Genetic Differentiation Between Populations of Orchesella cincta (Collembola) from Heavy Metal Contaminated Sites

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Abstract
(1) Genetic differentiation in Orchesella cincta L. (Collembola) populations from various sites contaminated by heavy metals was studied by comparing toxic effects of cadmium and zinc on first generation laboratory animals. (2) The effects were measured as growth responses for animals exposed to different concentrations of cadmium or zinc, by regular recording for weight-gains. (3) Individual growth reduction was calculated as the quotient of the linear growth rate during and before metal exposure, and expressed as an index of growth reduction. (4) In all populations the sexes had different growth rates, but showed a similar growth reduction following cadmium exposure. (5) The growth response to zinc differed slightly between the sexes: males showed increased growth, but females showed reduced growth, when exposed to a zinc concentration in the food of 68.8 .mu.mol g-1 dry wt. There was no difference in growth response to zinc between populations. (6) Growth responses to cadmium exposure differed between the populations. A significant reduction in growth occurred in populations descended from the reference site and from sites contaminated by industrial activities. Populations descended from highly contaminated sites with a long history of contamination showed no significant growth reduction. (7) As population differentiation was demonstrated in the first generation laboratory animals, there was evidence for genetic differences between the populations.