Reliable sample sizes for estimating similarity among macroinvertebrate assemblages in tropical streams

Abstract

-Studies in tropical streams are relatively few, and one of the still-unresolved methodological issues is sample size. Adequate sample size for temperate streams cannot be extrapolated for tropical sites, because of the differences in species richness and the proportions of rare species. We evaluated reliable sample size for estimation of resemblance among samples of macroinvertebrate assemblages inhabiting riffles of tropical streams, using the autosimilarity approach. Sample sizes were much larger than those currently employed in tropical studies. Sampling units consisted of individuals associated with single stones (15-20 cm). Evaluations employed the Bray-Curtis index for abundance data and the equivalent Sorensen index for presence-absence data. Autosimilarity curves were constructed using both sampling units and individuals. The estimation of resemblance among samples was strongly dependent upon sample size at reduced sampling effort, particularly for the Bray-Curtis index. For the same sampling effort, fixed counts of individuals obtained randomly from sampling units gave better estimations of resemblance, and their similarity curves tended to stabilize earlier than those using sampling units. A minimum of 9-15 sampling units (stones) or 150-850 individuals is necessary for adequate estimations of resemblance using presence-absence data, and 13-18 sampling units or 750-1550 individuals are required for relative abundance data in tropical streams.

Estimating vertebrate, benthic macroinvertebrate, and diatom taxa richness in raftable Pacific Northwest rivers for bioassessment purposes

“…We conclude that randomization analytical procedures, such as multiple-run Monte Carlo analyses, as recommended by Flotemersch et al (2010) and Schneck and Melo (2010) are useful for estimating sufficient sampling effort for assessing vertebrate, macroinvertebrate, and diatom taxa richness in rivers.…”

Stream biomonitoring using macroinvertebrates around the globe: a comparison of large-scale programs

“…However, it is still necessary to test family-level in a biomonitoring program for streams in the whole region, considering there is substantial difference of biota among the biomes. Finally, few studies in Latin America have dealt with developing and testing of other important aspects of biomonitoring protocols, such as sampling procedures and mesh sizes (Buss and Borges 2008), sample size (Schneck and Melo 2010), subsampling methods (Oliveira et al 2011a;Ligeiro et al 2013a), and taxonomic sufficiency (e.g., Melo 2005;Buss and Vitorino 2010).…”

Effects of fixed-count size on macroinvertebrate richness, site separation, and bioassessment of Chinese monsoonal streams

“…Others also have demonstrated that fixed-count size can affect richness estimates (e.g., McCord et al, 2007;Oliveira et al, 2011), the separation between sites or groups (e.g., Cao et al, 2002a;Schneck and Melo, 2010), and performance of MMIs (e.g., Doberstein et al, 2000) and O/E indices (e.g., Nichols et al, 2006;Ostermiller and Hawkins, 2004).…”

“…We expect that BC yielded higher CS than JC because BC provided proportional abundance data that are less variable than the pure richness data of JC, which is sensitive to rare taxa. Therefore, we also expected that CS (JC) needed a greater fixedcount size to achieve asymptotes than CS (BC) (Schneck and Melo, 2010).…”