Friends of mine: An invasive freshwater mussel facilitates growth of invasive macrophytes and mediates their competitive interactions

Abstract

Increasing rates of invasions in ecosystems worldwide necessitate experiments todetermine the role of biotic interactions in the success and impact of multiple alien species. Here, we examined competitive and facilitative interactions among various combinations of three widespread and often co-occurring invaders: the zebra mussel Dreissena polymorpha, and the macrophytes Elodea canadensis and Elodea nuttallii.2. Using a mesocosm-based, factorial experimental design, we assessed the effect of interspecific competition on macrophyte growth rates in the absence and presence at varying biomass of D. polymorpha.3. Growth rates (wet g/day) of E. canadensis and E. nuttallii were similar when grown in isolation. When grown together, in the absence of D. polymorpha, E. canadensis growth was not significantly reduced in the presence of E. nuttallii and vice versa. In the presence of D. polymorpha (26.0 ± 1 mm), monocultural growth of E. canadensis was largely unaffected, while E. nuttallii growth was strongly enhanced. Low (2.64 g) and medium (3.96 g) mussel biomass led to negative interspecific effects between E. canadensis and E. nuttallii; at high (5.28 g) mussel biomass, the effect of interspecific competition was negated. Overall, D. polymorpha alleviated competitive interactions between the two inva-sive macrophytes when all three species co-occurred, and substantially enhanced growth of E. nuttallii with increasing mussel biomass, thereby suggesting a possible influence on the relative dominance of these macrophytes in the field. Our study demonstrates how facilitations can cause shifts in dominance amongclosely related invaders. The consequences of such facilitations for the structure and function of communities remain to be explored generally. K E Y W O R D Sbiotic interactions, biotic resistance, facilitation, interspecific competition, invasional meltdown, mutualism edge support from NSERC Canada. We particularly thank Dr Patrick

Two centuries for an almost complete community turnover from native to non‐native species in a riverine ecosystem

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Better off dead: assessment of aquatic disinfectants and thermal shock treatments to prevent the spread of invasive freshwater bivalves

“…Invasive bivalve species, such as quagga mussel, Dreissena bugensis (Andrusov 1897), and zebra mussel, D. polymorpha (Pallas 1771), are considered a major threat to the function and biodiversity of freshwater ecosystems worldwide (Higgins and Vander Zanden 2010; Sousa et al 2014;Karatayev et al 2015). As dominant filter-feeders, invasive Dreissena species can alter ecosystem structure and function (Crane et al 2020a), through increased water clarity and the physical modification of benthic habitats (Karatayev et al 2015). Such changes can result in zooplankton declines (Kissman et al 2010), blooms of potentially toxic cyanobacteria (Knoll et al 2008), and increased populations of both benthic invertebrates and submerged aquatic vegetation, resulting in benthic orientated food-web structures (Mayer et al 2002;Zhu et al 2006;Miehls et al 2009).…”

Trophic structure of a pond community dominated by an invasive alien species: Insights from stomach content and stable isotope analyses

“…This is particularly true in freshwater ecosystems, which are vulnerable to biological invasions owing to the strong link of humans to water, the inconspicuousness of aquatic ecosystems (Rico‐Sánchez et al, 2020), and the high interconnectedness, and thus the dispersal ability, of freshwater species compared with terrestrial species (Selge, Fischer & van der Wal, 2011; Tricarico, Junqueira & Dudgeon, 2016). As a result, freshwater communities are often dominated by multiple invasive alien species (IAS) living in sympatry and interacting with each other (Gamradt & Kats, 1996; Kiesecker & Blaustein, 1998; Haubrock et al, 2020), and some of these may have facilitative effects (Crane et al, 2020).…”