Dr. J. L. Boone, Ph.D., Ecology

Patterns of temporal and geographic variation in the genetics and morphology
of cotton mice (Peromyscus gossypinus)

James L. Boone
Museum of Natural History and Institute of Ecology, University of Georgia, Athens, GA

ABSTRACT

More than 4,000 cotton mice, Peromyscus gossypinus, from throughout the species' range were examined for morphological variation in 29 characters, and 1,904 mice from 62 locations distributed throughout the range were examined for allozyme variation at 40 presumptive loci.

Significant morphological differences were found between the sexes and among adult age classes for most characters. A complex pattern of clinal variation was observed, and the current subspecies were interpreted as being arrayed along the cline. Genetically, this species was highly variable: 93% of loci were polymorphic, per population heterozygosity ranged from 0.02 to 0.12 and averaged 0.09, there were an average of 5.6 alleles per polymorphic locus, and virtually every population contained unique or rare alleles. The distribution of allozyme variation generally reflected geographic proximity rather than existing subspecies boundaries.

Temporal variation was evident in specimens collected between 1889 and 1991 for morphological analysis and between 1988 and 1993 for genetic analysis. Size generally decreased but shape also changed. Significant changes in allele frequencies occurred in all populations, but no trends were detected. Within-population changes were inconsistent across populations for both data sets.

Patterns in both data sets were inconsistent with boundaries of existing subspecies. Twelve groups have achieved what might be considered a subspecific level of differentiation. The groups were primarily supported by genetic data, although there was concordance between the data sets to support the distinction of nine insular groups. Despite the high levels of differentiation, concerns raised about the dynamic temporal and spatial changes in the data, and concern for the potentially high political and social costs incurred by formally recognizing these groups as subspecies, lead us to seek concordance with another independent data set before proposing formal subspecies designations. However, no data support subspecific status of the endangered Key Largo Cotton Mouse (P. g. allapaticola), and it was synonymized with the mainland subspecies, P. g. palmarius. Older subspecies should be reexamined using modern, replicatable, techniques before their taxonomic status is assumed and before they are granted endangered species status.

Key Words: Peromyscus gossypinus allapaticola, palmarius, restrictus, telmaphilus, megacephalus, allapaticola, Morphology, Genetics, Morphological Variation, Temporal Variation, Allozyme, Systematics, Taxonomy, Endangered Species

Note: All distances, elevations, and other facts are approximate.
; Last updated 081213