Complex patterns of phenotypic plasticity: interactive effects of temperature during rearing and oviposition

Abstract. Temperature profoundly affects growth and life history traits in ectothermic animals through selection (i.e., genetic) and through direct effects on the phenotype (i.e., nongenetic/plasticity). We examined the effects of rearing temperature (24Њ, 30Њ, and 36ЊC) on adult body size and development time and the interactive effects of temperature experienced during rearing and oviposition on several life history traits (age-at-first-reproduction, fecundity, egg size, egg development, and egg hatching) in two populations of the seed beetle, Stator limbatus, collected at different elevations. The higher elevation population was larger and matured sooner than the low-elevation population when raised at the lower temperature, but the reverse was true at the higher temperature suggesting that these populations have adapted to local temperature. There were interactions between the effects of rearing temperature and oviposition temperature for age-at-first-reproduction, fecundity, egg development, egg hatching, and two composite measures of fitness, generating complex reaction norms. The most dramatic example of this was a large maternal effect on egg hatching; females raised at low temperature produced eggs that had substantially reduced hatching when laid at high temperature. Our experimental design also allowed us to explore the adaptive significance of acclimation. Beetles reared at intermediate or low temperature had the highest fitness at multiple oviposition temperatures. There was little support for the ''beneficial acclimation hypothesis,'' which predicts that beetles should have higher fitness at the temperature at which they were reared; acclimation had only a small effect on fitness. This study shows that temperature-mediated plasticity can be complex, but these complex patterns can yield new insights into the evolution of phenotypic plasticity

Geographic variation in body size and sexual size dimorphism of a seed-feeding beetle.

abstract: Body size of many animals varies with latitude: body size is either larger at higher latitudes (Bergmann's rule) or smaller at higher latitudes (converse Bergmann's rule). However, the causes underlying these patterns are poorly understood. Also, studies rarely explore how sexual size dimorphism varies with latitude. Here we investigate geographic variation in body size and sexual size dimorphism of the seed-feeding beetle Stator limbatus, collected from 95 locations along a 38Њ range in latitude. We examine 14 variables to test whether clines in environmental factors are adequate to explain geographic patterns of body size. We found that body size and sexual size dimorphism of S. limbatus varied considerably with latitude; beetles were smaller but more dimorphic at lower latitudes. Body size was not correlated with a gradient in mean temperature, contrary to the commonly accepted hypothesis that clines are produced by latitudinal gradients in temperature. Instead, we found that three factors were adequate to explain the cline in body size: clinal variation in host plant seed size, moisture (humidity), and seasonality (variance in humidity, precipitation, and temperature). We also found that the cline in sexual size dimorphism was partially explainable by a gradient in moisture, though moisture alone was not sufficient to explain the cline. Other ecological or environmental variables must necessarily contribute to differences in selection on male versus female body size. The main implications of our study are that the sexes differ in the magnitude of clinal variation in body size, creating latitudinal variation in sexual size dimorphism, and that clines in body size of seed beetles are likely influenced by variation in host seed size, water availability, and seasonality