Long-term changes in mole cricket body size associated with enemy-free space and a novel range

Abstract

Exotic species can cause ecosystem and landscape-level changes in their novel ranges, but factors associated with novel ranges can also change the invaders. By tracking trait changes over space and time, we can learn about the future ecological and economic implications of invasive species’ dispersal. Here, we investigated body size changes of two invasive mole cricket species, Neoscapteriscus borellii and N. vicinus, introduced to the U.S. from South America (≈ 1904) without natural enemies, and later exposed to them (≈ 1980) through classical biological control. We compared body sizes of N. vicinus and N. borellii in the novel range from before biological control and 30 years after, as well as N. borellii in its native range at the same time period. Contrary to expectations, our data suggest that N. borellii and N. vicinus body sizes have increased since re-establishment of interactions with their natural enemies. Our results also suggest that N. borellii body size decreased in enemy-free space after U.S. invasion and prior to biological control. Selection or reduced intraspecific competition, both likely associated with biological control, may explain the changes in body size over time. Although these results warrant further research, they provide valuable insights into the long-term effects of invasion and classical biological control.