An experimental test of the role of male mating history on paternal effects in the livebearer fish Gambusia holbrooki

Abstract

Studies often show that paternal age affects offspring fitness. However, such effects could be due either to age, or to a male's previous mating effort (which is necessarily confounded with age). We experimentally tested whether differences in the mating history of old males affect offspring performance in the mosquitofish Gambusia holbrooki. Upon maturation, males were housed for a duration of the natural field-breeding season (23 weeks) either with mating access to females (lifetime-mating), or with visual but no physical access to females (no-mating). We then paired these males with a female to test whether male mating history had a significant effect on their mate's breeding success or offspring performance. The daughters, but not the sons, of 'no-mating' treatment males matured significantly sooner, and at a significantly smaller size, than those of 'lifetime-mating' treatment males. There was, however, no effect of male mating history on their daughters' initial fecundity, or on proxy measures of their sons' reproductive success. These results, when combined with earlier studies showing effects of male mating history on sperm quality, growth and immunity, suggest that variation in paternal effects currently attributed to male age could partly arise because older males have usually mated more often than younger males.

Keywords: ageing; mating history; paternal effects; poeciliids; sexual selection; sperm quality.

Figure 1.

Experimental protocol to determine how male mating history affects offspring performance in eastern mosquitofish (G. holbrooki). Females are represented by fish with a black gravid spot, and males by fish with an extended anal fin (the gonopodium).

Figure 2.

Gambusia holbrooki; the effect of mating history of old fathers on offspring reproductive traits: (a) the time (in days) for daughters (n = 103, ♀) and sons (n = 81, ♂) of fathers experiencing either ‘lifetime mating’ or ‘no mating’ to reach sexual maturity; and (b) the body size (standard length in millimetres) of these daughters (n = 103, ♀) and sons (n = 81, ♂) at sexual maturity. Box plots show median (horizontal line) and interquartile range of data.