Patterns of genetic variation in the common starling, Sturnus vulgaris, in South Africa

Abstract

Exotic species are non-native plants or animals that are introduced into areas where they do not naturally occur. Exotic species can out-compete natives by reproducing faster, competing for food and habitat more efficiently, and thrive in the absence of natural predators, and therefore widely expand their distribution range. In such cases, exotic species become invasive and can represent a major threat to global biodiversity, human health and lead to economic losses. South Africa has been subjected to many exotic introductions, some of which have established and became invasive such as the common starling (Sturnus vulgaris). Less than 20 individuals, native from the United Kingdom, were introduced to South Africa in the l890s. One century later, it has become invasive and it is found along the South African West and East Coast from Cape Town to Port Elizabeth. The objective of this study is to understand the population structure and dynamics in order to understand birds’ dispersal and spread; two very important points for management and pest control. We sampled common starlings across their distribution in South Africa, and analysed them using microsatellite and mitochondrial data. For comparative purposes, we also included material from Namibia and the United Kingdom. In this study, we differentiate the native population (England) from the introduced population (South Africa-Namibia). Within the introduced range, the observed heterozygosity is of 0.613 compared to 0.698 for the native English population. Genetic differentiation (FST>0.032) between native and introduced has been observed, however no structure in sub-population within the South African population was highlighted. Within the South African population, the genetic similarity between individuals decrease with geographic distance, indicating an isolation-by-distance pattern. The mean average squared of parent-offspring distance (σ²) was estimate to varying between 2 and 10 km². Combination of microsatellites, mitochondrial data and GIS analysis permit to identified short and long distance dispersion in starling populations.