Galled leaves as an improved resource for benthic detritivores

TAGLIAFERRO, MARINA; DÍAZ VILLANUEVA, VERÓNICA; WOLINSKI, LAURA; BOY, CLAUDIA CLEMENTINA

AQUATIC SCIENCES

BIRKHAUSER VERLAG AG

Año: 2021 vol. 83

1015-1621

Galled leaves are very frequent in southern beech (Nothofagus pumilio) forests. We compared the consumption of galled with ungalled leaves by two detritivores and the effect of this consumption on detritivore nutrient content. The amphipod Hyalella curvispina and larvae of the caddisfly Monocosmoecus hyadesi were exposed to two diet treatments: 1) ungalled leaves, and 2) galled leaves, for 30 days. Fungal biomass, carbon (C), nitrogen (N), and phosphorus (P) were measured in leaves and detritivores, and C:N:P molar ratios were calculated. We hypothesized that galls produce changes in litter nutrient content, affecting invertebrate consumption and nutrient content. Galled leaves had higher N and ergosterol content, and lower C:N ratios than ungalled leaves. Galled leaf consumption was higher than the ungalled for both detritivores. The two species differed in N and C (caddisfly > amphipod) and P (caddisfly < amphipod) content. The N:P ratio of the amphipod was similar to the ungalled control leaf ratio and increased when fed on galled leaves. In contrast, the N:P ratio of the caddisfly was much higher than the ungalled leaves and decreased when fed on galled leaves. Galls alter nutrient content in leaves and increase fungal biomass. Both detritivore species were highly homeostatic with regard to C:N ratio, but the caddisfly could overcome the limiting P content by increasing consumption. We highlight the impact of galls on aquatic detritivores, which in turn are relevant in forested streams for recycling organic matter and cascading effects through brown detritus-based aquatic food webs.