Differentiation of Fruiting Phenology and Seed Dispersal of Arisaema (Araceae) in Japan: The Effect of Fruiting Season on the Rates of Fruit Removal by Avian Frugivores

Abstract

We recorded the fruit ripening season of 47 taxa of Arisaema (Araceae) in the temperate forests of Japan. Most of the Arisaema species ripened in autumn/winter, but in six taxa, including A. undulatifolium group and A. seppikoense ripening occurred in summer. We used automatic cameras to compare Arisaema fruit removal rate and speed by frugivores between summer- and autumn/winter-fruiting of Arisaema. The fruits of Arisaema species ripening in autumn/winter were consumed by birds including Brown-eared bulbul (Hypsipetes amaurotis), Pale thrush (Turdus pallidus) and Copper pheasant (Syrmaticus soemmerringii). In contrast, the fruits of summer-fruiting species were exclusively consumed by Browneared bulbul. Both the fruit removal rates and speeds of summer-ripening species were much higher than those of autumn/winter-ripening species, because of the frequent fruit consumption by Brown-eared Bulbuls in summer. The Arisaema undulatifolium group and A. seppikoense in subsect. Pistillata, both ripening in summer, are considered to be derived from those species groups ripening in autumn/winter. Those summer ripening Arisaema species in subsection Pistillata might change their fruit ripening season from autumn/winter to summer during the differentiation. This is an interesting example of fruit-bird interaction between Arisaema species ripening in summer and their major fruit consumer Brown-eared bulbul resulting from the change of fruit ripening season.