Loss of genetic diversity through spontaneous colonization in the bog fritillary butterfly, Proclossiana eunomia (Lepidoptera: Nymphalidae) in the Czech Republic

Gabriel Nève,Martin Konvička,Alois Pavlíčko

doi:10.14411/eje.2009.002

Abstract

The butterfly Proclossiana eunomia (Lepidoptera: Nymphalidae) was discovered at a single locality in the Czech Republic in 1963. Until the 1980s, it was known from a restricted area, from which it spontaneously expanded during the 1980s to other localities up to 23 km from the source population. Samples were collected in 2002 from the source and ten other populations, totalling 274 specimens. All samples were analysed by electrophoresis for four polymorphic loci. Mean heterozygosity decreased with distance from the source population; this suggested a process of stepping stone colonization, involving the loss of rare alleles along the way. The populations close to the source population (less then ca. 15 km) retain a similar heterozygosity, whereas populations further away have a much reduced heterozygosity. Such a pattern of genetic differentiation and founder effect within a region is typical of specialized species with relatively low dispersal ability. The high level of genetic polymorphism found in the Sumava populations suggests that populations of this northern species in temperate-zone mountains are not just outposts of otherwise huge northern distribution, but represent genuine phylogeographic refugia. Survival of such species depends on the survival of the source population and of a sufficiently dense network of habitat patches.

Highlights

Colonization and migration events are key processes in metapopulation dynamics, ensuring the long term survival of species within a shifting range of habitat patches (Hanski, 1999)
Five of the six loci studied proved polymorphic; mannose phosphate isomerase (MPI), which proved to be polymorphic in the study area, was not scorable for some populations; it was not used in the present analyses
The allele apparently lost in the source population between 1994 and 2002 was still present in populations 1, 4, and 5 (Table 1)

Summary

Introduction

Colonization and migration events are key processes in metapopulation dynamics, ensuring the long term survival of species within a shifting range of habitat patches (Hanski, 1999). As the conditions near the refugium patches improve, the refugial population may serve as source of colonists for colonising newly appearing patches (e.g. Summerville, 2008). Some of these newly colonized habitat patches may in turn become sources of new propagules, leading to a stepping stone pattern of the species’ range expansion. In terms of genetic structure, frequent migration events among sets of occupied patches result in low to nonexistent population differentiation. If colonization involves only few individuals, founder effects becomes apparent and the populations furthest from the original colonization source will have an impoverished genetic makeup, detectable as lower heterozygosity (Eckert et al, 2008)

Methods

Results

Conclusion