Cirsium species show disparity in patterns of genetic variation at their range-edge, despite similar patterns of reproduction and isolation

Genetic variation was assessed across the UK geographical range of Cirsium acaule and Cirsium heterophyllum. A decline in genetic diversity and increase in population divergence approaching the range edge of these species was predicted based on parallel declines in population density and seed production reported seperately. Patterns were compared with UK populations of the widespread Cirsium arvense.Populations were sampled along a latitudinal transect in the UK and genetic variation assessed using microsatellite markers. Cirsium acaule shows strong isolation by distance, a significant decline in diversity and an increase in divergence among range-edge populations. Geographical structure is also evident in C. arvense, whereas no such patterns are seen in C.heterophyllum. There is a major disparity between patterns of genetic variation in C. acaule and C. heterophyllum despite very similar patterns in seed production and population isolation in these species. This suggests it may be misleading to make assumptions about the geographical structure of genetic variation within species based solely on the present-day reproduction and distribution of populations

Conservation priorities for chukar partridge in Israel based on genetic diversity across an ecological gradient

Recent studies suggest that patterns of genetic diversity significantly influence the viability and persistence of local populations. Revealing and mapping spatial patterns of genetic diversity within species' ranges may be vital when defining criteria and prioritizing areas for conservation. Chukar Partridges (Alectoris chukar) in Israel occur along a steep ecogeographical gradient extending from mesic Mediterranean zones in the north to steppe and desert regions in the south. To rest the hypothesis that the most genetically diverse populations within a species' range occur within the ecotone, an area of transition between ecosystems where a sharp environmental gradient exists, we examined the allozyme diversity of chukars collected at five locations within the species' continuous range in each of 2 years. Based on 32 allozyme loci, the genetic diversity of chukars increased significantly, along a gradient from population in Mediterranean regions to those at the ecotone in the northern Negev desert, despite close geographical proximity among populations Genetic diversity As estimated by percent polymorphic loci, observed and expected heterozygosity, and mean number of alleles was not homogeneous among sampling localities: single and multilocus Hardy-Weinberg and linkage disequilibria increased along the gradient toward the ecotone. Populations exhibited some isolation by distance effects in the face of substantial gene flow. We therefore recommend that higher conservation priority be assigned to the Mediterranean-Negev ecotone area. For Chukar Partridges, it supports the highest overall genetic diversity across ecological gradients. Rapid urbanization of Israeli landscapes, and management of chukars in Israel within a metapopulation context is an urgent requirement