The chromosomes of spiny rats, proechimys trinitatis, from Trinidad and Eastern Venezuela (Rodentia, Echimyidae)

Abstract

A detailed description of the karyotype of Proechimys trinitatis, (2n = 62, FN = SO), based on specimens from Trinidad, is given. It differs from the karyotype of Proechimys guyannensis (2n = 40) which is interpreted as an indication of the need of giving full species status to P. trinitatis. It also differs from the karyotype of P. urichi, a montane form living in Eastern Venezuela, and it is remarkably different from the karyotypes of members of the superspecies P. guairae from north-western and north-central Venezuela. Specimens from a sample of Cachipo, in the lowlands of Monagas State, proved to have a karyotype identical to that of the studied specimens of P. trinitatis from Trinidad. This is interpreted as an indication that P. trinitatis is also represented on the continent. Differences in size and in cranial characters of the Venezuelan specimens uggest hat the Cachipo sample might be separated as a distinct subspecies of P. trinitatis. ability is interpopulational (Reig et al., 1979). Therefore, when karyotypic differences are large enough as to imply postzygotic reproductive isolation by a high level of gametic aneuploidy in the F, hybrids (Capanna et al., 1977; Reig et al., 1979) these differences make a good tool for species recognition, even when this recognition is hard to make on morphological grounds. Consequently, chromosome investigations may contribute to the understanding of the confusing systematics of this genus, and help to gain further knowledge on the role played by karyotypic rearrangements in the speciation process, a subject which is becoming a point of primary attention in modem theory of speciation (White, 1978). We now report the karyotype of Proechimys trinitatis (Allen & Chapman) 1893, the type species of Proechimys (Allen, 1899), but which has been alleged (Ellerman, 1940) not to be separable at the species level from the earlier proposed Proechimys guyannensis (E. Geoffroy) 1803.