Management and its relation to hybridization, clonality and genetic structure of the Mexican palm Brahea dulcis

Abstract

Rural communities commonly manage native species promoting changes in the diversity of natural biota. In Mexico, the palm Brahea dulcis is a resource traditionally managed by the rural community Nahuas of Huitziltepec, Eduardo Neri, Guerrero. This palm is used for traditional crafts. The continuous cutting of leaves promotes a physiognomic change in palm populations, high intensity cutting promotes shorter plants, while low intensity cutting promotes somewhat taller plants, but still shorter than unmanaged palms. In this study, we evaluated how different management regimes (harvesting leaves) of this palm by the rural community of Nahuas are related to hybridization, clonal and genetic structure using Random Amplification Polymorphic DNA (RAPD). The study was carried out at six sites with different management regimes (two sites per regime: high and low intensity cutting, and unmanaged palms). Plant density was highest under high-intensity cutting and lowest with no cutting. Autocorrelation analyses at the ramet level showed an aggregated distribution of related genotypes at short distances and a random spatial distribution at larger distances. Also, at the genet level the autocorrelation analyses showed a random distribution. Clonal diversity was high in both management regimes (high-intensity: D=0.96, G/N=0.60; low intensity: D=0.98, G/N=0.77) in comparison with unmanaged palm populations (D=0.99, G/N=0.88). Expected heterozygosity increased with cutting intensity (high-intensity (0.37)>low-intensity (0.25)>unmanaged (0.14). While genetic differentiation among populations showed an inverse pattern: unmanaged (Φ=0.26)>low intensity (Φ=0.19)>high intensity (Φ=0.13). The greatest differentiation was observed for cutting regime (Φst|covariates=0.4802), followed by population (Φst|covariates=0.2453) and geographic location (Φst|covariates=0.1378). We observed hybridization between B. dulcis and Brahea nitida and a unidirectional pattern of gene flow towards B. dulcis, only in managed populations. Traditional management of B. dulcis is based on empirical Nahuatl knowledge which promotes high levels of clonal and genetic diversity, and sporadic hybridization, probably due to successful sexual reproduction, that allows gene flow among populations.