Life histories as mosaics: Plastic and genetic components differ among traits that underpin life‐history strategies

Abstract

Life-history phenotypes emerge from clusters of traits that are the product of genes and phenotypic plasticity. If the impact of the environment differs substantially between traits, then life histories might not evolve as a cohesive whole. We quantified the sensitivity of components of the life history to food availability, a key environmental difference in the habitat occupied by contrasting ecotypes, for 36 traits in fast-and slow-reproducing Trinidadian guppies. Our dataset included six putatively independent origins of the slow-reproducing, derived ecotype. Traits varied substantially in plastic and genetic control. Twelve traits were influenced only by food availability (body lengths, body weights), five only by genetic differentiation (interbirth intervals, offspring sizes), 10 by both (litter sizes, reproductive timing), and nine by neither (fat contents, reproductive allotment). Ecotype-by-food interactions were negligible. The response to low food was aligned with the genetic difference between high-and low-food environments, suggesting that plasticity was adaptive. The heterogeneity among traits in environmental sensitivity and genetic differentiation reveals that the components of the life history may not evolve in concert. Ecotypes may instead represent mosaics of trait groups that differ in their rate of evolution.

Copepod life history evolution under high‐ and low‐food regimes

“…We evaluated key life-history traits that have responded to food regime in other species (e.g. Trinidad guppies: Felmy et al, 2022), including size and age at maturity, egg size and fecundity, accounting for the effects of maternal size on reproductive traits due to potential correlations between egg size, fecundity, and mother size (Barneche et al, 2018;Moran & McAlister, 2009).…”

An ecological explanation for hyperallometric scaling of reproduction

“…The expression of life‐history traits in guppies often strongly depends on food availability (Felmy et al., 2022). Hence, it was unsurprising that guppies in the high food treatment were larger and reproduced more than same‐aged individuals in the low food treatment (Figure 3a).…”

“…The effects of individual differences in resource assimilation are non‐trivial. Resource‐dependent expression of life‐history traits often exceeds the effect of evolved differences between locally adapted populations (Felmy et al., 2022). Trait‐dependent differences in assimilation rates can flip predictions about life‐history evolution (Laskowski et al., 2021), generate eco‐evolutionary dynamics (Coulson, 2020) and contribute to the evolution of coexistence (Anaya‐Rojas et al., 2021).…”

“…The effects of individual differences in resource assimilation are non-trivial. Resource-dependent expression of life-history traits often exceeds the effect of evolved differences between locally adapted populations (Felmy et al, 2022).…”

Evolving to stay the same: life history evolution and tradeoffs in response to high and low total food

“…For example, restoration ecology was used in Daphnia to show shifts from ‘thrifty' higher growth efficiency and flatter reaction norms in ancient low phosphorus (P) environments to ‘opportunistic' lower growth efficiency modern genotypes with greater plasticity to P supply (Frisch et al 2014). High‐food regimes can select for either larger (in mosquitofish) or smaller (in copepods and guppies) offspring relative to low‐food regimes (Hulthén et al 2021, Felmy et al 2022, Blake and Marshall 2023). In copepods, egg size‐fecundity tradeoffs are hidden by countergradient variation, while in guppies they are not (Felmy et al 2022).…”