THERMAL ADAPTATION OF ENTOMOPATHOGENIC NEMATODES - NICHE BREADTH FOR INFECTION, ESTABLISHMENT, AND REPRODUCTION

1 We determined thermal niche breadths for infection, establishment, a nd reproduction of twelve species and strains of entomopathogenic nema todes collected from diverse climatic regions. 2. Steinernema riobravi s infected Galleria mellonella (wax moth) larvae at the widest tempera ture range (10-39 degrees C), whereas S. feltiae at the narrowest (8-3 0 degrees C). Thermal niche breadth for establishment within hosts was the widest for S. glaseri, (10-37 degrees C) and the narrowest for S. feltiae (8-30 degrees C). 3. Thermal niche breadth for reproduction w as widest for S. glaseri (12-32 degrees C) and the narrowest for S. ca rpocapsae (20-30 degrees C). Steinernema scapterisci (20-32 degrees C) , S. riobravis (20-35 degrees C), and Steinernema sp. (20-32 degrees C ) were more adapted to warm temperature reproduction, and S. feltiae t o cooler temperatures (10-25 degrees C). 4. Although heterorhabditids are endemic to warmer climates, the upper thermal limits and temperatu re optima for reproduction of Heterorhabditis bacteriophora and H. meg idis were cooler than that of some of the steinernematids from South A merica and the Caribbean. 5. Thermal niche breadths did not differ bet ween conspecific populations isolated from different localities, but w ere different for different species isolated from the same locality. 6 . We conclude that entomopathogenic nematode species have well-defined thermal niches which may be unaffected by their locality.