Tandem Androgenic and Psychological Shifts in Male Reproductive Effort Following a Manipulated “Win” or “Loss” in a Sporting Competition

Theory suggests that reproductive effort generally increases with age, but life-history models indicate that other outcomes are possible. Empirical data are needed to quantify variation in actual age-dependence. Data are readily attainable for females (e.g. clutch per egg size), but not for males (e.g. courtship effort). To quantify male effort one must: (i) experimentally control for potential age-dependent changes in female presence; and, crucially, (ii) distinguish between the likelihood of courtship being initiated, the display rate, and the total time invested in courting before stopping (‘courtship persistence’). We provide a simple experimental protocol, suitable for many taxa, to illustrate how to obtain this information. We studied courtship waving by male fiddler crabs, Uca annulipes . Given indeterminate growth, body size is correlated with age. Larger males were more likely to wave at females and waved more persistently. They did not, however, have a higher courtship rate (waves per second). A known female preference for males with higher display rates explains why, once waving is initiated, all males display at the same rate.

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The influence of male age and simulated pathogenic infection on producing a dishonest sexual signal

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2012.1914 ◽

2012 ◽

Vol 279 (1748) ◽

pp. 4740-4746 ◽

Cited By ~ 16

Author(s):

Emily K. Copeland ◽

Kenneth M. Fedorka

Keyword(s):

Reproductive Effort ◽

Reproductive Value ◽

Female Fitness ◽

Sexual Signal ◽

Terminal Investment ◽

Male Age ◽

Residual Reproductive Value ◽

Male Reproductive Effort ◽

Allonemobius Socius ◽

Pathogenic Infection

In recent years, studies have shown that reproductive effort decelerates in response to pathogenic infection. If infection substantially reduces a host's residual reproductive value (RRV), however, then an acceleration of effort may instead occur (e.g. terminal investment). Reproductive acceleration would theoretically allow hosts to maintain or exaggerate their sexual signal upon infection. This would create a deceptive message from the perspective of the chooser, who may unwittingly copulate with an infected mate to their detriment. Using the cricket Allonemobius socius , we assessed the potential for reduced RRV to accelerate male reproductive effort and create a dishonest signal. RRV was manipulated through male age and simulated pathogenic insult. Reproductive effort was measured as calling song energetics, mating success, latency to mate and nuptial gift size. We show that males adopted either an accelerated or decelerated reproductive strategy upon infection, and that this decision was probably mediated by RRV. Moreover, males who accelerated their effort produced a dishonest signal by increasing their song energetics while providing fewer paternal resources (i.e. smaller gifts). Our study is one of the few to document the existence of dishonest signals and relate dishonesty to a potential reduction in female fitness, underscoring the conflict inherent in sexual reproduction.

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Hermaphrodites and parasitism: size-specific female reproduction drives infection by an ephemeral parasitic castrator

Scientific Reports ◽

10.1038/s41598-019-55167-x ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 1

Author(s):

Caitlin R. Fong ◽

Armand M. Kuris ◽

Ryan F. Hechinger

Keyword(s):

Reproductive Effort ◽

Reproductive Function ◽

Simultaneous Hermaphrodite ◽

Female Reproduction ◽

Female Function ◽

Males And Females ◽

Selection For ◽

Parasitic Castrator ◽

Male Reproductive Effort ◽

The Relationship

AbstractSex can influence patterns of parasitism because males and females can differ in encounter with, and susceptibility to, parasites. We investigate an isopod parasite (Hemioniscus balani) that consumes ovarian fluid, blocking female function of its barnacle host, a simultaneous hermaphrodite. As a hermaphrodite, sex is fluid, and individuals may allocate energy differentially to male versus female reproduction. We predicted the relationship between barnacle size and female reproductive function influences the distribution of parasites within barnacle populations. We surveyed 12 populations spanning ~400 km of coastline of southern California and found intermediate-sized barnacles where most likely to be actively functioning as females. While it is unclear why larger individuals are less likely to be actively reproducing as females, we suggest this reduced likelihood is driven by increased investment in male reproductive effort at larger sizes. The female function-size relationship was mirrored by the relationship between size and parasitism. We suggest parasitism by Hemioniscus balani imposes a cost to female function, reinforcing the lack of investment in female function by the largest individuals. Within the subset of suitable (=female) hosts, infection probability increased with size. Hence, the distribution of female function, combined with selection for larger hosts, primarily dictated patterns of infection.

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