Riqueza y estabilidad de los polinizadores de los cirios (Fouquieria columnaris) del desierto sonorense: Un análisis comparativo
The floral visitors of the boojum tree [Fouquieria columnaris (Kellogg) Kellogg ex Curran] in the Sierra Bacha, Sonora were studied and compared with Humphrey's data collected 30 years ago. The boojum, a species protected by CITES, has a distribution restricted to Baja California and the Sierra Bacha, Sonora. In the later locality, the richness of the pollinator guild -including 18 species of bees, several arthropods and one hummingbird species- is higher than any of the sites studied by Humphrey in Baja California. This disjunct population apparently does not exhibit ecological interactions characteristic of a marginal population supporting the hypothesis of a broader continental distribution of boojum in the past. Its pollinator guild is clearly dominated by polylectic bees, generalists that depend on asynchronous flowering of other plant species offering nectar and pollen resources in this hyperarid landscape. It appears that the stability of this pollinator guild is limited by the large climatic variation between years in the Sierra Bacha, and its effect on the production of floral resources year by year. Although the flowers do not conform to the ornithophyllous floral syndrome of other memebers of the genus, "trap-lining" by hummingbirds -repeated visits of widely-spaced flowering trees- was observed in this population.