Refugial origin and postglacial colonization of holarctic reindeer and caribou

Abstract

Abstract:The classification and colonization of reindeer and caribou (Rangifer tarandus) was assessed from analysis of both proteins, nuclear DNA and mitochondrial DNA. I demonstrate that the current subspecies designations are not compatible with the differentiation at these markers, suggesting that the morphological differences among extant subspecies did not evolve in separate glacial refugia. Thus, morphological differences among extant subspecies probably evolved as adaptive responses to post-glacial environmental changes. An exception to this is the North American woodland caribou, where all three marker systems support a subspecies-specific refugium as the ancestral origin of these animals. Three major mtDNA haplogroups reported, represent three separate origins of the species during the last glaciation. The most influential origin has contributed to the gene pool of all extant subspecies, suggesting the existence of a large and continuous glacial population ranging across extensive areas of tundra in Eurasia and Beringia. The North American tundra forms (R.t. granti and groenlandicus) and the arctic forms (R.t platyrhynchus, R.t pearyi and R.t eogroenlandicus) almost exclusively comprise haplotypes of such an origin. Another small and isolated refugium seems to have arisen in western Eurasia in close connection to the extensive ice sheet that covered Fennoscandia. The two Eurasian subspecies R.t. tarandus and R.t. fennicus appear to have a diphyletic origin as both the putatively small and isolated Eurasian refugium and the large Beringia refugium have contributed to their gene pools. A third distinct and geographically well-defined refugial area was probably located south to the extensive North American continental ice sheet from where the ancestors of the present North American woodland caribou (R.t. caribou) likely originated.

Near-Total Loss of Caribou on South-Central Canadian Arctic Islands and the Role of Seasonal Migration in their Demise

“…They concluded that the Arctic Island caribou on the Canadian Arctic Islands south of 74˚ N latitude (which includes our study area) evolved from barren-ground caribou (R. t. groenlandicus) that spread northward from the mainland after glacial retreat and are most likely the ancestral stock for the Peary caribou (R. t. pearyi) found farther north (above 74˚ N) on the Queen Elizabeth Islands. Røed (2005) recently reached the same conclusions. In addition, both morphometric data (Thomas and Everson, 1982) and microsatellite DNA data (Zittlau, 2004) suggest a relatively high degree of diversity among these caribou, which allows their identification and separation into distinguishable ecotypes.…”

Phylogeographical Analysis of mtDNA Data Indicates Postglacial Expansion from Multiple Glacial Refugia in Woodland Caribou (Rangifer tarandus caribou)

“…In contrast, the temperate woodland caribou most likely originated from south of the Laurentide ice sheet [14], [32]–[34] whereas the other four (arctic/tundra) subspecies originated in northern refugia; possibly explaining part of the differentiation at the subspecies level. Previous genetic studies [34], [35] suggested that there was at least one major well-defined refugial area in North America for the woodland caribou south of the Laurentide ice sheet. Also, it has been indicated by a multimodal mismatch distribution pattern based on mtDNA sequence data [34] that there was either one large population/refugium with relative constant population size or alternatively that this refugial area included several smaller refugia [34], [35].…”

“…Previous genetic studies [34], [35] suggested that there was at least one major well-defined refugial area in North America for the woodland caribou south of the Laurentide ice sheet. Also, it has been indicated by a multimodal mismatch distribution pattern based on mtDNA sequence data [34] that there was either one large population/refugium with relative constant population size or alternatively that this refugial area included several smaller refugia [34], [35]. However, this issue could not be resolved at the time due to small sample sizes.…”

Colonizing the High Arctic: Mitochondrial DNA Reveals Common Origin of Eurasian Archipelagic Reindeer (Rangifer tarandus)

“…Svalbard reindeer are characterized by low genetic variability indicating isolation, possible bottlenecks, and subsequent genetic drift as important population processes [24, 25]. The Svalbard population is characterized by three control region (CR) haplotypes which were previously thought to be unique to Svalbard [26].…”