It has recently been suggested that the staggering diversity of male breeding colors in the mbuna cichlids found in Lake Malawi results from intense agonistic male-male interactions toward similarly colored conspecifics. The selection pressure to reduce such costs provides the driving force behind the observed diversification. If true, females must still mate with males who are reducing these interaction costs either through behavioral or morphological means. Behavioral means include avoiding interactions whereas morphological means include expressing coloration different from a potential aggressor. We tested the effect of these agonistic interactions on a proxy of female choice, association time, in the mbuna cichlid Metriaclima zebra. Females were allowed to see three types of male per interaction: submissive males who were moved from their territory to that of another male, dominant males who remained in their territory and were exposed to an invading, and therefore submissive male, and non-interacting males who were neither moved nor exposed to an intruder.
Results/Conclusions
We tested the effect of male behavioral interactions on female preferences and found that females associate preferentially with males assigned to the dominant role. Females equally preferred males who did not interact and males who were assigned the submissive role. As time progressed from the interaction, females spent significantly more time associating with those males who did not interact than they did immediately following interaction. These results are significant for two reasons. First, we found that male-male competition itself may be the focus of female choice in the mbuna cichlids and second, we found support for the developing narrative of mbuna diversification: that costly male interactions are driving speciation.
