Male Pacific blue-eye, Pseudomugil signifer

 

The exaggeration of sexually-selected traits is predicted to be constrained by the costs of both producing and maintaining these often elaborate ornaments. Females are thought to choose males with highly exaggerated traits because they are a reliable indicator of male quality due to underlying costs or handicap incurred by their display. The most commonly assumed cost for male ornamentation is predation pressure due to greater conspicuousness and decreased locomotor performance. Despite its intuitive basis, the physiological costs of male ornamentation are not well established.

 

Pacific blue-eye field site at Booloumba Creek, Kenilworth

 

 

Males often use multiple ornaments to signal independently to both rival males and potential mates. These multiple signals are also likely to vary in their associated costs. For example, elaborate signals to females may increase predation pressure via conspicuousness and reduced locomotor performance while intra-sexual signals of strength may have an enhanced metabolic requirement. Multiple signals may also provide a more detailed indicator of overall male quality, as only the highest quality males could bare the varied costs. To test this idea, we investigated the locomotor consequences of multiple ornaments for males of the pacific blue-eye (Pseudomugil signifer) and whether these signals are used differently during male competition and female choice.

 

Male Threadfin Rainbowfish, Iriatherina werneri

 

Recently, we have also examined the costs and benefits of highly exaggerated male fin ornaments in the threadfin rainbowfish (Iriatherina werneri). In this species, males posses high fan shaped 1st dorsal fin and multiple long thread-line tendrils that can extend beyond the caudal fin. We examined both the locomotor and metabolic consequences of male ornaments in threadfins and how the manipulation of these traits may alter the associated costs.