Mf. Smith et al., Testing models of diversification in mice in the Abrothrix olivaceus/xanthorhinus complex in Chile and Argentina, MOL ECOL, 10(2), 2001, pp. 397-405
Samples of the forest-dwelling mouse Abrothrix olivaceus and the steppe-dwe
lling A. xanthorhinus across a transect between 45 and 47 degrees S in sout
hern Chile were analysed using the mitochondrial cytochrome b (cyt b) seque
nce, substantially adding to the data presented previously for these taxa f
rom Argentina and Chile. The level of variation in the cyt b sequence throu
ghout the entire olivaceus/xanthorhinus complex is comparable to that seen
within a single species in many South American sigmodontine rodents, consis
tent with a previous conclusion that both taxa are sub-species of A. olivac
eus. Haplotypes of xanthorhinus have not yet achieved reciprocal monophyly
relative to those of olivaceus. We evaluate competing hypotheses for the mo
rphological divergence of xanthorhinus and olivaceus by allopatry in Pleist
ocene refuges versus postglacial diversification across ecological gradient
s. Two contrasting patterns are predicted for plots of the distribution of
pairwise genetic differences, depending on whether the taxa diverged in all
opatric refuges or through selection across a gradient. Examples of both mo
des of diversification are found in this complex.