Evolution and Phylogeography of Arctic and Alpine Plants in Europe: Introduction

Abstract

of the Arctic and alpine floras of has intrigued botanists for many decades. After formation of the European mountain system and world-wide climatic cooling during Late Tertiary, the evolution and radiation of the modem European arctic and alpine floras began. Geographic influences from central Asia, plus ancient Arctic and European elements, can be documented in plant diversity that now resides in our modem mountain systems. It has been shown that alloand autopolyploidy have been important evolutionary mechanisms. It has been hypothesized that recent evolutionary events have been driven by recurrent cycles of Quaternary glaciations, leading to formation of new species plus diversification (and divergence) of evolutionary lineages. Molecular methods offer new possibilities for studying the evolution of Arctic and alpine plant diversity in Europe. In particular, it is now possible to test hypotheses more effectively that deal with refugia, re-migrations, and survival on nunataks deriving from Pleistocene glaciations. In September 2002 at the Sixth International Congress of Systematic and Evolutionary Biology (ICSEB-VI) in Patras, Greece, a symposium entitled Evolution and Phylogeography of Arctic and Alpine Plants in Europe and organized by Andreas Tribsch and Tod F. Stuessy, was sponsored by the International Association for Plant Taxonomy (IAPT). The aim of the symposium was to provide an overview of recent studies on the mountain floras of Europe, ranging from Arctic and subarctic regions to the southern mountains. Evolutionary patterns and inferred processes are explored that involve infraspecific phylogeographic diversification, evolution of alpine species, and radiation of genera. Five invited presentations, which are featured here, were complemented by three papers and several posters. The success of the symposium and the importance of the collective synthesis recommended that the main contributions be published together. This issue of Taxon features those five papers. Christian Brochmann and co-authors present an overview of several phylogeographical studies that tackle in the North Atlantic biota the challenging question: Glacial survival or tabula rasa? Phylogeographical evidence from several taxa distributed in the North Atlantic r gion suggest that it is not necessary to assume glacial survival on nunataks to explain extant patterns. Endemism and disjunct distributions correlate to a large degree. All endemic taxa (except one) are polyploid, suggesting recent, even postglacial, origin. The observed patterns are in strong contrast to those of more southern latitudes, where vicariance during the ice ages has lead to partly strong phylogeographical patterns, evolutionary divergence of lineages, and remarkable patterns of endemism also on the diploid level. The second paper by Hans Peter Comes and coauthors reviews phylogeographic data from several European mountain taxa, both within and between species, to provide insights on the origin and evolution of the European high mountain flora. Results are congruent with hypotheses of evolution of alpine species from lowland forms from Asia and the Mediterranean region in the late Tertiary and allopatric diversification during the Quaternary. Pablo Vargas in the third paper reviews phylogenetic data from several oro-mediterranean taxa and gives a preliminary synthesis with special emphasis on the Iberian peninsula. The data document that modes of speciation and colonization routes are different in all taxa. While some taxa diversified in the mountain ranges of the Iberian peninsula and immigrated to other parts of Europe, others immigrated to the Iberian mountains from the outside. In any case at least at the infraspecific level, diversifications are dated to the Quaternary ice ages. A comparison of patterns of endemism and phylogeographic patterns in the Alps with presumed Pleistocene refugia is central in the fourth paper by Andreas Tribsch and Peter Sch6nswetter. For the Eastern Alps available paleontological and paleoclimatological data suggest that in some regions cold-adapted plants survived the Pleistocene in situ, although large areas were glaciated. Potential glacial refugia are at the eastern and southern margin of the Alps, which remained widely unglaciated, but also within the ice shield on peripheral nunataks. Refugial areas are characterized by high levels