Unusually extensive karyotype reorganization in four congeneric <i>Gerbillus</i> species (Muridae: Gerbillinae)

Abstract

Comparative analysis of the G- and C-banding patterns in four morphologically poorly differentiated Gerbillus species (G. pyramidum, G. perpallidus, G. tarabuli and G. occiduus) was carried out. These gerbils have similar karyotype morphology with 2n and NF equal to 38/76, 40/76, 40/78 and 40/80, respectively. Our study revealed that possibly 70 Robertsonian (Rb) fusions, two pericentric inversions, one tandem translocation and at least 13 non-identified rearrangements have occurred during the karyotypic evolution of these species. The number of chromosomal changes by which any of these species differ from each other ranges from 33 to 49. One Rb fusion was common to two of the species, with only a single autosome-gonosome translocation shared by all four, suggesting a monophyletic origin of these karyotypically highly divergent species. Based on the chromosomal data obtained here, the systematic and geographic implications for these North African species are also discussed.

Non-Sciuromorph Rodent Karyotypes in Evolution

“…It is hypothesized that chromosomal rearrangements need to be fixed in a short period of time [Britton-Davidian et al, 2000;Wang and Lan, 2000;Dobigny et al, 2005;Aniskin et al, 2006], so they may create reproductive isolation between populations [Ayala and Coluzzi, 2005]. According to a 'fragile site' breakage model of chromosomal evolution, there are some regions in a genome where the frequency of chromosomal rearrangements is very high.…”

“…They display a remarkable heterogeneity, and the species of this group differ from each other by a high number of structural interspecies rearrangements ( 1 30) and all share a gonosome-autosome translocation (or even 2 in the case of G. gerbillus ). They may display large intra-and interpopulation polymorphisms for both structural rearrangements and size of heterochromatic blocks [Aniskin et al, 2006]. On the contrary, the group of the 5 remaining species is characterized by a low amount of homogeneously stained heterochromatin ( !…”

“…10% of total karyotype length), by a low number of interspecies rearrangements (1-4), and all have conserved the original X-chromosome type. These sharply distinct genomic features, in morphologically and biologically otherwise rather similar species, strongly suggested a causal relationship between abundant amounts of cytologically (and molecularly) heterogeneous heterochromatin and unusually high rates of karyotype repatterning [Aniskin et al, 2006], although the precise mechanisms remain to be elucidated. Up to now, different types of heterochromatic repeat sequences were characterized [e.g.…”

Systematics and phylogeny of West African gerbils of the genus <i>Gerbilliscus</i> (Muridae: Gerbillinae) inferred from comparative G- and C-banding chromosomal analyses

“…This is lower than values detected in other murid genera. For example, 45, 10, 7 and 6 in Taterillus , Gerbillus (Aniskin et al, 2006), Acomys (Volobouev et al, 2002a) and Mastomys (ibid), respectively. As a consequence, genome repatterning within Gerbilliscus is to be considered as slow to moderate.…”

Description of Karyotype of Kerodon acrobata, an endemic rodent in Brazilian Cerrado

“…In general, chromosomal rearrangements are involved in the processes of speciation (King, 1993). It is hypothesized that chromosomal rearrangements need to be fixed in a short period of time (Aniskin et al, 2006), so they may create reproductive isolation between populations (Ayala and Coluzzi, 2005), because heterochromatic regions are regarded as the main contenders for the roleof stabilizing or destabilizing evolution (Graphodatsky, 1989;Hennig, 1999).…”