When do looks matter? Effects of mate quality and environmental variability on lifetime reproduction

Abstract

Inter-individual variation in lifetime reproduction is the key target for natural selection, and it is influenced by many factors. Yet, we lack an understanding of how abiotic and biotic factors interact to influence lifetime reproductive output (number of offspring) and reproductive effort (total biomass invested into reproduction). Thus, we used a factorial design to manipulate variability in food availability and temperature while also accounting for mate quality. We tested hypotheses related to estimates of lifetime reproductive output and effort in females of the wing-dimorphic sand field cricket (Gryllus firmus). Environmental variability influenced a temporal tradeoff of reproduction because females experiencing fluctuating temperatures had a particular bias toward reproductive output during early adulthood. Also, complex environmental variability (i.e., multiple and co-varying environmental factors) influenced differential allocation, which is when individuals adjust their reproductive efforts according to mate quality. Females mated to higher quality males laid more eggs only in environments that were highly stable (constant temperature and ad libitum food access). Reproductive effort was affected by a food–temperature interaction—fluctuating temperatures promoted egg production when food was limited, while constant temperature promoted egg production when food was abundant. Although a wing dimorphism mediates a well-established flight–fecundity tradeoff during early adulthood in G. firmus, short- and long-winged morphs exhibited similar lifetime reproduction and responded similarly to complex environmental variability. Given the natural co-variation of many environmental factors (e.g., water limitation often accompanies heat waves), we encourage continued work examining the role of complex environmental variability in tradeoffs related to reproductive decision-making and allocation. It is unclear how abiotic and biotic factors interact to influence lifetime reproductive output (number of offspring) and reproductive effort (total biomass invested into reproduction). Thus, we examined the effects of mate quality and complex environmental variability (variable food and temperature) on several metrics of lifetime reproduction. Female crickets mated to high-quality males had greater reproductive output, but only in highly stable or environmental conditions. Fluctuating temperatures biased reproductive output toward early adulthood, particularly in short-winged females. Reproductive effort was affected by a food–temperature interaction—fluctuating temperatures promoted egg production when food was limited, while constant temperature promoted egg production when food was abundant. Females can also retain unfertilized eggs, and egg retention (i.e., unrealized fitness potential) was influenced by a combination of mate quality and complex environments. Thus, it is important to carefully consider the interplay between biotic and abiotic factors in aspects of lifetime reproduction and reproductive decision-making.