“However, the red wolf adaptive management program in North Carolina has managed to establish a population and maintain the uniqueness of the wild red wolf gene pool despite two decades of interaction with coyotes (Gese et al. 2015).”
Describing a developing hybrid zone between red wolves and coyotes in eastern North Carolina, USA
Justin H. Bohling1*, Justin Dellinger2, Justin M. McVey3, David T. Cobb4, Christopher E. Moorman3, Lisette P. Waits1
1Department of Fish and Wildlife Resources, University of Idaho, Moscow, ID 83844
2School of Environmental and Forest Sciences, University of Washington, Seattle, WA 98195
3Department of Forestry and Environmental Resources, North Carolina State University, Raleigh, NC 27695
4North Carolina Wildlife Resources Commission, Raleigh, NC 27699
*Correspondence: Justin H. Bohling
Current affiliation: U.S. Fish and Wildlife Service, Abernathy Fish Technology
Center, Longview, WA 98632, USA
(article published in Ecological Applications and posted here under Creative Commons license 2.0)
When hybridizing species come into contact, understanding the processes that regulate their interactions can help predict the future outcome of the system. This is especially relevant in conservation situations where human activities can influence hybridization dynamics. We investigated a developing hybrid zone between red wolves and coyotes in North Carolina, USA to elucidate patterns of hybridization in a system heavily managed for preservation of the red wolf genome. Using non-invasive genetic sampling of scat, we surveyed a 2880 km2 region adjacent to the Red Wolf Experimental Population Area (RWEPA). We combined microsatellite genotypes collected from this survey with those from companion studies conducted both within and outside the RWEPA to describe the gradient of red wolf ancestry. A total of 311 individuals were genotyped at 17 loci and red wolf ancestry decreased along an east-west gradient across the RWEPA. No red wolves were found outside the RWEPA, yet half of individuals found within this area were coyotes. Hybrids composed only 4% of individuals within this landscape despite co-occurrence of the two species throughout the RWEPA. The low proportion of hybrids suggests that a combination of active management and natural isolating mechanisms may be limiting intermixing within this hybrid system.
Implications for conservation
Our findings have implications for the future of red wolf conservation and other species threatened by hybridization. From the red wolf perspective, our results disprove the common perception that red wolves have been consumed by a genetic swarm and no longer exist as a distinct genetic entity in North Carolina (Wildlife Management Institute 2014; NC Wildlife Resources Commission 2015a, b). This is especially pertinent as the USFWS has been faced with calls to modify or even cancel the red wolf program due a perceived lack of success (Wildlife Management Institute 2014; NC Wildlife Resources Commission 2015a, b). Our results provide insights into the status of the red wolf population and hybridization dynamics that will inform these discussions.
One of the issues at the heart of the red wolf recovery effort is whether the red wolf is a “conservation-reliant species\” that will forever require human intervention to persist in the wild (Scott et al. 2005, 2010; Goble et al. 2012). There is no feasible way to reduce the threat posed by hybridization with coyotes in North Carolina or anywhere in the red wolf historic range to zero. However, the red wolf adaptive management program in North Carolina has managed to establish a population and maintain the uniqueness of the wild red wolf gene pool despite two decades of interaction with coyotes (Gese et al. 2015). Management practices and policies were initially developed under the assumption that these species randomly interbreed when sympatric (Kelly et al. 1999; Stoskopf et al. 2005), yet this study and additional evidence suggests this is incorrect (Bohling & Waits 2015; Gese & Terletzky 2015; Gese et al. 2015; Hinton et al. 2015a). More importantly, although human management has undoubtedly helped keep the species in existence, it also counterbalances human actions that facilitate hybridization (Sparkman et al. 2011; Bohling & Waits 2015). Such complexity dictates a more nuanced perspective on “conservation-reliant\” and development of recovery goals that acknowledge these factors (Redford et al. 2011; Rohlf et al. 2014). Hybridization may not be completely avoidable, but creating policies, partnerships, and strategies that allow red wolves to maintain their genomic uniqueness through a combination of natural and management-assisted processes will be critical towards evaluating the viability of the species in the wild.
Although there have been attempts to manage the genetic composition of endangered populations in hybrid systems, none have been as comprehensive as the red wolf program. European nations are undertaking efforts to eradicate non-native ruddy ducks (Oxyura jamaicensis) to protect white-headed duck (O. leucocephala) populations from hybridization (Cranswick & Hall 2010). In the United States there are initiatives to cull individuals from public and private bison (Bison bison) herds that possess cattle (Bos taurus) ancestry (Dratch & Gogan 2010). At most these programs attempt to remove individuals with signatures of past introgression (e.g. bison, Siamese crocodiles [Crocodylus siamensis][Fitzsimmons et al. 2002]) or eliminate the “undesirable\” hybridizing species (e.g. ruddy ducks in Europe). They do not, however, couple real-time field monitoring with genetic analyses to limit introgression on a fine-scale as has been practiced with the red wolf. Such management has been a “success\” in terms of fostering the existence of a unique red wolf genetic unit and limited numbers of hybrids. For other species in similar situations, the red wolf program can be used as a model to develop conservation strategies. Combining knowledge of natural processes, sound management practices, and innovative policies will be critical for guiding conservation biologists addressing hybridization as it concerns endangered species conservation
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