Regional structuring of genetic variation in short-lived rock pool populations of Branchipodopsis wolfi (Crustacea: Anostraca) |
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Authors: | L Brendonck L De Meester B J Riddoch |
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Institution: | (1) Laboratory of Aquatic Ecology, Katholieke Universiteit Leuven, De Beriotstraat 32, 3000 Leuven, Belgium e-mail: luc.brendonck@bio.kuleuven.ac.be, Fax: +32-16-323714, BE;(2) Zoology Department, University of Botswana, Botswana, BW |
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Abstract: | The genetic structure of three metapopulations of the southern African anostracan Branchipodopsis wolfi was compared by analysing allozyme variation at four loci (PGM, GPI, APK, AAT). In total, 17 local populations from three
sites (metapopulations) were analysed from rock pools in south-eastern Botswana ranging from 0.2 to 21 m2 in surface area. In three populations we found significant deviations from Hardy-Weinberg (H-W) equilibrium at one or more
loci due to heterozygote deficiencies. Genetic variability at one site was significantly lower than at the other sites, which
may be linked to a greater incidence of extinction and recolonisation, as the basins at this site are shallower and have shorter
hydrocycles. Across all local populations, a significant level of population differentiation was revealed. More than 90% of
this variation was explained by differentiation among sites (metapopulations), although this differentiation did not correlate
with geographic distance, or with environmental variables. Genetic differentiation among populations within metapopulations
was low, but significant at all sites. At only one of the sites was a significantly positive association measured between
genetic and geographic distance among local populations. Our data suggest that persistent stochastic events and limited effective
long-range dispersal appear to dominate genetic differentiation among populations of B. wolfi inhabiting desert rock pools. The lack of association between geographic distance and genetic or ecological differences between
rock pool sites is indicative of historical stochastic events. Low heterozygosity, the significant deviations from H-W equilibrium,
and the large inter- but low intra-site differentiation are suggestive of the importance of short-range dispersal. Gene flow
between metapopulations of B. wolfi appears to be seriously constrained by distances of 2 km or even less.
Received: 28 June 1999 / Accepted: 10 January 2000 |
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Keywords: | Divergence Spatial genetic structure Gene flow Dispersal Egg banks |
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