure, with a simplified biogeographical structure. This fauna, which is distinguished by a high level of endemicity, although at a low taxonomic rank, includes a great share of deep-sea and subtidal elements. Ostracod populations of High and Low-Antarctic subzones differ qualitatively and quantitatively. A distinct impoverishment of fauna is observed in the region of the Antarctic divergence compared to the more northern areas. The number of species increases with depth to reach its maximum in the lower subtidal zone and on the upper continental slope at depths of 200–500 m. The number of species decreases with increasing depth. Myodocopida have not been yet found in the Antarctic waters deeper than 5000 m.

Nature conservation and ecological restoration in a changing climate: what are we aiming for?

Principles underpinning the goals of nature conservation and ecological restoration have traditionally involved preventing ecological change or restoring ecosystems or populations towards preferred historical states. Under global climate change, it is increasingly recognised that this may no longer be achievable, but there has been limited debate regarding new principles that can help guide goal-setting for nature conservation and ecological restoration in dynamic environments. To stimulate such debate, we established a framework of human motivations implicit in historically focussed nature conservation approaches. We drew on this and a literature survey to propose a palette of five principles to guide goal-setting for nature conservation and ecological restoration in a changing climate. Our framework proposes three broad sets of human motivations relevant to nature conservation: (1) basic survival and material needs (akin to provisioning and regulating ecosystem services), (2) psychological and cultural needs such as a sense of place (reflecting cultural ecosystem services), and (3) the need to fulfil moral or ethical obligations (e.g. intergenerational and interspecies equity). Meeting basic needs for current and future generations is supported by a commonly proposed principle to optimise ecological processes and functions (Principle 1); which in turn is dependent on maintaining the ongoing evolutionary potential in the world’s biota (Principle 2). Beyond this, motivations relating to psychological, cultural and moral needs demand not only an emphasis on healthy ecosystem functioning, but on the character and diversity of the ecosystems and species that contribute to these functions. Our subsequent three principles, minimise native species losses (Principle 3), maintain the evolutionary character and biogeographic structuring of the biota (Principle 4), and maintain wild natural ecosystems (Principle 5) contribute to these further goals. Although these principles can sometimes be conflicting, we argue that by connecting directly with underlying motivations, this broader palette will help take us forward towards more effective nature conservation in a rapidly changing world.

Extreme Diversity of Diplonemid Eukaryotes in the Ocean

The world's oceans represent by far the largest biome, with great importance for the global ecosystem [1-4]. The vast majority of ocean biomass and biodiversity iscomposed of microscopic plankton. Recent results from the Tara Oceans metabarcoding study revealed that a significant part of the plankton in the upper sunlit layer of the ocean is represented by an understudied group of heterotrophic excavate flagellates called diplonemids [5, 6]. We have analyzed thediversity and distribution patterns of diplonemid populations on the extended set of Tara Oceans V9 18S rDNA metabarcodes amplified from 850 size- fractionated plankton communities sampled across 123 globally distributed locations, for the first time also including samples from the mesopelagic zone, which spans the depth from about 200 to 1,000 meters. Diplonemids separate into four major clades, with the vast majority falling into the deep-sea pelagic diplonemid clade. Remarkably, diversity of this clade inferred from metabarcoding data surpasses even that of dinoflagellates, metazoans, and rhizarians, qualifying diplonemids as possibly the most diverse group of marine planktonic eukaryotes. Diplonemids display strong vertical separation between the photic and mesopelagic layers, with the majority of their relative abundance and diversity occurring in deeper waters. Globally, diplonemids display no apparent biogeographic structuring, with a few hyperabundant cosmopolitan operational taxonomic units (OTUs) dominating their communities. Our results suggest that the planktonic diplonemids are among the key heterotrophic players in the largest ecosystem of our biosphere, yet their roles in this ecosystem remain unknown.

Review of genetic diversification of bats in the Caribbean and biogeographic relationships to Neotropical species based on DNA barcodes.

DNA barcoding is helping in discovering high levels of cryptic species and an underestimation of biodiversity in many groups of organisms. Although mammals are arguably the most studied and one of the least speciose taxonomic classes, the rate of species discovery is increasing and biased for small mammals on islands. An earlier study found bats in the Caribbean as a taxonomic and geographic deficiency in the International Barcode of Life initiative to establish a genetic reference database to enable specimen identification to species. Recent surveys in Dominican Republic, Jamaica, and Martinique have documented and barcoded half of the 58 bat species known from the Caribbean. I analyze all available barcode data of Caribbean bats to investigate biogeography and cryptic species in the Neotropical region. Analysis of the mitochondrial DNA gene cytochrome c oxidase subunit 1 results in a phylogenetic tree with all but one species as well-supported and reciprocally monophyletic. With a broader sampling across the Neotropics, there are also divergent lineages that exhibit biogeographic structuring: (i) a phylogenetic split between northern and southern Dominican Republic in three species, (ii) two taxa with cryptic species associated with higher degree of island endemism, (iii) populations of two widely distributed species with deep divergence between the Caribbean and North and Central America, and (iv) one species in the Caribbean with affinities to taxa in South America.

Gauging scale effects and biogeographical signals in similarity distance decay analyses: an Early Jurassic ammonite case study

AbstractIn biogeography, the similarity distance decay (SDD) relationship refers to the decrease in compositional similarity between communities with geographical distance. Although representing one of the most widely used relationships in biogeography, a review of the literature reveals that: (1)SDDis influenced by both spatial extent and sample size; (2) the potential effect of the phylogenetic level has yet to be tested; (3) the effect of a marked biogeographical structuring uponSDDpatterns is largely unknown; and (4) theSDDrelationship is usually explored with modern, mainly terrestrial organisms, whereas fossil taxa are seldom used in that perspective. Using this relationship, we explore the long‐distance dispersal of the Early Jurassic (early Pliensbachian,c. 190.8 Ma to 187.6 Ma) ammonites of the western Tethys and adjacent areas, in a context of marked provincialism. We show that the long‐distance dispersal of these ammonites is not related to shell size and shape, but rather to the environmental characteristics of the province to which they belong. This suggests that their long‐distance dispersal may have been essentially driven by passive planktonic drift during early juvenile, post‐hatching stages. Furthermore, it seems that theSDDrelationship is not always an appropriate method to characterize the existence of a biogeographical structuring. We conductedSDDanalyses at various spatial, sampling and phylogenetic scales in order to evaluate their sensitivity to scale effects. This multi‐scale approach indicates that the sampling scale may influenceSDDrates in an unpredictable way and that the phylogenetic level has a major impact onSDDpatterns.

New Mycobacterium tuberculosis LAM sublineage with geographical specificity for the Old World revealed by phylogenetical and Bayesian analyses

We recently showed that the Mycobacterium tuberculosis sublineage LAM9 could be subdivided as two distinct subpopulations - each reflecting its unique biogeographical structure and evolutionary history. We subsequently attempted to verify if this genetic structuration could be traced in an enlarged global sample. For this purpose, we analyzed global evolutionary relationships of LAM strains in a large dataset (n=1923 isolates from 35 countries worldwide) with concomitant spoligotyping and MIRU-VNTR data, followed by a deeper analysis of LAM9 sublineage (n=851 isolates). Based on a combination of phylogenetical analysis and Bayesian statistics, a total of three different clusters, tentatively named LAM9C1, C2 and C3 were described in this dataset. Closer inspection of the phylogenetic tree with concomitant data on origin of isolates with genetic clusterization revealed LAM9C3 being the most tightly knit group exclusively found in the Old World as opposed to LAM9C2 being a loosely-knit group without any phylogeographical specificity; while LAM9C1 appeared with a majority of strains being well-clustered despite some isolates that intermixed with unrelated LAM clusters. Subsequently, we hereby describe a new M. tuberculosis LAM sublineage named LAM9C3 with phylogeographical specificity for the Old World. These findings open new perspectives to study respective migration histories and adaptation to human hosts of specific M. tuberculosis clones during the exploration and conquest of the New World. We therefore plan to reevaluate the nomenclature and evolutionary history of various LAM sublineages using Whole Genome Sequencing (WGS).

Biogeographic Variation in Host Range Phenotypes and Taxonomic Composition of Marine Cyanophage Isolates.

Despite the important role of phages in marine systems, little is understood about how their diversity is distributed in space. Biogeographic patterns of marine phages may be difficult to detect due to their vast genetic diversity, which may not be accurately represented by conserved marker genes. To investigate the spatial biogeographic structure of marine phages, we isolated over 400 cyanophages on Synechococcus host strain WH7803 at three coastal locations in the United States (Rhode Island, Washington, and southern California). Approximately 90% of the cyanophage isolates were myoviruses, while the other 10% were podoviruses. The diversity of isolates was further characterized in two ways: (i) taxonomically, using conserved marker genes and (ii) phenotypically, by testing isolates for their ability to infect a suite of hosts, or their “host range.” Because host range is a highly variable trait even among closely related isolates, we hypothesized that host range phenotypes of cyanophage isolates would vary more strongly among locations than would taxonomic composition. Instead, we found evidence for strong biogeographic variation both in taxonomic composition and host range phenotypes, with little taxonomic overlap among the three coastal regions. For both taxonomic composition and host range phenotypes, cyanophage communities from California and Rhode Island were the most dissimilar, while Washington communities exhibited similarity to each of the other two locations. These results suggest that selection imposed by spatial variation in host dynamics influence the biogeographic distribution of cyanophages.

What is Still Bay? Human biogeography and bifacial point variability

‘Still Bay’ is the name given to a cultural phase within the southern African Middle Stone Age, which remains critical to our understanding of modern human behavioural evolution. Although represented in only a handful of sites, the Still Bay is widespread geographically and, at certain localities, persisted over a substantial period of time. Many studies have focused on tracing the temporal range and geographic reach of the Still Bay, as well as inferring degrees of early modern human demographic connectedness from these parameters. Variation within the Still Bay, relative to the accuracy with which it can be identified, has received considerably less attention. However, demographic models based on the spread of the Still Bay in space and time hinge on the reliability with which it can be recognized in the archaeological record. Here we document patterns of bifacial point shape and size variation in some key Still Bay assemblages, and analyse these patterns using the statistical shape analysis tools of geometric morphometrics. Morphological variation appears to be geographically structured and is driven by the spatial separation between north-eastern and south-western clusters of sites. We argue that allometric variation is labile and reflects environmentally driven differences in point reduction, whereas shape differences unrelated to size more closely reflect technological and cultural fragmentation. Our results suggest that the biogeographic structure of Middle Stone Age populations was complex during the period associated with the Still Bay, and provide little support for heightened levels of cultural interconnectedness between distantly separated groups at this time. We briefly discuss the implications of our findings for tracing classic techno-traditions in the Middle Stone Age record of southern Africa, and for inferring underpinning population dynamics from these patterns.

Invading Africa: a novel transoceanic dispersal by a New World ant parasitoid

AbstractAimAn ant parasitoid wasp genus (Eucharitidae: Kapala) common in the New World exhibits the intriguing pattern of having one species distributed widely across tropical Africa and Madagascar. The unusual distribution prompted an investigation of the age, origins and diversification of the Afrotropical Kapala species. We evaluate a previous hypothesis that the species was anthropogenically introduced.LocationAfrica and Madagascar and the Neotropics.MethodsNumerous forms of evidence are incorporated to explain the origin of the Afrotropical species Kapala ivorensis, including phylogenetic relationships, molecular dating estimates, inter‐ and intraspecific genetic distances, morphology and geography. A phylogenetic analysis was performed using six gene regions (18S, 28S‐D2, 28S‐D3‐D5, ITS2, COI and COII), and network and haplotype analyses were executed with subsets of the data. Two mitochondrial gene fragments were used to calculate divergence times under a strict clock model. Additionally, we tested for a correlation between genetic distance and geographical distance in K. ivorensis populations.ResultsPhylogenetic analysis supports one evolutionary origin of K. ivorensis from within a clade of New World relatives. Network and haplotype analyses of the species show no biogeographical structure, and additionally, there is no statistical phylogeographical signal. These results, in conjunction with the low amount of phenotypic intraspecific variation and the genetic distance to the nearest New World relative, provide sufficient evidence to maintain the Old World Kapala as one species. Estimated mitochondrial mutation rates suggest that this species is over 1 Myr old, thus predating any potential for recent human introduction.Main conclusionsMultiple analytical methods indicate the Afrotropical K. ivorensis is molecularly distinct from the Neotropical sister species and originated from a single pre‐human dispersal. This is the first dated example of an insect that has colonized Africa via trans‐Atlantic dispersal from South America.

Strong spatial turnover in cichlid fish assemblages in the upper río Madera (Amazon basin) despite the absence of hydrological barriers

In freshwater ecosystems, spatial turnover in fish assemblages is often attributed to dispersal limitation imposed by fragmentation of water bodies. Other factors like environmental properties or biotic interactions have often been assumed to be minute relative to dispersal limitation when hydrogeological barriers are abundant. This study aims to describe the spatial differentiation of cichlid fish assemblages in the upper rio Madera in Bolivia, Brazil and Peru, a large drainage system characterized by the absence of significant hydrogeological barriers. We assessed the relative importance of spatial, climatic and geological predictors in the observed biogeographic structure using an integrative combination of cluster analyses, elements of metacommunity structure analysis, variation partitioning, and network analysis. Our results show that distinct assemblages of cichlid fish species replace each other across the landscape and that this turnover is partially determined by climate and geological gradients. A considerable fraction of the cichlid assembly structure could not be assigned to either space, climate or geology and might be explained by unmeasured parameters such as habitat structure or biotic interactions. Incorporating knowledge on spatial turnover of species assemblages into conservation strategies will be essential for the biodiversity management of the diverse aquatic fauna of the upper rio Madera.

Ecological patterns strongly impact the biogeography of western Palaearctic longhorn beetles (Coleoptera: Cerambycoidea)

We aim to unravel the biogeographic structuring of western Palaearctic longhorn beetles with focus on the location of different refugia, barriers to dispersal and postglacial range expansions with their particular filters. The interaction of different ecological features with these structures is analysed. The western Palaearctic was divided into 95 geographic entities. We produced presence-only matrices for all 955 Cerambycoidea species autochthonous to this area and derived species richness distributions and extracted faunal regions and faunal elements by cluster analyses and principal component analyses. Similar analyses were performed for sub-families and ecological groups. Longhorn beetles show a strong biogeographic structuring in the western Palaearctic. Species numbers strongly decrease to the north and west. Less mobile species and root feeders mostly contribute to the fauna of the Mediterranean region, whilst mobile species are more widespread. Feeders on broad-leaved trees dominate in western Europe, whilst feeders on coniferous trees are most important in northern Europe. Our results support multiple refugia in the Mediterranean region and underline the importance of Provence, Crimea and Crete as such refugia. Crete even might be an area of old endemism. The Atlanto- and the Ponto-Mediterranean regions are more strongly structured than assumed in classical biogeography. Mediterranean assemblages are mostly composed of non-flying species, root feeders and species with small distributions not found outside their glacial refugia. Tree feeders left their glacial retreats with their host plants. These range dynamics result in biogeographic structures with several dispersal barriers and filters composed of mountains, sea straits and climatic conditions.

A Community of Clones: Snow Algae Are Diverse Communities of Spatially Structured Clones

Premise of research. Snow algae are cosmopolitan and often colonize late-season snowpacks. These snow algae do not occur in isolation; rather, visible algal blooms consist of multispecies communities. Although several of these common snow algae have been characterized taxonomically, their inter- and intraspecific diversity remains unknown. Further, the phylogeographic and biogeographic structuring of snow algal species is poorly understood.Methodology. Algal communities were censused by sequencing the variable internal transcribed spacer 2 locus using Illumina MiSeq. We further analyzed two of the most common and abundant algal operational taxonomic units (OTUs) for biogeographic haplotype diversity.Pivotal results. Our data show that the communities are diverse and taxonomically broad (orders: Chlamydomonadales [74% of OTUs], Microthamniales [20% OTUs], and Chlorellales [6% OTUs]). We demonstrate that the two most common species (best nucleotide basic local alignment search tool match to Coenochloris sp....

Plastid genome sequencing reveals biogeographical structure and extensive population genetic variation in wild populations of Phalaris arundinacea L. in north‐western Europe

AbstractNew and comprehensive collections of the perennial rhizomatous reed canary grass (Phalaris arundinacea) were made in NW Europe along north‐to‐south and east‐to‐west clines from Denmark, Germany, Ireland, Poland, Sweden and the United Kingdom. Rhizome, seed and leaf samples were taken for analysis and genetic resource conservation. A subsample covering the geographical range was characterized using plastid genome sequencing and SNP discovery generated using a long‐read PCR and MiSeq sequencing approach. Samples were also subject to flow cytometry and all found to be tetraploid. New sequences were assembled against a Lolium perenne (perennial ryegrass) reference genome, and an average of approximately 60% of each genome was aligned (81 064 bp). Genetic variation was high among the 48 sequenced genotypes with a total of 1793 SNPs, equating to 23 SNPs per kbp. SNPs were subject to principal coordinate and Structure analyses to detect population genetic groupings and to examine phylogeographical pattern. Results indicate substantial genetic variation and population genetic structuring of this allogamous species at a broad geographical scale in NW Europe with plastid genetic diversity organized more across an east‐to‐west than a north‐to‐south cline.

Dinosaur biogeographical structure and Mesozoic continental fragmentation: a network‐based approach

AbstractAimTo reconstruct dinosaur macro‐biogeographical patterns through the Mesozoic Era using a network‐based approach. We test how continental fragmentation affected dinosaur macro‐biogeographical structure and evolutionary rates.LocationA global occurrence database of dinosaur families from the Late Triassic to the end‐Cretaceous was used for this study.MethodsBiogeographical and geographical network models were constructed. Continental landmasses were linked by direct continental contact and sea level (SL)‐conditioned connections in geographical networks, and by shared dinosaur families in biogeographical networks. Biogeographical networks were run with raw, novel and first‐step connections for all dinosaur, ornithischian, theropod, and sauropodomorph taxa.ResultsGeographical connectedness declines through time, from peak aggregation in the Triassic–Jurassic to complete separation in the latest Cretaceous. Biogeographical connectedness shows no common trend in the raw and novel connection network models, but decreases through time while showing some correlation with continental fragmentation in most of the first‐step network models. Despite continental isolation and high SLs, intercontinental faunal exchange continued right up to the end of the Cretaceous. Continental fragmentation and dinosaurian macro‐biogeographical structure do not share a common pattern with dinosaurian evolutionary rates, although there is evidence that increased continental isolation resulted in increased origination rates in some dinosaurian lineages. Spatiotemporal sampling biases and early Mesozoic establishment of family‐level distribution patterns are important drivers of apparent dinosaur macro‐biogeographical structure.Main conclusionsThere is some evidence to suggest that dinosaur macro‐biogeographical structure was influenced by continental fragmentation, although intercontinental exchange of dinosaur faunas appears to have continued up to the end of the Cretaceous. Macro‐biogeographical patterns are obscured by uneven geographical sampling through time and a residual earlier Mesozoic distribution which is sustained up to the end of the Cretaceous.

Evaluating the influence of connectivity and distance on biogeographical patterns in the south‐western deserts of North America

AbstractAimTo examine the role of geological history, connectivity and distance in shaping the biogeographical structure of North American desert clades that are restricted to habitat islands (sand dunes and relictual aquatic habitats), using statistical model choice on old and new probabilistic biogeographical models.LocationNorth America, Mojave, Sonoran and Chihuahuan Deserts.Materials and methodsDated phylogenies were estimated for three field‐sampled insect clades (Trigonoscuta,Rhaphiomidasand sand treader crickets), and five other literature‐sampled clades (the snailsAssiminea,PyrgulopsisandTryonia; the desert fringe‐toed lizardUma; and the desert pupfishCyprinodon).BioGeoBEARSwas used to statistically compare biogeographical models assuming unconstrained or connectivity‐constrained dispersal, with or without founder‐event speciation (jump dispersal) permitted. Finally, we introduce and test a novel distance‐based dispersal model (+x) where dispersal probability is multiplied by distance to the powerx.ResultsWe observed little concordance between biogeographical patterns and timing of geological events. Model comparisons were decidedly in favour of inclusion of founder‐event speciation in the models for most taxa, with only a small taxon,Uma, showing support for the model favouring vicariance. The inclusion of a constrained‐dispersal matrix was favoured by three of the eight taxa examined (Cyprinodon, sand treader crickets, andTrigonoscuta). Surprisingly, tests for distance influencing dispersal probability were mostly negative.Main conclusionsOur results do not show support for any one geological event shaping the biogeographical patterns of these desert taxa. Instead, the histories of desert dune and aquatic taxa are largely products of rare jump dispersal events, and can be considered island‐like systems. Although results are negative for the distance‐based dispersal model, this in itself demonstrates the superiority of explicit statistical model testing overa prioriassumption of fixed models in historical biogeography.

Globally distributed Xyleborus species reveal recurrent intercontinental dispersal in a landscape of ancient worldwide distributions.

BackgroundInvasive species can have devastating effects on native ecosystems and therefore impose a significant threat to human welfare. The introduction rate of invasive species has accelerated dramatically in recent times due to human activity (anthropogenic effects), with a steadily growing pool of widespread tramp species. We present an in-depth analysis of four pantropical species of Xyleborus ambrosia beetles (Xyleborus volvulus, Xyleborus perforans, Xyleborus ferrugineus, and Xyleborus affinis) with similar ecology (fungus cultivation in dead wood), reproductive biology (permanent inbreeding) and genetic system (haplodiploidy). The unique combination of reproductive traits and broad host plant usage pre-adapts these beetles for colonizing of new areas.ResultsWe found that all four species were broadly distributed long before human-assisted dispersal became common, and that the impact of anthropogenic effects varied among the species. For X. volvulus, X. perforans, and X. affinis there was evidence of ancient establishment in numerous regions, but also of abundant recent introductions into previously colonized areas. For X. ferrugineus, we found clear biogeographical structuring of old clades, but little evidence for recent successful introductions.ConclusionsOur results indicate that current human-aided transoceanic dispersal has strongly affected the genetic makeup of three of the species in this study. However, current biogeographical patterns of all four species are equally, if not more strongly, influenced by ancient establishment on different continents.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-016-0610-7) contains supplementary material, which is available to authorized users.

High population genetic substructure in Hypochaeris leontodontoides (Asteraceae), an endemic rupicolous species of the Atlas Mountains in NW Africa

Hypochaeris leontodontoides is a rupicolous species endemic to the Atlas Mountains (Morocco), where it occurs in scattered populations. This study aims to understand the biogeographic structure of a high mountain species in a rather small area of NW Africa. We used Amplified Fragment Length Polymorphism (AFLP) to investigate the population structure and phylogeography of H. leontodontoides in 19 populations sampled from the entire species distribution range. Multivariate analyses including PCoA, UPGMA analysis, and Bayesian clustering were applied to infer the influence of past biogeographic events. The AFLP differentiation among the populations was high (FST = 0.508). A significant geographical pattern by mountain region was found. The different phylogeographical analyses revealed four main groups corresponding to four well-defined geographic regions: Middle Atlas, Eastern High Atlas, Central High Atlas, and Western High Atlas, and highlighted the Western High Atlas as the most divergent group. Our data also indicate two regions as refuges during the Pleistocene ice ages: the Middle Atlas and the northernmost area of the Western High Atlas.

The first comprehensive description of the biodiversity and biogeography of Antarctic and Sub‐Antarctic intertidal communities

AbstractAimTo describe the distribution of biodiversity and biogeographical patterns of intertidal organisms in southern temperate and polar waters. We hypothesized that there would be differences in community structure between the Antarctic, which is most affected by ice, and the sub‐Antarctic and other neighbouring regions. We also hypothesized that rafting and West Wind Drift will be the significant drivers of biogeographical patterns. Additionally, the size, age, isolation, volcanic or glacial history of a region and the presence of large, beach dwelling, mammals and birds would all play a role in determining the level of biodiversity observed.LocationSouth Atlantic, Indian and Pacific Oceans and the Southern Ocean.MethodsWe examined all available intertidal records from the Antarctic and sub‐Antarctic with additional data from neighbouring regions for comparison and context. We compiled 3902 occurrences of 1416 species of high southern latitude intertidal organisms from 229 locations and used PRIMER 6 to perform multivariate statistical analyses.ResultsThe Antarctic and sub‐Antarctic are shown to be distinct biogeographical regions, with patterns driven by a small number of widely distributed species. These wide‐ranging molluscs and macroalgae dominate the biogeographical structure of the Southern Ocean intertidal, most likely as a result of rafting in the Antarctic Circumpolar Current. East Antarctic intertidal habitats are potentially isolated by the Ross and Weddell Sea ice shelves but represent a great unknown in this biogeographical scheme.Main ConclusionsThe view that the Antarctic intertidal is a lifeless desert does not hold true, with Antarctic Peninsula intertidal communities being richer and more diverse than those in southern South America and the sub‐Antarctic islands. Changing conditions in the Antarctic and sub‐Antarctic intertidal mean that a representative baseline is needed (acquired through standardized and quantitative sampling) to assess future changes and to detect any invasive species.

Genetic Structuration, Demography and Evolutionary History of Mycobacterium tuberculosis LAM9 Sublineage in the Americas as Two Distinct Subpopulations Revealed by Bayesian Analyses.

Tuberculosis (TB) remains broadly present in the Americas despite intense global efforts for its control and elimination. Starting from a large dataset comprising spoligotyping (n = 21183 isolates) and 12-loci MIRU-VNTRs data (n = 4022 isolates) from a total of 31 countries of the Americas (data extracted from the SITVIT2 database), this study aimed to get an overview of lineages circulating in the Americas. A total of 17119 (80.8%) strains belonged to the Euro-American lineage 4, among which the most predominant genotypic family belonged to the Latin American and Mediterranean (LAM) lineage (n = 6386, 30.1% of strains). By combining classical phylogenetic analyses and Bayesian approaches, this study revealed for the first time a clear genetic structuration of LAM9 sublineage into two subpopulations named LAM9C1 and LAM9C2, with distinct genetic characteristics. LAM9C1 was predominant in Chile, Colombia and USA, while LAM9C2 was predominant in Brazil, Dominican Republic, Guadeloupe and French Guiana. Globally, LAM9C2 was characterized by higher allelic richness as compared to LAM9C1 isolates. Moreover, LAM9C2 sublineage appeared to expand close to twenty times more than LAM9C1 and showed older traces of expansion. Interestingly, a significant proportion of LAM9C2 isolates presented typical signature of ancestral LAM-RDRio MIRU-VNTR type (224226153321). Further studies based on Whole Genome Sequencing of LAM strains will provide the needed resolution to decipher the biogeographical structure and evolutionary history of this successful family.

Breaking out of biogeographical modules: range expansion and taxon cycles in the hyperdiverse ant genus Pheidole.

AimWe sought to reconstruct the biogeographical structure and dynamics of a hyperdiverse ant genus, Pheidole, and to test several predictions of the taxon cycle hypothesis. Using large datasets on Pheidole geographical distributions and phylogeny, we (1) inferred patterns of biogeographical modularity (clusters of areas with similar faunal composition), (2) tested whether species in open habitats are more likely to be expanding their range beyond module boundaries, and (3) tested whether there is a bias of lineage flow from high‐ to low‐diversity areas.LocationThe Old World.MethodsWe compiled and jointly analysed a comprehensive database of Pheidole geographical distributions, the ecological affinities of different species, and a multilocus phylogeny of the Old World radiation. We used network modularity methods to infer biogeographical structure in the genus and comparative methods to evaluate the hypotheses.ResultsThe network analysis identified eight biogeographical modules, and a suite of species with anomalous ranges that are statistically more likely to occur in open habitat, supporting the hypothesis that open habitats promote range expansion. Phylogenetic analysis shows evidence for a cascade pattern of colonization from Asia to New Guinea to the Pacific, but no ‘upstream’ colonization in the reverse direction.Main conclusionsThe distributions of Pheidole lineages in the Old World are highly modular, with modules generally corresponding to biogeographical regions inferred in other groups of organisms. However, some lineages have expanded their ranges across module boundaries, and these species are more likely to be adapted to open habitats rather than interior forest. In addition, there is a cascade pattern of dispersal from higher to lower diversity areas during these range expansions. Our findings are consistent with the taxon cycle hypothesis, although they do not rule out alternative interpretations.