Adaptive reproductive variation along a pollution gradient in a wolf spider

Abstract

When populations are exposed to environmental pollutants, growth and reproduction might be strongly reduced due to an increased detoxification effort. Sublethal metal pollution is therefore to be expected to cause the same selection pressure as a low resource habitat and might alter the reproductive strategy. Optimality models of life history theory predict that when resource availability is reduced, growth and reproductive output are reduced and that the release of fewer but larger propagules will be favoured. This was tested by applying a life history model to reproductive trait measurements in six populations of the wolf spider Pirata piraticus in which the assumptions of the model are satisfied. Internal Cd, Cu and Zn body burden were strongly correlated with each other, and differed strongly between the populations, indicating consistently differing metal exposure at the different sites. Pb levels were extremely variable within each population and did not differ between the populations. Females from populations with high concentrations of the first three heavy metals showed a strongly reduced reproductive output and fecundity, indicating a high reduction in resource availability due to detoxification processes. Egg size in contrast was negatively correlated with fecundity and reproductive output and as a consequence positively related with internal metal burden. Our results are thus in strong agreement with the predictions of the optimality models and confirm the benefits of a larger propagule size when resource availability is reduced.

Effects of maternal diet quality on offspring performance in the rove beetle Tachyporus hypnorum

“…Reduced egg size as a response to a suboptimal diet has been found in other studies ( Jann & Ward, 1999 ), but the opposite effect of suboptimal diet has also been revealed ( Fox et al , 1995;Wainhouse et al , 2001 ). The latter is expected when eggs are laid in stressful environments ( Hendrickx et al , 2003 ), since larval performance is often egg-size dependent only under suboptimal conditions ( Braby, 1994;Fox & Mousseau, 1996 ). On the S. avenae diet both egg size and egg numbers were lowered.…”

Relationship between fluctuating asymmetry and fitness within and between stressed and unstressed populations of the wolf spider Pirata piraticus

“…In this study, we measured levels of FA in six populations of the wolf spider Pirata piraticus (Clerck, 1757) that vary in degree of metal exposure. In a previous study, life history patterns indicative for low growth and/or low reproductive environments were observed in the most contaminated populations (Hendrickx et al. , 2003a).…”

Scaling of body weight and fat content in fungus-gardening ant queens: does this explain why leaf-cutting ants found claustrally?

“…Ecological conditions influence body size within populations such that, if conditions are typically poor for juvenile growth, larger, better-provisioned offspring and parents that produce offspring from stored food will be selected (a capital breeding strategy; Sibly et al, 1988;Stearns, 1992;Bourke and Franks, 1995;Jönsson, 1997;Turnbull et al, 1999;Jakobsson and Eriksson, 2000;Hendrickx et al, 2003;Johnson, 2006). On the other hand, if an environment has more predictable sources of mortality and plentiful food resources, it would be adaptive to produce offspring from food gathered during the reproductive period (an 'income-breeding' strategy; Stearns, 1992;Jönsson, 1997;Johnson, 2006).…”