Rate Of Karyotype Evolution Research Articles

Chromosome painting shows that skunks (Mephitidae, Carnivora) have highly rearranged karyotypes

The karyotypic relationships of skunks (Mephitidae) with other major clades of carnivores are not yet established. Here, multi-directional chromosome painting was used to reveal the karyological relationships among skunks and between Mephitidae (skunks) and Procyonidae (raccoons). Representative species from three genera of Mephitidae (Mephitis mephitis, 2n = 50; Mephitis macroura, 2n = 50; Conepatus leuconotus, 2n = 46; Spilogale gracilis, 2n = 60) and one species of Procyonidae (Procyon lotor, 2n = 38) were studied. Chromosomal homology was mapped by hybridization of five sets of whole-chromosome paints derived from stone marten (Martes foina, 2n = 38), cat, skunks (M. mephitis; M. macroura) and human. The karyotype of the raccoon is highly conserved and identical to the hypothetical ancestral musteloid karyotype, suggesting that procyonids have a particular importance for establishing the karyological evolution within the caniforms. Ten fission events and five fusion events are necessary to generate the ancestral skunk karyotype from the ancestral carnivore karyotype. Our results show that Mephitidae joins Canidae and Ursidae as the third family of carnivores that are characterized by a high rate of karyotype evolution. Shared derived chromosomal fusion of stone marten chromosomes 6 and 14 phylogenetically links the American hog-nosed skunk and eastern spotted skunk.

Evolutionary Rates in Partially Self-Fertilizing Species

This article develops models of the rates of fixation of mutant genes in partially self-fertilizing populations, with particular emphasis on the effect of the level of dominance of a favorable mutation on its probability of fixation. It is shown that even a moderate rate of selfing greatly increases the probability of fixation of a favorable recessive mutation in a large population, If favorable recessive mutations are commoner than dominant ones, recessive alleles should frequently be fixed by selection in partially selfing populations, in contrast to what is found for autosomal loci in large random-mating populations. This expectation was tested by comparing the frequency of dominant versus recessive derived traits in cases of recent evolution in selfing populations and was found to be supported. The effect of the rate of serf-fertilization on the rate of fixation of deleterious mutations was found to be minor. The rate of fixation of chromosomal rearrangements with large heterozygous fertility losses is nonlinearly related to the rate of selfing unless population size is very small. This may explain comparative data on the relation between breeding system and rate of karyotypic evolution in plants.