Virus infection affects interspecific competition among the red imported fire ant, Solenopsis invicta Hymenoptera: Formicidae) and native ants in Taiwan
Date Issued
2009
Date
2009
Author(s)
Chen, Ying-Cheng
Abstract
The fire ant (Solenopsis invicta) eradication program has been carried out in Taiwan since 2004. It certainly effectively restrains the populations of fire ant on treatment areas. Unfortunately, the reinfection or new infection site by natural nuptial flight of monogyne colony are still promulgated. Current new approaches to manage fire ants are integrating biological control agents with baits applications. This study aims to investigate alternative suitable biological control agents in Taiwan, and examines how SINV-1 (Solenopsis invicta virus-1) infection affects interspecific competition between incipient S. invicta against two native ants, Pheidole fervens and Monomorium chinense, by conducting two levels of trial, colony interference and individual confrontation, in laboratory conditions. The results from colony interference study showed that both native ants owing numerical advantages were capable to kill either infected or healthy queens of S. invicta. There was a significant less time for M. chinense to eliminate SINV-1 infected S. invicta compared to healthy ones. All S. invicta could repulse the invading of equal worker numbers of P. fervens. Compared with healthy S. invicta, SINV-1 infected S. invicta spent longer time to terminate P. fervens colonies. Virus infection was observed to have significant effects on foraging behavior and invading willingness of S. invicta. SINV-1 infected S. invicta recruited lesser number of foragers than healthy one, and in particular on competitive native ants were present. In confrontation trial M. chinense caused significant greater mortality on infected S. invicta minors than did on healthy ones. However, S. invicta majors (either infected or healthy) performed high competitive abilities against M. chinense, which might account for chemical defense and/or size advantages. In dealing with P. fervens, one cannot but admit that soldiers indeed function in defense, which caused S. invicta high mortality. These data suggest that virus may somehow weaken the competitive ability of infected S. invicta and make them prone to be terminated by M. chinense but not by P. fervens. Chemical interference by M. chinense might be a more likely influencing factor on mortality of infected S. invicta than the physical combat by P. fervens. Results from this study highlight the likely success on area-wide control of S. invicta in Taiwan by an alternative strategy that involves integration of competitors and pathogen.
Subjects
Solenopsis invicta
Solenopsis invicta virus
interspecific competition
Monomorium chinense
Pheidole fervens
Type
thesis
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