Genetic Structure ofCarexSpecies from the Australian Alpine Region along Elevation Gradients: Patterns of Reproduction and Gene Flow

Abstract

Premise of research. Sixty percent of the vegetation in the alpine and subalpine region of Victoria, Australia, is endemic, making this region of prime importance for biodiversity and landscape conservation. Persistence of species under climate change may depend on genetic adaptation to changing environmental conditions, which in turn can be affected by patterns of gene flow and genetic variation for adaptive traits.Methodology. Carex hebes and Carex breviculmis are two sedge species commonly found across the Bogong High Plains of the Victorian alpine region. Carex hebes is common but restricted to alpine and subalpine areas, whereas C. breviculmis has a broader distribution. We used microsatellite markers to investigate the population structure of C. hebes and C. breviculmis along three elevation transects.Pivotal results. The genetic data indicated that both species reproduce mostly by sexual reproduction, with a low level of clonal (vegetative) reproduction. However, none of the populations sampled were at Hardy-Weinberg equilibrium, because of a high level of inbreeding in both species, resulting in a deficit of heterozygote individuals. Despite this, there was a high level of genetic diversity along all transects, with no associations between elevation and genetic diversity in C. breviculmis. There was an increase in inbreeding with elevation in C. hebes. The level of genetic differentiation between transects was low for C. breviculmis and higher for the more restricted species, C. hebes.Conclusions. These sexually reproducing species should have potential for adaptive shifts, although if inbreeding depression occurs it may result in lower fitness in both species, particularly for C. hebes at higher elevations.