Gymnosperms are either wind-pollinated (anemophilous) or wind-insect-pollinated (ambophilous). Ovular secretions play a key role in pollen capture, germination, and growth; pollination drops are also understood to serve as a possible reward for insect pollinators. Nepi et al. analyse the chemical composition of pollination drops of thirteen species representing all five lineages of extant gymnosperms.
Ambophilous species display a clear signal of pollinator-driven selection that may have evolved as a co-evolutionary response to feeding insects. Ginkgo biloba has a profile typical of ambophilous taxa, suggesting either that an insect pollination mode of for this species is hitherto undocumented, or that the species’ ancestral populations were insect pollinated in which case G. biloba ovular secretions represent ‘the ghost of evolution past’.
Nepi, M., Little, S., Guarnieri, M., Nocentini, D., Prior, N., Gill, J., … von Aderkas, P. (2017). Phylogenetic and functional signals in gymnosperm ovular secretions. Annals of Botany, 120(6), 923–936. https://doi.org/10.1093/aob/mcx103