Pollen morphology and pollination ecology of Amorphophallus species from North Western Ghats and Konkan region of India

Abstract

The present paper reports on palynology and pollination ecology of eight taxa of Amorphophallus from North Western Ghats (NWGS) and Konkan region of India. Out of ten known pollen exine ornamentations of the genus, six are represented – psilate, striate, fossulate, verrucate, scabrate and the new type ‘pseudofossulate’ of Amorphophallus commutatus var. wayanadensis. These diverse pollen exine ornamentations can be utilized as an important taxonomic tool to distinguish taxa and also to resolve taxonomic problems ( A. commutatus complex). The pollen of all eight taxa had retained their sculptured surface (exine ornamenatation type) after acetolysis. This clearly demonstrates that these taxa do not show susceptibility to the conventional acetolysis technique as reported earlier. The present study also highlights the importance of pollen surface morphology concerning phytogeography of the genus. Observation of pollination ecology of the studied Amorphophallus taxa reveals that all are mostly visited by beetles (Bostrichidae, Cetoniidae, Hybosoridae, Lyctidae, Nitidulidae, Rutelinae, Scarabaeidae, Staphylinidae), followed by flies (Drosophilidae, Muscidae), bees (Apidae: Trigone), ants (Formicidae, Dolichoderinae) and cockroaches (Blaberidae/Panesthiinae). The beetle families Bostrichidae, Lyctidae and Rutelinae, ant families Formicidae and Dolichoderinae and the cockroach family Blaberidae/Panesthiinae are for the first time reported as visitors in the genus Amorphophallus. Most of the taxa display features characteristic of cantharophily (beetle pollination) except A. commutatus var. commutatus and A. commutatus var. wayanadensis, where Trigona bees are the actual pollinators. The beetles (Cetoniidae, Nitidulidae, Scarabaeidae) and bees (Apidae: Trigona) are the real pollinators for the Amorphophallus species of NWGS and Konkan while rest of the insects are mere visitors for alimentary/food resources (staminode flowers, stigmatic fluid, pollen, appendix surface, appendix exudates) and using the inflorescences as mating and egg laying sites. Species belonging to the section Rhaphiophallus ( Amorphophallus konkanensis and Amorphophallus sylvaticus) are pollinated by Epuraea – Haptoncurina sp. (Nitidulidae) beetles only. Generally, the species of Amorphophallus in NWGS and Konkan region with short flowering peduncle are always pollinated by dung beetles or scarabs while species bearing a long flowering peduncle are usually pollinated by Epuraea – Haptoncurina sp. (Nitidulidae) beetles and Trigona bees. Based on the comparative observations, five different phases of insect trapping in Amorphophallus taxa are characterized, focusing on the intricacies of pollination strategies of various pollinators.