Species persistence in northerly glacial refugia of Europe: a matter of chance or biogeographical traits?

Aim The southern European peninsulas (Iberian, Italian and Balkan) are considered to have been refugia for many European species of plants and animals during the climatic extremes of the Pleistocene ice ages. A number of recent studies (fossil and genetic), however, have provided evidence for full‐glacial survival of some species beyond these peninsulas. Here we explore the biogeographical traits of these species, and ask whether they possessed certain characteristics that enabled them to persist in more northerly refugia. Location Europe. Methods Fossil and genetic evidence for refugial localities of species that survived in Europe during the last full‐glacial was obtained from the literature (totalling 90 species: 34 woody plants and 56 vertebrates). Forty‐seven of these species (23 woody plants and 24 vertebrates) had fossil evidence, whereas the remaining 43 species (11 woody plants and 32 vertebrates) had only genetic evidence. All species were scored according to their present geographical distribution, habitat preference and life‐history traits. The species were classified on the basis of these traits using hierarchical cluster analysis. Analysis of similarities was used to examine differences in vertebrate and woody plant species groups that survived only in southerly refugia and those that also persisted in more northerly locations. Non‐metric multi‐dimensional scaling was used to examine patterns observed between and within groups. Results Results from our analysis of species with fossil and genetic evidence for survival in refugia reveal that species that survived only in southerly refugia were large‐seeded trees or thermophilous vertebrates. In contrast, species that had a full‐glacial distribution, including more northerly locations, were wind‐dispersed, habitat‐generalist trees with the ability to reproduce vegetatively, and habitat‐generalist mammals with present‐day northerly distributions. Main conclusions Analysis of the geographical distribution, habitat preference and life‐history traits of the species studied suggests that underlying biogeographical traits may have determined their response to Pleistocene glaciation. The traits most commonly found in present populations with a northerly distribution in Europe enabled the same species to exist much farther north than the southern European peninsulas during the full‐glacial. It is possible that many of these species are now in restricted populations, within the ‘warm‐stage’ refugia of the current interglacial. The northerly full‐glacial survival of a number of woody plants and vertebrate species has significant implications for understanding migration rates of these species in response to climate change. It also has important implications for understanding current patterns of genetic diversity of European species. We suggest that both fossil and genetic evidence should be used to identify and prioritize for conservation of refugial localities in southern and northern Europe.     

Speciation in Mediterranean refugia and post‐glacial expansion of Zerynthia polyxena (Lepidoptera,Papilionidae)

Migration of populations to and from glacial refugia is responsible for various cases of speciation and subspeciation in Europe. The pattern of distribution and the degree of diversification between lineages originated by isolation in different glacial refugia usually depends on ecological traits, especially to their dispersal ability. Zerynthia polyxena is a philopatric species, scattered in small populations and rarely colonizing mountain areas. These characteristics probably caused repeated isolation during the Quaternary and may have favoured diversification. Actually two studies, based on both morphological and genetic data, suggest the existence of two highly distinct lineages in Europe having in Northern Italy their contact zone. In this study, I applied geometric morphometrics to male genitalia and demonstrated that (i) two morphotypes exist in Europe approximately facing on the two sides of the Po River; (ii) the two lineages probably survived glaciations in Italy and the Balkan Peninsula, respectively; then the Balkans lineage expanded to Central and Eastern Europe; (iii) no hybrid populations seem to exist in the contact area and, in one locality at least, the two lineages live in sympatry without any evidence of intermediates. These results suggest that (i) two sister species of Zerynthia exist in Europe. Accordingly, Papilio cassandra Geyer, 1828 is reinstated, as Zerynthia cassandra stat. rev., as the species to which the Zerynthia from Italy South of the Po River belong. Male genitalia differences with Zerynthia polyxena are described.     

Glacial vicariance in the Pacific Northwest: evidence from a lodgepole pine mitochondrial DNA minisatellite for multiple genetically distinct and widely separated refugia

The Canadian side of the Pacific Northwest was almost entirely covered by ice during the last glacial maximum, which has induced vicariance and genetic population structure for several plant and animal taxa. Lodgepole pine ( Pinus contorta Dougl. ex. Loud.) has a wide latitudinal and longitudinal distribution in the Pacific Northwest. Our main objective was to identify relictual signatures of glacial vicariance in the population structure of the species and search for evidence of distinct glacial refugia in the Pacific Northwest. A maternally inherited mitochondrial DNA minisatellite-like marker was used to decipher haplotype diversity in 91 populations of lodgepole pine located across the natural range. Overall population differentiation was sizeable ( G _ST = 0.365 and R _ST = 0.568). Four relatively homogeneous groups of populations, possibly representative of as many genetically distinct glacial populations, were identified for the two main subspecies, ssp. latifolia and ssp. contorta . For ssp. contorta , one glacial lineage is suggested to have been located at high latitudes and possibly off the coast of mainland British Columbia (BC), while the other is considered to have been located south of the ice sheet along the Pacific coast. For ssp. latifolia , two genetically distinct glacial populations probably occurred south of the ice sheet: in the area bounded by the Cascades and Rocky Mountains ranges, and on the eastern side of the Rockies. A possible fifth refugium located in the Yukon may have also been present for ssp. latifolia . Zones of contact between these ancestral lineages were also apparent in interior and northern BC. These results indicate the role of the Queen Charlotte Islands and the Alexander Archipelago as a refugial zone for some Pacific Northwest species and the vicariant role played by the Cascades and the American Rocky Mountains during glaciation.     

Invasion success of alien plants: do habitat affinities in the native distribution range matter?

Aim To assess how habitat affinities in the native distribution range influence the invasion success of 282 central European neophytes (alien plants introduced after ad 1500). Location Czech Republic. Methods Classification trees were used to determine which native habitats donate the most alien species, the correspondence between habitats occupied by species in their native and invaded distribution ranges, and invasion success of species originating from different habitats. Results The species most likely to naturalize in Central Europe are those associated with thermophile woodland fringes in their native range (81%), cultivated areas of gardens and parks (75%) and broad‐leaved deciduous woodlands (72%). The largest proportions of invasive species recruit from those that occur on riverine terraces and eroded slopes, or grow in both deciduous woodland and riverine scrub. When the relative role of habitats in the native range is assessed as a determinant of the probability that a species will become invasive in concert with other factors (the species’ residence time, life history, region of origin), the direct effect of habitat is negligible. However, the effect of native habitats on patterns of invasions observed in central Europe is manifested by large differences in the numbers of species they supply to the invaded region. More than 50 neophytes were recruited from each of the following habitats: dry grasslands, ruderal habitats, deciduous woodland, inland cliffs, rock pavements and outcrops, and tall‐herb fringes and meadows. Main conclusions Casual species recruit from a wider range of habitats in their native range than they occupy in the invaded range; naturalized but not invasive species inhabit a comparable spectrum of habitats in both ranges, and successful invaders occupy a wider range of habitats in the invaded than in the native range. This supports the idea that the invasive phase of the process is associated with changes in biological features that allow for extension of the spectrum of habitats invaded.