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

1 We determined thermal niche breadths for infection, establishment, and reproduction of twelve species and strains of entomopathogenic nematodes collected from diverse climatic regions. 2. Steinernema riobravis infected Galleria mellonella (wax moth) larvae at the widest temperature range (10-39 degrees C), whereas S. feltiae at the narrowest (8-30 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 was widest for S. glaseri (12-32 degrees C) and the narrowest for S. carpocapsae (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 to cooler temperatures (10-25 degrees C). 4. Although heterorhabditids are endemic to warmer climates, the upper thermal limits and temperature optima for reproduction of Heterorhabditis bacteriophora and H. megidis were cooler than that of some of the steinernematids from South America and the Caribbean. 5. Thermal niche breadths did not differ between conspecific populations isolated from different localities, but were 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.