Ecology and evolution of mate choice in a fish with paternal care (Pumpkinseed sunfish: Lepomis gibbosus)

An objective of sexual selection research is to explain the evolution of female mate choice. In many species males have evolved elaborate morphological and behavioural displays for attracting mates. Recent literature suggests that the size, symmetry and colour of these ornaments may be useful to females as an honest indicator of male quality. This idea was tested by examining the relationship between ornament size, symmetry and colour intensity and three measures of individual quality: body condition, parasite load and territory quality, in a wild population of pumpkinseed sunfish Lepomis gibbosus . Pumpkinseed grow fleshy extensions called flaps on their gill covers. The flaps are predominately black in colour with a posterior red pigmented spot bordered with white. These bilateral ornaments are presented by nesting males to females during courtship by erecting the gill covers in a dramatic frontal display. The results show that males grow larger flaps than females throughout their life-histories and that flap fluctuating asymmetry (FA) is negatively correlated with individual quality, but only in females. In contrast, both flap size and red spot size are positively correlated with individual quality, but only in males. Therefore, flap size and red spot size can provide potential information on male quality, but their FA can not. However, female pumpkinseed prefer to mate with males who possess the most symmetric flaps. The data suggest that male pumpkinseed preferentially allocate effort throughout their life-history to symmetric flap growth in response to selection from female choice. In this fish system, male ornament symmetry is not selected for because it is a signal of individual quality but rather, it is selected to enhance the true signal of individual quality which is revealed by the size of their flaps. Contrary to existing FA theory proposed by many researchers, ornament symmetry is not an ubiquitous signal of quality. In the pumpkinseed sunfish, individuals appear to manipulate the symmetry of their display ornaments in response to selection just like any other component of their phenotype.