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8 th International Symposium on Fruit Flies of Economic Importance. Valencia 2010.
INTRA AND INTERSPECIFIC LARVAL COMPETITION BETWEEN CERATITIS
CAPITATA AND ANASTREPHA FRATERCULUS.
Liendo, M. Clara *1,3 ; Devescovi, Francisco 1,3 ; Parreño, María A. 1 ; Milla, Fabián H. 1 ;
Carabajal Paladino, Leonela 1,3 ; Vera, M. Teresa 2,3 ; Segura, Diego F. 1,3 & Cladera, Jorge
L. 1
1 Instituto Nacional de Tecnología Agropecuaria (INTA), Instituto de Genética Ewald Favret (IGEAF); De Los
Reseros y N. Repetto, (1712), Castelar, Buenos Aires, Argentina. Email: mliendo@cnia.inta.gov.ar; 2 Estación
Experimental Agroindustrial Obispo Colombres (EEAOC), Tucumán, Argentina; 3 CONICET.
Background: Ceratitis capitata and Anastrepha fraterculus are two major fruit pests in
Argentina where they are commonly found sharing its host fruit with conspecific and
heterospecific larvae. As larvae are incapable of leaving the 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). The impact of competition
will depend both on the density of larvae within a particular fruit and the relative abundance of
each species. Here we studied both the effects of competing with conspecific and
heterospecific larvae for A. fraterculus and C. capitata.
Methods: Intraspecific competition was analyzed by transferring newly hatched larvae into a
fixed amount of larval diet at increasing densities. Interspecific competition was analyzed by
keeping total density constant and transferring different proportions of larvae of the two
species. We measured percentage of recovered pupae and adults, pupae weight, and larva-pupa
and larva-adult developmental times.
Results: Under intraspecific competition, C. capitata showed a density-dependent reduction in
pupae weight and percentage of recovered pupae. A. fraterculus showed also a density
dependent effect on pupae weight, and a decrease in larva-pupa developmental time.
Comparing the two species, in C. capitata the reduction in pupae weight was more
homogeneous among individuals, whereas in A. fraterculus a majority of pupae showed a
marked decrease in weight and only few pupae showed slight negative effects. Under
interspecific competition, we found that when the relative density of A. fraterculus larvae
increased, the percentage of recovered pupae and the pupae weight increased for C. capitata.
Likewise, A. fraterculus pupae weight increased when the relative density of C. capitata
increased.
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 homogeneous impact on their weight. Conversely, A. fraterculus
larvae showed a 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. Finally, we found that C. capitata and A. fraterculus larvae suffer more from
sharing the resource with conspecific larvae than heterospecific larvae.
Keywords: Ceratitis capitata, Anastrepha fraterculus, interspecific competition, intraspecific competition, larval
competition.