Temporal dynamics of taxonomic homogenization in the fish communities of the Laurentian Great Lakes

Abstract

Aim: As a result of the loss of native species and the spread of non-native species, fish communities are becoming increasingly homogenous globally. In the Laurentian Great Lakes, 21 native fish species have been extirpated from one or more lakes as a result of habitat alteration and destruction, overexploitation and invasive species since the 1800s. Over the same time period, 30 non-native species became established in at least one lake as a result of authorized and unauthorized introductions. This study examines temporal changes in taxonomic dissimilarity over 15 time periods spanning the last 150 years. Location: Laurentian Great Lakes, North America. Methods: Changes to the Great Lakes fish fauna were summarized in species lists by decade from 1870 to 2010. Taxonomic dissimilarity between and within communities was calculated using Jaccard's dissimilarity coefficient; the relative contribution of turnover (species replacement) and nestedness (species loss) to total taxonomic dissimilarity was also calculated. To test whether the Great Lakes have homogenized, we conducted a regression on multiple-site dissimilarity values over time. Results: Native species richness in the Great Lakes exhibits a latitudinal gradient that reflects post-glacial history and current climate. We demonstrate that the establishment of non-native species and extirpation of native species has changed fish communities in each of the Great Lakes, with communities in Lake Superior differentiating the most (~23%) and in Lake Ontario the least (~12%) since 1870. Multiple-site dissimilarity ranges between ~50% and 53% per decade, and communities have become ~5.9% more similar over time since 1870. Main Conclusions: Species introductions and extirpations have changed community composition, resulting in the fish communities becoming significantly more similar to one another over time and, thus, homogenized. As a result, ongoing management should prevent range expansion of native and non-native species to preserve the current distinctiveness of the Great Lakes fish communities.