When it's hot and dry: life-history strategy influences the effects of heat waves and water limitation

Abstract

The frequency, duration, and co-occurrence of several environmental stressors, like heat waves and droughts, are increasing globally. Such multiple stressors may have compounding or interactive effects on animals, resulting in either additive or non-additive costs, but animals may mitigate these costs through various strategies of resource conservation or shifts in resource allocation. Through a factorial experiment, we investigated the independent and interactive effects of a simulated heat wave and water limitation on life-history, physiological, and behavioral traits. We used the variable field cricket, Gryllus lineaticeps, which exhibits a wing dimorphism that mediates two distinct life-history strategies during early adulthood. Long-winged individuals invest in flight musculature and are typically flight capable, whereas short-winged individuals lack flight musculature and capacity. A comprehensive and integrative approach with G. lineaticeps allowed us to examine if life-history strategy influenced the costs and cost-limiting strategies due to multiple stressors. Concurrent heat wave and water limitation resulted in largely non-additive and single-stressor costs to important traits (e.g., survival and water balance), extensive shifts in resource allocation priorities (e.g., reduced prioritization of body mass), and a limited capacity to conserve resources (e.g., heat wave reduced energy use only when water was available). Life-history strategy influenced the emergency life-history stage because wing morphology and stressor(s) interacted to influence body mass, boldness behavior, and immunocompetence. Our results demonstrate that water availability and life-history strategy should be incorporated into future studies integrating important conceptual frameworks of stress across a suite of traits—from survival and life history to behavior and physiology.

Flight capacity drives circadian patterns of metabolic rate and alters resource dynamics

“…However, flight capacity in four Gryllus species, including G. lineaticeps, reduces the efficiency by which ingested food is converted into body mass (Figure 3a; Mole & Zera, 1993Zera et al, 1998) The costs and benefits of flight investment vary across taxa (reviewed in Dingle, 2014). In Gryllus, the relative advantages of flight capacity are environment-dependent (e.g., Glass & Stahlschmidt, 2019;Padda et al, 2021) and stable environments are predicted to favor the evolution of flightlessness in insects (Roff & Fairbairn, 1991;Roff, 1984). However, periods of food insecurity are expected to change in frequency and duration with global climate change (Ciais et al, 2005;Currano et al, 2008), and food may play an important role in the evolution of flightlessness in Gryllus.…”

“…On Day 6, SMR was determined using flow‐through respirometry (see Supporting Information) as described previously (Padda et al, 2021; Stahlschmidt & Glass, 2020). Carbon dioxide production rate ( V̇ CO2 ) was measured as an indirect estimate of SMR (Clark et al, 2016; Lighton, 2008; Nespolo et al, 2005), because CO 2 analyzers are typically more sensitive than O 2 analyzers (Harrison et al, 2012), and V̇ CO2 and V̇ O2 data in this study strongly correlated with one another ( R = 0.91; p < 0.001).…”

Body condition indices are better surrogates for lean mass and water content than for body fat content in an insect

“…Relationship between body size (femur length) and body mass for a reference population of adult G. firmus (n = 2947). Data for the reference population came from both sexes of adult short-winged (SW) and long-winged G. firmus from several published papers (Nguyen & Stahlschmidt, 2019;Glass & Stahlschmidt, 2019;Stahlschmidt et al, 2020aStahlschmidt et al, , 2020aPadda, Glass, & Stahlschmidt, 2021), as well as from unpublished data. However, subsets of data (e.g., male-only or SW-only data) were used to determine R i and Mi for each sex and wing morph because sexes and wing morphs exhibited different allometric relationships between body size and body mass.…”

Evidence for microbially-mediated tradeoffs between growth and defense throughout coral evolution

“…Tradeoffs in life-history strategy are key features in animal evolution (1, 2). These tradeoffs often involve differential investments in life-history traits such as growth rate (3); reproductive maturation, timing, and fecundity (4); or resistance to stress (5), predation (6) or disease (7). The fitness costs and benefits of these investments are often context-dependent.…”

“…The fitness costs and benefits of these investments are often context-dependent. Thus, shifts in ecological or environmental conditions can favor some life-history strategies over others (5), sculpting trait evolution within animal lineages and reshaping ecological communities. Global climate change is shifting the patterns and prevalence of disease in many animal taxa, while increasing the virulence of some pathogens (8,9).…”