CUTICULAR HYDROCARBONS AS CHEMOTAXONOMIC CHARACTERS OF PINE ENGRAVER BEETLES (IPS SPP) IN THE GRANDICOLLIS SUBGENERIC GROUP

Cuticular hydrocarbons were extracted, identified, and evaluated as ch emotaxonomic characters from all species of adult Ips pine engraver be etles in the grandicollis subgeneric group. The grandicollis group con sists of Ips grandicollis (Eichhoff), I. cribricollis (Eichhoff), I. l econtei Swaine, I. montanus (Eichhoff), I. paraconfusus Lanier, I. con fusus (LeConte), and I. hoppingi Lanier. In order to provide outgroups for a phylogenetic analysis, cuticular hydrocarbons were also analyze d from Orthotomicus caelatus (Eichhoff), I. latidens (LeConte) (latide ns subgeneric group), and I. pini (Say) (pini subgeneric group). Two h undred forty-eight hydrocarbon components were identified by gas chrom atography-mass spectrometry. The members of the grandicollis group pro vided 206 of these compounds. The components represented eight classes : n-alkanes, alkenes, alkadienes, terminally branched methylalkanes, i nternally branched methylalkanes, dimethylalkanes, trimethylalkanes, a nd tetramethylalkanes. Different populations of O. caelatus, I. grandi collis, I. lecontei, I. montanus, I. paraconfusus, I. confusus, and I. hoppingi provided no evidence for interpopulational variation in cuti cular hydrocarbons. Single populations only were analyzed for I. latid ens, I. pini, and I. cribricollis. Sexual dimorphism in cuticular hydr ocarbons occurred only in I. lecontei where females produced eight uni que components with a pentatriacontane parent chain. Several phylogene tic analyses based on hydrocarbon phenotypes agreed in general with th e established morphologically based system of relatedness and with pub lished phylogenies reconstructed from prorein and nucleic acid charact ers. Nearly all hydrocarbon analyses suggested a close relationship be tween I. grandicollis and I. cribricollis; between I. lecontei and I. montanus; and among the sibling species I. paraconfusus, I. confusus, and I. hoppingi. The presence or absence of specific n-alkanes (n-doco sane, n-triacontane); certain dimethylalkanes (terminally branched wit h octacosane and triacontane parent chains and internally branched wit h heptacosane, hentriacontane, and docotriacontane parent chains); and 3,7,11-; 3,7,15-trimethylheptacosane permit facile discrimination of I. paraconfusus, I. confusus, and I. hoppingi. These three sibling spe cies are difficult to resolve by external morphology. These data suppo rt the species status of I. hoppingi rather than it being considered a host race of the I. confusus complex. They also support the species s tatus of I. cribricollis rather than it being considered part of I. gr andicollis. In contrast to other published phylogenies reconstructed f rom molecular data, phylogenies reconstructed from cuticular hydrocarb ons repeatedly place I. lecontei as an integral part of the grandicoll is subgeneric group. Thus, cuticular hydrocarbon and pheromone alcohol composition of I. lecontei support its inclusion in the grandicollis subgeneric group.