Allometry and chromosomal speciation of the casiraguas Proechimys (Mammalia, Rodentia)

Morphometric characters (linear measurements) of the skull and mandible of the rodent Proechimys occurring in Venezuela and Columbia were investigated through multivariate techniques in order to describe static allometry and to relate allometric patterns to the recent evolution of these taxa. At least five species originated during the recent Pleistocene period in the upper Orinoco basin, all characterized by different karyotypes, one of them (P. guairae) being a Rassenkreis of karyomorphs. Species are characterized by unique static allometric patterns and the study of these patterns suggests a phylogenetic rather than an ecogenetic origin for these patterns; modifications in the shape of the skull and the mandible have originated during phyletic speciation and there is no apparent sign of functional adaptation.