Temporal variation in positive and negative interactions between marsh herbivores mediated by changes in plant traits

CANEPUCCIA, AD; ALVAREZ, MF; ESPINOSA VIDAL, E; ALEMANY, D; IRIBARNE, OO

MARINE ECOLOGY PROGRESS SERIES

INTER-RESEARCH

Año: 2020 vol. 634 p. 89 - 97

0171-8630

Studies on bidirectional benefactor−beneficiary interactions between organismshave generally neglected the importance of this feedback in trophic levels other than plants. The burrowing crab Neohelice granulata aids the development of larvae of the stem-boring moth Haim bachia sp. nov. within the stems of Spartina alterniflora. In our research, we evaluated whether the stem-boring moth subsequently influences crab feeding on these marsh plants. Surveys and experiments in a tidal marsh of the SW Atlantic coast (36° 22? S) showed that at the beginning of the stem-boring moth attack there was no difference in crab herbivory between plants with or without larvae of the stem-boring moth. However, after 3.5 mo, crabs foraged more on plants without larvae than on those with larvae. Plant tissue analyses showed a decrease in leaf tissue carbon concentrations in plants with larvae. This change in the nutritional quality of leaves, caused by construction of the stem-boring moth galleries, could explain the segregation in plant use between both herbivores. Unlike an allelochemical response, the non-specificity of the induced nutritional change could impair a wide variety of herbivores regardless of their feeding modes or taxonomic proximity. These effects could propagate bottom-up through the food-web,leading to more diffuse interspecific effects. Thus, here we show how the benefactor−beneficiary feedback between herbivores can be important for the maintenance of species coexistence and the functioning of communities.