Geographic distribution and systematic relationships
Until 1800 the wolf was dispersed across Europe apart from the British Isles. Now, large populations (500 wolves) survive only in Spain, Poland, Romania, Bulgaria, Serbia, the Baltic states, Ukraine, and central Russia (Boitani 2003). There are crude estimates of c.65 000 wolves living east of the Urals and in Asia, and probably a further 2000 living in Asia Minor and Egypt. The population in the Americas is judged to be about 60 000 individuals, of which only 10% are in the USA. Thus, based on estimates by Boitani (2003), there might be about 160000 wolves living in the Holarctic. In contrast, Ginsberg and Macdonald (1990) estimated around 300 000 wolves, and it is thought that wolves have lost more than 50% of their original habitat during the last few hundred years (Box 4.1).
The Grey wolf has always provided a lot of work for taxonomists. Some of the problems stem from the uncertainties surrounding the species concept. The situation is made even more complicated by the wolf's complex relation to various forms of domesticated and feral dogs. There is limited evidence that all Canis species can interbreed, with fertile offspring. Genetic studies revealed wolf-dog hybrids in Italy (Randi et al. 1993, Randi and Lucchini 2002), but they occur elsewhere too. Hybridization also takes place between wolf and coyote (Lehman et al. 1991) producing fertile offspring (see also Wilson et al. 2000). Thus according to the classical definition of a species, all Canis could be considered as a single species. However, the revised biological definition of species is based on interbreeding natural populations that are separated from other similar groups (Mayr 1963). This separates wolves from coyotes (or jackals), even if there is some limited evidence of hybridization between these species if their habitats overlap (Wayne and Vila 2001). This would argue for categorizing wolves and dogs into separate species. However, some taxonomists now seem to disagree whether the classic Linnaean categories (lupus and familiaris) are still valid. This has led to the unfortunate and confusing situation that many European zoologists, behavioural scientists, and geneticists over the world still refer to the dog as a separate species, while in many papers published by North American authors dogs are categorized as a subspecies of wolves (C.l. familiaris). The 'lumpers' argue that dogs and wolves are not differentiated enough to qualify for species-level discrimination (e.g. Wayne 1986a, b). However, the ecological species concept takes Mayr's definition even further by saying that species are adapted to a specific niche in their environment as a consequence of an evolutionary/ecological process. Thus if such a niche and a set of particular adaptations can be identified in a population, then a species-level categorization might be justified. This logic was applied by Coppinger and Coppinger (2001) and others when they argued that dogs show specific adaptive traits for living in an anthropogenic niche (Box 5.1). Since both the population-based and the ecological definition seem to be fulfilled by dogs, we will retain the original labels used by Linnaeus.
Similar problems at a different level emerged in the taxonomy of the lupus subspecies. Based mainly on the distribution of populations and morphological traits, wolves were categorized into various subspecies. For example, based on Hall and Kelson (1959), Mech (1970) listed 24 subspecies in North America, which were collapsed into 5 subspecies based on a detailed morphological analysis (Nowak 2003). Thus the present list includes the Arctic wolf C.l. arctos, Mexican wolf C.l. baileyi, Eastern wolf C.l. /ycflon, Plains wolf C.l. nubilus, and Northwestern wolf C.l. occidentalis. According to Nowak (2003) there are 9 living subspecies in Eurasia: Arctic wolf
C.l. albus, Arab wolf C.l. arabs, north-central wolf C.l. communis, C.l. cubanensis, Italian wolf: C.l. italicus, C.l. lupaster, common wolf C.l. lupus, and Indian wolf C.l. pallipes, but only 7 were listed in Mech (1970). However, there are problems with the present system too: C.l. chanco (originally described from China and Mongolia) is not mentioned by either source, which presents a problem because this subspecies has often been referred to in connection with the domestication process. Genetic analysis (see below) seems not to support the distinction between Italian and other European wolves. Moreover, the two 'arctic' wolves (arctos and albus) might create some confusion in the literature (Nowak 2003). Finally, if we define the wolf subspecies on the basis of geographical distribution then this does not fit with the idea of including the dog as an additional subspecies which is distributed all over the world.
It seems that the wolves escape our classic notion of species and subspecies. In suggesting a way forward, Wayne and Vila (2001) argue that instead of trying to categorize extant populations of wolves, we should regard them as a series of intergrading populations—a concept that is also supported by the genetic evidence.
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