Genetic diversity assessment of Tamarix in South Africa – Biocontrol and conservation implications

Abstract

Genetic diversity information can be valuable for establishing successful management strategies for indigenous and invasive species. Here we conducted a genetic assessment of two invasive and one native Tamarix species in South Africa, where all species are known to hybridize. Hybridization can encourage biological invasion by creating unique allele combinations that facilitate invasiveness in plants. Using 9 microsatellite markers, we genotyped 150 individuals from four Tamarix taxa, viz. T. usneoides, T. chinensis, T. ramosissima, and Tamarix hybrids. We investigated the genetic diversity in the indigenous and invasive Tamarix species, and their genetic differentiation in South Africa, and compared the genetic diversity between South African Tamarix hybrids to hybrids from the United States. We aimed to elucidate information useful for the biocontrol efforts against the invasive genotypes and the conservation of the indigenous species. Our results showed that there is clear genetic differentiation between the indigenous and invasive species of Tamarix in South Africa. The indigenous T. usneoides was found to have greater genetic diversity than the exotic T. chinensis, but lower than the alien T. ramosissima. Higher genetic diversity was detected in South African Tamarix hybrids compared to hybrids of the same species from the United States and there is substantial genetic differentiation between Tamarix hybrids from the two countries. Additionally, remote places in the northwest of South Africa contain private alleles suggesting non-polluted indigenous T. usneoides germplasm which should be preserved. These results suggest that there would be minimal risk of non-target effects on the indigenous species should a biocontrol program for the alien invasive species be implemented.