Chromosomal and Genetic Divergence in the Fossorial Lizards of the Family Anniellidae

Abstract

Chromosomal divergence within the family Anniellidae is extensive. Diploid chromosome numbers in somatic tissue range from 36 in Anniella geronimensis to 22 in northern and 20 in southern A. pulchra. One to four testicular supernumerary microchromosomes occur in A. p. pulchra populations in northern Baja California. There is a lack of congruency between the chromosomal and morphological races of A. pulchra. Within the infraorder Anguimorpha, anniellids have chromosomal similarities to both the diploglossans (Anguidae) and the platynotans (Varanidae). The genetic distances between the four populations of Anniella analysed electrophoretically correspond well with their currently recognized hierarchical relationships: DN = .282-.298 between the two species, .104-.119 between the two subspecies, and .003 between populations within subspecies. In comparison to other sympatric congeneric species of amphibians and reptiles, A. pulchra and A. geronimensis are only moderately divergent genetically. The genetic distance between populations of A. pulchra which differ in somatic karyotype is greater than that between the populations which differ only in supernumerary chromosomes. Allelic heterozygosity in populations of Anniella is notably low (ca. 1%). This low level of genetic variability and high level of chromosomal divergence accompanied by relatively few structural genomic changes appear to be important evolutionary correlates to the fossorial life-style of anniellid lizards.