Evidence for predatory flatworms as organizers of zooplankton and mosquito community structure in rice fields

摘要

I present evidence from two field studies and one laboratory experiment that the predatory flatworm, tentatively indentified asMesostomanr.lingua, can be important in organizing invertebrate communities in rice fields. In the first field study, I assessed the importance of various predators including two fishes, in explaining among-plot variation in mosquito abundance during a five week interval. Mosquitofish (Gambusia affinis) abundance was not significantly associated with densities of either mosquito,Culex tarsalisorAnopheles freeborni, except for the final week. Associations between green sunfish (Lepomis cyanellus) juveniles and mosquitoes were demonstrated for onlyA. freeborni— a positive association. Densities ofMesostomawere negatively associated withC. tarsalisandA. freebornidensities.C. tarsalis, protected from flatworms in small-mesh cages, had a much greater survival rate than those that were exposed in large-mesh cages.C. tarsalissurvival, when left unprotected in large-mesh cages, was negatively correlated with field densities of flatworms and with the number of flatworms found inside the cages. Survival was also positively correlated with field densities of mosquitoe