DOI: 10.5061/dryad.0p2ngf20g
title: Beta diversity of aquatic macroinvertebrate assemblages associated with leaf patches in neotropical montane streams

description: Over 70% of the total channel length in all river basins is formed by low
 order streams, many of which originate on mountaintops. Headwater streams
 play fundamental roles in processing and transporting terrestrial and
 aquatic organic matter, often harboring high biodiversity in bottom leaf
 patches deposited from riparian vegetation. The objective of this study
 was to assess the variation in taxonomic composition (measured by beta
 diversity of aquatic macroinvertebrates) among stream sites located in the
 Espinhaço Meridional Mountain Range, part of a UNESCO Biosphere Reserve in
 eastern Brazil. We tested two hypotheses. i) Taxa turnover is the main
 reason for differences in aquatic insect assemblages within stream sites;
 we predicted that turnover would be higher than nestedness in all stream
 sites. ii) Stream site altitude and catchment elevation range are the main
 explanatory variables for the differences in beta diversity; we predicted
 that local stream site variables would account for only minor amounts of
 variation. In both dry and wet seasons, we sampled twice in 2 habitat
 types (5 leaf patches in pools and 5 in riffles) in each of 9 stream sites
 distributed in 3 different river basins. We computed average pairwise beta
 diversity among sampling stations and seasons in each stream site by using
 Jaccard and Bray-Curtis indices, and calculated the percentages of
 diversity resulting from turnover and nestedness. Finally, we tested the
 degree that local- or catchment-level predictor variables explained beta
 diversity. We found that turnover was the main component of beta diversity
 and that both dissolved oxygen and elevation range best explained
 Bray-Curtis beta diversity. These results reinforce the importance of leaf
 patches in montane (sky islands) neotropical savanna streams as
 biodiversity hotbeds for macroinvertebrates, and that both local and
 landscape variables explained beta diversity.
description: In a 100-m long reach of each of the 9 stream sites, 2 sampling
 stations were set where we collected as targeted samples, with a Surber
 sampler (30 x 30 cm; 250 μm mesh), 5 leaf patches in riffles and 5 in
 pools in both dry (July 2006) and rainy (March 2007) seasons, totaling 180
 samples. In pool habitats, we used a Surber sampler simply to ensure the
 same collection area in pools as riffles, placed leaf deposits into the
 net by hand and transferred the net contents into plastic bags for
 subsequent processing. Leaf patches were chosen because, as
 Ligeiro <i>et
 al.</i> (2020) reported, they concentrate
 high abundance and diversity of macroinvertebrates, acting as biodiversity
 hotbeds. Consequently, they limit assemblage responses to the disturbance
 gradient when this substrate is targeted, as opposed to using multihabitat
 sampling. At the sites, leaves were washed with stream water over a sieve
 (mesh size: 250 μm), separated manually and then the macroinvertebrates
 and fine particulate organic matter were placed in plastic jars and fixed
 with 70% ethanol. In the laboratory, invertebrates were identified to
 family using taxonomic keys (Pérez, 1988; Merritt & Cummins, 1996;
 Fernández & Domínguez, 2001;
 Costa <i>et
 al.</i>, 2006;
 Mugnai <i>et
 al.</i>, 2010).