Influence of landscape homogenization due to river damming on dragonfly
(Odonata) community structuring in a subtropical forest in the southern
Atlantic Forest
Abstract
Human activities affect the structure, dynamics, and energy flow of
aquatic ecosystems. River damming, a common anthropic impact in Brazil,
changes solar incidence, water flow, and temperature of waterbodies,
thereby affecting their fauna. Due to their high sensitivity to
environmental changes, the Odonata may be indicators of these impacts.
We sampled two ecologically distinct sites, (1) a quasi-pristine
forested area; and (2) a nearby human-impacted reservoir landscape, to
evaluate the effects of damming on odonate community structure. The
species composition of quasi-pristine communities was more heterogeneous
and differed almost completely (indicating high turnover) from that of
the reservoir-area communities. The capacity of the reservoir to
maintain local fauna was almost nil. The communities in the changed
landscape had the highest local diversity, which is related to the high
occurrence of widespread generalist South American species. We also
tested two recently proposed bioindication ratio tools based on the
abundance of high-level taxonomic categories; both effectively
demonstrated the extent of the impacts of damming. The best performing
ratios were Coenagrionidae/other Zygoptera richness ratio,
Zygoptera/Anisoptera abundance ratio, and Libellulidae/other Anisoptera
richness ratio. The reservoir landscape promotes biotic homogenization.
However, the water supply system entails the preservation of part of the
native habitat in its surrounding areas, consequently maintaining local
biodiversity in quasi-pristine environments.