Individual, fruit, and annual variation in correlated mating in a Genipa americana population

Abstract

In this paper, we use six microsatellite loci to examine a spatially isolated population of Genipa americana in relation to mating system variation at the level of individual and among and within fruits, over two reproductive events. For our analysis, we sampled hierarchically among and within fruits open-pollinated seeds collected from 13 seed trees during the reproductive event in 2010 and 12 seed trees in 2011. The rate of mating among relatives (1 - t(s)) was significantly greater than zero and different between the investigated reproductive events, indicating that some seeds are inbred. The estimate of fixation index (F-o) was significantly higher than zero for seeds from both reproductive events (2010: F-o = 0.258; 2011: F-o = 0.294), confirming that seeds present inbreeding, probably originated from mating among full-sibs. The multilocus paternity correlation within fruits (r(p(w))) and among fruits (r(p(a))) varied among seed trees and reproductive events. The r(p(w)) was significantly higher than r(p(a)) in both reproductive events, suggesting that it is more likely to find full-sibs within fruits (2010: 36.4%; 2011: 72.4%), than among fruits (2010: 18.9%; 2011: 12.8%). Due to the presence of inbreeding, mating among relatives and correlated mating, the within families coancestry coefficient (Theta) was higher and the variance effective size (N-e) lower than expected in open pollinated families from panmictic populations (Theta = 0.125, N-e = 4). In practical terms for conservation programs, our results show the need to collect seeds from at least 60 seed trees to retain progeny arrays with a total effective size of 150.