Schneider, Harald , Navarro Gomez, Adriana , Pedersen, Niklas , Fletcher, Sally , Russell, Stephen J. , Grundmann, Michael , Ansell, Stephen , Vogel, Johannes C. .
Inferring the evolution of temperate asplenioid ferns.
The vast majority of extant ferns grow in tropical climates although ferns contribute considerable to the temperate plant diversity. The distinguished gradient from tropical to temperate fern diversity is congruent to the general latitudinal gradient of plant biodiversity. The asplenioid ferns are in particular suited to study this aspect of fern diversity/ evolution with three out of eight major lineages having a considerable element of their species occurring in northern temperate climates. One of these mainly to nearly exclusively temperate clades, the Pleurosorus clade, has an isolated position in the aspleniod phylogeny and compromise a remarkable limited amount of extant species in comparison to the next closely related clades which in turn show a mainly tropical distribution range. The Pleurosorus clade has several unique features attracting attention. Its biogeographic distribution is shaped by the contrast of highly disjunct distribution pattern of diploid species versus the large distribution ranges of polyploidy taxa. The differentiation of substrate specificity is a remarkable trait in these rock ferns with several species pairs showing a switch from acidic rock to limestone. Our inference of the relationships using DNA sequences of up to five chloroplast genomic markers retrieved a robust phylogeny of the Pleurosorus clade comprising three subclade, the A. adiantum-nigrum clade, A. hispanicum clade, A. ruta-muraria clade. The extant diversity and distribution of this clade was likely shaped by extinctions caused by late Cenozoic global cooling. The survival in isolated refugia resulted in the establishment of particular traits, e.g. substrate specificity. Polyploidy appears to be a major factor in the post-glaciations re-colonization of temperate habitats because diploid taxa show much more limited distribution ranges. In conclusion, our studies underlines the importance of extinction for the extant fern diversity and the superiority of polyploids during the re-colonization of temperate habitats.
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1 - Natural History Museum, Cromwell Road, London, SW7 5BD, UK
2 - Natural History Museum, Botany, Cromwell Road, London, SW7 5BD, united kingdom
3 - Natural History Museum, Botany, London, SW7 5BD, UK
4 - Natural History Museum, Department of Botany, Cromwell Road, London, SW7 5BD, England
evolution of biodiversity
Presentation Type: Oral Paper:Papers for Sections
Date: Monday, July 28th, 2008
Time: 3:45 PM