How important are rare species in aquatic community ecology and bioassessment?

Abstract

We examined the effects of excluding rare species on the comparison of species richness. A river benthic data set and a randomization resampling procedure were used to show the importance of this consideration in aquatic bioassessment in particular. The data set was manipulated by deleting species at three levels of rarity as defined by occurrence frequency: once in all 24 replicates from each of three sites, no more than twice, and no more than five times. We focused on differences in species richness because many other bioassessment metrics are dependent on species richness and species composition. Species abundance patterns at the three sites were very different, with many more rare species at the least impacted site than at the more impacted sites. As sample size increased, the diffcrcnces in species richness among the three sites markedly increased in the original data set. However, the exclusion of rare species at the same level of rarity substantially reduced species richness at the least impacted site but had little effect on the most impacted site. This result led to a serious underestimation of the differences in species richness among the sites in terms of both absolute numbers and species loss percentages. Deleting rare species can damage the sensitivity of community-based methods to detect ecological changes; rare species are critical for bioassessment.

Estimating sample representativeness in a survey of stream caddisfly fauna

“…For example, inclusion or exclusion of rare species (Gaston 1994) into analyses is a permanent question for community ecology and bioassessment. Some authors advocate the use of rare species in community analyses (Cao et al 1998, Nijboer & SchmidtKloiber 2004 whilst others argue against it (Marchant 1999(Marchant , 2002. Although the question of including or excluding rare species is largely dependent on the analyses, most researchers share the view that inclusion of rare species causes large sampling error (Bradley & Ormerod 2002) and decreases precision (Ostermiller & Hawkins 2004), in evaluating community structure of stream macroinvertebrates.…”

Bioassessment of a Drinking Water Reservoir Using Plankton: High Throughput Sequencing vs. Traditional Morphological Method

“…DNA sequencing allows approximately three orders of magnitude larger SSU rDNA sequencing [16]. Deleting rare species can affect the sensitivity of biotic indices to detect environmental degradation [53]. In the absence of other nuclear markers less susceptible to copy number variation, rDNA-based diversity studies need to be adjusted for confounding effects of copy number variation [50].…”

Combining Logistic Models with Multivariate Methods for the Rapid Biological Assessment of Rivers Using Macroinvertebrates

“…This is a question that has been subjected to discussion by many authors who use multivariate analysis for bioassessment (e.g. Cao et al, 1998Cao et al, , 2001). According to these authors, removing rare species can statistically improve the precision of species prediction, but can substantially shorten the list of species to be compared, which could lead to an underestimation of the difference between undisturbed and impacted sites.…”