The NSS Bulletin - ISSN 1090-6924
Volume 47 Number 2: 78-85 - December 1985

A publication of the National Speleological Society

Why All Cave Animals Do Not Look Alike-A Discussion on Adaptive Value of Reduction Processes
Boris Sket


Two antagonistic hypotheses have been postulated to explain reduction of eyes and some other structures in cave animals. The author, reconsidering arguements for "neutral mutation hypothesis," bears evidence of unreliability of some of them. He particularly denies an increased variability of organs in rudimentation in cave animals. On the other hand, some new arguments in favor of the "direct selection hypothesis" are given. The structure reduction grade in different populations of troglobitic species may be sometimes different, probably owing to different severity of ecological factors. A nice evidence for direct selection is given also by clinal variability in some cave animals.

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