An invasive foundation species enhances multifunctionality in a coastal ecosystem

Ramus, Aaron P.; Silliman, Brian R.; Thomsen, Mads S.; Long, Zachary T.

doi:10.1073/pnas.1700353114

Cited by 101 publications

(82 citation statements)

References 73 publications

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“…The more food web connections that are broken or altered by human‐induced disturbances, the larger the impact of invaders may be, as higher food web connectance correlates with invasion resistance (Smith‐Ramesh, Moore, & Schmitz, ). Evidence is currently building that invaders can have positive effects on disturbed ecosystems, with invaders replacing the function of lost or declining species, or providing new functions useful in the altered habitat (Carroll, ; Ramus, Silliman, Thomsen, & Long, ; Ricciardi et al., ; Schlaepfer, Sax, & Olden, ; Thomsen et al., ; Wallach et al., ). However, it is still poorly known under which conditions invaders stabilize rather than disrupt human‐altered environments and how common such positive effects are.…”

Section: Discussionmentioning

confidence: 99%

Environmental disturbance alters the ecological impact of an invading shrimp

2018

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Alien species are altering ecosystems around the globe. To predict and manage their impacts, the underlying mechanisms need to be understood. This is challenging in ecosystems undergoing multiple disturbances as unexpected interactions can alter the impact of individual disturbances. Such interactions are likely to be common in disturbed ecosystems, but have so far received little attention. We investigated whether interactions between an invading shrimp Palaemon elegans and another human‐induced disturbance, the population growth of a native mesopredator, the threespine stickleback, influences a third human‐induced disturbance, the increase in biomass of filamentous algae. Increases in both the native mesopredator population and algal biomass have been promoted by eutrophication and a trophic cascade triggered by declining predatory fish stocks. We used mesocosm and field enclosure experiments, combined with analyses of long‐term trends in the abundance of the invader and the native mesopredator, to dissect the influence of the two species on algal biomass when alone and when co‐occurring. The impact of the invader on algal biomass depended on the native mesopredator; shrimp on their own had no effect on algal growth, but mitigated algae accumulation when competing with the stickleback for resources. Competition caused the shrimp to shift its diet from grazers to algae, and its habitat choice from open to vegetated habitats. The native mesopredator, in contrast, increased algal biomass irrespective of the presence of the invader, by preying on grazers and inducing a trophic cascade. Our results show that the presence of a native mesopredator causes an invader to alter its behaviour and thereby its ecological impact. This demonstrates that interactions between invaders and other anthropogenic disturbances can alter the ecological impact of invaders, and, notably, that the impact of invaders can be positive and stabilize disturbed ecosystems. These results stress the importance of considering interactions among disturbances when investigating the ecological impact of alien species. A http://onlinelibrary.wiley.com/doi/10.1111/1365-2435.13078/suppinfo is available for this article.

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Section: Discussionmentioning

confidence: 99%

Environmental disturbance alters the ecological impact of an invading shrimp

2018

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“…Where present, hypotheses of abiotic mechanisms were most clearly stated in the case of invasive or domestic species that have physical effects on biogeochemical cycling (Constán‐Nava et al, ; Zhang et al, ). For example, in addition to altering local diversity, invasive plants may alter soil or sediment properties, such as water retention, stability, and biogeochemical cycling (Constán‐Nava et al, ; Quero, Maestre, Ochoa, García‐Gómez, & Delgado‐Baquerizo, ; Ramus et al, ). The activities of grazers may also impact soil properties and processes through trampling and dung and urine deposition (Allan et al, ; Peco, Navarro, Carmona, Medina, & Marques, ; Sircely & Naeem, ; Vandandorj et al, ; Zhang et al, ), resulting in altered EMF (Figure b).…”

Section: Toward a Mechanistic Understanding Of Global Change Impacts mentioning

confidence: 99%

A niche for ecosystem multifunctionality in global change research

Giling

Beaumelle

Phillips

et al. 2018

Global Change Biology

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Concern about human modification of Earth's ecosystems has recently motivated ecologists to address how global change drivers will impact the simultaneous provisioning of multiple functions, termed ecosystem multifunctionality (EMF). However, metrics of EMF have often been applied in global change studies with little consideration of the information they provide beyond single functions, or how and why EMF may respond to global change drivers. Here, we critically review the current state of this rapidly expanding field and provide a conceptual framework to guide the effective incorporation of EMF in global change research. In particular, we emphasize the need for a priori identification and explicit testing of the biotic and abiotic mechanisms through which global change drivers impact EMF, as well as assessing correlations among multiple single functions because these patterns underlie shifts in EMF. While the role of biodiversity in mediating global change effects on EMF has justifiably received much attention, empirical support for effects via other biotic and physicochemical mechanisms are also needed. Studies also frequently stated the importance of measuring EMF responses to global change drivers to understand the potential consequences for multiple ecosystem services, but explicit links between measured functions and ecosystem services were missing from many such studies. While there is clear potential for EMF to provide novel insights to global change research, predictive understanding will be greatly improved by insuring future research is strongly hypothesis‐driven, is designed to explicitly test multiple abiotic and biotic mechanisms, and assesses how single functions and their covariation drive emergent EMF responses to global change drivers.

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“…Bold face denotes statistical significance at a = 0.05. native taxa and increases in local biodiversity (Crooks 2002, Castilla et al 2004, Byers et al 2012, Wright et al 2014, Ramus et al 2017. The present study highlights the potential benefits of a weakly competitive nonnative habitat-forming species in mitigating the impacts of habitat degradation on native biodiversity.…”

Section: Discussionmentioning

confidence: 64%

“…Nonnative control should not be a goal in itself and should only be undertaken when it aids the aforementioned outcomes, for example, where a nonnative species is highly invasive and likely to exacerbate declines in biodiversity. We are not the first to suggest such an approach to nonnative species management (Zavaleta et al 2001, Schlaepfer et al 2011, Ramus et al 2017, but this study is among the first to demonstrate the ecological trap concept as an assessment framework that can provide evidence needed to guide an outcomes-focused and evidence-based management approach.…”

Section: Management Implicationsmentioning

confidence: 98%

A nonnative habitat‐former mitigates native habitat loss for endemic reef fishes

Barrett¹,

Dempster²,

Swearer³

2019

Preprint

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Animals that select the best available habitats are most likely to succeed in degraded environments, but ecological change can create evolutionarily unfamiliar habitats that may be under-or over-utilized by native fauna. In temperate coastal waters, eutrophication and grazing have driven a global decline in native seaweeds and facilitated the establishment of nonnative seaweeds that provide novel macrophyte habitat. We tested whether a nonnative kelp canopy (wakame Undaria pinnatifida) functions as a viable habitat or ecological trap for several endemic reef fishes on urchin-grazed reefs in southern Australia. We assessed the willingness of fish to utilize native vs. wakame kelp canopy via a laboratory habitat choice experiment and by recording natural recruitment to specially constructed boulder reefs with manipulated kelp canopy. We also compared fish communities on natural reefs using a beforeafter-control-impact survey of wakame patches, and to assess the quality of wakame habitat for resident fish, compared fitness metrics for fish collected from habitats with native vs. wakame kelp canopy. Endemic fishes did not distinguish between the native or wakame canopy but preferred both to barren reef habitats. On urchin-grazed natural reefs, fish occurred in higher abundance and diversity where seasonal wakame canopy was present. Fitness metrics in fish collected from wakame patches were comparable to those in fish from adjacent native kelp patches. These findings indicate that the nonnative canopy provides a viable habitat for endemic fish and may play a role in sustaining native fauna populations in this degraded ecosystem. More broadly, we recommend that managers consider the role of nonnative habitats within the context of environmental change, as endemic fauna may benefit from nonnative habitatformers in areas where their native counterparts cannot persist.

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An invasive foundation species enhances multifunctionality in a coastal ecosystem

Cited by 101 publications

References 73 publications

Environmental disturbance alters the ecological impact of an invading shrimp

Environmental disturbance alters the ecological impact of an invading shrimp

A niche for ecosystem multifunctionality in global change research

A nonnative habitat‐former mitigates native habitat loss for endemic reef fishes

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