Where are the glacial refugia in Europe? Evidence from pteridophytes

Abstract

In this paper we demonstrate that, by investigating polyploid complexes in d.\p/enium, it is possible to locate the areas in Europe that are southern glacial rcfugia, and arc likely to have been so since the tjcginning of the Plcistoccnc during the consecutive cold and warm periods in Europe. Identification and consenation of thrsc specific areas that s e n e as safe havens for plants, and perhaps animals, is of paramount importance for the maintcnancc of European liiodiversity because hlan's activities arc resulting in an ever-increasing loss of natural habitats and putting diversity at risk. The genus A.\pl~nium in Europe comprises some 50 taxa: half of these are diploid while the other half are polyploids derived from thr diploids. All aspleniums in Europe are (small) rock ferns with high suhstratc specificity. Today, most of mainland Europe, Scandinavia and the British Isles has been colonized by polyploid dsplenium species, while the diploids that gavc rise to these polyploids are distributed around (and more or less confined to) the hfcditcrrancan Basin. In the tetraploids genetic variation is partitioned mostly between sites, whereas diploids show a high dcp-cc of genetic variation both within and between sites. The tctraploid taxa seem capable of single spore colonization via intragametophytic selling, but the diploid taxa appear to he predominantly outbreeding, For most diploids at least two gametophytes, produced by different spores, have to tic prcscnt to achieve fertilization and subsequent sporophyte formation for the successful colonization of a new site. This results in a slower rate of colonization. The formation of auto-and allopolyploid taxa from diploid communities appears to have been a recurrent and common fcaturc in Europe. Minority cytotypc exclusion is likely to prevent the establishment of tetraploids within the diploid communities, but spores from tetraploids can cstaldish populations outside the diploid communities. The differences between colonization abilities of tetraploid and ancestral diploid taxa, resulting from their differcnt hrccding systems, has prevented thc merging and mingling of their ranges and led to the establishment of contact/ hybrid zoncs. This has resulted in the restriction of diploid populations to ancient glacial rcfugia and the colonization of the rest of Europe by polyploids. Mapping the rurrrnt distribution of these diploid communities and comparing the genetic diversity within and between outbrccding diploid i-l.cp/zninm taxa allows us to dcfinc the area, age and historical biogeography of thcsc rrfugia and to assess thrir importance for present day genetic and species diversity in Europe. 0 lW9 'l'tir Liiiiiriiii Socirt! 111 1.11ii1i11ii

Evidence for a residual postglacial founder effect in a highly dispersive freshwater invertebrate

“…The demographic history of a region, which may be influenced by past events such as glaciation, will also impact current levels of genetic diversity. In both North America and Europe, multiple taxa including vertebrates, invertebrates, and plants have revealed relatively high levels of genetic variation in or near sites that were refugia during the last glacial period, compared to sites that were more recently colonized once the ice had retreated (e.g., Hewitt 1996;Bernatchez and Wilson 1998;Vogel et al 1999). These regional discrepancies have been attributed to the inability of some refugial genotypes to colonize new areas following glacial retreat, either because of limited dispersal or because they were unable to invade previously established populations.…”

“…When the ice retreated, these taxa dispersed north beyond mountain ranges such as the Alps and the Pyrenees. These expansions often involved a series of founder effects, the genetic signatures of which can still be seen today in terms of reduced levels of genetic diversity in northern Europe compared to southern Europe (e.g., Hewitt 1996Hewitt , 1999Vogel et al 1999).…”

“…This may be attributed to leading edge colonization, in which individuals from the northerly limits of the refugia are the first to colonize recently unglaciated regions, and later immigrants cannot easily invade these established populations. The majority of genetic lineages thereafter remain in the regions of glacial refugia because they are unable to invade the expanding northerly populations (Vogel et al 1999).…”

Radiation in <i>Bythinella</i> Moquin-Tandon, 1856 (Mollusca: Gastropoda: Rissooidea) in the Balkans

“…The Balkans once harboured one of the main European glacial refugia (HEWITT 1996, VOGEL et al 1999, PETIT et al 2003, SCHMITT 2007, FALNIOW-SKI et al 2009b). Hence, they provide an interesting area for a study of radiation.…”

Analyse floristique et phytogéographique d'une région de l'Atlas saharien constantinois, les gorges du Ghouffi (Algérie)

“…C'est le cas des gorges de l'Assif Oumarhouz dans l'AntiAtlas marocain qui abritent plusieurs végétaux reliques d'affinité macaronésienne (Benabid & Cuzin, 1997 ;Médail & Quézel, 1999). Les milieux rupestres méditerranéens représentent en effet des habitats refuges déterminants (Quézel, 1957 ;Vogel et al, 1999...). Les zones refuges péri-méditerranéennes jouent un rôle majeur dans la conservation de certaines plantes et populations reliques, car elles ont bien moins subi l'impact des fluctuations climatiques engendrées par les cycles glaciaires-interglaciaires de la fin du Tertiaire et du Pléistocène (Médail & Diadema, en révision).…”