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Inbreeding depression is environmentally dependent such that a population may suffer from inbreeding depression in one environment but not another. We examined the phenotypic responses of 35 inbred (F = 0.672) lineages of the red flour beetle Tribolium castaneum in two different climatic environments. We found a significant environmental effect on males but not female~ More importang we found that the rank fitness order of lineages differs between environments; lineages of high fitness in one environment may have iow fitness in another environment This change in rank is evident in a significant genotype-byenvironment interaction for inbreeding depression for both females and malex These results suggest that even if we know the average environmental effect of inbreeding depression in a populatior6 for any particular lineage measurements of inbreeding depression in one environment may not predict the level of inbreeding depression in another envi-ronmenL Conservation biologists need to be aware of the environmental dependency of inbreeding depression when planning wildlife refuges or captive propagation programs for small populations. Ideally, captive propagation programs should maintain separate lineages for release effortg Refuge design programs should consider maintaining a range of habitat type£

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Despite the increasing number of studies on the magnitude of NJN ratios, much remains unknown about the effects of demographic and environmental variables on NJN. We determined NJN for seven population size treatments, ranging from N = 2 to N = 960, in the red flour beetle Tribolium castaneum. NJN decreased with increasing N, as evidenced by a significant negative relationship between log N and NJN. Our results are consistent with other published data on the relationship between NJN and N. Effective population sizes in large populations may be much smaller than previously recognized. These results have important implications for conservation and evolutionary biology.

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To determine whether field‐selected resistance of diamondback moth (Plutella xylostella L.) (Lepidoptera: Plutellidae) to Bacillus thuringiensis is based on behavioral or physiological adaptation, we measured mortality, consumption, and movement of larvae from a susceptible and a resistant colony when placed on untreated and B. thuringiensis treated cabbage. Colonies did not differ in mortality, consumption, or movement on untreated cabbage. However, for a given amount of consumption of treated cabbage, resistant larvae had lower mortality than susceptible larvae, demonstrating that resistance had a physiological basis. The movement patterns could not account for the differences between colonies in survival. Resistant larvae did not avoid B. thuringiensis more than did susceptible larvae. Thus, we found no evidence for behavioral resistance.