Pollen movement within a continuous forest of wind-pollinated Araucaria angustifolia, inferred from paternity and TwoGener analysis

Abstract

As a matter of fact, Araucaria angustifolia populations occur predominately in small and isolated stands; only a minor number of continuous natural forests of this dioecious wind-pollinated coniferous tree species remain. To implement reasonable conservation, breeding and restorations program it is necessary to have the knowledge of pollen dispersal distance and fine-scale genetic structure. In this paper, levels and dispersion distance of pollen and spatial genetic structure of A. angustifolia were investigated in a 14 ha transect in a continuous forest in Paraná State, Brazil. Analyses have been performed by the use of eight microsatellite loci, paternity and TwoGener approaches, and spatial autocorrelation analysis. In transect, 52 male and 56 female adult trees were mapped and genotyped, together with 190 seeds. In the present transect, A. angustifolia show spatial genetic structure at distances up to 75 m. Paternity analysis indicated that 54% of seeds were fertilized by pollen from trees outside the transect. The calculated average pollination distance within transect was 102 and 98 m based on the paternity analysis and TwoGener analysis, respectively. We found a significant pollen gene pool structure across seed-trees ( $\widehat\Phi _{ft} = 0.078$, P < 0.01) that corresponds to an effective number of pollen donors of 6.4 male trees or an effective pollination neighbourhood area (A _ep ) of 2.1 ha. The findings suggest long-distance pollen dispersion (>100 m) inside the continuous forest. However, the high proportion occurs in short-distance producing biparental and correlated mating as well as reducing the variance effective size.