Influence of historical and contemporary habitat changes on the population genetics of the endemic South African parrotPoicephalus robustus

Abstract

SummaryThe Cape ParrotPoicephalus robustusis a habitat specialist, restricted to forest patches in the Eastern Cape (EC), KwaZulu-Natal (KZN) and Limpopo provinces of South Africa. Recent census estimates suggest that there are less than 1,600 parrots left in the wild, although historical data suggest that the species was once more numerous. Fragmentation of the forest biome is strongly linked to climate change and exploitation of the forest by the timber industry. We examine the subpopulation structure and connectivity between fragmented populations across the distribution of the species. Differences in historical and contemporary genetic structure of Cape Parrots is examined by including both modern samples, collected from 1951 to 2014, and historical samples, collected from 1870 to 1946. A total of 114 individuals (historical = 29; contemporary = 85) were genotyped using 16 microsatellite loci. We tested for evidence of partitioning of genotypes at both a temporal and spatial scales by comparing shifts in allelic frequencies of historical (1870–1946) and contemporary (1951–2014) samples across the distribution of the species. Tests for population bottlenecks were also conducted to determine if anthropogenic causes are the main driver of population decline in this species. Analyses identified three geographically correlated genetic clusters. A southern group restricted to forest patches in the EC, a central group including birds from KZN and a genetically distinct northern Limpopo cluster. Results suggest that Cape Parrots have experienced at least two population bottlenecks. An ancient decline during the mid-Holocene (∼ 1,800-3,000 years before present) linked to climate change, and a more recent bottleneck, associated with logging of forests during the early 1900s. This study highlights the effects of climate change and human activities on an endangered species associated with the naturally fragmented forests of eastern South Africa. These results will aid conservation authorities with the planning and implementation of future conservation initiatives. In particular, this study emphasises the Eastern Cape mistbelt forests as an important source population for the species and calls for stronger conservation of forest patches in South Africa to promote connectivity of forest taxa.