Floral variation in Bejaria resinosa (Ericaceae) and its relation to flower visitors

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Cristina A. Lalama, E. Noraya Castro and Boris A. Tinoco, Biology, Universidad del Azuay, Cuenca, Ecuador, Michael N. Melampy, Biology and Geology, Baldwin Wallace University, Berea, OH

Background/Question/Methods
The Andean shrub Bejaria resinosa (Ericaceae) is characterized by individuals that produce either flowers with sticky corollas or flowers with non-sticky corollas. The proportions of each morph (sticky vs. non-sticky) vary substantially from one population to another. Our study sought to determine 1) if the morphs are cross and/or self compatible, 2) the extent to which nectar production and floral morphology are differentiated between morphs, and 3) the impact that flower visitors may have on the evolution of the morphs. We conducted field work at three sites located 52 km southwest of Cuenca, Ecuador. The rate of fruit production as a consequence of hand-pollinations within and between morphs was used to assess compatibility. Nectar samples extracted from bagged flowers at intervals of 6 and 24 hours were used to compare nectar volumes and sugar concentrations. Nectar standing crop was measured by extracting nectar from unbagged flowers. Morphometric measurements of fully open flowers were done in the field. The frequencies of different flower visitors to each morph were determined from photos taken at one second intervals for 12 hrs/day over the course of 3 days by cameras mounted at distances of 0.3 m or 1.0 m from the flowers.
Results/Conclusions
Although crosses within morphs produced fruits, the highest rate of fruit production among hand-polllinated flowers occurred as a result of crosses between different morphs. Flowers that were bagged and not hand-pollinated also produced fruits, especially among non-sticky flowers. Nectar and morphometric measurements revealed some differentiation between morphs, suggesting restricted pollen flow between them. Significant differences in nectar standing crop were found (volume: non-sticky > sticky; concentration: non-sticky < sticky), but no nectar differences were found for bagged flowers. Sticky flowers had longer pistils and corollas than did non-sticky flowers. Restricted pollen flow may result from differences in the pollinators visiting each morph. Most recorded flower visitors were bees (94.6%) although hummingbirds and avian flower piercers constituted a small percentage (5.4%) of the visitors. Honeybees (Apis mellifera) made approximately 0.48 legitimate visits (touching reproductive parts) per hour to non-sticky flowers but only 0.23 visits/hr to sticky flowers. Conversely, native bees made 0.21 visits/hr to non-sticky flowers and 0.62 visits/hr to sticky flowers. We conclude that bee behavior, especially that of a non-native species, may influence the floral evolution of Bejaria resinosa.