Abstract:
In the eastern part of the Pyrenees (France) the author describes a scenario of speciation in the cave species complex Speonomus delarouzeei (Coleoptera Bathysciinae); the speciation processes have been initiated by a breakdown of the ecological equilibrium induced during three glacial-interglacial episodes. The scenario is the following: — during the first glaciation (2.3-2.1 MY), psychrophilic populations ancestral to S. brucki were selected over the highest elevation of the range, by means of cold effect which produced an adaptive demographic advantage; adaptive characters of troglobitic species (K strategy) take place presumably in relation to colonization of caves and M.S.S.; — during the second glaciation (1.7-1.3 MY) and a more recent, S. charlottae, latter S. emiliae, diverged from troglobite ancestors of S. brucki without further adaptive characters, as result from stochastic and historical events. M.S.S. generated during erosional period of glacial event provided ways for migration and new niches for colonization. Bottleneck effect in size population of ancestors, founder effect, and colonization by local population which present genetic and behavioural geographical polymorphism, argue for a rapid speciation, presumably 100,000 years long and 50,000 generations in the case of S. emiliae.