Date of Award


Degree Type


Degree Name

Doctor of Philosophy


Most nesting male longear sunfish (Lepomis megalotis peltastes) excavate their nest in dense aggregations, while a small percentage nest solitarily. The importance of sexual selection in the evolution of this breeding system was evaluated by examining the influence of certain nest and male characteristics on spawning success and by comparing the reproductive success of social and solitary nesters. The hypothesis that males unlikely to attract mates benefit from group nesting because they increase their success by stealing fertilizations was tested.;Among social nesters, females spawned preferentially with males nesting early in the period and in central positions. Nest diameter and male size were also correlated with the predictors of spawning success, but apparently were not assessed directly by females. Positive relationships between predictors of success and the number of nest intrusions received and performed by each male were uncovered, indicating that unsuccessful males performed few intrusions into neighbours' nests. The success of fertilization stealing attempts is unknown.;Spawning period, which presumably reflected environmental conditions, was an important determinant of reproductive success. Solitary males tended to foster more larvae and probably enjoyed greater certainty of paternity than did social nesters. They were also significantly larger than social males.;The existence of nesting aggregations can be interpreted from a sexual selection perspective, as suggested in a previous study. Males unable to attract females nest around attractive males and thereby create groups. The few intrusions they perform may represent their only possibility of successful reproduction. Attractive males risk reducing their success by nesting socially and probably attempt nesting solitarily. High spawning synchrony, however, may prevent them from renesting elsewhere once other males aggregate around them. Females comply with this system by preferentially spawning with attractive social males and tolerating the intrusions they receive, but spawning opportunistically with large males who remained solitary.



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