Authors: Thayse Nery Dénes Schmera
Publish Date: 2015/06/17
Volume: 763, Issue: 1, Pages: 173-181
Abstract
Headwater stream macroinvertebrates play an important role in processing allochthonous leaf litter which suggests that bottomup forces control macroinvertebrates However because larvae of streambreeding salamanders are predators of macroinvertebrates and are abundant consumers in these ecosystems macroinvertebrates in fishless headwater streams might also be controlled by topdown forces through predation by salamander larvae The aim of this study was to test if and to what degree taxa richness abundance and biomass of macroinvertebrates are affected by bottomup and topdown forces We selected headwater streams with high abundances of fire salamander larvae 12–26 individuals per 1 m of shore length and manipulated bottomup and topdown forces on macroinvertebrates by leaf litter addition and by the exclusion of salamander larvae The amphipod Gammarus fossarum Koch 1836 was the dominant taxon and responded positively to litter addition Linear models showed that neither predator exclusion nor leaf litter addition affected richness However variation in biomass and density were both explained by the individual and joint effects of bottomup and topdown forces These findings suggest that macroinvertebrates in these streams are strongly dependent on the organic matter input and salamander larvae and headwater streams interact strongly with their adjacent terrestrial areasWe thank Dr Benedikt Schmidt University of Zurich for providing information about the distribution salamander larvae Peter Tanner Abteilung Natur und Landschaft Kanton Baselland Schweiz for permitting the collection of macroinvertebrates in the studied streams and Prof Dr Lee Kats and four anonymous reviewers for their comments on the manuscript We thank Dr Krystyna Haq and Dr Jo Edmondston for checking the English in the manuscript
Keywords: