Multiple paternity in a lek mating system: females mate multiply when they choose inexperienced sires

1.    Multiple mating by females is common and
often driven by social constraints on female mate choice. However, females
mate with multiple males even in systems without these social constraints
and rates of multiple mating tend to be highly variable within and between
populations. In lek mating systems, females are able to assess multiple
males and their choice is unrestricted by pair bonds or the need for
biparental care, yet some females mate with multiple males. 
2.    To better understand the factors
affecting variation in multiple mating, we investigated the occurrence of
multiple paternity within clutches in a highly polygynous lek mating
system.  3.    Using long-term data on
genetic paternity, survival, social status, and individual age from a
population of lance-tailed manakins (Chiroxiphia lanceolata), a species
where males lek in cooperative alpha-beta pairs, we tested five
non-exclusive hypotheses about causes of variation in multiple mating and
its benefits to females.  4.    We
found that inexperienced males, including new alphas and rare beta sires,
were disproportionately likely to share paternity when they sired any
chicks. In contrast, female age (experience) was unrelated to multiple
paternity. Multiple mating did not result in higher reproductive success
or reduced variance in success for females, and there were neither
consistently promiscuous females nor males that consistently shared
paternity. 5.    The occurrence of multiple
paternity in this lek mating system was best explained by female choice
related to male characteristics that change with male experience. Our
results support the hypothesis that there is a developmental component to
the occurrence of multiple mating, and suggest females choose to mate
multiply when their choices are not optimal.