Parental and Mating Effort: Is There Necessarily a Trade‐Off?

Abstract

One of the common assumptions in the study of the evolution of parental care is that trade‐offs exist between parental investment and other fitness‐related traits. In general, this body of work follows the traditional definition that parental investment (in the current offspring) decreases that individual’s ability to invest in future reproduction (Trivers 1972). However, examination of the empirical evidence shows that assuming a trade‐off between parental and mating effort is not always appropriate. This overemphasis on a trade‐off between mating and parental effort has arisen in part because of an oversimplification of female reproductive strategies, a failure to consider interactions between the sexes, and a tendency to consider behaviours as unifunctional, thereby ignoring the more complex relationship between mating and parental effort in many species. Here, we first examine the empirical evidence for trade‐offs between mating and parental effort in males and females to ask when trade‐offs occur and what pattern they take. By highlighting a number of exemplar species, we then explore how the presence or absence of trade‐offs relates to mate choice and sexual selection in both sexes. Finally, we highlight the importance of considering individual variation, which has been particularly overlooked in examinations of female investment, and how preferences in one sex may influence the existence and our interpretation of apparent trade‐offs in the other sex.

Too many men: the violence problem?

“…However, if successful provisioning depends on the control of resources through physical competition, high ASRs might be associated with violence. Much of the logic above assumes a tradeoff between parenting effort and mating effort, which is not always the case [96]. In some species, providing parental care can be a key element of the mate competition strategy of a male, as in two-spotted goby (Gobiusculus flavescens) [33].…”

Females allocate differentially to offspring size and number in response to male effects on female and offspring fitness

“…Increased fecundity could also be favoured when paternal care increases at greater clutch sizes [25,26]. However, these are largely qualitative post-hoc explanations of reproductive compensation [4], and therefore are somewhat unsatisfactory. A related problem is that male and female condition or age can affect offspring size and number [27,28], which can cloud one's ability to detect differential allocation and compensation [29].…”

“…Recent reviews of empirical studies of mating and reproductive investment [4,18] found evidence for both differential allocation and reproductive compensation in a wide range of taxa, including insects, fish, amphibians and birds. Evidence of differential allocation and compensation included several different response metrics, such as differential offspring survival and growth, egg size, clutch size and androgen levels (see e.g.…”

“…Evidence of differential allocation and compensation included several different response metrics, such as differential offspring survival and growth, egg size, clutch size and androgen levels (see e.g. table 2 in [4]), suggesting that maternal responses to male phenotypes can be diverse.…”

“…Understanding why and when a female should adjust her reproductive effort in response to male traits is a challenge [1][2][3][4]. Male traits can affect female investment in offspring size and number [1,[5][6][7][8][9][10][11][12][13], as well as the sex ratio of offspring [14,15].…”