Influence of male competition on male mating behaviour in the cave molly, Poecilia mexicana

Abstract

In many species, male mating behaviour is correlated with male body size, with large males often being preferred by females. Small surface-dwelling Poecilia mexicana males compensate for this disadvantage by being more sexually active and using sneaky copulations. In a cave-dwelling population, however, small males do not show this behaviour. Do small males alter their behaviour in the presence of a large rival? Here, we investigated the influence of male competition on male mating behaviour in the cave form. Two males of different sizes were mated with a female either alone or together with the other male. No aggressive interactions were observed between either fish. There was no statistically significant difference in the frequency of sexual behaviours between the two treatments. In both treatments, large males were more sexually active than small males. Thus, small cave molly males do not switch to an alternative mating behaviour in the presence of a larger rival. Possibly, the extreme environmental conditions in the cave (e.g. low oxygen content and high levels of hydrogen sulphide) favour saving energetic costs, resulting in the absence of alternative mating behaviour in small males.

Local adaptation and pronounced genetic differentiation in an extremophile fish, Poecilia mexicana, inhabiting a Mexican cave with toxic hydrogen sulphide

“…Compared to P. mexicana from typical surface habitats, cave mollies have strikingly reduced aggressive (Parzefall 1974, 1979) and shoaling behaviour (Parzefall 1993b), alternative male mating tactics (Plath et al . 2003, 2004a, 2005b; Riesch et al . 2006a) and species recognition mechanisms (Riesch et al .…”

Classification, Identification, and Manipulation of Relevant Factors for Adaptation and Behavioural Adjustment from a Psychological Point of View

“…Although all the parts of any organism are adapted to their life conditions, the modification of the individual behaviour, like mechanisms of adaptation or adjustment to the changing environmental conditions, and even of the anatomy of the species, is usually a function of the stimulatory differences that the organisms face (e.g. Lorenz, 1979;Riesch, Schlupp, & Plath, 2006;Taru, Kanda, & Sunobe, 2002;Vicente & Paulo, 1989). This suggests that if one of the elements that constitute the situation (i.e.…”

Use of microsatellite paternity analysis to determine male mating success in the western mosquitofish, Gambusia affinis

“…However, male size might also indirectly affect fitness via correlative associations with other traits (e.g., dominance status, aggression and condition; Haley et al, 1994;Teder, 2005;Candolin, 2005;Fisher et al, 2006). For example, larger males often have a competitive advantage over smaller males because they are more aggressive (Riesch et al, 2006) and, thus, more likely to court females (Morris, 1991;Savalli & Fox, 1999, but see Friedl & Klump, 2005). As a result, smaller males in some species often use alternative reproductive tactics such as sneaky or coercive (forced) matings, rather than the traditional courtship behaviors often exhibited by larger and/or dominant males Gross, 1996;Pilastro et al, 1997).…”

“…The livebearing fishes in the family Poeciliidae show considerable variation in male size (Snelson, 1989), making them good candidates for studies of body size effects on mating success. For example, large sailfin molly males display an enlarged, brightly colored dorsal fin to attract females, while smaller males, lacking the sail-like fin, coerce females (Riesch et al, 2006). Also, in the related guppy, larger, more colorful males court females, while smaller males use sneaky behaviors to obtain copulations (Houde, 1997).…”

“…A genetic link to male body size has also been shown in other livebearing fishes (Erbelding-Denk et al, 1994). Therefore, most studies on mating behavior mosquitofish and other livebearers assume some heritable component to male body size Pilastro et al, 1997;Riesch et al, 2006). However, there also is a known social component to male size at maturity (Campton & Gall, 1988;Snelson, 1989), further complicating the causal mechanisms of size of maturity in male mosquitofish.…”