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Degenerative and constructive features of a phylogeneticcaly young cave form of Poecilia sphenops (Pisces, Poeciliidae)
Author(s) -
Peters Nicolaus,
Peters Gabriele,
Parzefall Jakob,
Wilkens Horst
Publication year - 1973
Publication title -
internationale revue der gesamten hydrobiologie und hydrographie
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.524
H-Index - 52
eISSN - 1522-2632
pISSN - 0020-9309
DOI - 10.1002/iroh.19730580308
Subject(s) - biology , zoology , population , natural selection , demography , sociology
DARWIN's statement, that rudimentary parts of organisms are apt to be highly variable, is also true for the regressive structures of cavernicolous animals. On the other hand, adaptive traits develop under cave conditions, the variability of which is lowered rather than increased, compared to that of their precursors in the epigean population. These differences in the genetically controlled variability of constructive and degenerative features indicate action and nonaction of natural selection.