Journal Article

Isolated populations of a rare alpine plant show high genetic diversity and considerable population differentiation

Hafdís Hanna Ægisdóttir, Patrick Kuss and Jürg Stöcklin

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 104, issue 7, pages 1313-1322
Published in print December 2009 | ISSN: 0305-7364
Published online October 2009 | e-ISSN: 1095-8290 | DOI: http://dx.doi.org/10.1093/aob/mcp242
Isolated populations of a rare alpine plant show high genetic diversity and considerable population differentiation

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

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Background and Aims

Gene flow and genetic variability within and among alpine plant populations can be greatly influenced by the steep environmental gradients and heterogeneous topography of alpine landscapes. In this study, the effects are examined of natural isolation of alpine habitats on genetic diversity and geographic structure in populations of C. thyrsoides, a rare and isolated European Alpine monocarpic perennial with limited seed dispersal capacity.

Methods

Molecular diversity was analysed for 736 individuals from 32 populations in the Swiss Alps and adjacent Jura mountains using five polymorphic microsatellite loci. Pollen flow was estimated using pollen grain-sized fluorescent powder. In addition, individual-based Bayesian approaches were applied to examine population structure.

Key Results

High within-population genetic diversity (HE = 0·76) and a relatively low inbreeding coefficient (FIS = 0·022) were found. Genetic differentiation among populations measured with a standardized measure was considerable (GST = 0·53). A significant isolation-by-distance relationship was found (r = 0·62, P < 0·001) and a significant geographic sub-structure, coinciding with proposed postglacial migration patterns. Altitudinal location and size of populations did not influence molecular variation. Direct measures of pollen flow revealed that insect-mediated pollen dispersal was restricted to short distances within a population.

Conclusions

The natural isolation of suitable habitats for C. thyrsoides restricts gene flow among the populations as expected for a monocarpic species with very limited seed dispersal capacities. The observed high within-population genetic diversity in this rare monocarpic perennial is best explained by its outcrossing behaviour, long-lived individuals and overlapping generations. Despite the high within-population genetic diversity, the considerable genetic differentiation and the clear western–eastern differentiation in this species merits consideration in future conservation efforts.

Keywords: Alpine plant; Campanula thyrsoides; genetic diversity; gene flow; genetic differentiation; glacial history; G′ST; habitat isolation; microsatellites; monocarpy; SSR

Journal Article.  6564 words.  Illustrated.

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

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