Browsing by Subject "plant-pollinator interactions"

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  • Opedal, Oystein H.; Martins, Adriana A.; Marjakangas, Emma-Liina (2020)
    Euglossine bees are an ecologically important group, which due to their diverse resource needs act as pollinators of many neotropical plants. Male euglossines collect fragrant compounds used in mating displays from diverse sources, including the flowers of orchids and other plants. This aspect of euglossine biology has proven exceptionally useful for studies of euglossine bee populations, because male bees can be readily attracted to fragrance baits deployed in natural habitats. We synthesise the data accumulated over the 50 years since the introduction of euglossine bee baiting inventories and make these data openly available in the EUGCOMM database. By fitting hierarchical joint species distribution models to presence-absence and abundance data, we reveal that the assemblages of bees attracted depend on the baits used in interaction with species-specific fragrance preferences and that bee assemblages are most diverse at sites in landscapes characterised by partial but not complete forest cover. We suggest that these results reflect the diverse resource needs of euglossine bees and are consistent with the hypothesis that male euglossines establish home ranges incorporating multiple habitat types. These results may have important consequences for the design of nature reserves in the tropics, if these iconic pollinators are to be conserved for the future.
  • Opedal, Oystein H. (2018)
    Premise of research. Phenotypic traits that consistently mediate species' responses to environmental variation (functional traits) provide a promising approach toward generalizing ecological and evolutionary patterns and thereby gaining insights into the processes generating them. In the plant functional ecology literature, most trait-based studies have focused on traits mediating either resource competition or responses to variation in the abiotic environment, while traits mediating reproductive interactions have often been neglected. Methodology. Here, I discuss the value of herkogamy, the spatial separation of male and female functions in flowers, as a functional trait in plant reproductive biology and review the evidence relevant to the hypothesis that taxa exhibiting greater herkogamy have historically experienced more reliable pollination and more outcrossed mating systems. Pivotal results. A large body of work in the field of plant reproductive biology has identified a set of nearly ubiquitous correlations between average herkogamy and features of plant mating systems, notably, autofertility (seed set in the absence of pollinators) and outcrossing rate. Herkogamy often varies extensively among populations and species, and the adaptive interpretation is that herkogamy exhibits local adaptation to the reliability of the pollination environment. Conclusions. These results underline the value of herkogamy as a functional trait representing variation in mating histories. Many important insights are likely to emerge from studies leveraging herkogamy as an easily measured proxy of plant mating systems, as already demonstrated in comparative studies and studies of reproductive interactions. Greater consideration of herkogamy and other reproductive-function traits in studies of species coexistence may provide a more complete understanding of community assembly processes.
  • Opedal, Oystein H.; Gross, Karin; Chapurlat, Elodie; Parachnowitsch, Amy; Joffard, Nina; Sletvold, Nina; Ovaskainen, Otso; Friberg, Magne (2022)
    Natural selection on floral scent composition is a key element of the hypothesis that pollinators and other floral visitors drive scent evolution. The measure of such selection is complicated by the high-dimensional nature of floral scent data and uncertainty about the cognitive processes involved in scent-mediated communication. We use dimension reduction through reduced-rank regression to jointly estimate a scent composite trait under selection and the strength of selection acting on this trait. To assess and compare variation in selection on scent across species, time and space, we reanalyse 22 datasets on six species from four previous studies. The results agreed qualitatively with previous analyses in terms of identifying populations and scent compounds subject to stronger selection but also allowed us to evaluate and compare the strength of selection on scent across studies. Doing so revealed that selection on floral scent was highly variable, and overall about as common and as strong as selection on other phenotypic traits involved in pollinator attraction or pollen transfer. These results are consistent with an important role of floral scent in pollinator attraction. Our approach should be useful for further studies of plant-animal communication and for studies of selection on other high-dimensional phenotypes. In particular, our approach will be useful for studies of pollinator-mediated selection on complex scent blends comprising many volatiles, and when no prior information on the physiological responses of pollinators to scent compounds is available.
  • Reverte Saiz, Sara; Reverte Saiz, Sara; Arnan, Xavier; Roslin, Tomas; Stefanescu, Constanti; Antonio Calleja, Juan; Molowny-Horas, Roberto; Hernández-Castellano, Carlos; Rodrigo, Anselm (2019)
    Large-scale spatial variability in plant-pollinator communities (e.g. along geographic gradients, across different landscapes) is relatively well understood. However, we know much less about how these communities vary at small scales within a uniform landscape. Plants are sessile and highly sensitive to microhabitat conditions, whereas pollinators are highly mobile and, for the most part, display generalist feeding habits. Therefore, we expect plants to show greater spatial variability than pollinators. We analysed the spatial heterogeneity of a community of flowering plants and their pollinators in 40 plots across a 40-km(2) area within an uninterrupted Mediterranean scrubland. We recorded 3577 pollinator visits to 49 plant species. The pollinator community (170 species) was strongly dominated by honey bees (71.8% of the visits recorded). Flower and pollinator communities showed similar beta-diversity, indicating that spatial variability was similar in the two groups. We used path analysis to establish the direct and indirect effects of flower community distribution and honey bee visitation rate (a measure of the use of floral resources by this species) on the spatial distribution of the pollinator community. Wild pollinator abundance was positively related to flower abundance. Wild pollinator visitation rate was negatively related to flower abundance, suggesting that floral resources were not limiting. Pollinator and flower richness were positively related. Pollinator species composition was weakly related to flower species composition, reflecting the generalist nature of flower-pollinator interactions and the opportunistic nature of pollinator flower choices. Honey bee visitation rate did not affect the distribution of the wild pollinator community. Overall, we show that, in spite of the apparent physiognomic uniformity, both flowers and pollinators display high levels of heterogeneity, resulting in a mosaic of idiosyncratic local communities. Our results provide a measure of the background of intrinsic heterogeneity within a uniform habitat, with potential consequences on low-scale ecosystem function and microevolutionary patterns.
  • Opedal, Øystein H.; Hegland, Stein Joar (2020)
    1. Pollinator-mediated reproductive interactions among co-flowering plant species are prime examples of how species interactions may affect fitness and community assembly. Despite considerable interest in these issues, statistical methods for assessing signal of reproductive interactions in observational data on co-flowering species are currently lacking. 2. We propose a flexible method for quantifying potential reproductive interactions among co-flowering plant species using the hierarchical latent-variable joint models implemented in the Hierarchical Modelling of Species Communities (HMSC) framework. The method accommodates any measure of reproductive success, including pollinator visitation, stigma pollen loads, and seed set. We demonstrate the method by analysing a dataset on bumblebee visitation to a set of co-flowering plant species in a species-rich meadow in Norway, and provide R tutorials for this and additional data types. 3. The example analysis revealed both positive and negative effects of heterospecific flower abundances on visitation to co-flowering species, which we interpret as potential reproductive interactions. 4. Synthesis. Hierarchical joint models provide a flexible approach to analysing patterns of covariation in the reproductive success of co-flowering species, thus identifying potential species interactions. Important strengths include explicit consideration of community-level effects and the assessment of residual fitness correlations after controlling for covariates such as flower abundances and phenotypic traits, yielding more complete insights into pollinator-mediated reproductive interactions.