Quantitative parameters and ecological implications of a specialized tritrophic interaction involving a seed-feeding tortricid, Pseudargyrotoza conwagana, a braconid parasitoid, Bracon otiosus, and the wild privet, Ligustrum vulgare

Hernández, A., Falcó, J. (2014) - Quantitative parameters and ecological implications of a specialized tritrophic interaction involving a seed-feeding tortricid, Pseudargyrotoza conwagana, a braconid parasitoid, Bracon otiosus, and the wild privet, Ligustrum vulgare - Journal of Insect Science

Little is known about tritrophic interactions involving seed-feeding insects, parasitoid wasps, and wild fleshy fruits. Here, we examine relationships between Pseudargyrotoza conwagana (F.) (Lepidoptera: Tortricidae), Bracon otiosus Marshall (Hymenoptera: Braconidae), and the wild privet, Ligustrum vulgare L. (Lamiales: Oleaceae), after
collecting fruits in a hedgerow habitat in northwest Spain and rearing insects indoors. No other insect species was
detected in this trophic system. Each fruit contained one to four seeds, each infested fruit contained only one seedfeeding
tortricid caterpillar, and each parasitized caterpillar was affected by a single braconid individual, i.e., B. otiosus
was a solitary parasitoid. Almost half of the wild privet shrubs were infested by P. conwagana, and infestation
ranged from 2 to 32% of fruits per infested shrub. The general effect of P.conwagana on wild privet dispersal can be
considered low, as the overall rate of seed infestation was low (6% of seeds). The infestation rate was higher in wild
privet shrubs with a larger number of seeds per fruit, and tortricid caterpillars that left the fruits successfully ate
>80% of seeds. In total, the parasitism rate was moderate (25% of caterpillars), but varied considerably (0‒75%)
among shrubs where P. conwagana infestation was detected. Parasitism only occurred in shrubs showing high infestation
rates (19‒32% infested fruits), i.e., with high host densities; however, the parasitism rate was densityindependent
in these shrubs. The wild privets benefited from the action of B. otiosus in two ways: the tortricid caterpillar
population was partly eliminated, and the caterpillars were prevented from eating more than one seed per fruit.
The B. otiosus sex ratio was very balanced (1 male to 1.18 females). Winter diapause and protandry were prevalent
in B. otiosus.

Más información

SCI: 

SI

Tipo de Publicación: 

Artículos

ISSN: 

1536-2442

Volumen: 

14

Página Inicial: 

128

Página Final: 

128