Sammendrag
Gobies have proven to be excellent models for studies of variation in sexual selection and how such variation relates to e.g. nest site availability, reproductive rates and operational sex ratios (OSR). In sand gobies, Kvarnemo and co-workers have performed lab experiments and models addressing the dynamics of OSR, reproductive rates, mating competition and mate choice, and how these phenoma relate to water temperature. However, while potential reproductive rates of sand gobies are plastic in the lab, to our knowledge little is known about OSR and potential variation in mating competition (and sex roles) in the wild. In two-spotted gobies, field observations by Forsgren et al. have revealed a dramatic change in the OSR over the season, and a consequent shift in sex roles from conventional to reversed. Little is known, however, about the mechanisms modulating two-spotted goby sex roles. In common gobies, a field experiment by Borg et al. has shown that courtship roles shift when OSR become female biased due to a shortage of nest sites. There are also a number of studies on sand gobies by (mainly) Lindström et al. on how the opportunity of sexual selection is affected by e.g. variation in nest site availability. There is also evidence that mate choice vary in gobies according to various factors. Taken together, evidence from these three gobies provide interesting insights into reproductive dynamics. Even so, there are still far more questions than answers in this field. We invite participants to contribute to a discussion of what we currently know about variation in sexual selection and goby sex roles, what we would like to know, and how we should proceed to enhance our understanding of this variation in the wild, the underlying procesesses, and the implications of such variation. Are the dynamical nature of goby sex roles typical of many other wild fishes?
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