Dog Conservation and the Population Genetic Structure of Dogs
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CHAPTER 8 Dog conservation and the population genetic structure of dogs Ryan H. Boyko and Adam R. Boyko 8.1 Introduction threatened by the encroachment of non- indigenous dogs. On top of this, even genetically similar mod- The domestication of dogs likely began 12,500– ern breed dogs demonstrate substantial phenotypic 30,000 years ago, giving dogs more time to evolve diversity that could interest conservation biologists. and diversify than any other domesticated species In this chapter, we begin by addressing the ques- ( Clutton-Brock, 2012 ). Over the course of just 5,000– tions of what one might want to conserve and why. 10,000 generations, dogs adapted to a variety of We then proceed to summarize the current state of environments and niches, a process accelerated in dog diversity. Finally, we suggest ways to deter- many populations by artifi cial selection. The wide mine which populations should be conserved and assortment of shapes, sizes, temperaments, and be- present ideas on how to conserve them. haviors in modern dogs testifi es to the power with which human-directed selection can transform the 8.1.1 What are we conserving? dog genome to produce novel and desirable phe- notypes suited to diverse tasks and predilections. As wolves transformed into dogs, they arguably be- The ubiquitous distribution of dogs across the globe came integrated into our lives in a deeper and more testifi es to the dogs’ own ability to adapt to a wide complex manner than any other animal. We main- array of anthropogenic niches. tain working relationships of all sorts with dogs, us- In this chapter, we summarize what is known ing them to help us hunt, herd, guard, carry burdens, about the genetic and phenotypic distinctiveness of clear landmines, fi nd missing persons, assist disa- modern breed dogs and free-breeding dog popula- bled individuals, fi nd illicit substances, and detect tions, both truly feral populations (like dingoes) and cancers (e.g., VerCauteren et al., Chapter 9 ; Woollett the more common ‘village’ dog populations that are et al., Chapter 10 ; Koster and Noss, Chapter 11 ). De- found throughout much of the world (see Box 8.1 pending on the culture of an area, dogs are also used for an explanation of terms). Because of the relative- as food and companions. Given this diversity of ly recent origin (in evolutionary time-scales) of the uses, it is unsurprising that specifi c kinds of dog are dog, no dog population can fairly be described as a bred to have phenotypic and, perhaps, genetic ad- separate biological species. In fact, dogs can freely vantages in performing one or another of these func- interbreed with wolves ( Canis lupus ) and coyotes tions. For example, Poodles seem to contain more ( C. latrans ) (Leonard et al., Chapter 7 ), and hybridi- transcribed olfactory genes than Boxers, probably zation and introgression within the genus can make due to stronger selection on Poodles’ ability to smell it diffi cult to neatly apply traditional species con- game and truffl es ( Tacher et al., 2005 ). In these cases, cepts ( vonHoldt et al., 2011 ). Nevertheless, isolation conserving dogs with unique abilities will conserve and local adaptation created genetically distinct the genetics underpinning them and allow for their village dog populations, some of which are now continued use and study. Free-Ranging Dogs and Wildlife Conservation. Edited by Matthew E. Gompper © Oxford University Press 2014. Published 2014 by Oxford University Press. 009-Gompper-Chap08.indd9-Gompper-Chap08.indd 185185 99/14/13/14/13 110:360:36 AAMM 186 FREE-RANGING DOGS AND WILDLIFE CONSERVATION Box 8.1 Terminology To clarify our use of terms and to distinguish our use of these tend to show a genetic signature of their place of origin terms from other, sometimes confl icting, uses of the same and tend not to be closely related to major European dog terms, we provide the following guide to terminology used breeds, although in some places (e.g., Central Namibia and throughout this chapter. much of the Western Hemisphere) they show signifi cant Dogs: Canis familiaris including modern breed dogs, vil- admixture with European-derived dogs ( Boyko et al., 2009 ; lage dogs, New Guinea singing dogs, and dingoes, but not Castroviejo-Fisher et al., 2011 ). We use the term indigenous including wolves or coyotes despite their ability to occasion- village dog to refer to a village dog that has little admixture ally, albeit rarely, interbreed with dogs. with non-native dog breeds and admixed village dog to re- Breed/Purebred dogs: Dogs that have restrictive breed fer to a village dog that has signifi cant admixture with non- books and are generally recognized by kennel clubs (groups native (usually European) dog breeds. Compared to land of dog owners that collectively focus on the breeding, main- races, village dogs have a much wider variety of physical tenance, and promotion of particular breeds of dogs). Most appearances within a location. Free-breeding city-dwelling dog breeds underwent a bottleneck during breed formation dogs in Russia and India fi t this defi nition, as well as dogs with some breeds encountering subsequent bottlenecks living at the margins of Egyptian society or living in rural and/or inbreeding. Modern dog breeds come predominantly villages in Uganda and elsewhere. Populations of admixed from Europe (see Figure 8.2 ) and developed closed breeding village dogs may be consistently replenished by new stray populations sometime during or after the Victorian era of the dogs while indigenous village dog populations are usu- mid–late 1800s. Boxers and Poodles are examples. ally self-perpetuating, not requiring newly released dogs to Ancient breed dogs: In ancient times, some dogs were maintain their populations. deliberately bred for certain characteristics, although not Feral dogs: Dogs living completely or nearly completely necessarily with the rigorously maintained pedigree records free from human-derived resources (such as trash), for ex- of modern purebreds. Ancient breed dogs today are pure- ample dingoes. For our purposes of identifying conservation bred dogs with genetic signatures inherited from those dogs, targets based primarily on genetics, we differentiate popula- signatures that are identifi ably separate from the modern tions of feral dogs from village dogs based on the interac- European breeds. Basenjis and Salukis are examples. tions most individuals have with people. Land races: Dogs that exhibit physical traits and behavio- Free-breeding dogs: Dog populations with a substantial ral tendencies characteristic of dogs originating in a particu- proportion of dogs that often choose mating partners for lar place. These characters have developed over hundreds themselves, including village dogs and feral dogs. While or thousands of years though adaptation to the local en- we acknowledge that there is a range of dog breeding and vironment, possibly with breeding interference by humans husbandry practices across the globe, in general village dog (artifi cial selection), but without offi cial studbooks (and breeding involves more sexual/natural selection and less ar- thus despite interbreeding with sympatric or parapatric dog tifi cial selection than modern breed dog breeding practices. populations). In many ways they are similar to ancient breed This difference has important implications for the level of dogs but their breeding is less closely controlled and in most genetic and phenotypic diversity found in these populations, cases (e.g., the Africanis) it seems like the original land races and for the diversity found between different populations were mostly or completely genetically swamped by modern and breeds. We prefer this term to semi-feral dogs because it breed dogs brought to these areas. In other cases these land encapsulates the most important difference between village races may just be local village dogs that happen to comport dogs and breed dogs from a conservation standpoint, which to a certain physical appearance (e.g., the Indog). is their mating system and its effects on genetic diversity Village dogs: Dogs that live relatively free-breeding and and adaptation. It is also a more accurate term, as some oftentimes partially free-ranging existences as human com- village dog populations contain individuals that have nearly mensals or mutualists in many places around the world. no interaction with people (truly semi-feral) while others These dogs are not usually undergoing strong programs contain mostly individuals that interact extensively with a of human-directed breeding, but people may preferentially human owner, but in general most bitches in these popu- feed, shelter, or cull certain individuals. These dogs’ rela- lations are either allowed to breed freely with other local tionship with the local humans and other animals varies dogs or are bred with locally available sires in such a way greatly depending on cultural and ecological context. They continued 009-Gompper-Chap08.indd9-Gompper-Chap08.indd 186186 99/14/13/14/13 110:360:36 AAMM DOG CONSERVATION AND THE POPULATION GENETIC STRUCTURE OF DOGS 187 Box 8.1 Continued as to not overly skew the variance in reproductive success dogs are all capable of interbreeding and producing fertile between males and females or quickly diminish the popula- hybrids, they are often considered separate species on the tion’s genetic variation. basis that hybridization under natural conditions is rare. Introgression: The incorporation of portions of the ge- Where these species are sympatric, they remain genetically nome from individuals of one species/population to another distinct even though some hybridization may occur (Leonard through admixture or hybridization and back-crossing. et al., Chapter 7 ). Species: For sexually reproducing organisms, the bio- Artifi cial selection: Human-controlled selective breeding logical unit consisting of similar individuals capable of in- of individuals for particular traits. In this chapter, we gener- terbreeding and reproductively isolated from other such ally use the term to refer to directed breeding of particular groups.