Genetic and alarm call diversity across scattered populations of speckled ground squirrels (Spermophilus suslicus)

Abstract

Alarm calls of ground squirrels are innate signals, showing substantial geographical variation across populations without the masking effects of sex and age- related variation. This makes them a convenient model for studying population genetic effects on the evolution of alarm communication. We compared data on the alarm call structure and the mitochondrial DNA (mtDNA) complete control region (C-region) (998–1002bp) polymorphism in the same 90 individual speckled ground squirrels (Spermophilus suslicus) across 6 populations (15 individuals per population), separated by distances from 12 to 1274km. We calculated acoustic distances between each pair of populations based on acoustic variables of alarm calls, averaged for each individual using Euclidean distances of population centroids, in the space of canonical axes of discriminant function analysis. Genetic distances ranged of 0–1.1% within populations and of 0.5–4.9% between populations. Prominent differences were found between eastern and western populations separated by the Dnieper River. Both genetic and acoustic distances showed a significant positive correlation with geographical among populations. Positive correlation between acoustic and genetic distances did not reach significance. These results support effects of ecological selection on the alarm call variables rather than the genetic drift hypothesis. In addition, these results support the current taxonomic separation between subspecies of speckled ground squirrels differing in diploid chromosome sets 2n=34 (Spermophilus suslicus guttatus) and 2n=36 (Spermophilus suslicus odessanus).