Global collaborative research on the pollination biology of rare and threatened orchid species (Orchidaceae)

Charles Darwin (1862, 1877) conducted field and lab research on orchid pollination mechanisms before any protocols or laws protected orchid species or individual populations. Information on the reproductive ecology of rare and threatened orchids remains intrinsic to their conservation as populations continue to diminish during the Anthropocene. We provide case studies of species representing five genera (Calanthe R. Br., Corunastylis Fitzg., Cypripedium L., Spiranthes Rich., and Thelymitra J. R. Forst. & G. Forst.) in three countries (the United States, Australia, and China). We compare differences in their pollination systems and seasonal variations in their fertility rates. Declining rates of fruit set and/or seed development are compared to breeding systems, pollinator life histories/foraging behaviors, and climate cycles. We conclude that, while some orchid species are pollinator limited, several interrelated factors influence rates of fecundity in terrestrial/lithophytic orchids.