Characterizing each step of pollination in the wildflower, Phlox drummondii, reveals a single butterfly species predominates in the pollinator assemblage

<p>Premise: A central goal of pollination biology is to connect plants with the identity of their pollinator(s). While predictions based on floral syndrome traits are extremely useful, direct observation can reveal further details of a species' pollination biology. The wildflower, <em>Phlox drummondii</em>, has a floral syndrome consistent with pollination by a variety of lepidoptera. We describe pollination in <em>P. drummondii</em> and use empirical data to test this prediction.</p> <p>Methods: We directly observe each step of the pollination process in <em>P. drummondii</em>. First, we observe 55.5 hours of floral visitation throughout the day/evening (7:00-20:30) at sites across the species range. We use a temporal pollinator exclusion experiment to determine the contribution of diurnal and nocturnal pollination to reproductive output. We then quantify <em>P. drummondii</em> pollen pickup and deposition by the dominant floral visitor, <em>Battus philenor</em>. Finally, we test the effect of <em>B. philenor</em> visitation on <em>P. drummondii</em> reproductive output by quantifying fruit set following visitation to greenhouse-grown flowers.</p> <p>Results: <em>B. philenor</em> is the primary pollinator of <em>P. drummondii</em>. Pollination is largely diurnal, and we observe a variety of lepidopteran visitors during this period. However, <em>B. philenor</em> is by far the most frequent visitor, representing 88.5% of all observed floral visits. We show that <em>B. philenor</em> is not only an extremely common visitor but also an effective pollinator by demonstrating that individuals transfer pollen between flowers and that a single visit can elicit fruit set.</p> <p>Conclusion: Our data are consistent with the syndrome prediction of lepidopteran pollination and further reveal a single butterfly species, <em>B. philenor</em>, as the primary pollinator. Collectively, our study demonstrates the importance of empirical pollinator observations, adds to our understanding of pollination mechanics, and offers a specific case study of butterfly pollination.</p>