Ninety-five different mitochondrial haplotypes were identified. A median-joining network (a
) reveals an internal assemblage of haplotypes (I), which is connected to a few terminal star-like clusters (II, III, IV and V), corresponding to four highly supported clades in a phylogenetic tree (see figure S1 in the electronic supplementary material). It is likely that the large but poorly structured haplotype assemblage I represents the large reindeer population that was present across Beringia during the last glacial period (Guthrie & Matthews 1971
; Elias et al. 1996
; Flagstad & Røed 2003
). The terminal clusters may have arisen in smaller glacial refugia, or alternatively by random haplotype sorting and subsequent population expansion during postglacial re-colonization of the Eurasian arctic. The Beringian haplotype cluster is by far the most common in all Russian herds, whereas clusters II and III dominate in Fennoscandia (Norway, Sweden and Finland; b
). Haplotypes from cluster II are found in high frequencies in all Fennoscandian domestic herds and in the southwestern wild population in Norway. Notably, cluster III is restricted to wild herds in central Norway and was never observed in any of the 107 domestic reindeer sampled in Fennoscandia (b
Figure 1 (a) Median-joining network for mitochondrial DNA haplotypes found in Eurasian reindeer. Haplotypes found only in wild herds are represented by squares, whereas the triangles represent domestic haplotypes. Circles represent haplotypes found in both wild (more ...)
Haplotype sharing is very limited between Russia and Fennoscandia (a
), suggesting separate origins of domestic reindeer in the two regions. This implies limited exchange of animals between the reindeer herding people of Fennoscandia and the indigenous cultures in western Russia. This is particularly remarkable for the two Russian domestic herds sampled on the Kola peninsula (Rus-Dom 6 and Rus-Dom 7), which are located very close to the northernmost parts of Norway and Finland (b
). By sharp contrast, reindeer herds show high levels of haplotype sharing within regions, suggesting not only a common origin for the herds within each of these regions but also extensive intra-regional exchange and trade of animals. This interpretation is further supported by the high levels of genetic diversity in all domestic herds, which in some areas is even higher than that found in local wild herds (see table S1 in the electronic supplementary material). High levels of genetic diversity in domestic herds might further suggest that augmentation of domestic herds with animals from local wild herds has been common (Vilà et al. 2005
), which is also compatible with the extensive haplotype sharing observed between neighbouring wild and domestic herds, e.g. haplotype A in eastern Russia and haplotypes B and C in Fennoscandia (a
). Nevertheless, the most common haplotype in the central Norwegian wild population (E) and the wild Finnish population (F) are not found in any domestic herd () strongly suggesting that neither of these wild populations have been sources for domestic reindeer in Fennoscandia.
A clustering analysis at population level confirms that Russian and Scandinavian herds are strongly differentiated (). Three highly supported clades are evident in the microsatellite tree comprising (i) all Russian herds, (ii) the central Norwegian wild herds, and (iii) the rest of the Fennoscandian herds, wild as well as domestic. Virtually the same pattern appears from the mtDNA data, pointing towards the same origin for both sexes in the initial domestic herds. The division of the data into three main groups is also supported by an AMOVA () where there is a marked increase in the amount of variation explained at group level when separating herds in Russia and Fennoscandia and a further increase when separating the wild populations in central Norway from the rest of Fennoscandia (model G). Further division of the data gives only a marginal increase in the amount of variation explained at group level.
Figure 2 Population dendrograms as inferred from microsatellite and mtDNA data. Wild and domestic populations are represented by squares and triangles, respectively. Geographical origins are represented by different colours. Blue, Fennoscandia; Orange, western (more ...)
Table 1 AMOVA for wild (W) and domestic (D) reindeer herds in Eurasia. (The percentage of the total variation that can be explained at group level is given for one, two or three origins of domestication. Origins of domestication are based on the number of groups (more ...)
Similar to the analysis at population level, genetic variability at an individual level shows a partition of the sample into three main groups (a–c
), supporting independent origins of domestic reindeer in Fennoscandia and Russia. Reindeer herding in Fennoscandia, and particularly in the northern part, has traditionally been connected to the Saami culture. Thus, our analyses strongly point towards an independent origin of Saami reindeer herding. Notably, the domestic gene pools in Fennoscandia and Russia seem to meet in eastern Finland, where the examined herds appear as a mixture of the two origins (c
). This may reflect the frequent trade and transport of animals that occurred in the eighteenth century between the reindeer herders in eastern Finland (traditionally of Finnish origin) and the indigenous reindeer herding people towards the east as well as the north (Nieminen 2006
). In contrast to the sharp genetic boundary between Russia and areas inhabited by the Saami people, the Russian domestic gene pool appears remarkably homogeneous across a vast region (b
). However, when a factorial correspondence analysis is performed after removing the central Norwegian wild population, which clearly has not contributed to the domestic gene pool, a marked difference also appears between western and eastern Russian herds (d
). Domestic and wild reindeer individuals from each of these three geographical regions appear mixed within the three clusters, demonstrating little differentiation between domestic and wild herds within areas and that the main differentiation is found between the following geographical areas: Fennoscandia; western Russia; and eastern Russia. This division is supported by the very limited mtDNA haplotype sharing between these three regions (a
), and may suggest not only two but three different centres of domestication in Eurasian reindeer. Alternatively, local augmentation of domestic herds in western and eastern Russia could be partly or entirely responsible for this pattern.
Figure 3 Clustering analysis in Eurasian reindeer herds, using (a–c) Bayesian assignment and (d) a factorial correspondence analysis. (a) Mean likelihood (L(K) (±s.d.)) over 10 runs dividing the entire dataset into K populations, for K values between (more ...)
Although we often observe a similar genetic composition of wild and domestic herds within areas, our data reveal some striking exceptions. As discussed previously, the wild populations in Finland and central Norway have contributed little or nothing to the domestic gene pool. In addition, the wild reindeer residing in the mountain taiga in southeastern Russia (Rus-Wild 2) show a genetic composition that is markedly different from that of the local domestic herds. In fact, all of the 10 wild individuals analysed carried herd-specific mtDNA haplotypes whereas domestic reindeer from the same area (Rus-Dom 2) have a much stronger genetic affinity towards more westerly and northerly distributed herds (). These differences may indicate variation in domestication potential among different wild populations, possibly due to the behavioural differences or variation in herd structure and size. In fact, our data indicate that the animals used in the domestication process probably derived from the large tundra herds instead of the smaller herds residing in the forest. Among the reindeer analysed, the two populations with the most characteristic wild forest ecotype, the Finnish (Fin-Wild 1) and the southeastern Russian (Rus-Wild-2), seem to have contributed little or nothing to the domestic gene pool. The tundra type that inhabits open areas is more gregarious than the forest dwelling types and has evolved a more sophisticated social organization (Geist 2003
). This could represent an advantage for their exploitation by humans (Clutton-Brock 1987
), which was likely to be especially important during the course of the transition from transport reindeer herding (mobile hunting) to managing larger herds of reindeer for food and skins (large-scale reindeer pastoralism).
The domestication of mammals is a slow process, which in its early phases may involve the management and control of wild herds rather than the capture of a few individuals and their subsequent breeding in captivity (Troy et al. 2001
; Zeder 2006
; Zeder et al. 2006
). Archaeological evidence also suggests that these initial stages probably included the occasional augmentation of managed herds by adding wild individuals (Zeder 2006
; Zeder et al. 2006
). This is supported by a simulation study demonstrating that such backcrosses may have been common for several domestic species, contributing to their high genetic diversity (Vilà et al. 2005
). Active management of reindeer herds—for example, the use of leading fences or enclosures and corrals for handling animals—can be tracked for a few thousand years (Mirov 1945
; Aronsson 1991
). This could explain the high genetic diversity observed in domestic herds and their similarity to the local wild populations. The ancestors of many livestock species, such as horse and cattle, probably lived in herds similar to the wild reindeer herds (small forest herds and larger tundra herds) that are present across the Eurasian arctic today. However, since their wild ancestors have disappeared or are greatly reduced, there is little or no information about the distribution of genetic diversity at the time of domestication. Thus, it is difficult to be conclusive about the early domestication history of these species. However, given the ecological and behavioural similarity between reindeer and the wild ancestors of these livestock species, the patterns observed for reindeer and reported herein may well be representative to how the initial stages of domestication of other livestock species took place.
In recent years, there has been increased attention towards the history and cultural traditions of indigenous people within the framework of laws and regulations of land exploitation. Our data contribute to a more detailed understanding of an important part of this cultural history. Indeed, understanding the long-lasting interaction between humans and reindeer is a crucial element for understanding the recent history of our own species in northern latitudes.