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

Habitat simplification changes temporal patterns of invertebrate beta diversity in a high-Andean stream

“…Meanwhile, the undisturbed stretch reflects the flow and the substratum diversity in reference conditions. González-Trujillo [12] showed that both the riparian forest and the physical-chemical characteristics were similar in both sections.…”

“…Channelization reduces the spatial heterogeneity and the temporal variability of habitats' distribution, reducing the resource and refugium availability for invertebrate taxa [12,23,24]. Thus, we hypothesized that the effect of the hydrological variability on beta diversity would be higher at the channelized stretch than at undisturbed stretch.…”

“…The findings of Jacobsen [6], in particular, suggest that the flow regime primarily drives temporal beta-diversity patterns in Andean communities, since species composition is determined at random after a high-flow event. Subsequent studies revealed mixed shreds of evidence; while some support a random assembly after spate events [12,13], others found no significant differences before and after high-flow events [14,15]. These conflicting results may be explained by differences in habitat heterogeneity or species life histories as well as by methodological differences (e.g., distinct diversity indices).…”

“…In high-Andean streams, the substrate heterogeneity and the unpredictable high-flow events during rainy seasons are relevant determinants of invertebrate community structure in a temporal dimension [10,11]. Indeed, previous studies have shown that higher hydraulic stress and streambed movement during high-flow events alter community composition [6,12]; and consequently, shape beta-diversity patterns at lower spatiotemporal scales. The findings of Jacobsen [6], in particular, suggest that the flow regime primarily drives temporal beta-diversity patterns in Andean communities, since species composition is determined at random after a high-flow event.…”

“…For example, concerning its estimation, differences in abundances, richness, or sampling bias are some factors that may affect betadiversity patterns [18,19]. In light of this, beta diversity may be higher due to sampling bias (e.g., sampling only one type of substratum), since species occurrence and abundances are tightly coupled with the substratum type in tropical headwaters [12,20]. On the other hand, beta diversity could be higher if the used metric gives more weight to species abundances rather than to species identities since spates tend to affect species abundances rather than their occurrences [11,15].…”