Phylogenetic position of Abalosia and the evolution of the extant Octodontinae (Rodentia, Caviomorpha, Octodontidae)

VERZI, D.H.

ACTA THERIOLOGICA

Año: 2001 vol. 46 p. 243 - 268

0001-7051

South American octodontid rodents of the subfamily Octodontinae have today low species richness but great morphological and chromosomal diversity. Currently this diversity is interpreted alternatively as the remnant of a wider past radiation or as the result of saltational evolution. These hypotheses are discussed in relation to a phylogenetic analysis of the Late Pliocene octodontine Abalosia castellanosi. The results suggest that Abalosia, together with Tympanoctomys and Octomys, is part of a clade of desert specialist propalinal octodontids, which would have differentiated east of the Andes in the emergent semi-deserts of western Argentina. The presence of Abalosia in the coastal region of central Argentina during the Upper Marplatan Age (Late Pliocene) suggests a pulse of expansion of such arid environments, probably coeval with the global climatic deterioration detected around the transition Gauss-Matuyama magnetic ages. The phylogenetic position of A. castellanosi suggests that extinction events affected the clade of the octodontine desert specialists. Accordingly, regardless of how rough or gradual the differentiation of the octodontine’s diversity has been, the living representatives seem to be remnants of a wider radiation.