Floral visitors and potential pollinators of Calanthe discolor and C. striata in South Korea.

Abstract

Numerous Calanthe (Orchidaceae) species are considered food-deceptive orchids because they attract floral visitors without providing rewards. In this study, we investigated floral visitors and their different types of behaviour in natural populations of Calanthe discolor and C. striata in South Korea during peak flowering to identify pollinaria-carrying visitors and assess whether the observations suggest potential pollinator sharing between the two taxa. A total of 73 visitation events involving 17 insect species were recorded on C. discolor. Diptera accounted for most visitation events, but no dipteran or lepidopteran visitors carried pollinaria. Pollinaria attachment was confirmed only in hymenopteran visitors (Andrena opacifovea, Apis cerana, Ceratina japonica and Lasioglossum formosae) that probed deeply into the spur. In C. striata, a single visitation event by Eucera nipponensis was recorded and the observed individual carried pollinaria on the head and transported them between flowers. This observation is consistent with previous reports from Japan and suggests a possible mechanism of pollinator sharing that should be tested through broader temporal and population-level observations. The results reveal a clear mismatch between visitation frequency and pollinaria transport in C. discolor, with pollinaria attachment restricted to a subset of bee visitors. Together with previous studies, our findings support a generalised food-deceptive pollination strategy in C. discolor mediated by locally available bees. This study provides baseline field evidence on floral visitors and pollinaria transport in Korean Calanthe and establishes testable hypotheses for future studies of reproductive interactions amongst closely-related taxa.