Diel Foraging Patterns of Male Euglossine Bees: Ecological Causes and Evolutionary Responses by Plants
Male euglossine bees (Eugloua, Eulaema, Exaerete) were censused at regular intervals at chemical baits in Surinam, Trinidad, and Costa Rica. Fragrance foraging was initiated at ca 0700, peak activity occurred at ca 1100, and foraging ceased at ca 1430. Linear regression and path analysis on numbers of Euglossa at baits in Cosca Rica indicated that in the morning hours these bees were affected directly and positively by air temperature, which itself was controlled by time of day and cloud cover. After 1100 hr bees responded directly to time of day (or an unmeasured correlate of it) and were not directly affected by air temperature or cloud cover. The diel pattern of bee activity may have affected the evolution of diel patterns of floral activity in plants pollinated by male euglossines. Dalechampia brownsbergensis, which is pollinated by male euglossine bees, presents floral rewards and is receptive for pollination in the morning and early afternoon when male euglossines are most active. Species most closely related to D. brownsbergesis, however, are pollinated by female euglossine bees and present floral rewards in the late afternoon. The census data and phylogenetic analysis suggest that D. brownsbergesis evolved morning presentation of the floral reward as a result of the shift to pollination by male euglossines.