Pedigree and mating system analyses in a western larch (Larix occidentalis Nutt.) experimental population

•The mating pattern and gene flow in a western larch ( Larix occidentalis Nutt.) experimental population was studied with the aid of microsatellite markers and a combination of paternity-mating system analysis. The commonly difficult to assess, male gametic contribution was determined with 95% confidence and its impact on genetic gain and diversity was determined. • Male fertility success rate ranged between 0 and 11%. Male reproductive output parental imbalance was observed with 50% of the pollen being produced by the top 5% of males while the lower 39% males only produced 10% of the pollen. • A significant difference was observed between male effective population size (genetic diversity) estimates from paternity assignment compared to those based on population’s census number (21 vs. 41); however, this difference did not affect estimates of genetic gain. • A total of 221 full-fib families were identified (sample size range: 1–8) and were nested among the studied 14 seed-donors. • A combination of paternity-mating system analysis is recommended to provide a better insight into seed orchards’ mating dynamics. While pollen flow tends to inflate mating system’s outcrossing rate, the paternity analysis effectively determined the rate and magnitude of contamination across receptive females.