Reproductive value in a complex life cycle: heat tolerance of the pitcher‐plant mosquito, Wyeomyia smithii

Abstract

Because mortality accumulates with age, Fisher proposed that the strength of selection acting on survival should increase from birth up to the age of first reproduction. Hamilton later theorized that the strength of selection acting on survival should not change from birth to age at first reproduction. As organisms in nature do not live in uniform environments but, rather, experience periodic stress, we hypothesized that resistance to environmental stress should increase (Fisher) or remain constant (Hamilton) from birth to age at first reproduction. Using the pitcher‐plant mosquito, Wyeomyia smithii, we imposed heat stress by simulating the passage of a warm‐weather front at different preadult and adult stages. Contrary to either Fisher or Hamilton, stress tolerance declined from embryos to larvae to pupae to adults. Consequently, reproductive value appears to have been of little consequence in the evolution of stage‐specific tolerance of heat stress in W. smithii.

Stage-specific heat effects: timing and duration of heat waves alter demographic rates of a global insect pest

“…We suggest that the inconsistency between studies which has been observed may be due to potential differences in the types (acute vs. chronic) of heat stress and the life-stage at which the heat stress was imposed, leading to a shift in the balance of injury versus recovery. When the early stages of insects are stressed by a short extreme high temperature, compensatory mechanisms could likely restore all functions during subsequent stages-if individuals do not experience stressful conditions during these stages (Zani et al 2005;Potter et al 2011;Xing et al 2014;Zhang et al 2015). In contrast, when acute high temperatures applied during late pre-imaginal stages cause severe damage, organisms may not be able to recover before and during the adult stage, resulting in depressed reproduction (Ma et al 2004b;Zani et al 2005;Zhang et al 2015).…”

“…These hypotheses have been supported in laboratory experiments. For example, exposing early life-stages of P. xylostella (Xing et al 2014;Zhang et al 2015), eggs of Manduca sexta and Wyeomyia smithii (Zani et al 2005) and early instar nymphs/larvae of Metopolophium dirhodum (Ma et al 2004b) and Harmonia axyridis (Knapp and Nedvěd 2013) to acute [i.e. high amplitude but short duration (few hours)] heat stress did not affect female fecundity or adult phenotype.…”

“…When the early stages of insects are stressed by a short extreme high temperature, compensatory mechanisms could likely restore all functions during subsequent stages-if individuals do not experience stressful conditions during these stages (Zani et al 2005;Potter et al 2011;Xing et al 2014;Zhang et al 2015). In contrast, when acute high temperatures applied during late pre-imaginal stages cause severe damage, organisms may not be able to recover before and during the adult stage, resulting in depressed reproduction (Ma et al 2004b;Zani et al 2005;Zhang et al 2015). Consequently, heat stress at a life-stage closer to the adult stage causes more detrimental impacts on adult reproduction (Zhang et al 2015).…”

Life history consequences of temperature transients inDrosophila melanogaster

“…Weather fronts may not only alter an organism's performance during the front itself, but also induce carry-over effects that persist even after weather returns to normal. Surprisingly little is known about the impact of such thermal transients on the physiology and life history of ectotherms, except in regards to short-term exposure to extreme temperatures (Bubliy and Loeschcke, 2001;David et al, 2003;Gibert et al, 2001;Hercus et al, 2003;Krebs and Loeschcke, 1994a;Krebs and Loeschcke, 1994b;Lee et al, 1987;Maynard Smith, 1958;Rohmer et al, 2004;Sisodia and Singh, 2006;Zani et al, 2005a;Zani et al, 2005b).…”

Immobile and Mobile Life-History Stages Have Different Thermal Physiologies in a Lizard

“…Even in species with simpler life histories (e.g., hemimetabolous insects, fish, and reptiles), size and mobility generally change across ontogeny. Such variation in phenotype and habitat expose life-history stages to different thermal environments, and these differences are predicted to select for dissimilar thermal reaction norms at each life-history stage (Kingsolver and Gomulkiewicz 2003;Zani et al 2005;Marais and Chown 2008;Miller et al 2013). Mobile and immobile life-history stages, in particular, should experience distinct selective regimes due to the fundamental difference in how these stages interact with the thermal environment.…”