The influence of potential reproductive rate and variation in mate qualityon male and female choosiness in the sand goby, Pomatoschistus minutus

Recent models of choosiness in mate choice have identified two particularly important factors: the potential reproductive rate (PRR) of the choosing s ex relative to that of the chosen sex, and the variation in quality of pote ntial mates. This experimental study tested how these factors affected choo siness in male and female sand gobies, Pomatoschistus minutus. We manipulat ed relative PRR by means of water temperature, and mate quality by means of body length. The choosing male or female was offered a choice between two mates with either a small or a large difference in body length representing a small or a large variation in mate quality. Choosiness was measured as ( 1) preference for the larger mate, and (2) as whether or not spawning occur red with the smaller mate, while the larger mate was visible but screened o ff. We found that females preferred large males, and that their level of ch oosiness was affected by variation in male quality, but not by their own re lative PRR. Males, on the other hand, seemed unselective in all treatments and were in general more likely than females to spawn with their provided p artner. This suggests that in the sand goby, variation in male mate quality has a greater influence than relative PRR on facultative changes in female choosiness. However, a general difference in PRR between males and females may be one important factor explaining the observed sex difference in choo siness.