Positive biotic interactions in freshwaters: A review and research directive

Silknetter, Samuel; Creed, Robert P.; Brown, Bryan L.; Frimpong, Emmanuel A.; Skelton, James; Peoples, Brandon K.

doi:10.1111/fwb.13476

Cited by 51 publications

(79 citation statements)

References 213 publications

(355 reference statements)

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“…Additionally, positive interactions in both marine and terrestrial ecosystems can explain niche space expansion, which ultimately has implications for ecosystem functions and services (Bulleri et al ., 2016). A recent review highlighted myriad ways that positive interactions occur in freshwater ecosystems across plant and animal taxa (Silknetter et al ., 2020). For example crayfish feeding and burrowing activity facilitates benthic algal species and macroinvertebrate density, often in sediment‐polluted streams (Creed, 1994; Albertson and Daniels, 2016).…”

Section: Introductionmentioning

confidence: 99%

Uncovering patterns of freshwater positive interactions using meta‐analysis: Identifying the roles of common participants, invasive species and environmental context

et al. 2020

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Positive interactions are sensitive to human activities, necessitating synthetic approaches to elucidate broad patterns and predict future changes if these interactions are altered or lost. General understanding of freshwater positive interactions has been far outpaced by knowledge of these important relationships in terrestrial and marine ecosystems. We conducted a global meta‐analysis to evaluate the magnitude of positive interactions across freshwater habitats. In 340 studies, we found substantial positive effects, with facilitators increasing beneficiaries by, on average, 81% across all taxa and response variables. Mollusks in particular were commonly studied as both facilitators and beneficiaries. Amphibians were one group benefiting the most from positive interactions, yet few studies investigated amphibians. Invasive facilitators had stronger positive effects on beneficiaries than non‐invasive facilitators. We compared positive effects between high‐ and low‐stress conditions and found no difference in the magnitude of benefit in the subset of studies that manipulated stressors. Future areas of research include understudied facilitators and beneficiaries, the stress gradient hypothesis, patterns across space or time and the influence of declining taxa whose elimination would jeopardise fragile positive interaction networks. Freshwater positive interactions occur among a wide range of taxa, influence populations, communities and ecosystem processes and deserve further exploration.

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Section: Introductionmentioning

confidence: 99%

Uncovering patterns of freshwater positive interactions using meta‐analysis: Identifying the roles of common participants, invasive species and environmental context

et al. 2020

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“…Although our study provides the first evidence of a strong effect of a mutualism on freshwater community structure, there is growing evidence that other positive interactions may play important roles in some freshwater communities (Silknetter et al 2020). For example, bluehead chub ( Nocomis leptocephalus ) are a key species in many southeastern U.S. streams.…”

Section: Discussionmentioning

confidence: 71%

“…; Brown et al 2012). Host and symbiont identities along with symbiont density are also sources of context dependence (Silknetter et al 2020) so we used two different crayfish hosts, two different species of branchiobdellidan, and we varied symbiont density. Thus, we were able to assess how differences in both environmental and host–symbiont context influenced the outcome of this symbiosis on these communities.…”

Section: Methodsmentioning

confidence: 99%

“…Dodds and Whiles (2010) suggest that one explanation for this pattern is that freshwater systems have been in existence for a much shorter period of time relative to many marine and terrestrial communities and thus there has not been sufficient time for mutualisms to evolve. Alternatively, they also suggest, along with Holomuzki et al (2010) and Silknetter et al (2020), that freshwater mutualisms and their impacts on freshwater systems could have simply been overlooked.…”

Section: Introductionmentioning

confidence: 98%

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Strong effects of a mutualism on freshwater community structure

Creed

Skelton

Farrell

et al. 2020

Ecology

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Numerous mutualisms have been described from terrestrial and marine communities and many of these mutualisms have significant effects on community structure and function. In contrast, there are far fewer examples of mutualisms from freshwater habitats and there is no evidence that any mutualism has community‐wide or ecosystem‐level consequences. Northern hemisphere crayfish are host to a variety of ectosymbiotic worms called branchiobdellidans. The association between some of these “crayfish worms” and their hosts is a mutualism. The outcome of the association is context dependent and can be influenced by host size, symbiont number, and the environment. Here we document in two experiments that the mutualism between crayfish and these worms alters the effect of crayfish on stream community structure and sediment deposition, an important ecosystem variable. We enclosed crayfish stocked with 0 worms and intermediate (3–6) and high worm densities (12) in cages in streams in Boone, North Carolina and Clemson, South Carolina, United States. At both locations, there was a negative relationship between initial worm density and final macroinvertebrate abundance. There was a significant effect of worm treatment on macroinvertebrate community structure in both the Boone and Clemson experiments. In Boone, there were effects on both overall macroinvertebrate abundance and community composition, whereas in Clemson, changes to community structure were primarily driven by changes in total abundance. There was a negative relationship between benthic sediment volume and initial worm density in both experiments, primarily later in the experiments, though these effects were influenced by sediment deposition rates. Our results are the first to demonstrate strong effects of a mutualism on freshwater communities. Both members of this mutualism are found throughout the northern hemisphere, so similar impacts may occur in many other waterways. Given that various species in addition to crayfish function as keystone species and ecosystem engineers in freshwater systems throughout the world, mutualisms involving these strongly interacting species may be as important to the structure and functioning of freshwater systems as comparable mutualisms in marine and terrestrial systems.

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“…Fruit selection is linked to seed dispersal, both are key processes in the conservation of biodiversity (Terborgh & Andresen, 1998). Positive interactions with frugivores are strongly related to the succession patterns of plant communities (Silknetter et al, 2020). Therefore, food divergence can attenuate competition for food (Clink et al, 2017), possibly favoring greater efficiency in seed dispersal (Howe & Estabrook, 1977) and in the development of diffuse coevolution (Heithaus, 1982).…”

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confidence: 99%