Chromosoma

, Volume 85, Issue 2, pp 149–162 | Cite as

Genome evolution in pocket gophers (genus Thomomys)

I. Heterochromatin variation and speciation potential
  • James L. Patton
  • Steven W. Sherwood
Article

Abstract

A basic dichotomy exists in the amount and chromosomal position of constitutive heterochromatin (C-bands) in species of pocket gophers, genus Thomomys. Members of the “talpoides-group” of species (e.g., T. talpoides and T. monticola) have C-bands restricted to the centromeric regions. These taxa are characterized by Robertsonian patterns of karyotypic evolution. In contrast, species within the “bottae-group” are characterized by extensive amounts of heterochromatin, placed as whole-arm and apparent whole-chromosome (T. bottae) or as large interstitial blocks (T. umbrinus). These species are characterized by extensive non-Robertsonian variation in karyotype, variation which may be expressed from local population popymorphism to between population or species polytypy. Within T. bottae, the number of whole-arm heterochromatic autosomes is inversely proportional to the number of uniarmed chromosomes in the complement, which ranges from 0 to 36 across the species populations. In all-biarmed karyotypic populations, upward to 60 percent of the linear length of the genome is composed of heterochromatin. Populations with extensive heterochromatin variation and those with similar amounts meet and hybridize freely in nature. The implications of these data for current ideas on the function of heterochromatin, particularly as related to speciation models, are discussed.

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Copyright information

© Springer-Verlag 1982

Authors and Affiliations

  • James L. Patton
    • 1
  • Steven W. Sherwood
    • 1
  1. 1.Museum of Vertebrate ZoologyUniversity of CaliforniaBerkeleyUSA

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