Flowers as Islands: Spatial Distribution of Nectar-Inhabiting Microfungi among Plants of Mimulus aurantiacus, a Hummingbird-Pollinated Shrub
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Microfungi that inhabit floral nectar offer unique opportunities for the study of microbial distribution and the role that dispersal limitation may play in generating distribution patterns. Flowers are well-replicated habitat islands, among which the microbes disperse via pollinators. This metapopulation system allows for investigation of microbial distribution at multiple spatial scales. We examined the distribution of the yeast, Metschnikowia reukaufii, and other fungal species found in the floral nectar of the sticky monkey flower, Mimulus aurantiacus, a hummingbird-pollinated shrub, at a California site. We found that the frequency of nectar-inhabiting microfungi on a given host plant was not significantly correlated with light availability, nectar volume, or the percent cover of M. aurantiacus around the plant, but was significantly correlated with the location of the host plant and loosely correlated with the density of flowers on the plant. These results suggest that dispersal limitation caused by spatially nonrandom foraging by pollinators may be a primary factor driving the observed distribution pattern.
KeywordsFlower Density Floral Nectar Partial Mantel Test Nectar Volume Microbial Distribution
We thank Nona Chiariello and JRBP staff for assistance during field sampling, Chase Mendenhall for his contributions with hummingbird mist-netting, Trevor Hebert for assistance with Fig. S1, and the Biology 44Y students in the spring of 2011 for their assistance in collecting the data presented in Fig. S3. We also thank Bill Gomez, Nathan Kim, Christine Kyauk, Katrina Luna, Pat Seawell, Sebastian Calderon Bentin, and Diamantis Sellis for field and laboratory assistance; Annette Golonka and Carlos Herrera for technical advice; and Paul Ehrlich, Hal Mooney, Karen Nelson, members of the Fukami lab, and several anonymous reviewers for comments. Funding was provided by Stanford University.
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