Interspecific Competition for Pollination Lowers Seed Production and Outcrossing in Mimulus Ringens

Sympatric plant species with similar flowering phenologies and floral morphologies may compete for pollination, and as a consequence potentially influence each other\u27s reproductive success and mating system. Two likely competitors are Mimulus ringens and Lobelia siphilitica, which co-occur in wet meadows of central and eastern North America, produce blue zygomorphic flowers, and share several species of bumble bee pollinators. To test for effects of competition for pollination, we planted experimental arrays of Mimulus ringens, each consisting of genets with unique combinations of homozygous marker genotypes. In two arrays we planted mixtures of Mimulus and Lobelia. and in two additional arrays we planted Mimulus without a competitor for pollination. Bumble bee pollinators frequently moved between Mimulus and Lobelia flowers in the mixed-species arrays, with 42% of plant-to-plant movements being interspecific transitions. Pollinator movements between species were associated with a reduction in the amount of conspecific pollen arriving on Mimulus stigmas. The presence of Lobelia led to a significant 37% reduction in the mean number of Mimulus seeds per fruit. In addition, Mimulus had a significantly lower rate of outcrossing in the mixed-species arrays (0.43) than in the pure arrays (0.63). This is the first study to demonstrate that competition for pollination directly influences outcrossing rates. Our work suggests that in self-compatible populations with genetic load, competition for pollination may not only reduce seed quantity, but may also lower seed quality

Interspecific Variation in the Calls of Spheniscus Penguins

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Influence of pollen transport dynamics on sire profiles and multiple paternity in flowering plants.

In many flowering plants individual fruits contain a mixture of half- and full- siblings, reflecting pollination by several fathers. To better understand the mechanisms generating multiple paternity within fruits we present a theoretical framework linking pollen carryover with patterns of pollinator movement. This 'sire profile' model predicts that species with more extensive pollen carryover will have a greater number of mates. It also predicts that flowers on large displays, which are often probed consecutively during a single pollinator visitation sequence, will have a lower effective number of mates. We compared these predictions with observed values for bumble bee-pollinated Mimulus ringens, which has restricted carryover, and hummingbird-pollinated Ipomopsis aggregata, which has extensive carryover. The model correctly predicted that the effective number of mates is much higher in the species with more extensive carryover. This work extends our knowledge of plant mating systems by highlighting mechanisms influencing the genetic composition of sibships

Appendix B. A table showing results of a split-plot ANOVA for pollinator visitation as a function of Treatment, Day, and Array(trt).

A table showing results of a split-plot ANOVA for pollinator visitation as a function of Treatment, Day, and Array(trt)

Novel Consequences of Bird Pollination for Plant Mating

Pollinator behaviour has profound effects on plant mating. Pollinators are predicted to minimise energetic costs during foraging bouts by moving between nearby flowers. However, a review of plant mating system studies reveals a mismatch between behavioural predictions and pollen-mediated gene dispersal in bird-pollinated plants. Paternal diversity of these plants is twice that of plants pollinated solely by insects. Comparison with the behaviour of other pollinator groups suggests that birds promote pollen dispersal through a combination of high mobility, limited grooming, and intra- and interspecies aggression. Future opportunities to test these predictions include seed paternity assignment following pollinator exclusion experiments, single pollen grain genotyping, new tracking technologies for small pollinators, and motion-triggered cameras and ethological experimentation for quantifying pollinator behaviour.This work was supported by the Australian Research Council (ARC) through a Discovery Scheme grant to S.D.H., S.L.K., R.D.P., and D.G.R. combined with a Discovery Outstanding Researcher Award to S.D.H. (DP140103357), a DST-NRF South African Research Chairs Initiative grant to S.D.J, and a University of Wisconsin-Milwaukee Research Growth Initiative award to J.D. K. S.D.H. was also supported by grants from the Great Southern Development Commission and Jack Family Trust, and R. D.P. was also supported by an ARC Discovery Early Career Researcher Award (DE150101720)

Appendix C. A figure showing the number of consecutively probed flowers on individual Mimulus plants in the pure-species and mixed-species arrays.

A figure showing the number of consecutively probed flowers on individual Mimulus plants in the pure-species and mixed-species arrays

Appendix A. A figure showing species composition of bumble bee visitors to Mimulus ringens and Lobelia siphilitica in the experimental arrays.

A figure showing species composition of bumble bee visitors to Mimulus ringens and Lobelia siphilitica in the experimental arrays