The impact of species-specific traits and phylogenetic relatedness on allozyme diversity inCarex sect.Phyllostachys (Cyperaceae)

Allozyme variation was examined inCarex sect.Phyllostachys (Cyperaceae) to study the effects of species-specific traits and phylogenetic relatedness on genetic structure. In contrast to the findings of similar studies, genetic variability in thePhyllostachys is poorly correlated with geographic range and putative differences in breeding systems (as inferred from morphology). This suggests that other patterns of evolution, colonization, and gene flow characterize the species found in this section. Fixation indices are negative for all populations suggesting that mechanisms such as disassortative mating and selection are maintaining heterozygous excess within populations. Closely related taxa often exhibit different genetic variability statistics. In some instances, however, clades (e.g.C. jamesii andC. juniperorum) display very similar levels of genetic variability despite marked differences in species-specific traits. Recent speciation coupled with the ability to maintain historical levels of variation within populations may be factors accounting for this phenomenon. Contrary to similar studies, species restricted to known glacial refugia have lower genetic diversity than those species that underwent mass migrations in response to deglaciation. Narrowly endemic species were found to partition their genetic diversity within, as opposed to between populations. The opposite trend was evident in wider ranging congeners.