Differential survivorship among allozyme genotypes of Hyalella azteca exposed to cadmium, zinc or low pH

The survival functions (SF) during acute exposures to cadmium, zinc or low pH were examined for amphipods exhibiting variation at three loci. Signific ant differences were observed in eight of nine locus/toxicant combinations. Two general types of survival curve patterns were identified when genotype -related SF differences were observed. In the first pattern, the survival d ifferences between genotypes were immediately apparent with two SF curves s eparated at the beginning of exposure with little or no overlap. For the se cond pattern, both genotypes had similar SF for a period of time, during wh ich the two survival curves crossed or overlapped. After this period, the s urvival probability of one genotype dropped sharply relative to the other. While SF was related to genotype, it was not related to heterozygosity. Gen etic distance analysis showed that exposure to cadmium, zinc or low pH each resulted in directional selection, suggesting the potential use of genetic distance as a bioindicator. (C) 2001 Elsevier Science B.V. All rights rese rved.