Population genetics of the invasive australian shrub hakea sericea proteaceae in south africa

Dyer, C.; Richardson, D.M.

South African Journal of Botany 58(2): 117-124

1992


ISSN/ISBN: 0254-6299
DOI: 10.1016/s0254-6299(16)30881-x
Accession: 007668217

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Abstract
The shrub Hakea sericea, introduced from Australia in about 1858, has spread from limited plantings to occupy 4800 km2 or 14% of the area of mountain fynbos in the Cape Province of South Africa. Its range extends across about 1000 km and a range of climatic regimes (winter, all-year and summer rainfall). Eleven populations, representatives of the range of invaded habitats, were sampled to determine, by means of starch gel electrophoresis, the genetic structure of H. sericea in South Africa. Total genetic diversity (HT = 0.1157) is low compared with the average for plants (HT = 0.310), but is similar to that of other closed-cone (serotinous) species. Genetic diversity among populations (GST = 0.242) is close to the average for plants (GST = 0.224). Much of the inter-population diversity is attributable to differences between populations in the western Cape and those in the southern and eastern Cape. Cluster analyses of genetic and geographic differences are perfectly congruent, which suggests that genetic adaptation has occurred in the process of colonization. The possibility that populations in the two regions may have originated from different source populations in Australia cannot be discounted. The excess of heterozygotes in all populations implies an outbreeding mode of reproduction, suggesting very substantial heterozygote advantage.