Size Of Secondary Sexual Character Research Articles

Different reproductive tactics in male collared flycatchers signalled by size of secondary sexual character

Most studies of variation in male reproductive tactics have focused on conspicuous categorical differences in mating behaviour (i.e. variation in mating strategies). However, in the presence of trade–offs between investment in competition over matings, parental care and survival, a male's optimal allocation rule might vary according to his physiological condition and social or ecological environment. Thus, there may also be more subtle variation in male reproductive tactics. Here, I show that the reproductive effort (estimated as residual change in condition) of male collared flycatchers was affected by the size of their forehead patch (a secondary sexual character), age and date of arrival at the breeding grounds. Among early males (i.e. males with a high likelihood of both attracting more than one female and obtaining extra-pair copulations), large–patched males made a relatively large reproductive effort and as a result were in worse condition at the time of feeding offspring as compared to small–patched males. Furthermore, among early breeders, young males and males with experimentally increased forehead patch size made a relatively high effort. By contrast, regardless of age and badge size, there were no such patterns observed among late breeders. These results suggest that collared flycatchers use different reproductive tactics depending on both internal and external factors, and that the size of a secondary sexual trait may not only indicate variation in individual condition but also predict how resources will be allocated between pre– and post–mating reproductive activities.

Paternal genetic contribution to offspring condition predicted by size of male secondary sexual character

Whether females can obtain genetic benefits from mate choice is contentious, and the main problem faced by previous studies of natural populations is that many factors other than paternal genes contribute to offspring fitness. Here, we use comparisons between sets of naturally occurring maternal half-sibling collared flycatchers, Ficedula albicollis, to control for this problem. We show, first, that there are paternal genetic effects on nestling fledging condition, a character related to fitness in this species. Further, the magnitude of the paternal genetic contribution to this character is related to the size of a condition-dependent male secondary sexual character. Our results demonstrate that genetic benefits from mate choice can be predicted by the size of a secondary sexual character, and therefore provide direct support for indicator models of sexual selection.