Widespread continental mtDNA lineages prevail in the bumblebee fauna of Iceland.
ABSTRACT: Origins of the fauna in Iceland is controversial, although the majority of modern research supports the postglacial colonization of this island by terrestrial invertebrates rather than their long-term survival in glacial refugia. In this study, we use three bumblebee species as a model to test the hypothesis regarding possible cryptic refugia in Iceland and to evaluate a putative origin of recently introduced taxa. Bombus jonellus is thought to be a possible native Icelandic lineage, whereas B. lucorum and B. hortorum were evidently introduced in the second half of the 20th century. These phylogeographic analyses reveal that the Icelandic Bombus jonellus shares two COI lineages, one of which also occurs in populations on the British Isles and in mainland Europe, but a second lineage (BJ-02) has not been recorded anywhere. These results indicate that this species may have colonized Iceland two times and that the lineage BJ-02 may reflect a more ancient Late Pleistocene or Early Holocene founder event (e.g., from the British Isles). The Icelandic populations of both Bombus lucorum and B. hortorum share the COI lineages that were recorded as widespread throughout Eurasia, from the European countries across Russia to China and Japan. The findings presented here highlight that the bumblebee fauna of Iceland comprises mainly widespread ubiquitous lineages that arrived via natural or human-mediated dispersal events from the British Isles or the mainland.
Project description:Our study describes genetic lineages and historical biogeography of Rhodiola rosea a widely distributed arctic-alpine perennial species of the Northern Hemisphere based on sequence analysis of six chloroplast regions. Specimens of 44 localities from the Northern Hemisphere have been sequenced and compared with those available in the GenBank. Our results support the migration of the species into Europe via the Central Asian highland corridor, reaching the European Alpine System (EAS) and also the western European edge, the British Isles. The EAS proved to be an important center of genetic diversity, especially the region of the Eastern Alps and the Dolomites where signs of glacial refugia was observed. Apart from those of the EAS, a common lineage was detected along the Atlantic coast from the British Isles toward Scandinavia as well as Iceland and the eastern parts of North America. Accordingly, the British Isles represent a main link between the northern Atlantic and southern EAS lineages.
Project description:Accurate estimates of movement behavior and distances travelled by animals are difficult to obtain, especially for small-bodied insects where transmitter weights have prevented the use of radio-tracking.Here, we report the first successful use of micro radio telemetry to track flight distances and space use of bumblebees. Using ground surveys and Cessna overflights in a Central European rural landscape mosaic we obtained maximum flight distances of 2.5 km, 1.9 km and 1.3 km for Bombus terrestris (workers), Bombus ruderatus (worker), and Bombus hortorum (young queens), respectively. Bumblebee individuals used large areas (0.25-43.53 ha) within one or a few days. Habitat analyses of one B. hortorum queen at the landscape scale indicated that gardens within villages were used more often than expected from habitat availability. Detailed movement trajectories of this individual revealed that prominent landscape structures (e.g. trees) and flower patches were repeatedly visited. However, we also observed long (i.e. >45 min) resting periods between flights (B. hortorum) and differences in flower-handling between bumblebees with and without transmitters (B. terrestris) suggesting that the current weight of transmitters (200 mg) may still impose significant energetic costs on the insects.Spatio-temporal movements of bumblebees can now be tracked with telemetry methods. Our measured flight distances exceed many previous estimates of bumblebee foraging ranges and suggest that travelling long distances to food resources may be common. However, even the smallest currently available transmitters still appear to compromise flower handling performance and cause an increase in resting behavior of bees. Future reductions of transmitter mass and size could open up new avenues for quantifying landscape-scale space use of insect pollinators and could provide novel insights into the behavior and requirements of bumblebees during critical life stages, e.g. when searching for mates, nest locations or hibernation sites.
Project description:BACKGROUND: House mice (Mus musculus) are commensals of humans and therefore their phylogeography can reflect human colonization and settlement patterns. Previous studies have linked the distribution of house mouse mitochondrial (mt) DNA clades to areas formerly occupied by the Norwegian Vikings in Norway and the British Isles. Norwegian Viking activity also extended further westwards in the North Atlantic with the settlement of Iceland, short-lived colonies in Greenland and a fleeting colony in Newfoundland in 1000 AD. Here we investigate whether house mouse mtDNA sequences reflect human history in these other regions as well. RESULTS: House mice samples from Iceland, whether from archaeological Viking Age material or from modern-day specimens, had an identical mtDNA haplotype to the clade previously linked with Norwegian Vikings. From mtDNA and microsatellite data, the modern-day Icelandic mice also share the low genetic diversity shown by their human hosts on Iceland. Viking Age mice from Greenland had an mtDNA haplotype deriving from the Icelandic haplotype, but the modern-day Greenlandic mice belong to an entirely different mtDNA clade. We found no genetic association between modern Newfoundland mice and the Icelandic/ancient Greenlandic mice (no ancient Newfoundland mice were available). The modern day Icelandic and Newfoundland mice belong to the subspecies M. m. domesticus, the Greenlandic mice to M. m. musculus. CONCLUSIONS: In the North Atlantic region, human settlement history over a thousand years is reflected remarkably by the mtDNA phylogeny of house mice. In Iceland, the mtDNA data show the arrival and continuity of the house mouse population to the present day, while in Greenland the data suggest the arrival, subsequent extinction and recolonization of house mice--in both places mirroring the history of the European human host populations. If house mice arrived in Newfoundland with the Viking settlers at all, then, like the humans, their presence was also fleeting and left no genetic trace. The continuity of mtDNA haplotype in Iceland over 1000 years illustrates that mtDNA can retain the signature of the ancestral house mouse founders. We also show that, in terms of genetic variability, house mouse populations may also track their host human populations.
Project description:Silas Bossert, Barbara-Amina Gereben-Krenn, Johann Neumayer, Bernhard Schneller, and Harald W. Krenn (2016) The Bombus lucorum complex represents a group of three distinct but cryptic bumblebee species in Europe. With the advent of DNA-based identification methods, their species status was confirmed and the use of COI barcoding proved to be an especially useful tool for species identification within the group. Meanwhile, the identification based on morphology remains difficult and recent studies challenged the general distinguishability by revealing an important character to be unreliable. This has consequences for our understanding of the distribution and ecology of the species in Europe and aggravates our patchy knowledge of the situation in Austria and the whole area of the European Alps. In this study, we investigate the exact species composition and distribution of the Bombus lucorum complex in Austria based on the reliable species identification with COI sequence data. The habitat usage is studied and the first extensive investigation of altitudinal and climatic differentiation is provided. The results support three distinct genotypic groups in the Bombus lucorum complex. B. lucorum and B. cryptarum co-occur in several areas across the country, with B. lucorum being the most common and most widespread species. The study provides no evidence for the presence of B. magnus in Austria. The less common species, B. cryptarum, mainly occurs in the high mountains and is the predominant species of the complex above altitudes of 2100 m a.s.l. Further, B. cryptarum is almost absent from woodlands and is relatively more abundant in habitats with colder climate than B. lucorum in Austria. Additionally, the results indicate a very low intraspecific genetic variation within B. lucorum and B. cryptarum. This study confirms previous findings of three distinct species within the species complex. Based on reliable COI identification, the first coherent overview of the species complex in Austria can be achieved. The climatic data allows us to explain the differences in the distribution patterns. Moreover, the low intraspecific variation may indicate past bottleneck conditions for B. lucorum and B. cryptarum.
Project description:BACKGROUND AND AIMS: Although urban gardens provide opportunities for pollinators in an otherwise inhospitable environment, most garden plants are not native to the recipient biogeographical region and their value to local pollinators is disputed. This study tested the hypothesis that bumblebees foraging in English urban gardens preferentially visited sympatric Palaearctic-range plants over species originating outside their native range. METHODS: Twenty-seven surveys of flower availability and bumblebee visitation (Bombus spp.) were conducted over a 3-month summer period. Plants were categorized according to whether they were native British, Palaearctic or non-Palaearctic in origin. A phylogeny of the 119 plant species recorded was constructed and the relationship between floral abundance and the frequency of pollinator visits investigated by means of phylogenetically independent contrasts. Differentiation in utilization of plant species by the five bumblebee species encountered was investigated using niche overlap analyses. KEY RESULTS: There was conflicting evidence for preferential use of native-range Palaearctic plant species by bumblebees depending on which plants were included in the analysis. Evidence was also found for niche partitioning between species based on respective preferences for native and non-native biogeographical range plants. Two bumblebees (Bombus terrestris and B. pratorum) concentrated their foraging activity on non-Palaearctic plants, while two others (B. hortorum and B. pascourum) preferred Palaearctic species. CONCLUSIONS: The long-running debate about the value of native and non-native garden plants to pollinators probably stems from a failure to properly consider biogeographical overlap between plant and pollinator ranges. Gardeners can encourage pollinators without consideration of plant origin or bias towards 'local' biogeographical species. However, dietary specialist bumblebees seem to prefer plants sympatric with their own biogeographical range and, in addition to the cultivation of these species in gardens, provision of native non-horticultural ('weed') species may also be important for pollinator conservation.
Project description:Cryptic diversity within bumblebees (Bombus) has the potential to undermine crucial conservation efforts designed to reverse the observed decline in many bumblebee species worldwide. Central to such efforts is the ability to correctly recognise and diagnose species. The B. lucorum complex (Bombus lucorum, B. cryptarum and B. magnus) comprises one of the most abundant and important group of wild plant and crop pollinators in northern Europe. Although the workers of these species are notoriously difficult to diagnose morphologically, it has been claimed that queens are readily diagnosable from morphological characters. Here we assess the value of colour-pattern characters in species identification of DNA-barcoded queens from the B. lucorum complex. Three distinct molecular operational taxonomic units were identified each representing one species. However, no uniquely diagnostic colour-pattern character state was found for any of these three molecular units and most colour-pattern characters showed continuous variation among the units. All characters previously deemed to be unique and diagnostic for one species were displayed by specimens molecularly identified as a different species. These results presented here raise questions on the reliability of species determinations in previous studies and highlights the benefits of implementing DNA barcoding prior to ecological, taxonomic and conservation studies of these important key pollinators.
Project description:Previous attempts to investigate the origin of the Icelanders have provided estimates of ancestry ranging from a 98% British Isles contribution to an 86% Scandinavian contribution. We generated mitochondrial sequence data for 401 Icelandic individuals and compared these data with >2,500 other European sequences from published sources, to determine the probable origins of women who contributed to Iceland's settlement. Although the mean number of base-pair differences is high in the Icelandic sequences and they are widely distributed in the overall European mtDNA phylogeny, we find a smaller number of distinct mitochondrial lineages, compared with most other European populations. The frequencies of a number of mtDNA lineages in the Icelanders deviate noticeably from those in neighboring populations, suggesting that founder effects and genetic drift may have had a considerable influence on the Icelandic gene pool. This is in accordance with available demographic evidence about Icelandic population history. A comparison with published mtDNA lineages from European populations indicates that, whereas most founding females probably originated from Scandinavia and the British Isles, lesser contributions from other populations may also have taken place. We present a highly resolved phylogenetic network for the Icelandic data, identifying a number of previously unreported mtDNA lineage clusters and providing a detailed depiction of the evolutionary relationships between European mtDNA clusters. Our findings indicate that European populations contain a large number of closely related mitochondrial lineages, many of which have not yet been sampled in the current comparative data set. Consequently, substantial increases in sample sizes that use mtDNA data will be needed to obtain valid estimates of the diverse ancestral mixtures that ultimately gave rise to contemporary populations.
Project description:Level and partitioning of genetic diversity is expected to vary between contrasting habitats, reflecting differences in strength of ecological and evolutionary processes. Therefore, it is necessary to consider processes acting on different time scales when trying to explain diversity patterns in different parts of species' distributions. To explore how historical and contemporary factors jointly may influence patterns of genetic diversity and population differentiation, we compared genetic composition in the perennial herb Arabidopsis lyrata ssp. petraea from the northernmost parts of its distribution range on Iceland to that previously documented in Scandinavia. Leaf tissue and soil were sampled from ten Icelandic populations of A. lyrata. Seedlings were grown from soil samples, and tissue from above-ground and seed bank individuals were genotyped with 21 microsatellite markers. Seed bank density in Icelandic populations was low but not significantly different from that observed in Norwegian populations. While within-population genetic diversity was relatively high on Iceland (H(E) = 0.35), among-population differentiation was low (F(ST) = 0.10) compared to Norwegian and Swedish populations. Population differentiation was positively associated with geographical distance in both Iceland and Scandinavia, but the strength of this relationship varied between regions. Although topography and a larger distribution range may explain the higher differentiation between mountainous Norwegian relative to lowland populations in Sweden, these factors cannot explain the lower differentiation in Icelandic compared to Swedish populations. We propose that low genetic differentiation among Icelandic populations is not caused by differences in connectivity, but is rather due to large historical effective population sizes. Thus, rather than contemporary processes, historical factors such as survival of Icelandic lineages in northern refugia during the last glacial period may have contributed to the observed pattern.
Project description:Quaternary climatic fluctuations have had profound effects on the phylogeographic structure of many species. Classically, species were thought to have become isolated in peninsular refugia, but there is limited evidence that large, non-polar species survived outside traditional refugial areas. We examined the phylogeographic structure of the red fox (Vulpes vulpes), a species that shows high ecological adaptability in the western Palaearctic region. We compared mitochondrial DNA sequences (cytochrome b and control region) from 399 modern and 31 ancient individuals from across Europe. Our objective was to test whether red foxes colonised the British Isles from mainland Europe in the late Pleistocene, or whether there is evidence that they persisted in the region through the Last Glacial Maximum. We found red foxes to show a high degree of phylogeographic structuring across Europe and, consistent with palaeontological and ancient DNA evidence, confirmed via phylogenetic indicators that red foxes were persistent in areas outside peninsular refugia during the last ice age. Bayesian analyses and tests of neutrality indicated population expansion. We conclude that there is evidence that red foxes from the British Isles derived from central European populations that became isolated after the closure of the landbridge with Europe.