Geographic Variation in Vulnerability to Predation and Starvation in Larval Treehole Mosquitoes

Abstract

Laboratory experiments were used to test for defenses against predation and costs of such defense in several geographic strains of Aedes triseriatus, a tree-hole dwelling mosquito. Strains of A. triseriatus from sympatry with the tree-hole dwelling predator Toxorhynchites rutilus produced more surviving adults when exposed to predation than did strains from allopatry to the predator. Sympatric strains also had greater survivorship under low food conditions without predation than did allopatric strains, although allopatric strains produced larger adults and had shorter development periods. Estimated per capita rate of population change was always greater for sympatric strains than for allopatric strains. These results show lower vulnerability to predation of sympatric vs allopatric strains, but do not support the hypothesis that defense against predation has associated costs. No evidence was found for differential ability to use physical complexity as a refuge from predation. These results suggest that environmental differences between sympatric and allopatric regions, such as different climates and different numbers of potential competing species, along with presence/absence of the predator, may influence vulnerability to predation, developmental plasticity, and resource use. The initial approach of viewing predation as the dominant ecological difference between sympatric and allopatric regions may be too simple.