Abstract
BackgroundLate Pleistocene North America hosted at least two divergent and ecologically distinct species of mammoth: the periglacial woolly mammoth (Mammuthus primigenius) and the subglacial Columbian mammoth (Mammuthus columbi). To date, mammoth genetic research has been entirely restricted to woolly mammoths, rendering their genetic evolution difficult to contextualize within broader Pleistocene paleoecology and biogeography. Here, we take an interspecific approach to clarifying mammoth phylogeny by targeting Columbian mammoth remains for mitogenomic sequencing.ResultsWe sequenced the first complete mitochondrial genome of a classic Columbian mammoth, as well as the first complete mitochondrial genome of a North American woolly mammoth. Somewhat contrary to conventional paleontological models, which posit that the two species were highly divergent, the M. columbi mitogenome we obtained falls securely within a subclade of endemic North American M. primigenius.ConclusionsThough limited, our data suggest that the two species interbred at some point in their evolutionary histories. One potential explanation is that woolly mammoth haplotypes entered Columbian mammoth populations via introgression at subglacial ecotones, a scenario with compelling parallels in extant elephants and consistent with certain regional paleontological observations. This highlights the need for multi-genomic data to sufficiently characterize mammoth evolutionary history. Our results demonstrate that the use of next-generation sequencing technologies holds promise in obtaining such data, even from non-cave, non-permafrost Pleistocene depositional contexts.
Highlights
Late Pleistocene North America hosted at least two divergent and ecologically distinct species of mammoth: the periglacial woolly mammoth (Mammuthus primigenius) and the subglacial Columbian mammoth (Mammuthus columbi)
Conventional paleontological models [1,2,3,4] of North American mammoth evolution posit that at least two species occupied the continent during the late Pleistocene (150,000 to 10,000 years ago: Mammuthus primigenius (woolly mammoths (WMs)) evolved in Eurasia and immigrated to North America in the late Pleistocene, whereas Mammuthus columbi (Columbian mammoths (CMs)) evolved locally from an earlier Pleistocene immigrant ancestor (Mammuthus meridionalis [1,2] or Mammuthus trogontherii [3,4])
2 million reads mapped to the African elephant (Loxodonta africana) nuclear genome, providing approximately 0.03 × coverage of the entire nuclear genome of the animal, and bringing the total likely mammoth DNA read count to approximately 7% of all sequences
Summary
Late Pleistocene North America hosted at least two divergent and ecologically distinct species of mammoth: the periglacial woolly mammoth (Mammuthus primigenius) and the subglacial Columbian mammoth (Mammuthus columbi). One potential solution to both problems - and means to hone conceptions of Pleistocene mammoth evolution in general - is to sequence DNA from one or more closely related but distinct mammoth species and use it as a temporal and taxonomic calibration tool within the mammoth gene tree Owing to their apparently separate evolutionary history (Figure 1a) and reasonably welldated recent divergence from WMs about 1 to 2 million years ago [16], CMs are excellent candidates for this role. To this end we targeted CM remains for mitogenomic sequencing
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