Population genetic effects of forest fragmentation in Flanders (Belgium) on Coelotes terrestris (Wider) (Araneae : Agelenidae) as revealed by allozymes and RAPD

Due to an ever-increasing urbanisation, industrialisation, development of r oad infrastructure and an intensive agriculture, forests in Flanders have b ecome heavily fragmented. In general, organisms bound to small forest fragm ents have a reduced population size and are highly isolated from other popu lations. To assess the population genetic effects of forest fragmentation, we chose Coelotes terrestris (WIDER, 1834) as a model organism, because it is strongly bound to forest habitats. A first attempt to reveal the populat ion genetic structure of this species was made by using allozyme electropho resis. Only one enzyme (PGI) however showed good interpretable variation. T his low degree of polymorphism together with the sometimes-questioned neutr ality of allozyme markers made us choose genetic marker (RAPD). Ten forests , with a variable degree of isolation and a variable size were investigated . The majority (allozymes) and all (RAPD) pairwise comparisons of populatio n allele/marker frequencies were significantly different, implying a very h igh degree of genetic isolation between the spider populations inhabiting t he forests. Nd significant correlation could be found between the genetic d iversity of the populations and the size of the forest in which they predom inate.