Cypripedium lichiangense (Orchidaceae) mimics a humus-rich oviposition site to attract its female pollinator, Ferdinandea cuprea (Syrphidae).

Abstract

Most species in the genus Cypripedium (Cypripedioideae) produce trap flowers, making it a model lineage to study deceptive pollination. Floral attractants in most species studied appear to target bee species of different sizes. However, more recent publications report fly pollination in some subalpine species, suggesting novel suites of adaptive floral traits. Cypripedium lichiangense (section Trigonopedia) is an endangered subalpine species endemic to the Hengduan Mountains, China. We observed and analysed its floral traits, pollinators and breeding systems over 2 years insitu and in the lab. Cypripedium lichiangense was visited by females of Ferdinandea cuprea (Syrphidae). The pollinia were carried dorsally on the fly thoraces. The eggs of this fly were frequently found in the saccate labellum and on other floral organs, suggesting brood-site mimesis. The orchid is self-compatible, but cross-pollination produces more viable embryos. We propose a new mode of floral mimesis, humus-rich oviposition site mimicry, for C. lichiangense. Compared with the mimesis of aphid colonies attracting syrphid pollinators (subfamily Syrphinae), whose larvae are entomophagic, as reported in some Paphiopedilum species (Cypripedioideae), pollination by deceit in C. lichiangense represents a distinct and separate mode of exploitation of another saprophagic (or phytophagic) larvae syrphid lineage in the subfamily Eristalinae and appears to indicate diversity of pollination strategies in SectionTrigonopedia of Cypripedium. However, this new brood-site mimesis seems to be less attractive to pollinators. As a possible adaptation to the weak attracted pollination strategy, this plant species has a long flowering period and extended lifespan of individual flowers to ensure reproductive success.