Phenotypic plasticity in a complex world: interactive effects of food and temperature on fitness components of a seed beetle

Abstract

Most studies of phenotypic plasticity investigate the effects of an individual environmental factor on organism phenotypes. However, organisms exist in an ecologically complex world where multiple environmental factors can interact to affect growth, development and life histories. Here, using a multifactorial experimental design, we examine the separate and interactive effects of two environmental factors, rearing host species (Vigna radiata, Vigna angularis and Vigna unguiculata) and temperature (20, 25, 30 and 35 degrees C), on growth and life history traits in two populations [Burkina Faso (BF) and South India (SI)] of the seed beetle, Callosobruchus maculatus. The two study populations of beetles responded differently to both rearing host and temperature. We also found a significant interaction between rearing host and temperature for body size, growth rate and female lifetime fecundity but not larval development time or larval survivorship. The interaction was most apparent for growth rate; the variance in growth rate among hosts increased with increasing temperature. However, the details of host differences differed between our two study populations; the degree to which V. unguiculata was a better host than V. angularis or V. radiata increased at higher temperatures for BF beetles, whereas the degree to which V. unguiculata was the worst host increased at higher temperatures for SI beetles. We also found that the heritabilities of body mass, growth rate and fecundity were similar among rearing hosts and temperatures, and that the cross-temperature genetic correlation was not affected by rearing host, suggesting that genetic architecture is generally stable across rearing conditions. The most important finding of our study is that multiple environmental factors can interact to affect organism growth, but the degree of interaction, and thus the degree of complexity of phenotypic plasticity, varies among traits and between populations.

Speed over efficiency: locusts select body temperatures that favour growth rate over efficient nutrient utilization

“…Karl & Fisher 2008), but where interactive effects of diet and temperature upon growth have been investigated, consideration of body temperature preference and nutrient utilization were not the focus (e.g. Stillwell et al 2007).…”

Sex differences in phenotypic plasticity of a mechanism that controls body size: implications for sexual size dimorphism

“…A majority of plasticity studies and studies that have tested for sex differences in plasticity in body size have examined environmental variables independently of one another. Nevertheless, recent studies have shown that multiple environmental variables can interact, producing complex patterns of plasticity (Sultan et al 1998;Sultan 2001;Relyea 2004;Relyea & Auld 2005;Stillwell et al 2007b;Diamond & Kingsolver 2010). In addition, interactions between environmental variables can have different effects on the sexes, producing complexity in sex differences in plasticity in size and hence affecting patterns of SSD (De Block & Stoks 2003).…”

“…However, interactions produced by ANOVA can be misleading when the proportional or relative effects (i.e. ratios such as female/male size) are of interest because ANOVA tests for interactions by measuring linear differences between treatment means (Stanton & Thiede 2005;Stillwell et al 2007b;Fraker & Peacor 2008). In other words, when there is a large effect of one variable on the overall mean, linear differences do not translate into proportional changes.…”

“…Insects typically mature at larger sizes when raised at lower temperatures and when raised on higher quality diets (Atkinson 1994;Berrigan & Charnov 1994;Stillwell & Fox 2005;Stillwell et al 2007b;Kingsolver & Huey 2008). Insects also generally exhibit sex-specific plasticity in body mass in response to diet quality/quantity .…”

Genetic architecture underlying convergent evolution of egg-laying behavior in a seed-feeding beetle

“…All offspring developed at 25°C and 15:9 light:dark in a single growth chamber. We used mung bean as the rearing host because larval survivorship is high on this host for both the SI and BF populations (Stillwell et al 2007). The positions of dishes in the chamber were rotated daily.…”