Patterns of reproductive success determined by DNA fingerprinting in a communally breeding oceanic bird

Abstract

Using DNA fingerprinting we estimated the reproductive success of 49 adult birds belonging to 16 breeding groups of the sexually monomorphic brown skua (Catharacta lonnbergi) from the Chatham Islands (New Zealand). This population has a variable mating system, breeding in both monogamous and polyandrous groups. The parentage of 45 chicks produced over three breeding seasons was unequivocally determined using the multilocus probes 33.15 and 33.6. We found no evidence of either extra-pair or extra-group fertilization and there was no evidence to suggest egg dumping by females in any breeding group. Consequently, in the case of pairs, parentage of all chicks was assigned to the resident adult birds. In addition, band sharing analysis indicated that members of communal groups were not close relatives. In the 10 communally breeding groups examined, multiple paternity within a clutch was recorded on two of the 12 occasions in which two chicks were reared. Analysis of the parentage of offspring belonging to different groups, from different years, demonstrated that the number of chicks produced by some adult males varied considerably between seasons. In contrast, the reproductive success of other individuals was constant; for example, one male produced two chicks in each of the three seasons it was studied, while other males in communal groups did not produce any chicks during the course of this study. Fitness is a lifetime parameter, and any assessment of it requires studies over at least the average lifetime ofan individual. The findings presented in this study suggest that, for brown skuas, there are significant differences in the reproductive success of some adult males in different breeding seasons. These results indicate that estimates of reproductive fitness based on only a single breeding season's data can be seriously inaccurate. Should temporal changes in paternity (and/or maternity) be shown to be common phenomena in other species, then such results would have major implications for the interpretation of parentage studies.

Subordinate superb fairy-wrens (Malurus cyaneus) parasitize the reproductive success of attractive dominant males

“…Such high rates of direct reproduction by subordinates have previously been reported only in cooperatively breeding birds where paternity is shared among unrelated members within a group (e.g. white-browed scrubwrens, S. frontalis ; dunnocks, Prunella modularis (Burke et al 1989); Galapagos hawks, Buteo galapagoensis (Faaborg et al 1994); and brown skua, Catharacta lonnbergi (Millar et al 1994)). By contrast, this is, to our knowledge, the first study to show that subordinate males can achieve high levels of reproductive success through extra-group copulations.…”

Integrating Molecular Techniques with Field Methods in Studies of Social Behavior: A Revolution Results

“…In Barbary macaques, Macaca sylvanus, there was little reproductive dominance by the ''alpha'' male, and most males in a group sired offspring (von Segesser et al 1995). The caution sounded by Millar et al (1994) and Altmann et al (1996) about interpretation of studies based on a limited part of the reproductive lifetime are particularly pertinent here; more work is required before abandoning the theory that animals fight for high dominance rank because it confers higher fitness. The data indicate that the size of the group in which an individual lives may be especially important in the dynamic relationship between its dominance status and its reproductive success.…”

Life History and the Male Mutation Bias

“…EPP frequency is usually estimated by parentage testing based on minisatellite or microsatellite DNA profiling, and we used data on such frequencies from the compilation of Møller and Cuervo (2000). Exceptions included Icteria virens for which data was from Eckerle and Thompson (2001) and Catharacta antarctica for which data was from Millar et al (1994). For Larus ridibundus we used the EPP frequency estimated for the closely related Larus occidentalis (Gilbert et al 1998), and for Cygnus buccinator we used the estimate from the similarly closely related Cygnus columbianus (Rees et al 1996).…”