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, 5 (2), 288-99

Genetic Analysis Shows Low Levels of Hybridization Between African Wildcats (Felis Silvestris Lybica) and Domestic Cats (F. S. Catus) in South Africa

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Genetic Analysis Shows Low Levels of Hybridization Between African Wildcats (Felis Silvestris Lybica) and Domestic Cats (F. S. Catus) in South Africa

Johannes J Le Roux et al. Ecol Evol.

Abstract

Hybridization between domestic and wild animals is a major concern for biodiversity conservation, and as habitats become increasingly fragmented, conserving biodiversity at all levels, including genetic, becomes increasingly important. Except for tropical forests and true deserts, African wildcats occur across the African continent; however, almost no work has been carried out to assess its genetic status and extent of hybridization with domestic cats. For example, in South Africa it has been argued that the long-term viability of maintaining pure wildcat populations lies in large protected areas only, isolated from human populations. Two of the largest protected areas in Africa, the Kgalagadi Transfrontier and Kruger National Parks, as well as the size of South Africa and range of landscape uses, provide a model situation to assess how habitat fragmentation and heterogeneity influences the genetic purity of African wildcats. Using population genetic and home range data, we examined the genetic purity of African wildcats and their suspected hybrids across South Africa, including areas within and outside of protected areas. Overall, we found African wildcat populations to be genetically relatively pure, but instances of hybridization and a significant relationship between the genetic distinctiveness (purity) of wildcats and human population pressure were evident. The genetically purest African wildcats were found in the Kgalagadi Transfrontier Park, while samples from around Kruger National Park showed cause for concern, especially combined with the substantial human population density along the park's boundary. While African wildcat populations in South Africa generally appear to be genetically pure, with low levels of hybridization, our genetic data do suggest that protected areas may play an important role in maintaining genetic purity by reducing the likelihood of contact with domestic cats. We suggest that approaches such as corridors between protected areas are unlikely to remain effective for wildcat conservation, as the proximity to human settlements around these areas is projected to increase the wild/domestic animal interface. Thus, large, isolated protected areas will become increasingly important for wildcat conservation and efforts need to be made to prevent introduction of domestic cats into these areas.

Keywords: African wildcat; feral cats; genetic introgression; human population pressure; hybridization; population genetic structure.

Figures

Figure 1
Figure 1
African wildcat (Felis silvestris lybica) in Kgalagadi Transfrontier Park (South Africa/Botswana) (Photo M. Herbst).
Figure 2
Figure 2
Distribution of collection sites of cats included in this study across South Africa in relation to formal protected areas and human footprint pressure. The proportion Bayesian assignments based 13 microsatellites of sampled localities to the African wildcat (qAWC) and domestic cat (qDC) genetic groups are indicated as bar graphs. As African wildcat genetic purity (proportion Bayesian assignment to the African wildcat cluster) increases, there is an associated decrease in the global human footprint influence index (= 0.0003) and an increase in the distance to the nearest town (= 0.026).
Figure 3
Figure 3
(A) Scatter plot of Principle Components Analysis showing the genetic structure between putative African wildcats (red), African wildcats from the Kgalagadi Transfrontier Park (purple), domestic cats (yellow), and morphological hybrids (light blue). (B) STRUCTURE bar plots where vertical axes illustrate the proportional assignment of individual genomes to the inferred genetic groups (= 2) for African wildcats outside protected areas, domestic cats, morphological hybrids, and individuals from the Kgalagadi Transfrontier Park. Membership of each individual's genome (qAWC/DC) to the two identified genetic clusters is indicated by different colors of vertical bars (red, African wildcat; yellow, domestic cat).
Figure 4
Figure 4
(A) Boxplots illustrating the variation in assignment probabilities to the African wildcat genetic cluster (qAWC) based on simulated genotypes for pure parental African wildcat (AWC), F1, F2, and backcrossed individuals identified in STRUCTURE. Dashed lines indicate actual qAWC –values of admixed individuals obtained from our field-collected data that did not assign with high probability (qAWC/DC ≥0.8) to any of the parental genetic clusters. (B) STRUCTURE bar plots of simulated pure parental, F1, F2, and backcrossed genotypes (100 each). Membership of each individual's genome (qAWC/DC) to the two genetic clusters (domestic, yellow and African wildcat, red) is indicated by vertical bars.
Figure 5
Figure 5
Box-and-whisker plot illustrating levels of genetic dispersion inside and outside protected areas. All putative wildcat samples collected between 0 and 5 km of a protected area were classified as “inside” (= 47) and samples >5 km were classified as “outside” (= 53) protected areas. Bayesian assignment values (to AWC genetic cluster) were significantly less dispersed for African wildcats inside protected areas, compared to those from outside protected areas (Kruskal–Wallis χ2 = 5.2705, = 0.02169, df = 99).

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