Loss of genetic variation in declining populations of Aricia artaxerxes in Northern Hungary

Abstract

Rapid decline of population size often gives rise to loss of genetic variation and may result in a reduction in fitness. It is, therefore, essential to detect past demographic changes in populations of endangered species. Aricia artaxerxes occurs in two regions of Northern Hungary: Bukk Mts. and the Aggtelek Karst region. The species prefers short-grass habitats, which are subject to succession. Due to climatic differences between the two regions succession is more rapid in the Bukk plateau resulting in the decline and isolation of A. artaxerxes populations there. In contrast, most populations have remained rather large and stable in the Karst region. This situation provides an excellent possibility to compare the genetic composition of stable and declining populations. A. artaxerxes was collected in four populations of the Bukk Mountains and in ten in the Aggtelek Karst region in 2002 and 2005. We analysed 19 polymorphic allozyme loci in all samples. The results revealed an extremely high level of enzyme polymorphism in A. artaxerxes. Most parameters of polymorphism proved to be significantly higher in the Karst region compared to the Bukk. The shape of the distribution of alleles among the frequency classes indicated the effect of bottleneck in three Bukk and one Karst population. Though heterozygote excess was only significant in one Bukk population a tendency was observed for higher values of standardised heterozygote excess in those populations that had a typical bottleneck distribution of alleles. Our results clearly demonstrated that those populations/subpopulations that compose a network with intense migration are able to maintain their genetic diversity in a long run, while the isolated small populations of the Bukk plateau have lost a sizeable part of their variation.