GENETIC-STRUCTURE IN CAVE BEETLES AND PAST ENVIRONMENT CHANGES

Electrophoretic divergence between five different populations of the t roglobitic subspecies Speonomus pyrenaeus pyreneaus has been interpret ed in the light of knowledge of the evolution of the environment durin g the last glaciation in order to understand the changes in allele fre quencies in populations isolated by a geographic barrier during the Wu rm glaciation. This subspecies seems highly structured (F(ST) = 0.64) with fixation of alternate alleles and a reduced genetic variability ( H(obs) = 0.04). Two phenomena may have influenced the genetic structur e and the dynamics of these cave populations: the isolation of populat ions during the last main glacier advance (80-60 ka) and the founder e ffect during the post-Wurm colonization of the karst habitat.