Gene flow among Hancornia speciosa (Apocynaceae) varieties and hybrid fitness

Abstract

The fate of hybrids and the temporal and spatial dynamics of hybrid zones depend on hybrid fitness in comparison to non-hybrids. We studied cross-pollination among Hancornia speciosa varieties and compared progeny fitness in a nursery to address whether hybrid fitness differed from non-hybrids and whether maternal and paternal taxa contribute differentially to offspring fitness. This species has edible fruit pulp that is used as a raw material for candies, ice cream, and juice by small- and medium-sized enterprises in Central-West and Northeast Brazil. We genotyped 258 adults from a germplasm collection and 320 seeds using seven microsatellite loci to estimate genetic parameters and determine pollen donors. Fitness components, days to shoot, growth rate (mm/day), leaf width (mm), leaf length (mm), stem diameter (mm), and plant height (cm) were analyzed in 200 individuals. Genetic diversity and polymorphism did not differ neither between adults and progeny arrays nor among the four varieties. Genetic differentiation among varieties (F CT = 0.019, p < 0.001) and among populations within varieties (F SC = 0.053, p < 0.001) was significant but low. We detected mating among the four varieties, and no self-pollination was observed in parentage analysis, confirming that H. speciosa is self-incompatible with a high outcrossing rate (t m = 0.990, SE = 0.007). No significant effect of heterosis or exogamic depression was detected for any fitness component, but maternal contribution significantly affected plant height.