INTRASPECIFIC LARVAL COMPETITION IN ANASTREPHA FRATERCULUS AND CERATITIS CAPITATA (WIEDEMANN): EVIDENCES OF TWO DISTINCTIVE STRATEGIES.

LIENDO, MARÍA CLARA; DEVESCOVI, FRANCISCO; MILLA, FABIÁN H; CARABAJAL PALADINO, LEONELA; VERA, MARÍA T; SEGURA, DIEGO F; CLADERA, JORGE L

Valencia

Simposio; 8th International Symposium on Fruit Flies of Economic Importance.; 2010

Background: Anastrepha fraterculus and Ceratitis capitata are fruit fly pests that are frequently found in Argentina sharing its host fruit with conspecific larvae. As larvae are incapable of leaving the fruit in search of an uninfested (or less infested) fruit, they are forced to share nutritional resources, and eventually compete for them with other larvae. Larval competition can occur by direct interference (contest) or exploitation (scramble). Here we studied the effect of intraspecific larval competition in A. fraterculus and C. capitata, and compared the strategies between these species. Methods: Newly hatched larvae were transferred into a container with a fixed amount of larval diet at increasing densities. Several biological parameters that estimate the reproductive success of individuals were measured, including percentage of recovered pupae, pupae weight, larva-pupa developmental time, percentage of emergence and pupa-adult developmental time. Results: C. capitata, only pupae weight showed a density-dependent behavior (decreasing as the number of competitors in the container increased). In A. fraterculus density effect was evident in pupae weight and larva-pupa development time. The negative effect of sharing resources was observed at a higher density for C. capitata than for A. fraterculus. It was also noted that the strategies of the two species were different. In C. capitata the reduction in pupae weight was consistent among individuals, whereas in A. fraterculus was more heterogeneous, with a majority of pupae showing a marked decrease in weight and only few pupae showing slight negative effects or no effect at all. Conclusions: Our results suggest that C. capitata larvae facing a shortage of resources develop a strategy of resource distribution similar to that described as scramble competition, because the individuals showed a very homogeneous impact on their weight. Conversely, A. fraterculus larvae showed a different response, similar to that described as contest competition, because as the number of individuals in the container increases, the negative effect is not the same for every individual.