Understanding Variation in Complex Displays and Mate Choice in a Lekking Species with Cooperative Dual-Male Courtship - Understanding Variation in Complex Displays and Mate Choice in a Lekking Species with Cooperative Dual-Male Courtship

Motor displays (displays that involve visible body movements) are an integral component of many courtship displays and have the potential to be important signals of male quality to females during mate choice. The whole organism is used in the execution of movements, and so the performance of motor displays may be an even more valuable signal than static traits commonly studied in sexual selection literature. In lekking species where a female chooses a mate from among displaying males, motor displays provide an especially interesting opportunity for studying mate choice. Which male a female decides to mate with is dependent on which males she observes. Therefore, it is important to not only look at variation in male motor performance and mating success across the entire lek, but also at the phenotypic variation between the males each female is actively choosing between. My dissertation research investigates the causes of variation in the performance of complex, acrobatic displays in the lance-tailed manakin (Chiroxiphia lanceolata; Aves: Pipridae), and the resulting fitness consequences of that variation. Courtship displays in this species vary from being cooperative, with a dominant alpha and subordinate beta male present, to solo, involving only the alpha. Males also perform displays in the absence of females that are very similar to courtship displays. One potential cause of variation in the performance of complex displays is social context. I examined the effects of social context on male displays by quantifying the predictability of display elements in the presence and absence of females. I found that the predictability of individual performance within the dual-male interaction did not differ with female presence; however, entropy metrics describing the interaction of the alpha and beta male indicated that displays for females were more predictable and coordinated. This suggests that the dual-male phenotype is likely an important factor in female mate choice for cooperatively displaying species. The use of male-male cooperation in displays is also variable in this species, and so I next investigated what influences a male’s decision to cooperate and how this decision, in addition to other factors, influences female choice. I found that more experienced alphas were less likely to display cooperatively. Surprisingly, females were more likely to copulate after a solo display, independent of alpha experience. Females that were older, renesting, and closer to egg-laying were more likely to copulate after any given display. Considering effects of the sequence of displays viewed by individual females revealed that females were more likely to observe cooperative displays if they had done so in their previous visit, and more likely to copulate if they had copulated during their previous visit. My results demonstrate non-independence of female visits, suggesting females accumulate information in extended mate searches. These results also challenge the view that cooperative courtship primarily serves to enhance mating success via female choice, and more generally challenges the tendency to assume that the most obvious traits are the most salient for female choice. The complexity of displays and the limitation of current analytical techniques for incorporating sequences of events led me to discover a novel approach called multi-channel sequence analysis (MCSA) to analyze simultaneously the sequences of male and female behaviors during courtship. This approach, to my knowledge, has never before been applied to behavioral ecology. I identified three distinct clusters of display types, based on the combination of male and female behavioral sequences. Displays belonging to the first cluster were more likely to involve male-male cooperation, and those belonging to the second cluster more likely to end in copulation. These results suggest that behavioral sequences from multiple interacting individuals can be productively combined to provide new perspectives on displays, and that MCSA has the potential to be an important new tool in the field of behavioral ecology. In summary, mate choice is a complicated process, and various factors including social context and individual characteristics of males and females can influence the performance of complex displays. This research provides insight into cooperative behavior and utilizes novel statistical approaches that provide a more holistic view of complex displays. This dissertation includes two supplementary video files “Video B-1-Cooperative display example-Chiroxiphia lanceolata.mp4” and “Video B-2-Solo Display Example-Chiroxiphia lanceolata.mp4” that correspond with Appendix B for Chapter 3. These videos are examples of a lance-tailed manakin cooperative and solo display, respectively.