Maternal response to environmental unpredictability

Abstract

Mothers are expected to use environmental cues to modify maternal investment to optimize their fitness. However, when the environment varies unpredictably, cues may not be an accurate proxy of future conditions. Under such circumstances, selection favors a diversifying maternal investment strategy. While there is evidence that the environment is becoming more uncertain, the extent to which mothers are able to respond to this unpredictability is generally unknown. In this study, we test the hypothesis that Daphnia magna increase the variance in maternal investment in response to unpredictable variation in temperature consistent with global change predictions. We detected significant variability across temperature treatments in brood size, neonate size at birth, and time between broods. The estimated variability within‐brood size was higher (albeit not statistically significant) in mothers reared in unpredictable temperature conditions. We also detected a cross‐generational effect with the temperature history of mothers modulating the phenotypic response of F1's. Notably, our results diverged from the prediction that increased variability poses a greater risk to organisms than changes in mean temperature. Increased unpredictability in temperature had negligible effects on fitness‐correlated traits. Mothers in the unpredictable treatment, survived as long, and produced as many F1's during lifetime as those produced in the most fecund treatment. Further, increased unpredictability in temperature did not affect the probability of survival of F1's. Collectively, we provide evidence that daphnia respond effectively to thermal unpredictability. But rather than increasing the variance in maternal investment, daphnia respond to uncertainty by being a jack of all temperatures, master of none. Importantly, our study highlights the essential need to examine changes in variances rather than merely on means, when investigating maternal responses.

A global synthesis of offspring size variation, its eco‐evolutionary causes and consequences

“…Theory supports this idea when the offspring size fitness function is modelled as dome‐shaped (Marshall et al., ), but not when offspring fitness is a positive function of offspring size (Einum & Fleming, ; McGinley, Temme, & Geber, ). Correlative studies suggest a positive relationship between environmental predictably and the level of offspring size variation within broods (Morrongiello, Bond, Crook, & Wong, ), but few studies have manipulated the offspring environment to explore maternal bet‐hedging responses (but see Barbosa et al., ).…”

“…Correlative studies suggest a positive relationship between environmental predictably and the level of offspring size variation within broods (Morrongiello, Bond, Crook, & Wong, 2012), but few studies have manipulated the offspring environment to explore maternal bet-hedging responses (but see Barbosa et al, 2015).…”

Individual variation in reproductive behaviour is linked to temporal heterogeneity in predation risk

“…All rights reserved. selection favours different phenotypes at different times, investing in the diversification of individual strategies is adaptive [10][11][12]. As such, individual diversification in behavioural strategies is often more pronounced in temporally heterogeneous conditions than in more homogeneous ones [13].…”

Evolution of alternative insect life histories in stochastic seasonal environments

“…2009; Barbosa et al. 2015), and the diversity of alternative developmental pathways and consequent alternative phenotypes in the animal kingdom (Lively 1986; Harvell 1990; Brönmark and Miner 1992; McCollum and Van Buskirk 1996; Radwan et al. 2002; West‐Eberhard 2003; Bonte et al.…”

“…However, stochasticity effects on insect life history evolution and polyphenic expression of life history phenotypes have largely been neglected (but see Roff 1983;Halkett et al 2004). This is surprising given the diversity and ecological significance of insects (Stork 2003), the effect of climate variability on biological processes where insects are involved (e.g., the parasitism rate of caterpillars: Stireman et al 2005), the studies on various stochasticity and seasonality effects on life history evolution and plasticity in other arthropods (Arba ciauskas 2001; Varpe et al 2009;Barbosa et al 2015), and the diversity of alternative developmental pathways and consequent alternative phenotypes in the animal kingdom (Lively 1986;Harvell 1990;Br€ onmark and Miner 1992;McCollum and Van Buskirk 1996;Radwan et al 2002;West-Eberhard 2003;Bonte et al 2014), many of which arise via predictive plasticity.…”