Long-term changes in mole cricket body size associated with enemy-free space and a novel range
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.
KeywordsEnemy release hypothesis Density-dependence Entomopathogenic nematodes Invasive species Parasitism
We sincerely thank the Florida farm managers for their cooperation during this study. Christine W. Miller and Anne Donnelly provided critical assistance in the initiation of this project and the mechanisms by which the data were collected. We thank J. Howard Frank and Thomas J. Walker, who both provided valuable insight and input, which were highly valuable for the design and methodology used in this study. We also thank Tim Forrest, who provided his raw data collected in the 1980s from a previous publication, which played a key role in this study. Nicole Benda, Rebecca Perry, and Alex LoCastro each provided essential help with field work and data collection. We thank Barukh Rohde, Avraham Brun-Kestler, and Custom Engineered Solutions for acoustic trap development and maintenance. Funding for this work was provided by United States Department of Agriculture-National Institute of Food and Agriculture Grant 2016-38,503-25899 to AGD, and the University of Florida Agricultural Experiment Station.
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