Symbiosis and competition: Complex interactions among beetles, fungi and mites

Symbioses among bark beetles and their fungal and mite associates involve c omplex, multi-level interactions. Dendroctonus frontalis attacks and kills southern pines, introducing fungi into the tree. Ophiostoma minus, may init ially aid beetles in killing trees, but later this "bluestain" fungus becom es an antagonist, competing with larvae for host phloem. Two additional fun gi, Entomocorticium sp. A and Ceratocystiopsis ranaculosus are carried with in a specialized mycangium and inoculated into phloem where they are fed up on by beetle larvae. The beetle also vectors several species of phoretic mi tes which transport spores of O. minus and C. ranaculosus and can complete their life cycle upon these two fungi. A similar interaction occurs between Ips avulsus and its fungal (Entomocorticium spp.) and mite (Elattoma benne tti) symbionts. Larval beetles feed on fungus as do the mites. Female mites feed on fungus growing within beetle galleries, swelling to many times the ir normal size. Larval mites develop and mate within the females who burst open, giving birth to reproductively mature females. These relationships ma y be best understood by considering the manner in which symbioses vary with time and resources, and the degree to which other species may affect inter actions among symbionts.