Pollinators of Arisaema nambae (Araceae), endemic to Okayama and Hiroshima prefectures, western Japan

Abstract

Effective pollinators of Arisaema nambae Kitam., endemic to western Okayama and eastern Hiroshima prefectures, western Japan, were determined, and 113 insects from 24 spathes of A. nambae in three populations in Okayama Prefecture were collected. Most floral visitors were fungus gnats (Mycetophilidae and Sciaridae). Their maximum body width was less than the internal diameter (ca. 2 mm) of the exit at the bottom of the staminate spathe. Pollen grains of Arisaema attached to the bodies of fungus gnats collected from pistillate spathes provided evidence that they visited the pistillate spathe after escaping from staminate spathes. Based on their visitation frequency, size compatibility between their body and the exit from the staminate spathes and the pollen loads they carry, fungus gnats appear to play an important role in the pollination of A. nambae.