Internal dispersal of seed-inhabiting insects by vertebrate frugivores: a review and prospects.

The finding that some seed-inhabiting insects can survive passage through the entire digestive tract of seed-dispersing vertebrates is relatively recent, but evidence suggests that it does occur. Here, I document this phenomenon, discuss its qualitative and quantitative dimensions, and offer suggestions for further research. The few documented cases that I review include plant species belonging to different families, with varied fleshy fruit types, number of seeds per fruit and seed size. The vertebrate frugivores involved include passerines that feed on relatively small fruits, and galliforms, and perissodactyls and primates that feed on larger fruits. The seed-inhabiting insects involved are the larvae of seed-infesting wasps, parasitoid wasps and seed-infesting beetles. The phenomenon has been verified in open, rural ecosystems in North America and Southern Europe, and in tropical and subtropical forests in South America. These varied scenarios suggest that the qualitative dimension of the phenomenon is considerably greater than known thus far. A simple method for detecting new events is proposed. However, research must also focus on the identity and biology of seed-feeding insects of wild fleshy fruits and their parasitoids. High survival rates of seed-inhabiting insects after vertebrate gut passage are predominant. This phenomenon generally appears to favor insect dispersal.