Breeding systems of dominant perennial plants of two disjunct warm desert ecosystems.

A comparison of the floral syndromes, flower biomasses, pollen and total sugar production of the dominant perennial species of two climatically similar but disjunct desert scrub ecosystems was made to assess the degree of convergence in breeding systems. Results indicate that the dominants at the northern site in the Sonoran Desert near Tucson Arizona, USA, possess more diverse floral types, utilize more reproductive methods, produce a greater annual biomass of flowers, provide more rewards for potential pollinators and employ a wider array of pollen vectors than those at the southern site near Andalgalá, Catamarca, Argentina. The discrepancies in these features can be best explained in terms of the differences in the annual dispersion of rainfall at the two sites. However, when compared to the dominant species of two Mediterranean scrub ecosystems, the breeding systems of the dominants of the desert scrub sites proved to be more similar to one another than to those of a neighboring but different ecosystem type.