Numerical analysis of the floristic composition of localities including Hierochloë(Poaceae) species in Northern Europe

Lists were made of the vascular plant species associated with Hierochloë australis (5 localities), H. odorata ssp. odorata (79 localities), H. odorata ssp. baltica (20 localities), H. hirta ssp. hirta (17 localities), H. hirta ssp. arctica (53 localities) and H. alpina ssp. alpina (5 localities). The localities were classified by the TABORD computer program to produce phytosociological tables. An ordination of localities and of selected species was also made using the ORDINA program. Significant groups of species were distinguished by using Fisher's exact test of probability. All the H. australis localities were in mixed forests. In general, the natural habitats of H. odorata spp. odorata are fens and grasslands in the mountains and on the seashores of Scandinavia, those of H. odorata ssp. baltica are on brackish-water shores of the Baltic, those of H. hirta ssp. hirta on sandy or gravelly river banks and lake-shores, and those of H. hirta ssp. arctica are on fens and grasslands in the northern boreal forests. These latter four taxa occur, in addition, in various anthropogenic, or semi-natural, disturbed and/or unstable habitats. Their scattered occurrence in S Scandinavia and C Europe is probably more related to sporadic long-distance dispersal, than to their being glacial relicts. The natural habitats of H. alpina ssp. alpina are exposed mountain heaths. It is suggested that H. odorata ssp. odorata, and possibly H. alpina ssp. alpina, survived the last glaciation in refugia off the Norwegian coast, and that H. odorata ssp. baltica and H. hirta ssp. hirta may have arisen by polyploidy within Scandinavia during the Post-glacial period. H. hirta ssp. arctica probably immigrated into Scandinavia from the east during the Post-glacial and H. australis from the south. The results are considered in relation to the views previously expressed in the literature and the analytic techniques used are discussed. This work has been supported by grants from the University of Lund, for which I am duly grateful.     

Comparative phylogeography and population structure of European Betula species, with particular focus on B. pendula and B. pubescens

Aim  To compare the population genetic structures of the haplotype-sharing species Betula pendula and B. pubescens and to draw phylogeographic inferences using chloroplast DNA markers. In particular, we tested whether B. pendula and B. pubescens exhibited the same or different phylogeographic structures.
Location  Western Europe and Russia.
Methods  In this study we used both chloroplast DNA polymerase chain reaction-restriction fragment length polymorphism and microsatellites to genotype B. pendula , B. pubescens and, to a limited extent, B. nana , in 53 populations across Eurasia. A spatial amova ( samova ) was used to identify major clusters within each species.
Results  The low level of phylogeographic structure previously observed in B. pendula was confirmed, and the samova analysis retrieved only two major clusters. In contrast, seven clusters were observed in B. pubescens , although the overall level of population differentiation was similar to that of B. pendula .
Main conclusions  We detected a difference in the population genetic structure between the two species, despite extensive haplotype sharing. It is difficult to ascribe this finding to a single factor, but divergence in ecology between the two species may provide part of the explanation. For both species, the contribution of southern western populations to the recolonization after the Last Glacial Maximum seems to have been limited, and eastern and western European populations apparently had different histories.     

Phylogeography of the brown hare (Lepus europaeus) in Europe: a legacy of south‐eastern Mediterranean refugia?

Aim We analysed the population genetics of the brown hare (Lepus europaeus) in order to test the hypothesis that this species migrated into central Europe from a number of late glacial refugia, including some in Asia Minor. Location Thirty‐three localities in Greece, Bulgaria, Italy, Croatia, Serbia, Poland, Switzerland, Austria, France, Germany, the Netherlands, Spain, the United Kingdom, Turkey and Israel. Methods In total, 926 brown hares were analysed for mitochondrial DNA (mtDNA) variation by restriction fragment length polymorphism (RFLP) performed on polymerase chain reaction‐amplified products spanning cytochrome b (cyt b)/control region (CR), cytochrome oxidase I (COI) and 12S–16S rRNA. In addition, sequence analysis of the mtDNA CR‐I region was performed on 69 individuals, and the data were compared with 137 mtDNA CR‐I sequences retrieved from GenBank. Results The 112 haplotypes detected were partitioned into five phylogeographically well‐defined major haplogroups, namely the ‘south‐eastern European type haplogroup’ (SEEh), ‘Anatolian/Middle Eastern type haplogroup’ (AMh), ‘European type haplogroup, subgroup A’ (EUh‐A), ‘European type haplogroup, subgroup B’ (EUh‐B) and ‘Intermediate haplogroup’ (INTERh). Sequence data retrieved from GenBank were consistent with the haplogroups determined in this study. In Bulgaria and north‐eastern Greece numerous haplotypes of all five haplogroups were present, forming a large overlap zone. Main conclusions The mtDNA results allow us to infer post‐glacial colonization of large parts of Europe from a late glacial/early Holocene source population in the central or south‐central Balkans. The presence of Anatolian/Middle Eastern haplotypes in the large overlap zone in Bulgaria and north‐eastern Greece reveals gene flow from Anatolia to Europe across the late Pleistocene Bosporus land‐bridge. Although various restocking operations could be partly responsible for the presence of unexpected haplotypes in certain areas, we nevertheless trace a strong phylogeographic signal throughout all regions under study. Throughout Europe, mtDNA results indicate that brown hares are not separated into discernable phyletic groups.     

Glacial in situ survival in the Western Alps and polytopic autopolyploidy in Biscutella laevigata L. (Brassicaceae)

Past climatic changes and especially the ice ages have had a great impact on both the distribution and the genetic composition of plant populations, but whether they promoted speciation is still controversial. The autopolyploid complex Biscutella laevigata is a classical example of polyploidy linked to glaciations and is an interesting model to explore migration and speciation driven by climate changes in a complex alpine landscape. Diploid taxa survived the last glacial maximum in several never-glaciated areas and autotetraploids are clearly dominant in the central parts of the Alps; however, previous range-wide studies failed to identify their diploid ancestor(s). This study highlights the phylogeographical relationships of maternal lineages in the Western Alps and investigates the polyploidy process using plastid DNA sequences (trnS-trnG and trnK-intron) combined with plastid DNA length polymorphism markers, which were transferable among Brassicaceae species. Twenty-one distinct plastid DNA haplotypes were distinguished in 67 populations densely sampled in the Western Alps and main lineages were identified by a median-joining network. The external Alps harboured high levels of genetic diversity, while the Central Alps contained only a subset of haplotypes due to postglacial recolonization. Several haplotypes were restricted to local peripheral refugia and evidence of in situ survival in central nunataks was detected by the presence of highly differentiated haplotypes swamped by frequent ones. As hierarchical genetic structure pointed to an independent evolution of the species in different biogeographical districts, and since tetraploids displayed haplotypes belonging to different lineages restricted to either the northern or the southern parts of the Alpine chain, polytopic autopolyploidy was also apparent in the Western Alps.     

Adaptive and Neutral Genetic Variation and Colonization History of Atlantic Salmon, Salmo salar

Synopsis I combined neutral microsatellite markers with the major histocompatibility complex (MHC) class IIB to study genetic differentiation and colonization history in Atlantic salmon, Salmo salar, in the Baltic Sea and in the north-eastern Atlantic. Baltic salmon populations have lower levels of microsatellite genetic variation, in terms of heterozygosity and allelic richness than Atlantic populations, confirming earlier findings with other genetic markers, suggesting that the Baltic Sea populations have been exposed to genetic bottlenecks, most likely at a founding event. On the other hand, the level of MHC variation was similar in the Baltic and in the north-eastern Atlantic, indicating that positive balancing selection has increased the level of MHC-variation. Both microsatellite and MHC class IIB genetic variation give strong support to the hypothesis that the Baltic salmon are of a biphyletic origin, the southern population in this study is strongly differentiated from both the northern Baltic salmon populations and from the north-eastern Atlantic populations. Salmon may have colonized the northern Baltic Sea either from the south, via the so called “N?rke strait” or from the north, via a proposed historical connection between the White Sea and the northern Baltic. At microsatellites, no significant isolation-by distance was found at either colonization route. At the MHC, populations were significantly isolated by distance when assuming that colonization occurred via the “N?rke strait”.     

The influence of contemporary and historic landscape features on the genetic structure of the sand dune endemic,Cirsium pitcheri (Asteraceae)

Narrow endemics are at risk from climate change because of their restricted habitat preferences, lower colonization ability and dispersal distances. Landscape genetics combines new tools and analyses that allow us to test how both past and present landscape features have facilitated or hindered previous range expansion and local migration patterns, and thereby identifying potential limitations to future range shifts. We have compared current and historic habitat corridors in Cirsium pitcheri, an endemic of the linear dune ecosystem of the Great Lakes, to determine the relative contributions of contemporary migration and post-glacial range expansion on genetic structure. We used seven microsatellite loci to characterize the genetic structure for 24 populations of Cirsium pitcheri, spanning the center to periphery of the range. We tested genetic distance against different measures of geographic distance and landscape permeability, based on contemporary and historic landscape features. We found moderate genetic structure (Fst=0.14), and a north–south pattern to the distribution of genetic diversity and inbreeding, with northern populations having the highest diversity and lowest levels of inbreeding. High allelic diversity, small average pairwise distances and mixed genetic clusters identified in Structure suggest that populations in the center of the range represent the point of entry to the Lake Michigan and a refugium of diversity for this species. A strong association between genetic distances and lake-level changes suggests that historic lake fluctuations best explain the broad geographic patterns, and sandy habitat best explains local patterns of movement.     

Hidden phylogeographic complexity in the Sierra Madre Oriental: the case of the Mexican tulip poppy Hunnemannia fumariifolia (Papaveraceae)

Aim A phylogeographic study of the endemic Mexican tulip poppy Hunnemannia fumariifolia (Papaveraceae) was conducted to determine: (1) the historical processes that influenced its geographical pattern of genetic variation; (2) whether isolation by distance was one of the main factors that caused genetic divergence in populations of this species; and (3) whether genetic flow still exists between populations from northern arid zones (Chihuahuan Desert and Sierra Madre Oriental) and those from southern arid zones (Tehuacán‐Cuicatlán Valley) – populations that are separated by the Transvolcanic Belt. Location Xerophytic vegetation in Mexico. Methods Chloroplast DNA (cpDNA) sequences of three regions, trnH‐psbA, rpl32‐trnL(UAG) and ndhF‐rpl32, were obtained for 85 individuals from 17 populations sampled in the field, covering the entire range of H. fumariifolia. The evolutionary history of these populations was investigated using a nested clade phylogeographic analysis and also by conducting various population genetic analyses. Results In total, 17 haplotypes were detected, 14 of which were found in the Sierra Madre Oriental. Differentiation among populations based on cpDNA variation (G_ST = 0.787, SE 0.0614) indicated population structure in H. fumariifolia, corroborated by a fixation index (F_ST) of 0.907. Results from analysis of molecular variance found that most of the total variation (90.71%, P < 0.001) was explained by differences among populations. Three regions were determined based on geological correspondence – the Chihuahuan Desert, Sierra Madre Oriental and Tehuacán‐Cuicatlán Valley – and the variation between them was significant (43.39%, P < 0.001). Results of a Mantel test showed a significant correlation between genetic and geographic distances (r = 0.511; P = 0.0001), suggesting a pattern of isolation by distance, which was corroborated by nested clade phylogeographic analysis. Mismatch distribution analysis indicated a sudden demographic expansion. Main conclusions Our study found that isolation by distance influenced genetic divergence in populations of H. fumariifolia. The finding that allopatric fragmentation influenced genetic divergence in populations in the Sierra Madre Oriental may be a reflection of the complex geology of the area. Our results suggest that the areas located in the north of the Sierra Madre Oriental acted as post‐glacial refugia for some populations.     

The fourth paradigm pattern of post-glacial range expansion of European terrestrial species: the phylogeography of the Marbled White butterfly (Satyrinae, Lepidoptera)

Aim Three paradigm patterns of post‐glacial dispersal are known for terrestrial species in Europe. However, the possibility of a fourth arises with the Italian and the Balkan lineages expanding to central Europe and the Iberian one being trapped by the Pyrenees. We test this hypothesis by analysing the molecular biogeography of the Marbled White butterfly. Location Twelve populations distributed over a major part of the European range of Melanargia galathea and M. lachesis. Methods We studied 18 allozyme loci of 403 individuals from 12 populations. Butterflies were sampled in the field, frozen in liquid nitrogen and stored under these conditions until analysis. We used cellulose acetate plates for allozyme electrophoresis. Results We detected three major genetic lineages within the M. galathea/lachesis complex. The M. lachesis sample from the southern Pyrenees was strongly genetically differentiated from M. galathea (F_CT: 0.312). Melanargia galathea splits into two major genetic lineages (F_CT: 0.115), which both were found in post‐glacially invaded regions. The further differentiation within these lineages was comparably low (F_SC: 0.028). The genetic diversity within populations was high compared with other butterfly species. Main conclusions Our findings support the existence of a fourth pattern with only the Iberian lineage not contributing considerably to the post‐glacial colonization of central Europe. Preliminary studies in other butterfly species of dry grasslands support the importance of this pattern possibly representing a fourth paradigm. The high genetic diversity within populations might be one reason for the recently observed expansions at the northern distribution limits.     

Sex chromosome variability outlines the pathway to the chromosomal evolution in Microtus thomasi (Rodentia, Arvicolinae)

The underground vole Microtus thomasi , a Balkan endemic, displays remarkable variability in sex chromosome size and morphology. In the present study, we demonstrate this variability in two of its chromosomal races with 2 n  = 44 (i.e. 'thomasi' and 'atticus') with the use of C-banding on a sample of 189 individuals from 50 localities of Greece. In 'thomasi', five different, acrocentric X chromosome variants (X₀–X₄) are described, which differ significantly in size, due to heterochromatin addition. Also, three Y chromosome variants are described (Y₀–Y₂), ranging in size from very small (Y₀) to large (Y₂). The 'atticus' race displays three subtelocentric variants of the X chromosome (X_st0–X_st2), which differ in arm length ratio and heterochromatin content. In Peloponnesus, males of this race exhibit Y₀ and Y₁, whereas, in Attiki (south-east Sterea Ellada), males carry the small metacentric, Y_m. Overall, there is a trend towards sex chromosome size increase in a south to north direction. We propose that the last glaciation must have restricted M. thomasi to a refugium in southern Peloponnesus. During post-glacial colonization, limited northward expansion of its distribution area must have been accompanied by consecutive heterochromatin addition, which is proven today by comparatively larger sex chromosomes in the northern populations of 'thomasi' and 'atticus' in Greece than in their southern populations.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 96 , 685–695.