Genetic variation in an endangered cedar (Widdringtonia cedarbergensis) versus two congeneric species

Janet C. Thomas, William J. Bond
1997 South African Journal of Botany  
ReL'cived 20 Oc/obr-r J996: revl.\'cd 2 April/f)!)7 Widdringlonia cedarbergensis is a southern African conifer species under threat at extinction. This study exp lored the genetic status of the species to assess whether loss of genetic variation may be contributing to population declines. Widdringtonia nodiflora and W schwarzii were used as benchmarks against which to compare genetic diversity in W cedarbergensis. Isozyme electrophoresis was used to reso lve seventeen isozyme loci in seedlings
more » ... f the three species. Genetic diversity was greatest in W nodiffora, followed by W cedarbergensis and W schwarzii. There is no evidence that W cedarbergensis has undergone a genetic bottleneck relative to its sister species. Patterns of genetic va riation varied between species with most of the variation occurring within populations of W cedarbergensis, between popu lations of W schwarzii, and within population 'neighbourhoods' of the more widespread W nodiflora. The isozyme data indicate inbreeding, probably du e to self~po ll i nation, in W cedarbergensis and W nodiflora. Populations of W schwarz;; were outbreeding. Selting in W cedarbergensis may be caused by a change in population density from dense to sparse stands with potentially deleteri ous genetic consequences.
doi:10.1016/s0254-6299(15)30725-0 fatcat:fcy6usww5rd3foqpzwd2phopam