The IUCN/SSC Canid Specialist Group's
African Wild Dog Status Survey and Action Plan (1997)

Chapter 2
Genetic Perspectives on Wild Dog Conservation

by Derek J. Girman & Robert K. Wayne

Wild dogs are the only extant representatives of a distinct lineage of wolf-like canids. As a result of this phylogenetic distinctiveness, they have a high conservation value.

In the past, wild dogs from East and southern Africa were considered members of distinct sub-species. However, new data suggest that this is unlikely - genetic exchange seems to have occurred between these populations until recently. Unique mitochondrial haplotypes and nuclear alleles are found in wild dogs from South Africa and the north of East Africa, but intermediate populations in Botswana and Zimbabwe contain a mixture of 'easternµ and 'southern' genotypes. Furthermore, we have identified a unique West African mitochondrial haplotype through examinations of museum skins. Although we cannot recognize separate sub-species at present, the genetic differences mean that populations in southern, eastern and West Africa must all be conserved if wild dogs' genetic diversity is to be preserved.

Within populations, wild dogs appear to have strong inbreeding avoidance behaviour. Probably as a result of this, free-ranging populations retain high levels of genetic variability. However, captive populations risk loss of genetic variability. For this reason, efforts geared towards active management and preservation of wild populations is preferable to a strategy of captive breeding and reintroduction.

• Background
• Taxonomy
• Genetic Variation within Wild and Captive Populations

Background

Studies of wild dog genetics have a great deal to contribute to plans for their conservation. At the largest scale, molecular genetic comparisons of wild dogs with other species can help us to define their phylogenetic uniqueness, an increasingly important component of priority-setting in conservation (Vane-Wright et al. 1991). Comparisons among wild dog populations can be used to identify local subspecies or ecotypes, helping us to evaluate the conservation value of different populations. Finally, genetic studies can be used to look for evidence of inbreeding in both wild and captive populations, allowing us to devise the most effective management strategies.

Ancient population fragmentation followed by subsequent dispersal may characterize wild dogs. They are known to be highly mobile, having home range sizes estimated to be as large as 2,000km² (Frame et al. 1979; Fuller et al. 1992a). In addition, animals may sometimes disperse over long distances, although the frequency of such events is uncertain (Frame et al. 1979; Fuller et al. 1992b; Girman et al. in press). However, wild dog populations have declined dramatically during the past century, leading to the development of fragmented populations of wild dogs in many parts of their former range (Chapter3).

Taxonomy

Wild dogs represent a unique lineage within the wolf-like canids. They are the only members of the genus Lycaon, and some taxonomists have placed them in a sub-family, the Simocyoninae, distinct from most of the other canids (Wozencraft 1989). Although this sub-family division is no longer recognized (Wozencraft 1989), recent phylogenetic analyses using molecular genetics have supported wild dogs' place in their own genus (Girman et al. 1993). An analysis of sequence data from 2001 b.p. of the cytochromeb, cytochrome oxidase I, and cytochrome oxidase II genes showed that wild dogs are distinct from the wolves and jackals of the genus Canis (Figure 2.1, Girman et al. 1993). This phylogenetic distinctiveness places a high conservation value upon wild dogs: their extinction would represent the loss of a unique canid lineage several million years old.

Genetic and morphological analyses also show some differences between wild dogs from different parts of Africa. Our initial studies employed an analysis of mitochondrial DNA (mtDNA) restriction fragment length polymorphisms (RFLPs), and direct sequencing of the cytochrome b gene of 92 wild dogs from two localities in eastern Africa (the Masai Mara National Reserve, Kenya, and Serengeti National Park, Tanzania) and two localities in southern Africa (Hwange National Park, Zimbabwe and Kruger National Park, South Africa, Table 2.1, Girman et al. 1993). In addition, we carried out multivariate analyses of morphological measurements from skulls taken from eastern and southern Africa. Levels of genetic variability in both eastern and southern African populations were similar. In addition, this study suggested that there was a genetic and morphologic distinction between eastern and southern African populations. Based on these results, we recommended separate subspecific designations for eastern and southern African wild dogs (Girman et al. 1993).

However, this distinction between eastern and southern populations of wild dogs was surprising, given the dispersal capabilities of wild dogs. Consequently, we sought many more genetic samples from a greater portion of wild dogs' range in eastern and southern Africa (Table2.1). We also used the most variable portion of the mtDNA genome, the control region, to develop a more fine-scaled analysis of these populations. In addition, since the maternal inheritance of mtDNA may provide a biased picture of gene flow and population differentiation, we carried out further investigations using nuclear loci to develop a complete understanding of the genetic structure of African wild dogs. In our follow-up study we assessed the patterns of gene flow and genetic differentiation of 270 African wild dogs from seven wild populations in eastern and southern Africa, and two captive populations in South Africa, through the analyses of mitochondrial DNA control region sequences and eleven dinucleotide repeat loci (microsatellites) (Girman 1996). We used an AMOVA (analysis of molecular variance) approach to conduct parallel analyses of both the mtDNA and microsatellite data (Excoffier et al. 1992). This parallel approach allowed us to examine the hierarchy of population subdivision, and to estimate the patterns and rates of gene flow among the seven sampling localities.

The control region sequences revealed two groups of haplotypes, forming two distinct clades in a parsimony analysis (Figure2.2). However, the geographic distribution of haplotypes did not coincide entirely with the divisions suggested by the mitochondrial tree (Figure2.3). The new mtDNA data suggest a pattern of past separation of eastern and southern populations: there are unique haplotypes from different clades at either end of the geographic range. However, there also appears to be recent mixing of haplotypes from the different clades in the intervening populations in Botswana and Zimbabwe (Figure2.3).

Our study shows that the population in the Selous region of southern Tanzania is particularly interesting. In this population there appears to be a predominant haplotype that is most closely related to a haplotype so far found only in the Kruger National Park, South Africa (Girman 1996). The only other mtDNA haplotype found in our sample of 31 individuals from this population is found in Botswana and Zimbabwe. No mtDNA haplotypes are shared between the Selous population and the Serengeti and Masai Mara populations, which are also in eastern Africa. Thus the Selous population represents a distinct and interesting population that requires further sampling and analysis. These initial results suggest it may have an affinity with South African wild dogs.

Our analysis of microsatellite data showed that gene flow among all populations was significantly higher than that measured with the mitochondrial data (Girman 1996). The microsatellite data suggest a pattern of differentiation with geographic distance. Differences between the nuclear and mitochondrial datasets may indicate higher levels of long-distance dispersal by males. This is consistent with previous behavioural and genetic studies, which found that males tend to have longer dispersal distances (Frame et al. 1979; Fuller et al. 1992b; Girman et al. in press). The Kruger population contains one unique mtDNA genotype and three unique microsatellite alleles, suggesting some degree of distinction from the other populations. Likewise, unique microsatellite alleles are found in the East African populations (Selous, Serengeti, and Masai Mara), and the Masai Mara and Serengeti populations share a unique mtDNA haplotype (Girman 1996). These results suggest that only populations in Serengeti-Masai Mara and Kruger have a high level of genetic isolation. Those populations in between represent admixture zones. Since most management and captive breeding efforts have focused on southern African populations, we recommend increased effort focusing on the preservation and management of north-eastern African wild dog populations.

An examination of control region sequences from museum skin samples suggests that West African wild dogs have a unique haplotype (Girman 1996; Roy et al. 1994). For example, a museum sample from Nigeria (provided by the British Museum of Natural History) contains a unique mtDNA haplotype that is distinct from the two clades containing the eastern and southern African mtDNA haplotypes (Figure2.2). Clearly, much more investigation of West African wild dog populations is warranted to determine the degree of distinction of these populations. West Africa may contain populations that are quite distinct from the eastern and southern populations that we have studied thus far.

Genetic Variation within Wild and Captive Populations

Levels of genetic variability in the eastern and southern African wild dog populations are similar (Girman 1996). All of the free-ranging populations sampled appeared to have relatively high levels of genetic variability (heterozygosity levels ranging from 0.56 to 0.66) with an average of 0.603 over all seven populations measured (Table2.2). Also, allelic variability was relatively high among free-ranging populations of African wild dogs, with the average number of alleles per locus ranging from 3.4 to 4.1 (Table2.2). High levels of variability may be due to strong inbreeding avoidance behaviour. A study of a single population in Kruger National Park demonstrated that male and female wild dogs that formed new packs did so only with unrelated members of the opposite sex (Girman et al. in press). This was true even though most males and females dispersed to territories very near their close relatives. We found no evidence for inbreeding in the Kruger population.

To examine the genetic status of captive wild dogs, we compared the levels of genetic variability in two captive populations with those in seven free-ranging populations. The captive populations had lower genetic variability than all of the wild populations (Girman 1996). This suggests that careful genetic management is needed in captive populations to maintain variability levels similar to those found in the wild. In addition, pedigree information provided by the the managers of captive groups were not consistent with parentage analyses using microsatellites (D.Girman, Unpublished data) suggesting that accurate assessment of parentage is difficult in captivity without genetic analyses. The only way to regulate breeding is to break up the natural pack groupings through the isolation of breeding pairs. In contrast, wild dogs in natural populations are extremely effective at inbreeding avoidance and naturally maintain high levels of genetic admixture without compromising the natural structure of wild dog packs. Therefore, from a genetic perspective, active management of wild populations is preferable to captive breeding and reintroduction by humans where possible.

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© 1997 International Union for the Conservation of Nature and Natural Resources.