Internal mesquite-seed predators: Nine species exploiting one resource

Background/Question/Methods

Females of some insects deposit their eggs inside immature mesquite-seed pods. There they attack and destroy the maturing seeds. I surveyed the internal mesquite-seed predators of eleven species of mesquite (Prosopis spp.) in the United States and Mexico. What might allow these predators to be found together? In particular, how might they avoid violating the competitive exclusion principle? I assessed how much overlap in space these seed predator species have. Looking for temporal patterns, I also sampled across seasons and years. Finally I determined whether they prey upon different mesquite species.

Results/Conclusions

I found nine species of internal mesquite-seed predators on the eleven species of mesquite. Patterns of seed predators on mesquites reveal many ecological differences among these species. First, species exploit resources at different stages in seed-pod development. Early seed feeders may even help later ones by putting holes in the hardened pod as suggested by the correlation between oviposition guild and the timing of oviposition. Second, species presence may depend on resource availability with certain species disappearing locally when resources are scarce and then recolonizing when they are abundant again. The dispersal ability of these insects most likely plays an important role in determining spatial patterns of presence on a particular tree. Finally, though most of these species are only found on the genus Prosopis, there are very little specificity within the genus.