Abstract
Life‐history theory predicts trade‐offs between reproductive and survival traits such that different strategies or environmental constraints may yield comparable lifetime reproductive success among conspecifics. Food availability is one of the most important environmental factors shaping developmental processes. It notably affects key life‐history components such as reproduction and survival prospect. We investigated whether food resource availability could also operate as an ultimate driver of life‐history strategy variation between species. During 13 years, we marked and recaptured young and adult sibling mouse‐eared bats (Myotis myotis and Myotis blythii) at sympatric colonial sites. We tested whether distinct, species‐specific trophic niches and food availability patterns may drive interspecific differences in key life‐history components such as age at first reproduction and survival. We took advantage of a quasi‐experimental setting in which prey availability for the two species varies between years (pulse vs. nonpulse resource years), modeling mark‐recapture data for demographic comparisons. Prey availability dictated both adult survival and age at first reproduction. The bat species facing a more abundant and predictable food supply early in the season started its reproductive life earlier and showed a lower adult survival probability than the species subjected to more limited and less predictable food supply, while lifetime reproductive success was comparable in both species. The observed life‐history trade‐off indicates that temporal patterns in food availability can drive evolutionary divergence in life‐history strategies among sympatric sibling species.
Highlights
Life-history theory provides a framework for understanding how evolution shapes life cycles, where natural selection is the ultimate driver of species-s pecific vital rates and breeding tactics (Stearns, 1976)
The delayed availability of the main food source of the lesser mouse-eared bat, that is, the lower food supply it usually experiences in early spring, results in a median delay in parturition of approximately 10 days compared to the greater mouse-eared bat (Arlettaz et al, 2001)
This comparative demographic analysis of two closely related sympatric bat species corroborates several predictions derived from life- history theory about the effects of interspecific niche differentiation on vital rates (Stearns, 1992)
Summary
Life-history theory provides a framework for understanding how evolution shapes life cycles, where natural selection is the ultimate driver of species-s pecific vital rates and breeding tactics (Stearns, 1976). The delayed availability of the main food source of the lesser mouse-eared bat (bush crickets), that is, the lower food supply it usually experiences in early spring, results in a median delay in parturition of approximately 10 days compared to the greater mouse-eared bat (Arlettaz et al, 2001) Such a temporal difference may have an impact on the age at first reproduction because mating in both species takes place in late summer, with late-born pups being unlikely to reach sexual maturity as yearlings (Frick, Reynolds, & Kunz, 2010). To achieve state-o f-t he-art analysis, we relied on probabilistic capture– recapture models that account for imperfect detection and deliver accurate estimates of life-history traits
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