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Phylogeography and genetic structure of the orchid Himantoglossum hircinum (L.) Spreng. across its European central–marginal gradient

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Abstract:

Abstract Aim 

This study aims to link demographic traits and post-glacial recolonization processes with genetic traits in Himantoglossum hircinum (L.) Spreng (Orchidaceae), and to test the implications of the central–marginal concept (CMC) in Europe. Location 

Twenty sites covering the entire European distribution range of this species. Methods 

We employed amplified fragment length polymorphism (AFLP) markers and performed a plastid microsatellite survey to assess genetic variation in 20 populations of H. hircinum located along central–marginal gradients. We measured demographic traits to assess population fitness along geographical gradients and to test for correlations between demographic traits and genetic diversity. We used genetic diversity indices and analyses of molecular variance (AMOVA) to test hypotheses of reduced genetic diversity and increased genetic differentiation and isolation from central to peripheral sites. We used Bayesian simulations to analyse genetic relationships among populations. Results 

Genetic diversity decreased significantly with increasing latitudinal and longitudinal distance from the distribution centre when excluding outlying populations. The AMOVA revealed significant genetic differentiation among populations (FST = 0.146) and an increase in genetic differentiation from the centre of the geographical range to the margins (except for the Atlantic group). Population fitness, expressed as the ratio NR/N, decreased significantly with increasing latitudinal distance from the distribution centre. Flower production was lower in most eastern peripheral sites. The geographical distribution of microsatellite haplotypes suggests post-glacial range expansion along three major migratory pathways, as also supported by individual membership fractions in six ancestral genetic clusters (C1–C6). No correlations between genetic diversity (e.g. diversity indices, haplotype frequency) and population demographic traits were detected. Main conclusions 

Reduced genetic diversity and haplotype frequency in H. hircinum at marginal sites reflect historical range expansions. Spatial variation in demographic traits could not explain genetic diversity patterns. For those sites that did not fit into the CMC, the genetic pattern is probably masked by other factors directly affecting either demography or population genetic structure. These include post-glacial recolonization patterns and changes in habitat suitability due to climate change at the northern periphery. Our findings emphasize the importance of distinguishing historical effects from those caused by geographical variation in population demography of species when studying evolutionary and ecological processes at the range margins under global change.

Keywords: AFLP; Europe; Himantoglossum hircinum; demography; geographical genetic structure; orchids; phylogeography

Document Type: Research Article

DOI: https://doi.org/10.1111/j.1365-2699.2009.02168.x

Affiliations: 1: Centre d’Ecologie Fonctionnelle et Evolutive, UMR 5175 Montpellier, France 2: Estación Biológica de Doñana, CSIC, Avda. María Luisa s/n, Sevilla, Spain 3: Museo di Storia Naturale della Calabria ed Orto Botanico, Università della Calabria, 87030 Arcavacata di Rende, Cosenza, Italy 4: Jodrell Laboratory, Royal Botanic Gardens, Kew, Richmond, Surrey, UK 5: Centre for Ecology and Hydrology, Monks Wood, Abbots Ripton, Huntingdon, Cambridgeshire, UK 6: Institute of Vegetation Ecology and Nature Conservation, University of Potsdam, Maulbeerallee 2, Potsdam, Germany

Publication date: 2009-12-01

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