Evolutionary aspects of ecological generalism with special reference to conservation biological control

1. If ecological generalism is an evolving heritable trait, we need to study the underlying genetics in order to understand the nature of this fundamental phenomenon. 2. I consider two alternatives. Under the Type I mechanism, ecological generalism is exclusively a population property. Under the Type II mechanism, generalism can vary among genotypes as well as among populations. 3. The genetics underlying the Type I mechanism is straightforward, whereas Type II genetics is less so. I propose that a broad adaptive range of generalist genotypes can be a result of a pleiotropic modifier that, when expressed, renders fitness of the carrier relatively insensitive to environmental variance. 4. A review of the theory and the data indicates that stable ecological generalism is more likely to occur under the Type II compared to the Type I mechanism. Type II generalism appears to be relatively more common and more compatible with patterns observed in the wild. 5. Generalism of natural enemies is a key factor influencing the effectiveness of conservation biological control (CBC). I argue that natural enemies with Type II generalism are relatively more suitable for CBC applications, and spell out directions for further research.