Beetle pollination of Luisia teres (Orchidaceae) and implications of a geographic divergence in the pollination system

Abstract

The epiphytic orchid Luisia teres on Okinawa Island, the Ryukyus, Japan, sexually attracts male Protaetia beetles for pollination through floral scent. Here, the pollination system of L. teres on the Satsuma Peninsula, Kyushu, located approximately 600 km north of Okinawa Island, is reported. The inconspicuous flowers depend on the Cetoniinae beetles Protaetia orientalis submarumorea and Pseudotorynorrhina japonica, which both usually feed on fermented sap/ripe fruits, for pollination. The flower‐visiting P. orientalis submarumorea beetles included both males and females, and pseudocopulation was never observed. Pollinaria removal and pollination were achieved while beetles fed on floral nectar. Although P. orientalis submarumorea did not necessarily remove pollinaria more frequently than Ps. japonica, the pollinaria attached precisely to the central part of their clypeus, unlike on Ps. japonica. Our findings suggest that a geographic divergence in the pollination system occurs in Japanese L. teres. In the Ryukyus, the orchid adopts a specialized pollination system with only male‐attractive olfactory stimuli, whereas in Kyushu it has a relatively more generalized system based on only a food reward.

Sexual deception of a beetle pollinator through floral mimicry

“…13 However, despite exhibiting occasional copulatory behavior, the chafer beetles also consume nectar on the floral lip. This, taken together with a recent report that female beetles also pollinate flowers in some populations, 12 suggests that the Luisia system is transitional between a foodrewarding system and sexual deception. 22 Role of volatiles in attraction of beetles Male C. hessei beetles arriving at flowers of D. forficaria exhibited slow zig-zag flight paths typical of odor-tracking insects.…”

Ecosystem functions and functional traits for the study of phytophagous scarab beetles (Coleoptera: Scarabaeidae)

“…In addition, Cetoniinae beetles have been closely associated with the reproduction of Orchidaceae plants, whose floral scent and spur length appear to be important traits for floral visits (Peter & Johnson, 2009, 2014). In fact, there is discussion about the shift from bee pollination to beetle pollination as a driver of floral divergence in a species complex within this plant family (Peter & Johnson, 2009, 2014; Sugiura et al, 2021).…”

Specialization for Tachinid Fly Pollination in the Phenologically Divergent Varieties of the Orchid Neotinea ustulata

“…In other complex pollination systems, the flypollinated Gorteria diffusa Thunb. (Asteraceae) attracts flies seeking food, but male flies are also sexually attracted and try to copulate with the black petal ornamentation (Ellis and Johnson, 2010); similarly, some populations of the beetlepollinated Luisia teres Gaudich attracts nectar-feeding females and male beetles, whereas others sexually attract males (Sugiura et al, 2021). Hence, the combination of traits present in N. ustulata indicates that this orchid would exploit not only food-based signals but also sexual ones (e.g., gender-specific pheromones).…”