Feeding Specialization of Flies (Diptera: Richardiidae) in Aroid Infructescences (Araceae) of the Neotropics.

Evolution and radiation between insects and flowering plants are both opportunistic and obligatory when the former feeds on the reproductive structures of the latter, whereas direct and indirect effects can influence the fitness of individuals, populations, and plant communities. The Araceae family constitutes an important element of the tropical rainforest of the Neotropics, and its morphology and floral biology provide a remarkable system for studying trophic interactions with insects, including the Richardiidae flies (Diptera). We studied the trophic interactions of the aroid-fly system, assessing infestation rates under natural conditions over an annual cycle. In the Neotropical region, we discovered for the first time that seven aroid species became infested by four richardiid species: Beebeomyia tuxtlaensis Hernández-Ortiz and Aguirre with Dieffenbachia oerstedii Schott and D. wendlandii Schott; B. palposa (Cresson) with Xanthosoma robustum Schott; Beebeomyia sp.3. in association with Philodendron radiatum Schott, P. tripartitum (Jacq.) Schott, and P. sagittifolium Liebm.; while Sepsisoma sp. only infested Rhodospatha wendlandii Schott. Infestation rates differed significantly among hosts, but comparisons with morphological traits did not provide evidence of a causal factor of the infestation. In contrast, larval density and time of development both exhibited significant differences between hosts. The findings suggest the high specialization of the flies, and that intrinsic factors of the plants, such as the presence of secondary metabolites and their maturation periods, may influence their infestation rates.

Vertical and Horizontal Trophic Networks in the Aroid-Infesting Insect Community of Los Tuxtlas Biosphere Reserve, Mexico.

Insect-aroid interaction studies have focused largely on pollination systems; however, few report trophic interactions with other herbivores. This study features the endophagous insect community in reproductive aroid structures of a tropical rainforest of Mexico, and the shifting that occurs along an altitudinal gradient and among different hosts. In three sites of the Los Tuxtlas Biosphere Reserve in Mexico, we surveyed eight aroid species over a yearly cycle. The insects found were reared in the laboratory, quantified and identified. Data were analyzed through species interaction networks. We recorded 34 endophagous species from 21 families belonging to four insect orders. The community was highly specialized at both network and species levels. Along the altitudinal gradient, there was a reduction in richness and a high turnover of species, while the assemblage among hosts was also highly specific, with different dominant species. Our findings suggest that intrinsic plant factors could influence their occupation, and that the coexistence of distinct insect species in the assemblage could exert a direct or indirect influence on their ability to colonize such resources.