Spatial and temporal dynamics of lekking behavior and female mate choice in the blue-crowned manakin (Lepidothrix coronata, AVES: Pipridae)
Lekking is a rare behavior that has evolved multiple times over several taxa. In species presenting this unusual mating system, males aggregate at display grounds called 'leks' that females visit to assess potential mates and to copulate. Lekking systems are not resource-based, to the extent that males do not hold any resources critical to females (besides their own gametes) and females carry out all parental duties unaided. As a result, males are under strong sexual selection pressure and often vary widely in their reproductive output. This dissertation investigates how spatial and temporal factors influence the lekking dynamics and female mate choice of a Neotropical frugivorous bird, the blue-crowned manakin Lepidothrix coronata, in eastern Ecuador. The first chapter is related to the spatial dynamics of lekking behavior, and specifically investigates whether leks are formed by the establishment of territorial males on sites where they maximize their contact with females (the 'hotspot hypothesis'). We tested this hypothesis by combining field data and GIS modeling to predict the spatial distribution of females on two 100-ha plots, and then contrasting these predictive maps to the distribution and size of existing leks. Contrary to the expectations, leks were found to be located not in female "hotspots," but rather in "coldspots," i.e., in sites where males may expect to encounter fewer females than expected by chance. A proportion of males were indeed settled at hotspots, but, contrary to predictions of the hypothesis, they belonged to smaller leks than males located outside hotspots. Our results indicate that this lack of spatial correlation between males and females results partly from differences in sexspecific habitat preferences. The second chapter is related to the temporal aspects of lekking behavior, and specifically investigates how leks are formed and change over time, and how leks, which are very traditional in location, can persist in face of relatively high rates of male turnover. The fate of individual territorial males was followed during 4 years at up to 15 leks, allowing us to estimate rates of persistence at territories, recruitment, and expected tenure times, as well as to investigate the role of lek size, age, and display rate as correlates of persistence time and/or recruitment probabilities. Finally, we used these estimates to simulate changes in lek size and composition over longer periods of time. Our results suggest that leks rapidly converge to a mean size of 3 males, and that rates of male recruitment and disappearance compensate each other such that leks have the potential to persist for several decades after the original males have disappeared from them. In the third chapter, we used molecular analyses of paternity to investigate the process of female mate choice at two spatial scales, within- and among-leks. First, we tested the hypothesis that females prefer to mate at larger leks, such that costs of mate search would be lowered. Second, we investigated whether female mate choice within leks is driven by genetic benefits, by asking whether females prefer to mate with individuals that are highly heterozygous or less related to them. Third, we investigated the role of vocalization rates as a correlate of male mating success and as an indicator of heterozygosity, a measure of genetic quality. Females moved beyond their regular home ranges to mate, suggesting that they increase travel costs to assess a larger number of potential mates. In particular, females nesting near small leks tended to travel further and mate at larger leks. In the population at large, however, there is not a preference for larger leks, and even solitary males may sire young. Siring males were not less related to females than expected by chance. Vocalization rates were positively correlated to the mean d² index (a measure of heterozygosity). In addition, males with higher vocal display within a given lek were more likely to sire young. However, as males adjust their display to lek size, vocalization rates alone are not a reliable indicator of male heterozygosity. A possible exception is for males at larger leks, where males tend to be more heterozygous and have increased display, such that vocalization rates should more honestly reflect the physiological and genetic quality of those males
Thesis, Dissertation, English, 2008
University of Missouri--St. Louis, St. Louis, Mo., 2008