No consistent pollinator‐mediated impacts of alien plants on natives

Charlebois, Julia A.; Sargent, Risa D.

doi:10.1111/ele.12831

Cited by 56 publications

(64 citation statements)

References 91 publications

(211 reference statements)

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“…). For example, a recent meta‐analysis found that presence of co‐flowering plants does not significantly reduce seed and fruit production (Charlebois and Sargent ), suggesting that manipulating co‐flowering plants should have a relatively small effect on selection on floral traits (e.g., Wassink and Caruso ). Alternatively, other biotic factors could have a relatively small effect on selection because variation in floral traits has a weaker effect on the probability of antagonistic and/or competitive interactions than on pollination (e.g., Sandring and Ågren ).…”

Section: Discussionmentioning

confidence: 99%

A meta‐analysis of the agents of selection on floral traits

et al. 2018

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Floral traits are hypothesized to evolve primarily in response to selection by pollinators. However, selection can also be mediated by other environmental factors. To understand the relative importance of pollinator‐mediated selection and its variation among trait and pollinator types, we analyzed directional selection gradients on floral traits from experiments that manipulated the environment to identify agents of selection. Pollinator‐mediated selection was stronger than selection by other biotic factors (e.g., herbivores), but similar in strength to selection by abiotic factors (e.g., soil water), providing partial support for the hypothesis that floral traits evolve primarily in response to pollinators. Pollinator‐mediated selection was stronger on pollination efficiency traits than on other trait types, as expected if efficiency traits affect fitness via interactions with pollinators, but other trait types also affect fitness via other environmental factors. In addition to varying among trait types, pollinator‐mediated selection varied among pollinator taxa: selection was stronger when bees, long‐tongued flies, or birds were the primary visitors than when the primary visitors were Lepidoptera or multiple animal taxa. Finally, reducing pollinator access to flowers had a relatively small effect on selection on floral traits, suggesting that anthropogenic declines in pollinator populations would initially have modest effects on floral evolution.

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Section: Discussionmentioning

confidence: 99%

A meta‐analysis of the agents of selection on floral traits

et al. 2018

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“…Indeed, there is growing evidence (and concerns) that invasive mutualists may competitively displace native mutualists (e.g., Grove et al. , but see Charlebois and Sargent ). Yet, while it is widely recognized that species compete for commodities, the consistency and strength of competition are rarely measured (Jones et al.…”

Section: Discussionmentioning

confidence: 99%

Coexistence and competitive exclusion in mutualism

Johnson

Bronstein

2019

Ecology

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The competitive exclusion principle is fundamental to understanding coexistence. Well‐established theories predict the conditions for coexistence in consumer–resource interactions. Given that species often compete for commodities offered by mutualists, competitive exclusion theory should also be critical to understanding how mutualisms function. We explicitly apply the competitive exclusion principle to mutualism and derive a rule analogous to Tilman's R* rule for exploitative competition. Coexistence is impossible when competitors compete solely for a shared partner‐provided commodity because superior competitors deplete that commodity sufficiently to exclude inferior competitors. We then investigate how competition between two guild members for a partner‐provided commodity and a resource external to the mutualism affects competitor coexistence. There are three key results. First, coexistence is possible via partitioning of a partner‐provided commodity and another resource. Second, unlike in classic R* Theory, competitive outcomes are influenced both by species’ abilities to obtain commodities and their mutualisms with the shared commodity‐providing partner, which can indirectly alleviate competitors’ commodity limitation. Third, the outcome of competition has important consequences for the commodity‐providing partner, which depend on the type of mutualism and the competitive abilities of competing mutualists. This theory provides a novel framework for investigating how competitors for mutualistic commodities coexist in nature.

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“…To date, there has been little support for a consistent effect of species invasions on pollinator visitation network structure (Vil a et al, 2009;Albrecht et al, 2014). A recent meta-analysis (Charlebois & Sargent, 2017) found no consistent effects of invasive plant species' presence on visitation and seed set in coflowering native species. There is reason to predict, however, that in some cases, introduced species have strong impacts on pollen transfer dynamics and native species reproductive fitness.…”

Section: Introductionmentioning

confidence: 99%

Consequences of invasion for pollen transfer and pollination revealed in a tropical island ecosystem

Johnson

Ashman

2018

New Phytologist

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Pollination is known to be sensitive to environmental change but we lack direct estimates of how quantity and quality of pollen transferred between plant species shifts along disturbance gradients. This limits our understanding of how species compositional change impacts pollen receipt per species and structure of pollen transfer networks. We constructed pollen transfer networks along a plant invasion gradient in the Hawaiian dry tropical forest ecosystem. Flowers and stigmas were collected from both native and introduced plants, pollen was identified and enumerated and floral traits were measured. We also characterized pollen loads carried by individuals of the dominant invasive pollinator, Apis mellifera. Species flowering in native-dominated sites were more tightly connected by pollen transfer than those in heavily invaded sites. Compositional turnover in the pollen loads of A. mellifera was correlated (70%) with turnover in the composition of pollen transfer networks. Floral traits predicted species roles within pollen transfer networks, but many of these differed qualitatively depending on whether plants were native or introduced. Our work indicates that pollen transfer networks change with invasion. Floral morphology and foraging behaviour of the introduced super-generalist pollinator are implicated as key in determining the roles introduced species play within native pollen transfer networks.

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No consistent pollinator‐mediated impacts of alien plants on natives

Cited by 56 publications

References 91 publications

A meta‐analysis of the agents of selection on floral traits

A meta‐analysis of the agents of selection on floral traits

Coexistence and competitive exclusion in mutualism

Consequences of invasion for pollen transfer and pollination revealed in a tropical island ecosystem

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