• GOAL = determine the paternity of 1206 Alberta offspring to see if one dominant male does the majority of the breeding on a lek in a given year or if multiple males are successful at reproducing
• ABSTRACT = Greater sage-grouse (Centrocercus urophasianus) have a lek-based mating system in which only a few males are expected to obtain the majority of matings in a single breeding season and females are believed to mate once with a single male. We used 13 microsatellites to genotype samples from 604 adults and 1206 offspring from 191 clutches (1999 – 2006) from Alberta, Canada to determine paternity, polygamy (males and females mating with multiple individuals), and reproductive variance among individuals. We found that most clutches had a single father and mother, but there was evidence of multiple paternity and intraspecific nest parasitism. Annually, most males fathered only one brood, very few males fathered multiple broods, and the proportion of all males in the population fathering offspring averaged 45.9%, suggesting that more males breed in Alberta than previously expected for the species. Twenty-six eggs (2.2%) could be traced to intraspecific nest parasitism and 15 of 191 clutches (7.9%) had multiple fathers. Reproductive variance, measured as the opportunity for selection, was higher among males than females, lower than expected if only a small proportion of the male population mates, and within the range exhibited by other lekking species. A more equitable distribution of mating success for males in Alberta likely helps to maintain effective population size and genetic diversity, which has positive implications for the conservation of this peripheral and small northern population.