Multiple colonization and dispersal events hide the early origin and induce a lack of genetic structure of the moss Bryum argenteum in Antarctica

The dispersal routes of taxa with transoceanic disjunctions remain poorly understood, with the potential roles of Antarctica not yet demonstrated. Mosses are suitable organisms to test direct intra‐Antarctic dispersal, as major component of the extant Antarctic flora, with the cosmopolitan moss Bryum argenteum as ideal target species. We analyzed the genetic structure of B. argenteum to provide an evolutionary time frame for its radiation and shed light into its historical biogeography in the Antarctic region. We tested two alternative scenarios: (a) intra‐Antarctic panmixia and (b) intra‐Antarctic genetic differentiation. Furthermore, we tested for evidence of the existence of specific intra‐Antarctic dispersal routes. Sixty‐seven new samples (40 collected in Antarctica) were sequenced for ITS nrDNA and rps4 cpDNA regions, and phylogenetic trees of B. argenteum were constructed, with a focus on its Southern Hemisphere. Combining our new nrDNA dataset with previously published datasets, we estimated time‐calibrated phylogenies based on two different substitution rates (derived from angiosperms and bryophytes) along with ancestral area estimations. Minimum spanning network and pairwise genetic distances were also calculated. B. argenteum was potentially distributed across Africa and Antarctica soon after its origin. Its earliest intra‐Antarctic dispersal and diversification occurred during a warming period in the Pliocene. On the same timescale, a radiation took place involving a dispersal event from Antarctica to the sub‐Antarctic islands. A more recent event of dispersal and diversification within Antarctica occurred during a warm period in the Pleistocene, creating favorable conditions also for its colonization outside the Antarctic continent worldwide. We provide evidence supporting the hypothesis that contemporary populations of B. argenteum in Antarctica integrate a history of both multiple long‐range dispersal events and local persistence combined with in situ diversification. Our data support the hypothesis that B. argenteum has been characterized by strong connectivity within Antarctica, suggesting the existence of intra‐Antarctic dispersal routes.     

Genetic structure of Micromeria (Lamiaceae) in Tenerife,the imprint of geological history and hybridization on within‐island diversification

Geological history of oceanic islands can have a profound effect on the evolutionary history of insular flora, especially in complex islands such as Tenerife in the Canary Islands. Tenerife results from the secondary connection of three paleo‐islands by a central volcano, and other geological events that further shaped it. This geological history has been shown to influence the phylogenetic history of several taxa, including genus Micromeria (Lamiaceae). Screening 15 microsatellite markers in 289 individuals representing the eight species of Micromeria present in Tenerife, this study aims to assess the genetic diversity and structure of these species and its relation with the geological events on the island. In addition, we evaluate the extent of hybridization among species and discuss its influence on the speciation process. We found that the species restricted to the paleo‐islands present lower levels of genetic diversity but the highest levels of genetic differentiation suggesting that their ranges might have contracted over time. The two most widespread species in the island, M. hyssopifolia and M. varia, present the highest genetic diversity levels and a genetic structure that seems correlated with the geological composition of the island. Samples from M. hyssopifolia from the oldest paleo‐island, Adeje, appear as distinct while samples from M. varia segregate into two main clusters corresponding to the paleo‐islands of Anaga and Teno. Evidence of hybridization and intraspecific migration between species was found. We argue that species boundaries would be retained despite hybridization in response to the habitat's specific conditions causing postzygotic isolation and preserving morphological differentiation.     

Genetic differentiation of continental and island populations of Bombus terrestris (Hymenoptera: Apidae) in Europe

Ten microsatellite loci and a partial sequence of the COII mitochondrial gene were used to investigate genetic differentiation in B. terrestris, a bumble bee of interest for its high-value crop pollination. The analysis included eight populations from the European continent, five from Mediterranean islands (six subspecies altogether) and one from Tenerife (initially described as a colour form of B. terrestris but recently considered as a separate species, B. canariensis). Eight of the 10 microsatellite loci displayed high levels of polymorphism in most populations. In B. terrestris populations, the total number of alleles detected per polymorphic locus ranged from 3 to 16, with observed allelic diversity from 3.8 ± 0.5 to 6.5 ± 1.4 and average calculated heterozygosities from 0.41 ± 0.09 to 0.65 ± 0.07. B. canariensis showed a significantly lower average calculated heterozygosity (0.12 ± 0.08) and observed allelic diversity (1.5 ± 0.04) as compared to both continental and island populations of B. terrestris. No significant differentiation was found among populations of B. terrestris from the European continent. In contrast, island populations were all significantly and most of them strongly differentiated from continental populations. B. terrestris mitochondrial DNA is characterized by a low nucleotide diversity: 0.18%± 0.07%, 0.20%± 0.04% and 0.27%± 0.04% for the continental populations, the island populations and all populations together, respectively. The only haplotype found in the Tenerife population differs by a single nucleotide substitution from the most common continental haplotype of B. terrestris. This situation, identical to that of Tyrrhenian islands populations and quite different from that of B. lucorum (15 substitutions between terrestris and lucorum mtDNA) casts doubts on the species status of B. canariensis. The large genetic distance between the Tenerife and B. terrestris populations estimated from microsatellite data result, most probably, from a severe bottleneck in the Canary island population. Microsatellite and mitochondrial DNA data call for the protection of the island populations of B. terrestris against importation of bumble bees of foreign origin which are used as crop pollinators.     

Genetic structure of the Canarian palm tree (Phoenix canariensis) at the island scale: does the ‘island within islands’ concept apply to species with high colonisation ability?

• Oceanic islands are dynamic settings that often promote within‐island patterns of strong population differentiation. Species with high colonisation abilities, however, are less likely to be affected by genetic barriers, but island size may impact on species genetic structure regardless of dispersal ability.
• The aim of the present study was to identify the patterns and factors responsible for the structure of genetic diversity at the island scale in Phoenix canariensis, a palm species with high dispersal potential. To this end, we conducted extensive population sampling on the three Canary Islands where the species is more abundant and assessed patterns of genetic variation at eight microsatellite loci, considering different within‐island scales.
• Our analyses revealed significant genetic structure on each of the three islands analysed, but the patterns and level of structure differed greatly among islands. Thus, genetic differentiation fitted an isolation‐by‐distance pattern on islands with high population densities (La Gomera and Gran Canaria), but such a pattern was not found on Tenerife due to strong isolation between colonised areas. In addition, we found a positive correlation between population geographic isolation and fine‐scale genetic structure.
• This study highlights that island size is not necessarily a factor causing strong population differentiation on large islands, whereas high colonisation ability does not always promote genetic connectivity among neighbouring populations. The spatial distribution of populations (i.e. landscape occupancy) can thus be a more important driver of plant genetic structure than other island, or species′ life‐history attributes.

     

Palaeo‐islands as refugia and sources of genetic diversity within volcanic archipelagos: the case of the widespread endemic Canarina canariensis (Campanulaceae)

Geographical isolation by oceanic barriers and climatic stability has been postulated as some of the main factors driving diversification within volcanic archipelagos. However, few studies have focused on the effect that catastrophic volcanic events have had on patterns of within‐island differentiation in geological time. This study employed data from the chloroplast (cpDNA haplotypes) and the nuclear (AFLPs) genomes to examine the patterns of genetic variation in Canarina canariensis, an iconic plant species associated with the endemic laurel forest of the Canary Islands. We found a strong geographical population structure, with a first divergence around 0.8 Ma that has Tenerife as its central axis and divides Canarian populations into eastern and western clades. Genetic diversity was greatest in the geologically stable ‘palaeo‐islands’ of Anaga, Teno and Roque del Conde; these areas were also inferred as the ancestral location of migrant alleles towards other disturbed areas within Tenerife or the nearby islands using a Bayesian approach to phylogeographical clustering. Oceanic barriers, in contrast, appear to have played a lesser role in structuring genetic variation, with intra‐island levels of genetic diversity larger than those between‐islands. We argue that volcanic eruptions and landslides after the merging of the palaeo‐islands 3.5 Ma played key roles in generating genetic boundaries within Tenerife, with the palaeo‐islands acting as refugia against extinction, and as cradles and sources of genetic diversity to other areas within the archipelago.     

Parasites and the island syndrome: the colonization of the western Mediterranean islands by Heligmosomoides polygyrus (Dujardin, 1845)

Aim Populations of free‐living vertebrates on islands frequently differ from their mainland counterparts by a series of changes in morphometric, life‐history, behavioural, physiological and genetic traits, collectively referred to as the ‘island syndrome’. It is not known, however, whether the ‘island syndrome’ also affects parasitic organisms. The present study establishes the colonization pattern of the Mediterranean islands by the nematode Heligmosomoides polygyrus, a direct and specific parasite of rodent hosts of the Apodemus genus, and evaluates the effects of island colonization by this species on two components of the island syndrome: the loss of genetic diversity and the enlargement of the ecological niche. Location Heligmosomoides polygyrus was sampled on seven western Mediterranean islands ? Corsica, Crete, Elba, Majorca, Minorca, Sardinia and Sicily ? as well as in 20 continental locations covering the Mediterranean basin. Methods The mitochondrial cytochrome b gene (690 base pairs) was sequenced in 166 adult H. polygyrus individuals sampled in the 27 continental and island locations. Phylogenetic reconstructions in distance, parsimony, maximum likelihood and Bayesian posterior probabilities were carried out on the whole cytochrome b gene data set. The levels of nucleotide, haplotype and genetic divergence (Kimura two‐parameter distance estimator) diversities were estimated in each island population and in the various continental lineages. Results Phylogenetic reconstructions show that the mainland origins of H. polygyrus were continental Spain for the Balearic Islands (Majorca, Minorca), northern Italy for the Tyrrhenian Islands (Corsica, Sardinia, Elba), southern Italy for Sicily, and the Balkan region for Crete. A comparison of island H. polygyrus populations with their mainland source populations revealed two characteristic components of the island syndrome in this parasite. First, island H. polygyrus populations display a significant loss of genetic diversity, which is related (r² = 0.73) to the distance separating the island from the mainland source region. Second, H. polygyrus exhibits a niche enlargement following insularization. Indeed, H. polygyrus in Corsica is present in both A. sylvaticus and Mus musculus domesticus, while mainland H. polygyrus populations are present exclusively in Apodemus hosts. Main conclusions Our results show that H. polygyrus has undergone a loss of genetic diversity and a niche (host) enlargement following colonization of the western Mediterranean islands. To our knowledge, this study provides the first evidence for components of the ‘island syndrome’ in a parasitic nematode species.     

Ecogeographical patterns of morphological variation in pygmy shrews Sorex minutus (Soricomorpha: Soricinae) within a phylogeographical and continental‐and‐island framework

Ecogeographical patterns of morphological variation were studied in the Eurasian pygmy shrew Sorex minutus aiming to understand the species’ morphological diversity in a continental and island setting, and within the context of previous detailed phylogeographical studies. In total, 568 mandibles and 377 skulls of S. minutus from continental and island populations from Europe and Atlantic islands were examined using a geometric morphometrics approach, and the general relationships of mandible and skull size and shape with geographical and environmental variables were studied. Samples were then pooled into predefined geographical groups to evaluate the morphological differences among them using analyses of variance, aiming to contrast the morphological and genetic relationships based on morphological and genetic distances and ancestral state reconstructions, as well as assess the correlations of morphological, genetic, and geographical distances with Mantel tests. We found significant relationships of mandible size with geographical and environmental variables, fitting the converse Bergmann's rule; however, for skull size, this was less evident. Continental groups of S. minutus could not readily be differentiated from each other by shape. Most island groups of S. minutus were easily discriminated from the continental groups by being larger, indicative of an island effect. Moreover, morphological and genetic distances differed substantially and, again, island groups were distinctive morphologically. Morphological and geographical distances were significantly correlated, although this was not the case for morphological and genetic distances, indicating that morphological variation does not reflect genetic subdivision in S. minutus. Our analyses showed that environmental variables and insularity had important effects on the morphological differentiation of S. minutus.     

First report of the invasive Reticulitermes flavipes (Kollar, 1837) (Blattodea,Rhinotermitidae) in the Canary Islands

Reticulitermes flavipes, one of the most harmful subterranean termite pests, is reported for the first time from Tenerife (Canary Islands, Spain). Cytochrome oxidase II was sequenced from five specimens in order to confirm the identification. To date, this invasive species has been detected in a limited area in the northeast of the island, affecting buildings, crops and native plant species. Another colony with the identical haplotype found in the southwest, 60 km away from the main population, indicates that this invasive insect may be more widespread over the island.     

Species delimitation in the Chinese bamboo partridge Bambusicola thoracica (Phasianidae; Aves)

Although tropical and subtropical Asia harbour a high level of species diversity, their species richness can be underestimated because species which are in fact distinct have not been separately identified. In this study, we delimit Bambusicola thoracica into two full species, the Chinese bamboo partridge (B. thoracica) in continental Asia and the Taiwanese bamboo partridge (B. sonorivox) on the island of Taiwan, using coalescent‐based multilocus division and diagnosable vocalization patterns. Isolation‐with‐migration analysis indicated that the two bamboo partridges diverged approximately 1.8 million years ago, with gene flow present most probably during the early stages of their divergence. This conclusion supports the hypothesis that diverging lowland lineages spread across the Asian mainland, and continental islands have more opportunities for secondary contact than highland ones when the sea level was low. Our results imply that conservation of biodiversity in tropical and subtropical Asia could be hindered by overlooking numerous ‘hidden’ species and highlight the importance of re‐examining the taxonomic statuses of species in this region traditionally defined as polytypic.     

Origin of, and conservation units in, the Irish red squirrel (Sciurus vulgaris) population

Knowledge of genetic relationships among wildlife populations is fundamental to their conservation, particularly where translocations are concerned. This study involved a survey of mitochondrial DNA variation in the Irish red squirrel population. Our main aims were: (1) to determine whether the Irish red squirrel population is distinct from that found in Britain, given known translocations that took place from Britain in the 1800’s; and (2) whether inclusion of Irish data into a reanalysis of European red squirrel data could reveal patterns of postglacial spread in Ireland. We found evidence that the current Irish red squirrel population may be a mixture of native and translocated stock, and relationships between Irish and European haplotypes supported a number of colonisation events of the island. Although only one haplotype was common to both Ireland and Britain, it is probable that the most common haplotypes in Ireland are British introductions that have since become extinct in Britain. There was a significant regional genetic structure in Ireland (P < 0.001), as well as between all Irish and British regions. Although it is likely that the red squirrel will not be fundamental in tracing the colonisation of Ireland by mammals, the data demonstrated that individual regions within Ireland, as well as the Irish population as a whole, are distinct both from the British population and from each other and, therefore, these populations should be treated as separate Management Units (MU) in conservation strategies.     

Rejecting strictly allopatric speciation on a continental island: prolonged postdivergence gene flow between Taiwan (Leucodioptron taewanus,Passeriformes Timaliidae) and Chinese (L. canorum canorum) hwameis

Allopatry is conventionally considered the geographical mode of speciation for continental island organisms. However, strictly allopatric speciation models that assume the lack of postdivergence gene flow seem oversimplified given the recurrence of land bridges during glacial periods since the late Pliocene. Here, to evaluate whether a continental island endemic, the Taiwan hwamei (Leucodioptron taewanus, Passeriformes Timaliidae) speciated in strict allopatry, we used weighted‐regression‐based approximate Bayesian computation (ABC) to analyse the genetic polymorphism of 18 neutral nuclear loci (total length: 8500 bp) in Taiwan hwamei and its continental sister species, the Chinese hwamei (L. canorum canorum). The nonallopatry model was found to fit better with observed genetic polymorphism of the two hwamei species (posterior possibility = 0.82). We also recovered unambiguous signals of nontrivial bidirectional postdivergence gene flow (N_em » 1) between Chinese hwamei and Taiwan hwamei until 0.5 Ma. Divergence time was estimated to be 3.5 to 2 million years earlier than that estimated from mitochondrial cytochrome b sequences. Finally, using the inferred nonallopatry model to simulate genetic variation at 24 nuclear genes examined showed that the adiponectin receptor 1 gene may be under divergent adaptation. Our findings imply that the role of geographical barrier may be less prominent for the speciation of continental island endemics, and suggest a shift in speciation studies from simply correlating geographical barrier and genetic divergence to examining factors that facilitate and maintain divergence, e.g. differential selection and sexual selection, especially in the face of interpopulation gene flow.     

Multispecies genetic structure and hybridization in the Betula genus across Eurasia

Boreal and cool temperate forests are the major land cover of northern Eurasia, and information about continental‐scale genetic structure and past demographic history of forest species is important from an evolutionary perspective and has conservation implications. However, although many population genetic studies of forest tree species have been conducted in Europe or Eastern Asia, continental‐scale genetic structure and past demographic history remain poorly known. Here, we focus on the birch genus Betula, which is commonly distributed in boreal and cool temperate forests, and examine 129 populations of two tetraploid and four diploid species collected from Iceland to Japan. All individuals were genotyped at seven to 18 nuclear simple sequence repeats (nSSRs). Pairwise among the six species ranged from 0.285 to 0.903, and genetic differentiation among them was clear. structure analysis suggested that Betula pubescens is an allotetraploid and one of the parental species was Betula pendula. In both species pairs of B. pendula and B. plathyphylla, and B. pubescens and B. ermanii, genetic diversity was highest in central Siberia. A hybrid zone was detected around Lake Baikal for eastern and western species pairs regardless of ploidy level. Approximate Bayesian computation suggested that the divergence of B. pendula and B. platyphylla occurred around the beginning of the last ice age (36 300 years BP, 95% CI: 15 330–92 700) and hybridization between them was inferred to have occurred after the last glacial maximum (1614 years BP, 95% CI: 561–4710), with B. pendula providing a higher contribution to hybrids.     

A comparative phylogeographic study reveals discordant evolutionary histories of alpine ground beetles (Coleoptera,Carabidae)

Taiwan, an island with three major mountain ranges, provides an ideal topography to study mountain–island effect on organisms that would be diversified in the isolation areas. Glaciations, however, might drive these organisms to lower elevations, causing gene flow among previously isolated populations. Two hypotheses have been proposed to depict the possible refugia for alpine organisms during glaciations. Nunatak hypothesis suggests that alpine species might have stayed in situ in high mountain areas during glaciations. Massif de refuge, on the other hand, proposes that alpine species might have migrated to lower ice‐free areas. By sampling five sympatric carabid species of Nebria and Leistus, and using two mitochondrial genes and two nuclear genes, we evaluated the mountain–island effect on alpine carabids and tested the two proposed hypotheses with comparative phylogeographic method. Results from the phylogenetic relationships, network analysis, lineage calibration, and genetic structure indicate that the deep divergence among populations in all L. smetanai, N. formosana, and N. niitakana was subjected to long‐term isolation, a phenomenon in agreement with the nunatak hypothesis. However, genetic admixture among populations of N. uenoiana and some populations of L. nokoensis complex suggests that gene flow occurred during glaciations, as a massif de refuge depicts. The speciation event in N. niitakana is estimated to have occurred before 1.89 million years ago (Mya), while differentiation among isolated populations in N. niitakana, N. formosana, L. smetanai, and L. nokoensis complex might have taken place during 0.65–1.65 Mya. While each of the alpine carabids arriving in Taiwan during different glaciation events acquired its evolutionary history, all of them had confronted the existing mountain ranges.     

Species–area relationships and additive partitioning of diversity of native and nonnative herpetofauna of the West Indies

To evaluate the regional biogeographical patterns of West Indian native and nonnative herpetofauna, we derived and updated data on the presence/absence of all herpetofauna in this region from the recently published reviews. We divided the records into 24 taxonomic groups and classified each species as native or nonnative at each locality. For each taxonomic group and in aggregate, we then assessed the following: (1) multiple species–area relationship (SAR) models; (2) C‐ and Z‐values, typically interpreted to represent insularity or dispersal ability; and (3) the average diversity of islands, among‐island heterogeneity, γ‐diversity, and the contribution of area effect toward explaining among‐island heterogeneity using additive diversity partitioning approach. We found the following: (1) SARs were best modeled using the Cumulative Weibull and Lomolino relationships; (2) the Cumulative Weibull and Lomolino regressions displayed both convex and sigmoid curves; and (3) the Cumulative Weibull regressions were more conservative than Lomolino at displaying sigmoid curves within the range of island size studied. The Z‐value of all herpetofauna was overestimated by Darlington (Zoogeography: The geographic distribution of animals, John Wiley, New York, 1957), and Z‐values were ranked: (1) native > nonnative; (2) reptiles > amphibians; (3) snake > lizard > frog > turtle > crocodilian; and (4) increased from lower‐ to higher‐level taxonomic groups. Additive diversity partitioning showed that area had a weaker effect on explaining the among‐island heterogeneity for nonnative species than for native species. Our findings imply that the flexibility of Cumulative Weibull and Lomolino has been underappreciated in the literature. Z‐value is an average of different slopes from different scales and could be artificially overestimated due to oversampling islands of intermediate to large size. Lower extinction rate, higher colonization, and more in situ speciation could contribute to high richness of native species on large islands, enlarging area effect on explaining the between‐island heterogeneity for native species, whereas economic isolation on large islands could decrease the predicted richness, lowering the area effect for nonnative species. For most of the small islands less affected by human activities, extinction and dispersal limitation are the primary processes producing low species richness pattern, which decreases the overall average diversity with a large among‐island heterogeneity corresponding to the high value of this region as a biodiversity hotspot.     

Absence of founder effect and evidence for adaptive divergence in a recently introduced insular population of white‐tailed deer (Odocoileus virginianus)

Islands are generally colonized by few individuals which could lead to a founder effect causing loss of genetic diversity and rapid divergence by strong genetic drift. Insular conditions can also induce new selective pressures on populations. Here, we investigated the extent of genetic differentiation within a white‐tailed deer (Odocoileus virginianus) population introduced on an island and its differentiation with its source mainland population. In response to their novel environmental conditions, introduced deer changed phenotypically from mainland individuals, therefore we investigated the genetic bases of the morphological differentiation. The study was conducted on Anticosti Island (Québec, Canada) where 220 individuals were introduced 120 years ago, resulting in a population size over 160,000 individuals. We used genotyping‐by‐sequencing (GBS) to generate 8,518 filtered high‐quality SNPs and compared patterns of genetic diversity and differentiation between the continental and Anticosti Island populations. Clustering analyses indicated a single panmictic island population and no sign of isolation by distance. Our results revealed a weak, albeit highly significant, genetic differentiation between the Anticosti Island population and its source population (mean F_ST = 0.005), which allowed a population assignment success of 93%. Also, the high genetic diversity maintained in the introduced population supports the absence of a strong founder effect due to the large number of founders followed by rapid population growth. We further used a polygenic approach to assess the genetic bases of the divergent phenotypical traits between insular and continental populations. We found loci related to muscular function and lipid metabolism, which suggested that these could be involved in local adaptation on Anticosti Island. We discuss these results in a harvest management context.     

Scrophularia arguta,a widespread annual plant in the Canary Islands: a single recent colonization event or a more complex phylogeographic pattern?

Many studies have addressed evolution and phylogeography of plant taxa in oceanic islands, but have primarily focused on endemics because of the assumption that in widespread taxa the absence of morphological differentiation between island and mainland populations is due to recent colonization. In this paper, we studied the phylogeography of Scrophularia arguta, a widespread annual species, in an attempt to determine the number and spatiotemporal origins of dispersal events to Canary Islands. Four different regions, ITS and ETS from nDNA and psbA‐trnH and psbJ‐petA from cpDNA, were used to date divergence events within S. arguta lineages and determine the phylogenetic relationships among populations. A haplotype network was obtained to elucidate the phylogenetic relationships among haplotypes. Our results support an ancient origin of S. arguta (Miocene) with expansion and genetic differentiation in the Pliocene coinciding with the aridification of northern Africa and the formation of the Mediterranean climate. Indeed, results indicate for Canary Islands three different events of colonization, including two ancient events that probably happened in the Pliocene and have originated the genetically most divergent populations into this species and, interestingly, a recent third event of colonization of Gran Canaria from mainland instead from the closest islands (Tenerife or Fuerteventura). In spite of the great genetic divergence among populations, it has not implied any morphological variation. Our work highlights the importance of nonendemic species to the genetic richness and conservation of island flora and the significance of the island populations of widespread taxa in the global biodiversity.     

Population structuring in the monogonont rotifer Synchaeta pectinata: high genetic divergence on a small geographical scale

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Contemporary human‐altered landscapes and oceanic barriers reduce bumble bee gene flow

Much of the world's terrestrial landscapes are being altered by humans in the form of agriculture, urbanization and pastoral systems, with major implications for biodiversity. Bumble bees are one of the most effective pollinators in both natural and cultivated landscapes, but are often the first to be extirpated in human‐altered habitats. Yet, little is known about the role of natural and human‐altered habitats in promoting or limiting bumble bee gene flow. In this study, I closely examine the genetic structure of the yellow‐faced bumble bee, Bombus vosnesenskii, across the southwestern US coast and find strong evidence that natural oceanic barriers, as well as contemporary human‐altered habitats, limit bee gene flow. Heterozygosity and allelic richness were lower in island populations, while private allelic richness was higher in island populations compared to mainland populations. Genetic differentiation, measured for three indices across the 1000 km study region, was significantly greater than the null expectation (F_ST = 0.041, F’_ST = 0.044 and D_est = 0.155) and correlated with geographic distance. Furthermore, genetic differentiation patterns were most strongly correlated with contemporary (2011) not past (2006, 2001) resistance maps calibrated for high dispersal limitation over oceans, impervious habitat and croplands. Despite the incorporation of dramatic elevation gradients, the analyses reveal that oceans and contemporary human land use, not mountains, are the primary dispersal barriers for B. vosnesenskii gene flow. These findings reinforce the importance of maintaining corridors of suitable habitat across the distribution range of native pollinators to promote their persistence and safeguard their ability to provide essential pollination services.     

Wing morphology of the active flyer Calliphora vicina (Diptera: Calliphoridae) during its invasion of a sub‐Antarctic archipelago where insect flightlessness is the rule

The cosmopolitan blowfly Calliphora vicina became established in the sub‐Antarctic Kerguelen Islands in the late 1970s, following a warming period that allowed its full development. Although temperature and wind may limit flight activity, the fly invaded the archipelago, reaching sites remote from the introduction point. Most native competitors have converged to flightlessness as a response to stringent environmental conditions and therefore the flight strategy of C. vicina might be either a handicap or a competitive advantage under ongoing climate change. Using geometric morphometrics, we investigated whether the wing had changed over time in C. vicina within the archipelago (1998 vs. 2009) and compared its morphology with that of a continental population from a temperate area (1983 vs. 2009). Wing shape plasticity to temperature was also experimentally investigated. We found no clues of relaxed selection on flight morphology in the range invaded. However, rapid changes of wing shape occurred over time in females from the Kerguelen Islands compared with both males and females of the continental population, despite a shorter time‐lag between samples in the former. The thermal reaction norms for wing shape found for C. vicina from Kerguelen were also different from those of the continental population, but it remains unknown whether this resulted from or preceded the introduction. These combined findings are consistent with a fingerprint of local adaptation in the invasive population. However, the adaptive significance of the changes, in terms of their aerodynamic consequences and the future evolution of C. vicina in the Kerguelen Islands, requires further investigation. From an evolutionary standpoint, sustaining flight capability under the novel sub‐Antarctic conditions might be critical to the invasive success of C. vicina as most competitors are flightless.     

Biological and environmental characteristics of three cosmopolitan mosses dominant in continental Antarctica

Abstract. Bryum argenteum, B. pseudotriquetrum and Ceratodon purpureus are the predominant mosses in Victoria Land, continental Antarctica. All have cosmopolitan distributions and are widespread throughout Antarctica with wide ecological amplitudes resulting in considerable morphological variation. They are well adapted to tolerate the physiological stresses imposed by the severe environment. This study investigates aspects of their growth, physiology and survival in response to habitat constraints, especially hydrology. Their distribution is controlled almost exclusively by moisture availability. Each species tends to predominate in a specific zone along hydrological gradients, with B. pseudotriquetrum on moist soil, C. purpureus on drier soil, and B. argenteum on unstable stream margins, fluvial deposits and the marginal capillary zone. Where conditions are optimal, each species can form a turf 6–10 cm thick. Nutrient status of the soil does not appear to be an important determinant in the distribution pattern within communities. The thermal regime of the moss turf varies according to its moisture content; for a period of ca. six weeks during the summer, with the frequent long spells of 24-h sunshine, temperatures remain above 0 °C for much of the time even though air temperatures are frequently below the freezing point. This allows growth and metabolic activity to proceed continuously at a relatively rapid rate for quite long periods. Annual shoot incremental growth can exceed 3.5 mm in each species. Growth of B. argenteum may be inhibited by UV- B radiation. The optimal temperature for photosynthesis in each species is around 15 °C, but significant carbon fixation occurs at 5 °C. Photosynthetic rates at 5, 10 and 20 °C were B. argenteum > B. pseudotriquetrum > C. purpureus.