Plastic sex‐roles in the common goby – the effect of nest availability

Abstract

One of the most important factors shaping animal sex‐roles is the operational sex ratio, since a skew of this ratio promotes mating competition in the more abundant sex. In this study, we wanted to see if a change in sex‐roles, related to an environmental induced change in operational sex ratio, could be demonstrated in a field situation. Common goby (Pomatoschistus microps) males build nests under bivalve shells and provide exclusive parental care. Therefore, available nest sites are crucial for successful breeding in this species and should also affect the operational sex ratio. We addressed the question of whether the availability of nest sites, through an effect on the operational sex ratio, affects courtship and mating competition in the common goby. We increased nest site availability in the field by adding potential nest material (bivalve shells) to one location. We then compared the reproductive behaviour of the gobies at this and another location with lower nest site abundance. In general, the reproductive behaviour differed as predicted. Under nest shortage, males occupied new nests and received eggs faster than under nest excess. Behavioural observations of nests revealed that males initiated courtship more often than females where nest sites were abundant, whereas female courtship dominated where nests were scarce. Males more often rejected females attempting to enter their nests under nest shortage, male sneaking attempts were also more common in this bay. Male‐male aggression was frequent at both locations, whereas agonistic interactions between females only occurred in the nest shortage bay. Thus, males should be subject to sexual selection in both bays even though courtship roles differed. These results suggest that nest site availability affects mating competition and courtship roles in the common goby.

Fluctuating mate preferences in a marine fish

“…Recently, sand goby females have been found to use multiple cues in mate choice, exhibit individual variation in mate preferences and make context-dependent mating decisions (Lehtonen & Lindström 2008;Lehtonen & Wong in press). In addition, the strength of female mate choice in two closely related gobiid fish has been shown to change over the course of the breeding season (Borg et al 2002;Forsgren et al 2004). However, as far as we are aware, very few studies (on any species) have examined longer-term fluctuations in mate choice (for a recent exception in birds, see Chaine & Lyon 2008).…”

Lonely hearts or sex in the city? Density-dependent effects in mating systems

“…The study of Bonenfant et al (2003) is one of many that highlight that the population structure and the strength of sexual selection can be modified by environmental factors, such as variations in visibility (Seehausen et al 1997;Seehausen & van Alphen 1998;Järvenpää & Lindströ m 2004) or the availability of nest sites or other necessary resources for reproduction (Simmons 1992;Forsgren et al 1996;Borg et al 2002;Debuse et al 2003). Low-visibility scenarios mimic low population density if individuals detect each other visually.…”

“…Forsgren et al 1996;Borg et al 2002), but they very rarely consider the full demographic loop: the behaviour of the two sexes leads to a particular pattern of reproductive output, which then determines population structure and thus feeds back to the behavioural options experienced by individuals (but see e.g. Horth & Travis 2002).…”

Full of eggs and no place to lay them: hidden cost of benthic development

“…Other examples of substrate limitation for egg deposition have been reported (Pechenik 1978, Brenchley 1981, D'Asaro 1986, DeMartini 1991, Hastings 1992, Warner et al 1995, Kuhlmann 1997, Borg et al 2002, but how common is this situation? Swanson (2004) measured crawling distances of a snail that were large relative to spacing of potential deposition sites.…”