Regional genetic differentiation in Western Australian sandalwood (Santalum spicatum) as revealed by nuclear RFLP analysis

Abstract

Western Australian sandalwood, Santalum spicatum, is widespread in the semi-arid and arid regions of Western Australia, and there is some morphological variation suggestive of two ecotypes. The level and structuring of genetic diversity within the species was investigated using anonymous nuclear RFLP loci. Santalum spicatum showed moderate levels of genetic diversity compared to other Australian tree species. The northern populations in the arid region showed greater levels of diversity and less population differentiation than the southern populations in the semi-arid region due to differences in the distribution of rare alleles. Equilibrium between drift and gene flow in the northern populations indicated that they have been established for a long period of time with stable conditions conducive to gene flow. In contrast, the southern populations showed a relationship between drift and gene flow indicative of a pattern of fragmentation and isolation where drift has greater effect than gene flow. The different patterns of diversity suggest that the ecotypes in the two regions have been subject to differences in the relative influences of drift and gene flow during their evolutionary history.

Phylogeography and divergence in the chloroplast genome of Western Australian Sandalwood (Santalum spicatum)

“…Significant structuring of the diversity occurs with two main clades that are geographically separated, one centred on the southern region and one centred in the north of the distribution. This differentiation of two lineages is consistent with the identification of differences between the regions in the influence of genetic processes on the nuclear genome (Byrne et al, 2003). It is also consistent with the identification of two ecotypes in these regions, based on morphological variation.…”

“…The genetic patterns in the nuclear and chloroplast genomes both suggest that the southern populations have been established more recently than the northern populations. However, the nuclear genome showed greater differentiation in southern populations (southern y ¼ 0.108, northern y ¼ 0.055; Byrne et al, 2003), whereas the chloroplast genome identified greater differentiation in the northern populations (northern G ST ¼ 95%, southern G ST ¼ 81%). This suggests that the lower differentiation in the chloroplast genome is not likely to be a result of population sampling, higher seed dispersal or greater abundance, but may be due to less time for fragmentation to influence divergence.…”

“…Genetic analysis of the nuclear genome identified an equilibrium between drift and gene flow in the northern region indicating that the region had existed under stable conditions of dispersal for a long period of time (Byrne et al, 2003). In contrast, the southern region showed a genetic pattern indicating that the populations have been more recently established, and that they have been fragmented and influenced to a greater degree by genetic drift than by gene flow.…”

“…Trees in the arid areas also show higher concentrations of oil in the wood (Loneragan, 1990). A genetic study using nuclear restriction fragment length polymorphism (RFLP) markers showed some evidence of differentiation of ecotypes, but it was not significant (Byrne et al, 2003). However, the study did show significant differences in the genetic influences within the two regions, with the northern region showing stable history with equilibrium between drift and gene flow, and the southern region showing no drift-gene flow equilibrium and variances consistent with fragmented, isolated populations under greater influence of drift than gene flow.…”

Genetic diversity and biogeographic history inform future conservation management strategies for the rare sunset frog (Spicospina flammocaerulea)

“…However, this information is rarely available for either flora or fauna in any ecosystem. South-western Australia is known for its extreme diversity of plants and highly threatened ecosystems, but there are comparatively few datasets analysing genetic differentiation within species that might lead to an understanding of processes generating that diversity (but for plants see Coates and Hamley 1999;Byrne and Macdonald 2000;Byrne et al 2003aByrne et al , 2003bCoates et al 2003;Broadhurst et al 2004;Byrne and Hines 2004;Wheeler and Byrne 2006; and for animals see Driscoll 1998asee Driscoll , 1998bReid 2002;Munasinghe et al 2004;Gouws et al 2006;Edwards 2007a;2007b;Edwards et al 2007Edwards et al , 2008. Genetic data documenting variation within species can be used for conservation management in two ways: (1) to assess common patterns of variation that reflect historical events such as climate shifts, patterns of isolation or tectonic activity that might define the spatial array of genetic diversity and inform management actions (e.g.…”