Mating system parameters in a high density population of andirobas in the Amazon forest

Abstract

The objective of this work was to estimate the mating system parameters of a andiroba (Carapa guianensis) population using microsatellite markers and the mixed and correlated mating models. Twelve open‑pollinated progeny arrays of 15 individuals were sampled in an area with C. guianensis estimated density of 25.7 trees per hectare. Overall, the species has a mixed reproductive system, with a predominance of outcrossing. The multilocus outcrossing rate (t_m = 0.862) was significantly lower than the unity, indicating that self‑pollination occurred. The rate of biparental inbreeding was substantial (t_m ‑ r_s = 0.134) and significantly different from zero. The correlation of selfing within progenies was high (r_s = 0.635), indicating variation in the individual outcrossing rate. Consistent with this result, the estimate of the individual outcrossing rate ranged from 0.598 to 0.978. The multilocus correlation of paternity was low (r_p(m) = 0.081), but significantly different from zero, suggesting that the progenies contain full‑sibs. The coancestry within progenies (Θ = 0.185) was higher and the variance effective size (N_e(v) = 2.7) was lower than expected for true half‑sib progenies (Θ = 0.125; N_e(v) = 4). These results suggest that, in order to maintain a minimum effective size of 150 individuals for breeding, genetic conservation, and environmental reforestation programs, seeds from at least 56 trees must be collected.