Comparative long-term mark-recapture studies of guppies (Poecilia reticulata): Differences among high and low predation localities in growth and survival

Abstract

Life history theory predicts that high extrinsic mortality rates will cause the evolution of earlier maturity and increased reproductive effort. Guppies that co-occur with predators support these predictions because they attain maturity at an earlier age and have higher levels of reproductive effort than their counterparts from localities that lack predators. In the past, we used short term (12 day) mark-recapture studies to show that guppy populations that co-occur with predators do in fact have higher mortality rates than those that do not. Here we extend this result to long term mark-recapture studies with a single recapture interval of over 200 days. We show that the recapture probabilities after these longer intervals are very similar to what one would predict based on the short term studies. Because of the multiplicative nature of mortality rate, the differences in recapture rates in guppies from low as opposed to high predation sites are now much more dramatic, on the order of 20 to 30 fold after 200+ days, as opposed to being around 15% higher after 12 days. The earlier short-term studies also revealed that guppies from high predation localities grow faster, in part as an indirect effect of predators because they reduce guppy population densities and increase per capita food availability. The long-term studies reported here yield the same result, but the difference between high and low predation localities is again far more dramatic as a consequence of the longer duration of the recapture interval. These observations, in combination with those of the earlier work, support the hypothesis that the increased mortality that accompanies predation represents a plausible mechanism that causes the evolution of the observed differences in life histories; however, the confounding of mortality rate and growth rate also suggests that more complex life history models that include density regulation and eco-evolutionary interactions may provide a better explanation for life history evolution in guppies. © Finnish Zoological and Botanical Publishing Board 2007.