Single pollinator species losses reduce floral fidelity and plant reproductive function

Abstract

Understanding the functional impacts of pollinator species losses on plant populations is critical given ongoing pollinator declines. Simulation models of pollination networks suggest that plant communities will be resilient to losing many or even most of the pollinator species in an ecosystem. These predictions, however, have not been tested empirically and implicitly assume that pollination efficacy is unaffected by interactions with interspecific competitors. By contrast, ecological theory and data from a wide range of ecosystems show that interspecific competition can drive variation in ecological specialization over short timescales via behavioral or morphological plasticity, although the potential implications of such changes in specialization for ecosystem functioning remain unexplored. We conducted manipulative field experiments in which we temporarily removed single pollinator species from study plots in subalpine meadows, to test the hypothesis that interactions between pollinator species can shape individual species' functional roles via changes in foraging specialization. We show that loss of a single pollinator species reduces floral fidelity (shortterm specialization) in the remaining pollinators, with significant implications for ecosystem functioning in terms of reduced plant reproduction, even when potentially effective pollinators remained in the system. Our results suggest that ongoing pollinator declines may have more serious negative implications for plant communities than is currently assumed. More broadly, we show that the individual functional contributions of species can be dynamic and shaped by the community of interspecific competitors, thereby documenting a distinct mechanism for how biodiversity can drive ecosystem functioning, with potential relevance to a wide range of taxa and systems.ecosystem function | ecosystem services | phenotypic plasticity | foraging biology G lobal pollinator declines are ongoing (1, 2), leading to concerns about the functional impacts of pollinator species losses on both pollination-dependent native plants (3) and crop production (4). Network-based simulation models of pollinator species losses, however, predict that major functional impacts on plant species persistence will not typically result until many, or even most, pollinator species are lost from a system (5-7), but these results have not been tested empirically. These predictions are based in part on redundancies in pollination networks: most plant species are visited by several pollinator species, contributing to the robustness of such networks (5). This robustness, however, is dependent on the implicit assumption that the functional roles of pollinator species are static. If interspecific interactions can dynamically alter species' functional contributions-such as the efficacy of a particular plant-pollinator relationship-pollinator species losses may have greater cascading impacts on plant communities than predicted by current models (5-7).Such dynamic changes in species functional roles are p...

Low functional diversity promotes niche changes in natural island pollinator communities

“…Owing to the usually intimate associations between long-tongued pollinators and flowers with specialized floral organs, such as long corolla tube and spur ( [31,32]; figure 1), declines in long-tongued pollinators can lead to such plants becoming pollinator-limited [16,19,20,33]. However, few studies of natural ecosystems have investigated the impacts of long-tongued pollinator declines and the resulting niche changes on a whole flower community (but see Brosi & Briggs [17] and Kadoya & Ishii [22]). …”

“…Ideally, these effects would be examined by experimental removal of long-tongued species in a natural ecosystem, but removing multiple native species from a pristine habitat throughout the year is both technically difficult and ethically problematic (e.g. Brosi & Briggs [17] and Kadoya & Ishii [22] removed a single Bombus species at each study site).…”

Adaptive foraging behaviour of individual pollinators and the coexistence of co-flowering plants

“…This is more challenging than simple resource competition [3], because pollinator-mediated competition may inhibit the establishment of an initially rare plant species in a community owing to heterospecific pollen interference [4], as the rarer species receives a disproportionately smaller fraction of effective pollination from generalist pollinators. However, pollination niche overlap between plant species is often dynamic as individual pollinators may change their preferences and foraging behaviour, and partition their niches according to perceived resource availability, which is subject to but also shapes the community dynamics [5,6].…”

Reduced-risk insecticides in Neotropical stingless bee species: impact on survival and activity

“…Furthermore, the reliance on the honeybee for insecticide toxicity assessments may compromise more susceptible pollinator species, such as stingless bees, and thus impair agricultural production and plant diversity in the neotropics. 4,13,14 The general focus on the impact of neonicotinoids on pollinators, particularly honeybees, has led to an expansion and incentives of reduced-risk pesticides and particularly of biopesticides. [15][16][17][18] The encouragement for the use of such compounds is illustrated by European Pesticide Regulation No.…”

“…Such stingless bees' species are important native pollinators in the Neotropical America. [10][11][12][13]25 The group activity and flight take-off of adult workers exposed to azadirachtin or chlorantraniliprole were also assessed for impact prediction on behavior of both native bee species.…”