Peter Schönswetter

Patterns of endemism and comparative phylogeography confirm palaeo- environmental evidence for Pleistocene refugia in the Eastern Alps

Climatic fluctuations during Quaternary glaciations had a significant influence on the distribution of taxa and on their intraspecific genetic structure. In this paper, we test hypotheses on Pleistocene refugia for mountain plants in the eastern part of the European Alps derived from palaeoenvironmental and geological results, with new data on distributional patterns of 288 vascular plant endemics and molecular phylogeographies of selected species. High numbers of endemics are found in calcareous regions at the southern and the eastern border of the Eastern Alps, which remained unglaciated during the Pleistocene. The distribution of local endemic taxa in general, and of silicicolous taxa in particular, shows a clear relationship with hypothetical glacial refugia in the southern, southeastern, easternmost, and northeastern Alps. Molecular phylogeographic data from several silicicolous alpine species ( Androsace alpina , Androsace wulfeniana , Eritrichium nanum , Phyteuma globulariifolium , Ranunculus glacialis , Saponaria pumila ) are not completely congruent. However, all genetically defined population groups are in congruence with hypothetical refugia. In general, results from distributions of endemic taxa and data from intraspecific phylogeography are compatible with previously hypothesized refugia suggesting that refugial situations have shaped the current patterns. The combination of patterns of endemism with molecular phylogeographic data provides an efficacious approach to reveal glacial refugia in vascular plants.

Vicariance and dispersal in the alpine perennial Bupleurum stellatum L. (Apiaceae)

Using Amplified Fragment Length Polymorphism (AFLP), we explored the intraspecific phylogeography of the alpine vascular plant Bupleurum stellatum (Apiaceae), disjunctly distributed in the Alps and Corsica. Within the Alps, the species’ distribution area is also not contiguous, spatially isolated groups of populations occuring in the Dolomites (Italy) and the Montafon (Austria). A main goal of our study was to explore the degree of differentiation of the isolated populations in Corsica, the Dolomites and the Montafon from the populations in the main distributional area and to test for hypotheses of vicariance or dispersal. We also sought a better general knowledge of glacial refugia of low alpine silicicolous plants. Phenetic as well as cladistic analyses of the AFLP multilocus phenotypes reveal a substantial north-south split through the contiguous distribution area of B. stellatum in the Alps. The resulting phylogeographic groups can be related to glacial refugia in peripheral areas of the Alps that were recognised in previous studies. The disjunct populations in Corsica, the Dolomites and the Montafon, however, are less strongly differentiated. For example, the Corsican population clustered with high bootstrap support with populations from the Eastern Alps, suggesting immigration to Corsica from that region. Our study shows that deep phylogeographic splits resulting from old vicariance events can be concealed by presently contiguous distribution areas. In contrast, disjunctions, if they are due to dispersal events, need not be accompanied by genetic divergence.

Several Pleistocene refugia detected in the high alpine plant Phyteuma globulariifolium Sternb. & Hoppe (Campanulaceae) in the European Alps

Phyteuma globulariifolium is a high alpine plant species growing in the European Alps and the Pyrenees. In order to elucidate its glacial history, 325 individuals from 69 populations were analysed using the amplified fragment length polymorphism (AFLP) technique. A strongly hierarchical phylogeographical pattern was detected: Two major east–west vicariant groups can be separated along a gap in the distributional area. A further subdivision into at least four populational groups is in congruence with presumed peripheral glacial refugia. There is no indication for survival on unglaciated mountain tops (nunataks) in the interior of the Pleistocene ice shield covering the Alps. Our results favour glacial survival in peripheral, unglaciated or not fully glaciated areas. Populations of P. globulariifolium in the Pyrenees are the result of relatively recent long‐distance dispersal. Within the Alps, there is strong differentiation among groups of populations, whereas within them the differentiation is weak. This suggests high levels of gene‐flow over short to middle distances.

Out of the Alps: colonization of Northern Europe by East Alpine populations of the Glacier Buttercup Ranunculus glacialis L. (Ranunculaceae)

Ranunculus glacialis ssp. glacialis is an arctic‐alpine plant growing in central and southern European and Scandinavian mountain ranges and the European Arctic. In order to elucidate the taxons migration history, we applied amplified fragment length polymorphism (AFLP) to populations from the Pyrenees, Tatra mountains and Northern Europe and included data from a previous study on Alpine accessions. Populations from the Alps and the Tatra mountains were genetically highly divergent and harboured many private AFLP fragments, indicating old vicariance. Whereas nearly all Alpine populations of R. glacialis were genetically highly variable, the Tatrean population showed only little variation. Our data suggest that the Pyrenees were colonized more recently than the separation of the Tatra from the Alps. Populations in Northern Europe, by contrast, were similar to those of the Eastern Alps but showed only little genetic variation. They harboured no private AFLP fragments and only a subset of East Alpine ones, and they exhibited no phylogeographical structure. It is very likely therefore that R. glacialis colonized Northern Europe in postglacial times from source populations in the Eastern Alps.

Saponaria pumila (caryophyllaceae) and the ice age in the European alps.

The polymerase chain reaction (PCR)-based amplified fragment length polymorphism (AFLP) technique was applied to elucidate the glacial history of the alpine cushion plant Saponaria pumila in the European Alps. Special emphasis was given to a dense sampling of populations. Our data support a survival of S. pumila during the last ice age in at least three refugia, which are characterized by unique marker sets. Patterns of genetic diversity and divergence can be explained by survival in peripheral refugia and additional in situ survival within the ice sheet on peripheral nunataks. A nunatak survival in interior parts of the Alps needs not be postulated to explain our results. The level of genetic diversity is dramatically different between populations (Shannons diversity index: 0.87-19.86). Some peripheral populations are characterized by a high number of rare fragments indicating long isolation, but not necessarily by a high level of genetic diversity. Parts of the present distributional area were recolonized via recent long-distance dispersal, leading to severely bottlenecked populations lacking private or rare fragments. The combination of our data with palaeogeological and palaeoclimatological evidence allows us to confine Pleistocene refugia to certain regions and to draw a detailed scenario of the glacial and postglacial history of S. pumila.

Complex distribution patterns of di-, tetra-, and hexaploid cytotypes in the European high mountain plant Senecio carniolicus (Asteraceae).

DNA ploidy levels were estimated using DAPI-flow cytometry of silica-dried specimens of the European mountain plant Senecio carniolicus (Asteraceae), covering its entire distribution area in the Eastern Alps (77 populations, 380 individuals) and the Carpathians (five populations, 22 individuals). A complex pattern of ploidy level variation (2x, 4x, 5x, 6x, and 7x cytotypes) was found in this species, which has been considered uniformly hexaploid. Hexaploids predominated in the Eastern Alps and was the only cytotype found in the Carpathians, while odd ploidy levels (5x, 7x) constituted a small fraction of the samples (<1.3%). Tetraploids occurred in two disjunct areas, which correspond with putative Pleistocene refugia for silicicolous alpine plants. Diploids occurred in large portions of the Alps but were absent from areas most extensively glaciated in the past. Intrapopulational cytotype mixture was detected in 22 populations-the majority involving diploids and hexaploids-with intermediate ploidy levels mostly lacking, suggesting limited gene flow and the evolution of reproductive isolation. Significant and reproducible intracytotype variation in nuclear DNA content was observed. Higher genome size in western diploids might be due to ancient introgression with the closely related S. incanus or to different evolutionary pathways in the geographically separated diploids.

Genetic diversity in widespread species is not congruent with species richness in alpine plant communities

The Convention on Biological Diversity (CBD) aims at the conservation of all three levels of biodiversity, that is, ecosystems, species and genes. Genetic diversity represents evolutionary potential and is important for ecosystem functioning. Unfortunately, genetic diversity in natural populations is hardly considered in conservation strategies because it is difficult to measure and has been hypothesised to co-vary with species richness. This means that species richness is taken as a surrogate of genetic diversity in conservation planning, though their relationship has not been properly evaluated. We tested whether the genetic and species levels of biodiversity co-vary, using a large-scale and multi-species approach. We chose the high-mountain flora of the Alps and the Carpathians as study systems and demonstrate that species richness and genetic diversity are not correlated. Species richness thus cannot act as a surrogate for genetic diversity. Our results have important consequences for implementing the CBD when designing conservation strategies.

Range-wide phylogeography of Juniperus thurifera L., a presumptive keystone species of western Mediterranean vegetation during cold stages of the Pleistocene.

We investigate the range-wide population structure and phylogeography of thuriferous juniper (Juniperus thurifera L.), a species with a highly disjunct distribution in the western Mediterranean. We genotyped a total of 327 individuals from 20 populations using amplified fragment length polymorphisms (AFLP). Different analyses such as principal co-ordinate analysis (PCoA), nonmetric multidimensional scaling of F(ST) distances among populations, unweighted pair group method with arithmetic mean (UPGMA), and Bayesian clustering revealed that the Strait of Gibraltar acted as an efficient barrier against gene flow between the Moroccan and European populations for a very long time, and consequently support that the Moroccan populations should be recognised as a distinct subspecies (J. thurifera L. subsp. africana (Maire) Romo and Boratyńsky). The Algerian population was genetically more closely related to the European than to the Moroccan ones, probably due to dispersal events from Europe to Algeria. With respect to the mainland European populations, our data are not conclusive to reject any of the two following hypotheses: (1) the Iberian Peninsula was subdivided into different gene pools, and was the source for the colonisation of the Pyrenees and the Alps; and (2) the pattern we see today is partly the result of immigration into the Iberian Peninsula, e.g. from the Alps. Finally, the Corsican population was closely related genetically to two northern Iberian populations most probably due to relatively recent long-distance dispersal.

Historical divergence vs. contemporary gene flow: evolutionary history of the calcicole Ranunculus alpestris group (Ranunculaceae) in the European Alps and the Carpathians

Although many species have similar total distributional ranges, they might be restricted to very different habitats and might have different phylogeographical histories. In the European Alps, our excellent knowledge of the evolutionary history of silicate‐dwelling (silicicole) plants is contrasted by a virtual lack of data from limestone‐dwelling (calcicole) plants. These two categories exhibit fundamentally different distribution patterns within the Alps and are expected to differ strongly with respect to their glacial history. The calcicole Ranunculus alpestris group comprises three diploid species of alpine habitats. Ranunculus alpestris s. str. is distributed over the southern European mountain system, while R. bilobus and R. traunfellneri are southern Alpine narrow endemics. To explore their phylogenetic relationships and phylogeographical history, we investigated the correlation between information given by nuclear and chloroplast DNA data. Analyses of amplified fragment length polymorphism fingerprints and matK sequences gave incongruent results, indicative for reticulate evolution. Our data highlight historical episodes of range fragmentation and expansion, occasional long‐distance dispersal and on‐going gene flow as important processes shaping the genetic structure of the group. Genetic divergence, expressed as a rarity index (‘frequency‐down‐weighted marker values’) seems a better indicator of historical processes than patterns of genetic diversity, which rather mirror contemporary processes as connectivity of populations and population sizes. Three phylogeographical subgroups have been found within the R. alpestris group, neither following taxonomy nor geography. Genetic heterogeneity in the Southern Alps contrasts with Northern Alpine uniformity. The Carpathians have been stepwise‐colonised from the Eastern Alpine lineage, resulting in a marked diversity loss in the Southern Carpathians. The main divergence within the group, separating the ancestor of the two endemic species from R. alpestris s. str., predates the Quaternary. Therefore, range shifts produced by palaeoclimatic oscillations seem to have acted on the genetic structure of R. alpestris group on a more regional level, e.g. triggering an allopatric separation of R. traunfellneri from R. bilobus.

Comparative phylogeography of the Veronica alpina complex in Europe and North America

The Veronica alpina complex comprises eight species of alpine habitats over a wide range of mountain systems in the Northern Hemisphere. The occurrence of sympatric species in the European and North American mountain systems allowed us not only to investigate the effect of the ice ages on intraspecific phylogeographical patterns and genetic diversity in different continents of the Northern Hemisphere, but also to compare these patterns in closely related species. Plastid DNA trnL‐F sequences and AFLP (amplified fragment length polymorphism) fingerprints were used to infer the phylogenetic history of the group and phylogeographical patterns within species. Hybrid origin of tetraploid eastern North American V. wormskjoldii from western North American V. nutans (= V. wormskjoldii s.l.) and Eurasian V. alpina is suggested. A number of phylogeographical groups have been found both in V. alpina from Europe and in V. nutans from western North America. Phylogeographical substructuring in the Alps is inferred for V. alpina but not for V. bellidioides, which is moreover characterized by an overall very low genetic diversity. Western North American V. cusickii is much more genetically diverse than its sympatric relative, V. nutans, an effect that is likely due to differences in the breeding system. Populations of V. nutans are differentiated into three groups, those from the Cascades and from the southern and the northern Rocky Mountains. Genetic diversity seems to be higher in the North American V. nutans than in the morphologically and ecologically similar European V. alpina. A possible scenario to explain this pattern is suggested.