Genetic diversity within and between remnant populations of the endangered calcareous grassland plant <Emphasis Type="Italic">Globularia bisnagarica</Emphasis> L. |
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Authors: | O Honnay D Adriaens E Coart H Jacquemyn I Roldan-Ruiz |
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Institution: | (1) Biology Department, Division of Plant Ecology and Systematics, University of Leuven, Kasteelpark Arenberg 31, B-3001 Heverlee, Belgium;(2) Division of Forest, Nature and Landscape Research, University of Leuven, Celestijnenlaan 200, B-3001 Heverlee, Belgium;(3) Department of Plant Genetics and Breeding (CLO-DvP), Agricultural Research Centre, Caritasstraat 21, B-9090 Melle, Belgium |
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Abstract: | Changes in agricultural production methods over the last century have caused a massive reduction and fragmentation of the
area of European semi-natural grasslands. It remains unclear whether small and isolated grassland fragments can support viable
plant populations in a sustainable way. In our study area in southern Belgium, the extent of calcareous grasslands was reduced
from c. 650 ha in 1775 to less than 30 ha in 2004. We used AFLP markers to quantify the effects of present and historical
grassland fragmentation on the genetic structure of 27 populations of the rare perennial plant species Globularia bisnagarica. Given the mixed breeding system of the species and the relatively small area of the studied system, the populations were
characterized by high genetic differentiation (F
st range: 0.42–0.48; Φst=0.53). A Mantel test revealed significant isolation by distance of the populations. Average within population genetic diversity,
measured as expected heterozygosity or gene diversity, was low (H
j
=0.081) and was negatively related to population isolation. This suggests more gene flow into less isolated populations. Population
size and local habitat characteristics did not significantly influence population genetic diversity. Both, high selfing rates
in G. bisnagarica and a population genetic response to habitat fragmentation may explain our findings. Finally, a clear geographical clustering
was observed, with cluster membership partially explainable by historical grassland connectivity. If populations indeed started
to differentiate after fragmentation, this process was not (yet) strong enough to erase the genetic similarity between fragments
that historically belonged to the same large grassland fragment. |
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Keywords: | AFLP Belgium Gene flow Habitat fragmentation Habitat connectivity Historical landscape Semi-natural grassland |
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