
The magnitude of pollen limitation is highly variable among habitats, species and differing plant communities. Alonso et al. analyse natural variability in pollen receipt and tube formation, and compare pollen quality and quantity between co-flowering endemics and non-endemics at three biodiversity hotspots in Andalusia, California and Yucatan. They find that only a combination of abundant and good quality pollen and a low number of ovules per flower can confer relief from pre-zygotic pollen limitation. Endemics are not always disadvantaged: the relative pollination success of endemic and non-endemic species, and its quantity and quality components, are community dependent.