Host discrimination ability can be overlooked in choice tests due to intrapopulation variability in the fruit fly parasitoid Diachasmimorpha longicaudata

F DEVESCOVI; MARIANA M. VISCARRET; CLADERA, J; DIEGO F. SEGURA

Conferencia; 3rd International Conference of Entomophagous Insects; 2013

Host discrimination ability in insect parasitoids has been commonly addressed by fitting the observed egg distribution to a random (Poisson) distribution. A different approach based on the observation of female behavior can also provide direct evidence. The aim of this study was to evaluate host discrimination ability in D. longicaudata using C. capitata larvae through direct and indirect approaches. Direct methods involved offering four parasitized and four unparasitized larvae arranged in an alternated fashion in a 24-well plate to a single young experienced female for 30 min. We recorded the first visited larva and the status of the first and second parasitized larvae. D. longicaudata visited parasitized larvae first and the rate of rejection did not differ between types of larvae. For the indirect approach, we exposed 24 healthy larvae to a single female for 4h using the same arena. Larvae were dissected and the number of eggs/host was recorded, obtaining the frequency distribution to be compared to a Poisson distribution. For distributions that only comprised zero and one egg/host, we used the Poisson probability function to obtain the expected frequencies for a goodness of fit Chi2 test. Nine of 29 egg distributions were not random, suggesting host discrimination ability. Even when direct observations did not reveal host discrimination ability, indirect methods suggest that this parasitoid still might have it, though a high variability among females masks this behaviour when data are analyzed together. Nevertheless, direct methods could serve in a future step to improve egg distribution models.