Trait-based responses of caddisfly assemblages to the partial channelization of a High-Andean stream

Abstract

The importance of channel complexity in maintaining biological integrity and ecosystem functioning has been addressed by several researchers. In spite of this, High-Andean streams are being channelized without regard to the effect that channelization might have on stream communities. To attempt to determine these effects, the present study evaluated how caddisfly assemblages respond to channelization in a High-Andean stream. A trait-based approach was used to compare trait-based responses, and the degree of functional homogenization caused by channelization. A total of seven traits are described: (i) ‘Food,’ (ii) ‘Feeding habits,’ (iii) ‘Maximum body size,’ (iv) ‘Adaptation to flow constrains,’ (v) ‘Body flexibility,’ (vi) ‘Case-material,’ and (vii) ‘Case-shape.’ Both the functional structure of the assemblages and the channel complexity of the channelized site were characterized and compared to those of two undisturbed sites. The results suggest that certain genera become dominant as a result of the environmental changes caused by partial channelization. Specifically, assemblages underwent significant specialization in ‘Food,’ ‘Feeding habits,’ and ‘Case-shape,’ and this was linked to the homogenization in mesohabitat type and in hydraulic variability. The trends evident in the trait-based responses may serve as a basis for proposing and assessing strategies to restore the hydromorphological integrity of High-Andean streams.