No support for purported effects of salt-tolerant stream invertebrates on the salinity responses of salt-sensitive stream invertebrates
Bruce C. Chessman
Centre for Ecosystem Science, School of Biological, Earth and Environmental Sciences, UNSW Sydney, NSW 2052, Australia. Email: brucechessman@gmail.com
Marine and Freshwater Research - https://doi.org/10.1071/MF20163
Submitted: 26 May 2020 Accepted: 23 July 2020 Published online: 26 August 2020
Journal Compilation © CSIRO 2020 Open Access CC BY
Abstract
Increases in salinity can severely affect freshwater ecosystems, and research on the salt tolerances of freshwater species, and factors that modify tolerance, can improve our understanding and prediction of the effects of salinity. In order to test the hypothesis that salt-tolerant freshwater invertebrates can alter the salinity responses of salt-sensitive freshwater invertebrates, publicly available data from a recent study of artificial mesocosms that claimed to confirm this hypothesis were analysed in the present study. No supporting evidence was found for the hypothesis, with apparent salinity responses of salt-sensitive invertebrates varying no more with greater or lesser exposure to salt-tolerant invertebrates than expected merely by chance. The original findings were apparently misguided through unrecognised confounding of the experimental design, inadequate statistical hypothesis testing and accepting ostensible effects without considering their biological and ecological plausibility.
Keywords: biotic interaction, experimental design, mesocosm, statistical confounding.
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