POLLEN LIMITATION AND REPRODUCTIVE ASSURANCE IN THE FLORA OF THE COASTAL ATACAMA DESERT

Abstract

Pollen limitation (PL) in plant populations is supposed to be particularly strong in variable pollinator environments. Here, we examined the extent of PL in the coastal Atacama Desert, where low and unpredictable rainfall drives large interannual variation in plant cover and pollinator abundances. We estimated PL levels and the capacity for autonomous selfing (autofertility) in 16 annual and perennial species. In addition, we compared fruit set of emasculated and intact flowers to test whether selfing provides reproductive assurance. We also examined the relationships between autofertility and life forms, between PL and autofertility, and between PL and flower size. We found a low level of PL (mean ¼ 0:28) and a high incidence of autofertility, which was negatively correlated with PL and closely related to life form. Our results suggest that the low PL levels in autonomous-selfing species result from the reproductive assurance provided by selfing. Considering nonautonomous species only, the mean PL (0.44) was similar to that reported for other habitats. We detected no association between PL and flower size. In summary, high rates of PL were not a general pattern among plants in the Atacama Desert. The low levels of PL can be attributed to the high incidence of autofertility.