Conservation genetics of the Hooded vulture Necrosyrtes monachus.

Abstract

African vulture species have experienced rapid population declines, due to many anthropogenic threats. Hooded vultures are no exception and have experienced dramatic declines and are now listed as Critically Endangered on the IUCN Red Data list. Two subspecies of Hooded vulture have been described : Necrosyrtes monachus monachus which occurs in West Africa and Necrosyrtes monachus pileatus which occurs in East and southern Africa. The two subspecies differ in their feeding behaviour and morphology supporting the validity of the subspecies status. However, the validity of this taxonomic grouping is still being questioned. Clarifying the taxonomic status of the subspecies is important as if the two subspecies are genetically distinct then they should not be managed as a single species and current conservation policies would need to be updated. In addition, there is limited information available on many aspects of Hooded vulture life history including the factors affecting reproduction in the wild. In Chapter 2 I use microsatellite data collected from across the distributions of the two subspecies and Approximate Bayesian Computation (ABC) to test the hypothesis that the two subspecies are genetically distinct and should be elevated to separate species. In Chapter 3 I examine the genetic variation present in the South African Hooded vulture population. This population only includes 100-200 individuals and is at the edge of the southern range of the species. The conservation value of peripheral populations is debatable as these populations are often isolated and smaller with genetic drift and inbreeding leading to reduced genetic variability. In contrast, studying the genetic diversity in range-edge populations is important for understanding range shifts and adaptive capacity under climate change. These edge populations could potentially also retain unique genetic diversity which helps with the adaptation of species to different environments. Vulture colonies act as “food finding information hubs” allowing for the exchange of information regarding potential food resources. This explains, in part, the high-levels of relatedness often found within colonies as close relatives are more likely to tolerate the cost of sharing food by increasing their inclusive fitness. Hooded vultures are tree nesters with a single breeding pair per tree. In Chapter 4 I use the genetic data to test if individuals nesting close to each other are closely related and if the same individuals use the same nest over multiple years. The analyses conducted in Chapter 2 did not support the existence of the two subspecies classification, due to different demographic events experienced between the two groups. The next factor indicating that there is no subspeciation is the contemporary gene flow that is still seen between the population (m = 0.188) and the little variance seen between the two subspecies (11.9%). Structure analysis also does not support the formation of two distinct subspecies. Thus, this study supports the claim made by Mundy 2021 that it is size cline and not speciation. In Chapter 3 the genetic data did not support the hypothesis that the small South African population was genetically depauperate, instead the results show that the South African population contained similar levels of genetic diversity (Ho = 0.495) to that recorded for the Ghanaian population (Ho = 0.315) where Hooded vultures are more abundant. Levels of heterozygosity were similar to those recorded for other species of Old World vultures such as Cape Vultures (Gyps coprotheres, Ho = 0.380), and Bearded vultures (Gypaetus barbatus Ho = 0.400 – 0.480), but differed from the Griffon Vulture (Gyps fulvus Ho = 0.530 – 0.600) found in Europe. Worryingly, both populations of Hooded vultures show elevated levels of inbreeding and relatedness. The bottleneck analysis for both populations show no sign of a recent bottleneck and a normal L shaped distribution for both populations. In Chapter 4 breeding pairs were not found to reuse the same nests over multiple years. A negative correlation was seen between genetic distance and geographical distance (R2 = 0.0117; p-value = 0.012) the closer related individuals thus tend to nest further away from each other. The spatial autocorrelation shows a positive correlation between genetic and geographical distance between distance classes 8 km – 16km, 32 km – 40km and then between 88 km – 112km, but no clear support for increased relatedness between closer nesting individuals. Thus no support is seen for the formation of loose colonies to function as food finding information sharing hubs. African vultures are facing a number of challenges and most species are considered of conservation concern. Despite this limited genetic data is available for many species. This study aimed to fill this knowledge gap by generating and analysing microsatellite data for the Critically Endangered Hooded vulture to answer a number of key hypotheses. As such this study makes an important contribution towards the conservation of Hooded vultures across Africa.