PHEROMONAL SPECIFICITY OF SOUTHEASTERN IPS PINE BARK BEETLES REFLECTS PHYLOGENETIC DIVERGENCE (COLEOPTERA: SCOLYTIDAE)

The attractiveness of the aggregation pheromones produced by males of four species of Ips pine bark beetles was assessed to determine whether competition for a private communication channel among sympatric species or phylogenetic divergence better explains the current pheromonal specificity among the species. In the southeastern United States, Ips calligraphus (Germar), I. grandicollis (Eichhoff), and I. avulsus (LeConte) are broadly sympatric and they represent three different species groups. A member of the I. grandicollis species group, I. confusus (LeConte), is allopatric to the other three and native to the southwestern United States. Only the pair of species from the same species group were pheromonally cross-attractive. Broadly allopatric species from dissimilar species groups were not cross-attractive. Thus, their pheromonal specificity paralleled their taxonomic relationship regardless of geographic overlap and competitive interaction.