EFFECTS OF INBREEDING IN 3 LIFE STAGES OF DROSOPHILA-BUZZATII AFTER EMBRYOS WERE EXPOSED TO A HIGH-TEMPERATURE STRESS

The interaction between inbreeding and high-temperature stress was exa mined in the cactsphilic fruit fly, Drosophila buzzatii. Embryos of fo ur inbreeding levels (F=0, F=0.25, F=0.375, F=0.5) were either maintai ned at 25 degrees C throughout egg-to-adult development or were expose d to 41.5 degrees C for 110 min at an age of 20 h. Hatching, larva-to- pupa survival, pupato-adult survival, and egg-to-adult survival were e stimated. Heat shock reduced hatching rates, but survival to adulthood for individuals that hatched was unaffected by the heat shock. Inbree ding reduced the proportion of eggs hatching in the 25 degrees C contr ol group only. For larva-to-pupa and pupa-to-adult survival there was no interaction between inbreeding and stress. The effect of inbreeding on egg-to-adult survival was stronger in the 25 degrees C control gro up compared with the group exposed to heat shock. The results imply en vironmental dependency of inbreeding depression and suggest that stres s tolerance may not always be reduced by inbreeding. The thermal micro environment of cactus rots in the field was assessed by measuring temp eratures inside 17 rots. Internal rot temperatures varied with a maxim um temperature of 48 degrees C during the day. Selection for temperatu re tolerance in nature may have depleted genetic variation for this tr ait limiting the effect of inbreeding on thermal resistance.