Disease, contagious cannibalism, and associated population crash in an omnivorous bug, Geocoris pallens

Authors: ROSENHEIM, JAY - University Of California; BOOSTER, NICHOLAS - University Of California; CULSHAW-MAUER, MICHAEL - University Of California; MUELLER, TOBIAS - University Of California; KUFFEL, RANDALL - University Of California; LAW, Y-H - University Of California; GOODELL, PETER - University Of California; PIERCE, T - University Of California; Hunter, Wayne; SADEH, A - Volcani Center (ARO)

Submitted to: Oecologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/24/2019
Publication Date: 5/2/2019
Citation: Rosenheim, J.A., Booster, N.A., Culshaw-Maurer, M., Mueller, T.G., Kuffel, R.L., Law, Y-H., Goodell, P.B., Pierce, T., Godrey, L., Hunter, W.B., Sadeh, A. 2019. Disease, contagious cannibalism, and associated population crash in an omnivorous bug, Geocoris pallens. Oecologia. https://doi.org/10.1007/s00442-019-04407-y.
DOI: https://doi.org/10.1007/s00442-019-04407-y

Interpretive Summary: The big-eyed bug, Geocoris pallens, is a beneficial predatory insect of pest species. Field monitoring in California populations, detected severe population reduction. Studies identify highly cannibalistic behavior in some females that ate their own eggs and eggs of others. Highly cannibalistic females exhibited reduced egg laying, correlated with presence of several viral pathogens. Elevated cannibalism was not correlated with reduced prey availability or elevated field densities of G. pallens. Geocoris pallens population crashes appear to reflect the combined consequences of direct viral infections on insect survival and --indirect virulence—mortality of both infected and uninfected individuals due to elevated cannibalism by infected individuals. Understanding the causes of population decline may aid efforts to increase the beneficial impacts to be gained from Geocoris pallens as a generalist predator.

Technical Abstract: The big-eyed bug, Geocoris pallens, is a beneficial predatory insect of pest species. Field monitoring in California populations, detected highly cannibalistic females exhibited reduced egg laying, which was correlated with viral pathogens. A few cannibalistic females exhibited elevated egg laying, suggesting that cannibalism might also facilitate recycling of nutrients in eggs. Elevated cannibalism was not correlated with reduced prey availability or elevated field densities of G. pallens. Geocoris pallens population crashes appear to reflect the combined consequences of direct pathogen virulence—adverse pathogen effects on the infected host’s physiology—and indirect virulence—mortality of both infected and uninfected individuals due to elevated cannibalism in infected cohorts. Understanding the causes of population decline may aid efforts to increase the beneficial impact gained from Geocoris as a generalist predator.