ALLOZYME GENOTYPE AND DIFFERENTIAL RESISTANCE TO MERCURY POLLUTION IN THE CADDISFLY, NECTOPSYCHE-ALBIDA .2. MULTILOCUS GENOTYPES

While a number of papers document that sensitivity to pollution is correlated with single-locus genotype, only one has addressed associations with multilocus complexes. We exposed larval caddisflies, Nectopsyche albida to inorganic mercury and recorded individual times to death, genetically characterized each individual at six polymorphic loci by starch gel electrophoresis, and tested the effects of multilocus genotype on time to death. Two two-locus complexes and two three-locus complexes were significantly correlated with survival time. This supports earlier studies that monitoring multilocus and single-locus genotype frequencies may be useful in detecting and measuring environmental impacts; however, we disagree that variation in survival time among genotypes per se supports selectionist theory, because no heritability of resistance has been demonstrated. We also disagree that enzyme systems not exhibiting such variation are nonadaptive and discuss how the elimination of sensitive multilocus genotypes may hinder population persistence.