Does biodiversity self limit?

Pollination of endemic and non-endemic species in highly diverse plant communities


Pollen of Fumana baetica and Helianthemum croceum
In this proyect, we inderectly estimate pollination success of different plants species by observing pollen grains and tubes of wilted open pollinated flowers. To do so we collect styles in alcohol and stain them to become visible under a UV microscope. Pollen grain size and morphology is highly characteristic, allowing distinction of species or groups of closely related taxa at different samples.

Changes in the frequency of stigmas without pollen grains together with average pollen loads per stigma indicate differences in visitation rates. The relationship between pollen deposition and pollen tubes developed along the style of naturally pollinated flowers allows estimating the relative contribution of quantity and quality of pollen received to pollination success and testing for differences of their magnitudes among species.(read more).

During a flowering season natural variations in pollen receipt and pollen tube formation were analysed for 20 insect-pollinated plants. We found that pollen tubes did not frequently exceed the number of ovules per flower. Only the combination of abundant and good quality pollen and a low number of ovules per flower conferred relief from pre-zygotic pollen limitation in the three stochastic pollination environments studied. Further, we found a gradient of pollen receipt among communities from highest doses in serpentine seeps of California to lowest loads and increased variability in the clearings of coastal dry scrublands of the Yucatan. The relative pollination success of endemic and non-endemic species, and its quantity and quality componets, was community dependent (see here).

Finally, to understand pollination success from a community perspective we need to estimate pollinators sharing among species and how frequently co-flowering species indirectly facilitate each others or compete for pollination service. Heterospecific pollen on stigmas indirectly indicates pollen transfer among species (see here). Both the magnitude of this phenomenon and its consequences for species reproductive success remain poorly understood and we have already evidences of a large variation among our study species.