Ecological Indicators (Feb 2023)
Seasonal patterns of functional alpha and beta redundancies of macroinvertebrates in a disturbed (sub)tropical river
Abstract
Functional redundancy is an essential component of ecological insurance and indicates the properties of community assembly, maintenance of ecosystem functions, and stability under disturbance. It can be measured as alpha redundancy within a local community and beta redundancy between pairs of local communities. Although functional redundancy has been measured and discussed widely, its spatial and temporal patterns remain unclear. We hypothesized that high functional alpha redundancy accumulates within local communities under low environmental disturbance and limited interspecific competition, while high functional beta redundancy can occur under small environmental distances due to trait similarity between local communities. To test these hypotheses, we surveyed macroinvertebrates in a (sub)tropical medium river subjected to multiple anthropogenic stressors in two hydrologically different disturbance regimes: wet and dry seasons. Following the framework of Ricotta and co-workers, functional alpha (beta) redundancy was defined as the fraction of species diversity (dissimilarity) that was not expressed by functional diversity (dissimilarity). Functional alpha redundancy reduced significantly under high hydrological disturbance during the wet season. That is, the functional alpha redundancy accumulated in the dry season enhanced community resilience and provided insurance to maintain the stability of community functional diversity during the flooding period. Taxonomic and functional beta diversities decreased synchronously from the dry to wet seasons. There were no significant seasonal changes in functional beta redundancy. Our study provides a case for quantitatively measuring functional alpha and beta redundancies in macroinvertebrates and their seasonal changes in (sub) tropical disturbed rivers.
