Relationships between floral morphology and pollinator fauna in insular and main island populations of Hosta longipes (Liliaceae)

We compared the floral morphologies and pollinator fauna and morphologies of Hosta longipes var. longipes on the main Japanese island of Honshu and var. latifolia on the Izu Islands to examine the differentiation processes of H. longipes in the island system. The corolla length was shorter on the southern Izu Islands than on the main island and northern Izu Islands. However, the size of other flower parts of H. longipes did not simply decrease across main island Honshu and the Izu Islands, unlike other Izu endemic plant species studied previously. Instead, the floral morphology showed a complicated variation pattern. Pollinator fauna of H. longipes on the Izu Islands varied more widely than those on the main island. The diverse pollinator fauna may have influenced the morphological differentiation of H. longipes on these islands.