Ecology and Evolution of the Pitcher-Plant Mosquito. 3. Resource Tracking by a Natural Population

Ecology and Evolution of the Pitcher-Plant Mosquito. 2. The Substructure of Fitness

“…10 for a univoltine life cycle suggests that a population of all diapausers might just maintain itself from year-toyear in nature, but the situation is clearly marginal. It is puzzling why the warm-season diapause exists in the population at all (see Istock et al, 1976). At present, we have no information about the relation between warm-season and winter diapause except that both come in the same instar.…”

“…Both models focus on the role of density in natural selection. Since the W. smithii population experiences both density-dependent and density-independent periods in the same season (Istock et al, 1976), it is tempting to suggest that these differing and recurring selection regimes favor different phenotypes, or, to put it more carefully, different parts of the fitness-phenotype continuum. The slower development and diapause tendency of the diapauser modality may lead such individuals to concentrate larval growth and development in the energy rich, mid-summer period of density-independence.…”

Survival, development and predatory effects of mosquito larvae in Venezuelan phytotelmata

“…Because of their simplicity, replicability and manipulability, phytotelmata have been used by ecologists for experimental investigations of factors regulating community structure. Addicott (1974) showed through density manipulations that grazing by mosquito larvae reduced the number of species of protozoan cohabitants in leaves of the pitcher plant Sarracenia purpurea L. Other experiments in pitcher plants revealed that mosquito growth is density dependent, the intensity of resource limitation varying both seasonally and geographically (Bradshaw & Holzapfel 1983a, Istock et al 1976. When phytotelmata such as treeholes harbour an obligate carnivore, mosquito numbers are kept below carrying capacity by predation (Bradshaw & Holzapfel 1983b).…”

Variable Iteroparity as a Life-History Tactic in the Pitcher-Plant Mosquito Wyeomyia smithii

“…Mosquito larvae experience limiting density throughout the entire year. In the north (43°N), Istock et al (1976) found that the biomass oflarvae in pitcher-plant leaves was at or near saturation in the spring or fall but well below saturation levels during the summer. Thus, in the south there is a continual excess of adult fecundity above the carrying capacity of the environment for their offspring, while in the north, there are periods when collective adult survivorship and fecundity are not sufficient to saturate available resources.…”

“…These prey constitute the resource base of the community and, consequently, determine the density per unit resource of mosquitoes in that leaf. Thus, despite seasonal components to density dependence in both the south (Bradshaw and Holzapfel, 1983) and the north (Istock et al, 1976), there is probably a large stochastic element in the degree of density-dependence among leaves. While very little is known about actual adult demography in nature, the above observations indicate that the impact of natural selection on larvae relative to adults declines with either latitude or altitude.…”