Genetic variability of the Antarctic brachiopod Liothyrella notorcadensis and its bearing on mass extinction hypotheses

Abstract

Genetic variation has been studied in 34 loci coding for soluble proteins and enzymes in a natural population of the brachiopod Liothyrella notorcadensis from Antarctica. The proportion of polymorphic loci is 23.5 percent, and the average proportion of heterozygous loci per individual is 3.9 +- 1.9 percent. Thus L. notorcadensis is one of the least genetically variable invertebrate species yet studied. With respect to hypotheses of the ecological regulation of genetic variability, our results favor models that correlate low genetic variability with instability in trophic resource supplies. To this extent also our results favor extinction models that predict high genetic variability that promotes specialization in the inhabitants of stable regimes; these inhabitants would tend to become extinct when environments become unstable or otherwise change significantly. (auth)