BIOSYSTEMATICS OF PISSODES GERMAR (COLEOPTERA: CURCULIONIDAE): FEEDING PREFERENCE AND BREEDING SITE SPECIFICITY OF P. STROBI AND P. APPROXIMATUS

Abstract

AbstractPissodes strobi (Peck) and P. approximatus Hopkins are sibling species that can produce fertile hybrids in the laboratory, but in nature they are isolated by differences in their breeding habits. In a laboratory assay for feeding preference, these species exhibited similar patterns of acceptance of most conifer hosts in the fall, but differed distinctly in their preferences for certain conifers in the spring. Both species had high levels of feeding on white spruce in the fall and spring tests, hut these data apparently do not reflect host preference in nature. In field tests, P. strobi males and females confined on 1-year-old terminal leaders of eastern white pine (their usual breeding sites) produced abundant progeny, whereas P. approximatus pairs confined on leaders produced few progeny. Mixed species pairs were successful in killing and breeding in white pine leaders when the females were P. strobi, but not when the females were P. approximatus. Laboratory-reared hybrids were unsuccessful when forced to breed in leaders. When confined on red pine bolts (the usual breeding sites of P. approximatus), P. strobi and hybrids produced substantially fewer progeny than did P. approximatus. Breeding site separation provides compelling evidence of reproductive isolation between these sympatric species.