Journal Article

Phylogeographic patterns, genetic affinities and morphological differentiation between <i>Epipactis helleborine</i> and related lineages in a Mediterranean glacial refugium

Valentina Tranchida-Lombardo, Donata Cafasso, Antonia Cristaudo and Salvatore Cozzolino

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 107, issue 3, pages 427-436
Published in print March 2011 | ISSN: 0305-7364
Published online December 2010 | e-ISSN: 1095-8290 | DOI: http://dx.doi.org/10.1093/aob/mcq256
Phylogeographic patterns, genetic affinities and morphological differentiation between Epipactis helleborine and related lineages in a Mediterranean glacial refugium

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  • Ecology and Conservation
  • Evolutionary Biology
  • Plant Sciences and Forestry

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Background and Aims

In the Mediterranean basin, the Italian peninsula has been suggested to be one of the most important glacial refugia for temperate tree species. The orchid genus Epipactis is widely represented in the Italian peninsula by widespread species and several endemic, localized taxa, including selfing and outcrossing taxa. Here the phylogenetic and phylogeographic relationships in a group of closely related taxa in Epipactis are investigated with the aim of understanding the role of this refugial area for cladogenesis and speciation in herbaceous species, such as terrestrial orchids.

Methods

Ribosomal DNA (rDNA) was employed to assess phylogenetic relationships, and plastid sequence variation in the rbcLaccD spacer was used to reveal phylogeographic patterns among plastid haplotypes using a parsimony network.

Key Results

Low genetic variation and shared ribotypes were detected in rDNA, whereas high levels of sequence variation and a strong phylogeographic structure were found in the examined plastid region. The parsimony plastid haplotype network identified two main haplotype groups, one including E. atrorubens/microphylla/muelleri/leptochila and the other including all accessions of E. helleborine and several localized and endemic taxa, with a combination of widespread and rare haplotypes detected across the Italian peninsula. A greater genetic divergence separated the Italian and other European accessions of E. helleborine.

Conclusions

Phylogenetic and phylogeographic patterns support a working hypothesis in which the Italian peninsula has only recently been colonized by Epipactis, probably during the most recent phase of the Quaternary age and, nevertheless, it acted as a remarkable centre of diversification for this orchid lineage. Changes in pollination strategy and recurrent shifts in mating system (from allogamy to autogamy) could have represented the mechanism promoting this rapid diversification and the observed high taxonomic complexity detected in the E. helleborine species complex.

Keywords: Epipactis; chloroplast DNA; genetic variation; plastid haplotype network; mating systems; orchids; plastid spacer; ribosomal spacer

Journal Article.  7717 words.  Illustrated.

Subjects: Ecology and Conservation ; Evolutionary Biology ; Plant Sciences and Forestry

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