Regressive und rekonstruktive Evolution bei Höhlenfischen -zwei Formen besonders schnellen phylogenetischen Wandels

Regressive and reconstructive evolution in cave fishes - two modes of especially rapid phylogenetic change If a characteristic loses its biological significance, it is no IonGer reulated by a stabilizing selection rocess. Its polygene system will be progressively inactivatecf by continual mutation, and the characteristic will degenerate by regressive evolution. However, if a system of modifying genes faces uncontrolled exposure to general mutation pressure and gradually loses its effectiveness, a derepression of fundamental genetic potencies can occur, bringing about the expansion of a trait that is already present, a reconstructive evolution. Both modes of evolution result in the extensive morphological and behavioral alterations of cave fishes before a reproductive separation from their surface-dwelling ancestral forms has occurred, making them distinct species.