Evolutionary patterns and genetic structure in localized and widespread species in theStylidium caricifoliumcomplex (Stylidiaceae)

Abstract

The Stylidium caricifolium (Stylidiaceae) complex consists of seven currently recognized species and a taxon of putative hybrid origin endemic to southwest Western Australia. These taxa vary in geographical distribution from widespread, extending over a range of 500 km, to extremely localized, covering a range of only 0.5 km. Patterns of allozyme variation were investigated in 61 populations covering all taxa and two closely related species. Measures of genetic diversity were consistently lower and in some cases significantly lower in four rare and geographically restricted taxa compared with their widespread relatives. In contrast, genetic diversity in two other localized taxa was comparable or higher than in the widespread taxa. The level of divergence among populations was moderate to high, with a significant trend of higher F(ST) values for the widespread species to lower values for the geographically restricted and rare taxa. Phylogenetic relationships and levels of divergence indicate that most taxa are probably relictual rather than recently evolved. Geographical localization and rarity in this complex can be attributed to a range of factors associated with habitat specificity, historical and ecological processes that characterize the southwest region, and mode of origin.

Evidence for convergent evolution among phylogenetically distant rare species of Tetratheca (Elaeocarpaceae, formerly Tremandraceae) from Western Australia

“…Byrne et al 2001;Coates et al 2003). For these taxa, a secondary consequence of the climatic and habitat instability that forged much of the diversity of the South-west Australian Floristic Region (Hopper and Gioia 2004) has been extinction throughout much of their range, such that they now persist in geographically restricted and fragmented or disjunct populations (Coates et al 2003). The relationships identified here in the Koolyanobbing Tetratheca show similar combinations of relict species diverged over long time frames and more recently evolved taxa.…”

“…This has led to both old relictual taxa and relatively ancient fragmented population systems within some species complexes (e.g. Byrne et al 2001;Coates et al 2003). For these taxa, a secondary consequence of the climatic and habitat instability that forged much of the diversity of the South-west Australian Floristic Region (Hopper and Gioia 2004) has been extinction throughout much of their range, such that they now persist in geographically restricted and fragmented or disjunct populations (Coates et al 2003).…”

“…Speciation processes across the topographic and edaphic mosaics that characterise the Transitional Rainfall Province and South Coastal Province of Western Australia are hypothesised to have been driven, in part, by late Tertiary-Quaternary climatic oscillations and resultant episodes of population fragmentation and genetic isolation (Hopper 1979;Coates et al 2003;Hopper and Gioia 2004). This has led to both old relictual taxa and relatively ancient fragmented population systems within some species complexes (e.g.…”

Genetics and Conservation of Plant Species of Extremely Narrow Geographic Range

“…In the literature, there are many examples of ENEs, although these have not been formally named as such in the original publications. For example, it has been mentioned that some species of the complex Stylidium caricifolium show <0.5 km in their total range [7], and 10.55% of 2930 assessed species of New Caledonia are distributed along distances of <10 km and occupy one locality [8]. In addition, most of the ENEs have counted only a few dozen individuals as their total population size [6,8].…”

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.…”