Mating system and pollen dispersal in Dipteryx alata Vogel (Leguminosae): comparing in situ and ex situ conditions

Abstract

Dipteryx alata is a Neotropical tree widely distributed throughout the Brazilian Cerrado biome and is popularly known as baru. In this study, we evaluated the mating system of D. alata and compared pollen dispersal patterns between the in situ and ex situ conditions. For this, we used 515 genotypes of adults, juveniles, and progeny from a natural population (in situ) in Orizona-GO, Brazil. In addition, we used 488 genotypes of adults and progeny from a germplasm collection (ex situ) located at the Federal University of Goiás. Both locations are situated in central Brazil. The genetic diversity, cross-pollination rates, and pollen dispersal distance under both conditions were estimated. Genetic diversity and polymorphism differed between the in situ and ex situ conditions. The average number of alleles found in situ (5.2) and ex situ (6.2) showed that the germplasm collection stores greater genetic diversity than the in situ condition. Cross-pollination detected among mother trees under both the in situ and ex situ conditions were high (t m = 0.815 and t m = 0.934, respectively), indicating that the species has a mixed reproductive system that was predominantly allogamous. The difference between t m and t s indicated that the in situ condition shows greater biparental inbreeding. Our results showed that, across generations, the ex situ condition preserved a larger number of alleles, confirming that the D. alata germplasm collection plays a role in conserving genetic diversity. The presence of self-fertilization suggests self-compatibility. Paternity correlation and the dispersal distance of the pollen donors were higher in the in situ condition, a maximum distance of 2.9 km of pollen flow. This can be explained by the number of pollinators and tree spatial distribution.