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Microsatellite diversity and genetic structure of fragmented populations of the rare, fire‐dependent shrub Grevillea macleayana
Author(s) -
England Phillip R.,
Usher Annette V.,
Whelan Robert J.,
Ayre David J.
Publication year - 2002
Publication title -
molecular ecology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.619
H-Index - 225
eISSN - 1365-294X
pISSN - 0962-1083
DOI - 10.1046/j.1365-294x.2002.01500.x
Subject(s) - biology , biological dispersal , genetic diversity , genetic drift , population , habitat fragmentation , seed dispersal , genetic structure , small population size , ecology , effective population size , evolutionary biology , population fragmentation , genetic variation , population bottleneck , isolation by distance , selfing , gene flow , microsatellite , allele , habitat , genetics , demography , sociology , gene
Recent habitat loss and fragmentation superimposed upon ancient patterns of population subdivision are likely to have produced low levels of neutral genetic diversity and marked genetic structure in many plant species. The genetic effects of habitat fragmentation may be most pronounced in species that form small populations, are fully self‐compatible and have limited seed dispersal. However, long‐lived seed banks, mobile pollinators and long adult lifespans may prevent or delay the accumulation of genetic effects. We studied a rare Australian shrub species, Grevillea macleayana (Proteaceae), that occurs in many small populations, is self‐compatible and has restricted seed dispersal. However, it has a relatively long adult lifespan ( c . 30 years), a long‐lived seed bank that germinates after fire and is pollinated by birds that are numerous and highly mobile. These latter characteristics raise the possibility that populations in the past may have been effectively large and genetically homogeneous. Using six microsatellites, we found that G. macleayana may have relatively low within‐population diversity (3.2–4.2 alleles/locus; H exp = 0.420–0.530), significant population differentiation and moderate genetic structure ( F ST = 0.218) showing isolation by distance, consistent with historically low gene flow. The frequency distribution of allele sizes suggest that this geographical differentiation is being driven by mutation. We found a lack mutation‐drift equilibrium in some populations that is indicative of population bottlenecks. Combined with evidence for large spatiotemporal variation of selfing rates, this suggests that fluctuating population sizes characterize the demography in this species, promoting genetic drift. We argue that natural patterns of pollen and seed dispersal, coupled with the patchy, fire‐shaped distribution, may have restricted long‐distance gene flow in the past.