Genetic investigations on mammoth (Mammuthus primigenius)

Previous authors have disagreed about the interpretation of molecular data concerning the phylogenetic affiliation of Mammuthus with respect to Elephas and Loxodonta. We compare sequence data of the mitochondrial cytochrome b gene, the gene studied by most authors. Hagelberg et al. (1994) as well as Hauf et al. (1995) found a closer affinity of Mammuthus to Loxodonta, whereas Yang et al. (1996) and Ozawa et al. (1997) found a common branch of Mammuthus with Elephas. This was rejected by Noro et al. (1998) whose data supported again a Loxodonta- Mammuthus association, whereas Hauf et al.(1999) gave additional support to an Elephas- Mammuthus clade. However Derenko et al. (1997) as well as Hauf et al. (1999/2000) could not find any evidence for either of these alternatives, while analyses by Barriel et al. (1999) and Thomas et al. (2000) support an association of Mammuthus with Loxodonta, but not with a satisfying certainty. In this contribution, we present new partial cytochrome b sequences for seven Wrangel island mammoths, but do not claim to present the definite solution. When all data now available for cytochrome b are taken together, the possibly synapomorphic bases counted for Elephas + Mammuthus are only slightly more in number than those countable for Loxodonta + Mammuthus, whereas less support is found for an Elephas-Loxodonta clade. A remarkable observation is that different portions of the same gene may indicate different phyletic affinities. We discuss the possible reasons for differing results and point out a way to solve the dilemma. Shortcomings of previous papers include: (1) Only one or two mammoth individuals were used, which sometimes even differed in their base sequence, yet intraspecific variability was largely disregarded; (2) The outgroup chosen was too distant (Mastodon or Dugong should be taken); (3) Sequences were too short (even 1000 bases do not provide sufficient phylogenetic signal); (4) Tree reconstructions were based on single-base transitions, which are probably switching easily back and forth between apomorphic and plesiomorphic states, hiding phylogenetic signal; (5) Computer methods were used uncritically. More data are needed to clarify the phylogenetic affiliation of Mammuthus.