The role of positive feedback in formation of macroevolutionary trends by the example of adaptation of terrestrial pulmonates (Mollusca, Gastropoda) to wet litter [Russian]

摘要

The morphological adaptations of terrestrial pulmonates (shell reduction, formation of shell streamline shape, and development of aperture armature as a conchological mechanism of shell management) to the locomotion in the lower layers of leaf litter are described. These adaptations are supposed to be accompanied by the formation of evolutionary cycles with a positive feedback development. The cycle includes the following positions: (1) effect of environmental factors on an organism; (2) initiation of adaptive response; (3) origination of evolutionary constrains as side results of the adaptive response, canalizing subsequent changes; (4) development of specialization. Elements of chance in macroevolutionary processes appear to be due to the selection of adaptive responses. The origination of a system with a positive feedback results in the formation of macroevolutionary trends.