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Abstract Many plants have evolved nutrient rewards to attract pollinators to flowers, but most research has focused on the sugar content of floral nectar resources. Concentrations of sodium in floral nectar (a micronutrient in low concentrations in nectar) can vary substantially both among and within co‐occurring species. It is hypothesized that sodium concentrations in floral nectar might play an important and underappreciated role in plant–pollinator interactions, especially because many animals, including pollinators, are sodium limited in nature. Yet, the consequences of variation in sodium concentrations in floral nectar remain largely unexplored. Here, we investigate whether enriching floral nectar with sodium influences the composition, diversity, and frequency of plant–pollinator interactions. We experimentally enriched sodium concentrations in four plant species in a subalpine meadow in Colorado, USA. We found that flowers with sodium‐enriched nectar received more visits from a greater diversity of pollinators throughout the season. Different pollinator species foraged more frequently on flowers enriched with sodium and showed evidence of other changes to foraging behavior, including greater dietary evenness. These findings are consistent with the “salty nectar hypothesis,” providing evidence for the importance of sodium limitation in pollinators and suggesting that even small nectar constituents can shape plant–pollinator interactions.
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Predicting how pollinator behavior causes reproductive isolation
Abstract Pollinator behavior is an important contributor to plants speciation, yet how variation in pollinator behavior causes variation in reproductive isolation (RI) is largely uncharacterized. Here I present a model that predicts how two aspects of pollinator behavior, constancy and preference, contribute to a barrier to reproduction in plants. This model is motivated by two observations: most co‐occurring plants vary in frequency over space and time, and most plants have multiple pollinators that differ in behavior. Thus, my goal was to understand how relative frequencies of plants and pollinators in a community influence ethological RI between co‐occurring plants. I find that RI for a focal plant generally increases with increasing relative plant frequency, but the shape of this relationship is highly dependent on the strength of pollinator behavior (constancy and preference). Additionally, when multiple pollinators express different behavior, I find that pollinators with stronger preference disproportionately influence RI. But, I show that RI caused by constancy is the average RI predicted from constancy of each pollinator weighted by pollinator frequency. I apply this model to examples of pollinator‐mediated RI inPhloxand inIpomopsisto predict the relationships between plant frequency and ethological RI in natural systems. This model provides new insights into how and why pollinator specialization causes RI, and how RI could change with changing biological communities.
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- Award ID(s):
- 1844906
- PAR ID:
- 10397031
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Ecology and Evolution
- Volume:
- 12
- Issue:
- 4
- ISSN:
- 2045-7758
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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