Genetic Structure of Southern Pine Beetle Populations

Abstract

Abstract The pattern of geographic variation among southern pine beetle (SPB) populations of the enzootic infestations of 1978 was similar to that found among populations in the declining epizootic of 1977. Results for two Texas collections made in 1977 and 1978 indicated that these populations were genetically differentiated from each other. Allele frequencies estimated for the Arkansas and Mississippi populations provided evidence that they belonged to the more genetically uniform group of populations found outside of Texas. Two different types of population structures were found in the infestations studied in Arkansas and North Carolina. Infestations within Arkansas were slightly differentiated genetically but displayed little variation in allele frequencies among single-tree subpopulations within infestations. In the North Carolina populations, allele frequencies did not differ among infestations or among single-tree subpopulations within infestations; however, homozygosity in some single-tree subpopulations was greater than expected for random mating. Evidence for considerable two-locus linkage disequilibria was found in subpopulations of unexpanded infestations studied in North Carolina. Within subpopulations of the expanded infestations however, linkage disequilibria were less extensive. For. Sci. 33(1):52-69.