VOGEL, JOHANNES1*, HARALD SCHNEIDER2,3, MARY GIBBY4, ISTVAN PINTER5, STEVE TREWICK6, MARY MORGAN-RICHARDS6, JOHN BARRETT7, STEPHEN RUSSELL1, SALLY HENDERSON1, and FRED RUMSEY1. 1Department of Botany, The Natural History Museum, SW7 5BD London, UK; 2Albrecht-von-Haller Institut of Plant Sciences, University of Goettingen, 37073 Goettingen, Germany; 3Department of Biology, Duke University, NC 27708, USA; 4Royal Botanic Garden Edinburgh, 20A Inverleith Row, Edinburgh EH3 5LR, Scotland; 5Department of Genetics, Eoetvoes Lorand University, Budapest, H-1088, Hungary; 6Department of Plant and Microbial Sciences, University of Canterbury, Christchurch, New Zealand; 7Department of Genetics, University of Cambridge, UK. - Polyploidy, phylogeography and Pleistocene refugia of the rockfern Asplenium ceterach: evidence from cpDNA and allozymes.
Phylogeographic methods have provided the opportunity to elucidate the
effects of large-scale historical events (such as Pleistocene climate
change) on the distribution and subdivision of biota and put in
context the role of reproductive biology in the genetic structuring of
species. A broad spectrum of organisms have provided grist to the
phylogeographic mill including animal and various plant groups, but as
yet there are few published studies of fern phylogeography. The
phylogeny of the subgenus Ceterach (Aspleniaceae) was resolved
by chloroplast DNA sequencing. Allozyme electrophoresis and cpDNA
sequencing was employed to study diversity, distribution and
prevailing breeding systems of the, mainly European, A.
ceterach polyploid complex, comprising diploid, tetraploid and
hexaploid taxa. We studied patterns of diversity within the known
populations of diploid A. ceterach in Greece, the Balkans,
Sicily and mainland Italy, located unreported diploid populations that
might be alternative progenitors of colonising tetraploids, determine
whether there have been multiple origins of polyploids, identified the
origins of hexaploids, and mapped phylogeographic structure within and
between ploidy levels with a view to further resolution of Pleistocene
refugia in Europe. DNA sequences were obtained from c. 450
Asplenium ceterach plants representing 180 populations from
throughout the range of the complex in Europe, plus outlying sites in
North Africa, the near East and Asia. We identified nine distinct
haplotypes from a 900 bp fragment of trnL-trnF gene. Patterns
of haplotype diversity in diploid communities point towards evidence
for the persistence of some populations in long term Mediterranean and
a northern Pannonian-Balkan refugia, while haplotype diversity
patterns in polyploid communities are either interpreted as the result
of a rapid postglacial expansion or point towards secondary,
Weichselian refugia in the western Mediterranean. Our cpDNA and ploidy
data indicate at least six independent origins of polyploids, four
among tetraploids and two amongst hexaploids.
Key words: Asplenium ceterach, chloroplast DNA, DNA sequence, multiple origins, Pleistocene, polyploidy, Pteridophyte