Two closely related species of the Arisaema ovale group (Araceae) selectively attract male fungus gnats of different Anatella species (Diptera: Mycetophilidae)

Arisaema sect. Pistillata (Araceae) is a rapidly diversifying taxon in the Japanese archipelago. Several sympatric Arisaema species selectively attract different fungus gnats (Mycetophilidae and Sciaridae), suggesting that frequent pollinator shifts induce adaptive radiation. Since no study has compared pollinator species between sister Arisaema species, we examined the floral visitor assemblages of two closely related species (Ar. nagiense and Ar. ovale) in sympatric, parapatric, and allopatric populations. In all six sites, at the level of genus, male Anatella spp. (Mycetophilidae) dominated the floral visitors in both Arisaema species, but Ar. nagiense and Ar. ovale selectively attracted different Anatella species. The pollinator shift during the allopatric speciation of the two sister Arisaema species suggests the contribution of a species-specific pollination system to the rapid diversification of Japanese Arisaema species.