Different refuge types dampen exotic invasion and enhance diversity at the whole ecosystem scale in a heterogeneous rive
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ORIGINAL PAPER
Different refuge types dampen exotic invasion and enhance diversity at the whole ecosystem scale in a heterogeneous river system Louis Astorg . Sarah Sanderson . Virginy Coˆte´-Gravel . Freedom Sorbara . Matthew J. S. Windle . Andrew P. Hendry . Alison M. Derry
Received: 2 December 2019 / Accepted: 24 September 2020 Ó Springer Nature Switzerland AG 2020
Abstract Refuges that result from environmental heterogeneity within ecosystems have an important yet under-appreciated role in maintaining native community diversity in face of exotic invasion. The objective of our study was to determine if different refuge types constrain invasion impacts on native biodiversity at the whole ecosystem-scale of the Upper St. Lawrence River. We focused on the voracious round goby fish as a sentinel exotic species whose spatial distribution within this ecosystem is also representative of the species distributions of several Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10530-020-02374-7) contains supplementary material, which is available to authorized users. L. Astorg V. Coˆte´-Gravel A. M. Derry (&) De´partement des sciences biologiques, Universite´ du Que´bec a` Montre´al, Succursale Centre-Ville, C.P. 8888, Succursale Centre-Ville, Montre´al, QC H3C 3P8, Canada e-mail: [email protected] L. Astorg S. Sanderson A. P. Hendry A. M. Derry Groupe de recherche interuniversitaire en limnologie (GRIL), Montre´al, Canada S. Sanderson F. Sorbara A. P. Hendry Redpath Museum and Department of Biology, McGill University, 859 Sherbrooke St. West, Montre´al, QC H3A 0C4, Canada M. J. S. Windle St. Lawrence River Institute of Environmental Sciences, 2 St. Lawrence Dr, Cornwall, ON K6H 4Z1, Canada
other Ponto-Caspian invaders. We first explored if wetlands were acting as unknown refuges in reducing the local abundance of the round goby fish. We then tested the relative influence of a known broad-scale conductivity gradient compared with local wetlands on structuring the composition, diversity, and abundance of native macroinvertebrate and fish communities inside and outside each of these refuge types. We found that the two types of refuges, broad-scale conductivity gradient and local wetlands, limited round goby abundances at the whole ecosystem scale, and structured macroinvertebrate and fish community diversity. The broad-scale conductivity refuge was twice stronger than wetlands in limiting round goby abundance. Although wetlands were effective in constraining round goby abundance, the direct effect of wetlands rather than their indirect effects through limiting round goby abundance, were more powerful in explaining maintenance of macroinvertebrate and fish community diversity in invaded high conductivity waters. Our findings underscore the important role of environmental heterogeneity in producing different types of refuges that buffer invasion effects in freshwater ecosystems, and we advocate the preservation of we
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