BIOSYSTEMATICS OF THE GENUS IPS (COLEOPTERA: SCOLYTIDAE) IN NORTH AMERICA. HOPPING'S GROUPS IV AND X

Abstract

AbstractThe taxonomic concepts of the Ips species of groups IV and X were tested by controlled breeding, bioassay of sex pheromone specificity, and examination of morphological and karyological details. No changes were made in the status of Ips pini, I. bonanseai, and I. avulsus of group IV. I. interstitialis of group X is removed from synonymy with I. calligraphus, and I. ponderosae, also previously considered a synonym of I. calligraphus, is assigned subspecific rank. Assertions of close phylogenetic relationship of the Eurasian I. duplicatus and I. sexdentatus with groups IV and X, respectively, are rejected.I. pini from widely separated localities were interfertile although egg hatchability was subnormal in some crosses involving F1 from matings of beetles from western and eastern North America. I. pini and I. bonanseai readily mated but less than 3% of the eggs hatched and the larvae died. There was no evidence of breeding incompatibility in crosses of I. c. calligraphus from Florida and California or I. c. ponderosae from New Mexico and South Dakota. However, hatchability differed drastically between reciprocal pairings of the I. calligraphus subspecies, possibly as a result of cytoplasmic incompatibility. All eggs produced in pairings of I. interstitialis with either of the I. calligraphus subspecies failed to hatch.First meiotic metaphase of I. pini, I. bonanseai, and both I. calligraphus subspecies invariably showed the formula 15AA + Xyp. This karyotypic formula also applied to I. avulsus except for a few individuals that had 2 small supernumerary chromosomes. The karyotype of I. interstitialis was not determined. Heteromorphic bivalents and univalents were detected in hybrids of the I. calligraphus subspecies.Cross attractiveness to sex pheromones was demonstrated for I. pini from different regions, for I. pini and I. bonanseai, and for the I. calligraphus subspecies. When samples of attractive frass from eastern and western I. pini males were presented simultaneously, eastern females responded equally to both samples but western females favored western frass by a margin of 2 to 1. Similarly, I. c. calligraphus clearly discriminated in favor of consubspecific pheromone while I. c. ponderosae did not.The locality of several of Eichhoff’s holotypes is noted.