Variation of carabid life cycles along climatic gradients: An adaptive perspective for life-history evolution under adverse conditions

Abstract

Abstract Life-history variation along climatic gradients towards higher altitudes and latitudes, and its evolutionary implications, are considered for temperate carabid beetles by integrating information from physiological and population ecology, biogeography, and mathematical theory. Among the two major categories of seasonal life cycles in carabids, autumn breeders with larval overwintering are better adapted to colonize cool habitats than spring breeders that cannot overwinter as larvae. The success of autumn breeders depends on the fact that both larvae and adults can overwinter, so that development can last two years, and semivoltinism can develop. Simple life-history models were used to determine the optimal seasonal life cycle and its relation to the degree of iteroparity. The models predict that, under environmental adversity expected in cool habitats, adult carabids maximize fitness by reducing the amount of reproductive activity per year and enhancing adult survivorship. When slow development in cool habitats results in delayed maturity in the first year of adult life, semivoltinism rather than univoltinism tends to be the optimal strategy. In general, the significance of iteroparity increases as habitats become cooler.