Cladistical analysis of primitive G-band sequences for the karyotype of the ancestor of the Cricetidae complex of rodents

Abstract

Homologous segments identified by G-banding sequences of chromosomes of Peromyscus boylii, Neotoma micropus, Oryzomys capito, (Family Cricetidae) Rattus norvegicus, Melomys burtonL and Apodemus sylvaticus (Family Muridae) were used to hypothesize a chromosomal condition for the cricetid ancestor. A critical assumption in proposing the primitive G-banding sequences for a given chromosome is that if the outgroup and ingroup taxa have a specific sequence, then the ancestor of the ingroup taxa also had that same sequence. Using this methadology, (chromosome numbers refer to proposed homology to the standardized karyotype for Peromyscus)

Resolving Systematic Relationships With G-bands: a Study of Five Genera of South American Cricetine Rodents

“…These systematic assumptions are consistent with some classification schemes (Hooper and Musser, 1964;Hershkovitz, 1966Hershkovitz, , 1972Reig, 1977) and allow the determination of primitive and derived G-band seq.uences at several points in the chromosomal evolution of Neotropical cricetines examined. The primitive chromosomal complement (14 largest pairs) for the Cricetidae was determined by Koop et al (1984a) to be like that found in Neotoma micropus. In this study we have analyzed characters of the South American taxa relative to that of N. micropus in order to determine polarity in transition series.…”

“…In chromosome 9, the proposed ancestral G-band sequence (Koop et al, 1984a) was found in Neotoma micropus, S. hispidus, Nectomys squamipes, H. brasiliensis, 0. capito, 0. palustris, 0. couesi, and 0. caliginosus. Oryzomys sp.…”

“…In Nectomys squamipes the 1 1 sequence appears to be derived from the 1 sequence. The proposed primitive sequence of chromosome 11 for cricetines is I as determined by Koop et al (1984a). The 11 sequence can be explained by a whole arm paracentric inversion or centric shift in the I sequence.…”

“…Also, as a standard reference, the Oryzomys capito G-bands used in Koop et al (1984a) are shown in Figures 1, 2, and 3.…”

“…Sigmodon hispidus (2N = 52)-used from Elder (1980). Neotoma micropus (2N = 52)-used from Koop et al (1984a).…”