Morphological variation and reproductive characteristics of wild giant taro (Alocasia macrorrhizos, Araceae) populations in Vanuatu

Abstract

This investigation was aimed at understanding the morphological variation and reproductive biology of wild populations of giant taro (Alocasia macrorrhizos) in Vanuatu. It is an aroid species, which grows in vigorous, relatively small and dense populations, consisting of phenotypically uniform or very similar individuals. The most variable traits observed in wild populations are number of inflorescences, number of infructescences per plant, and corm length. These traits are highly variable even within genetically uniform populations and are highly influenced by age differences between plants. Flowering is frequent and most of the plants are highly fertile. However, sexual reproduction is rare due to self‐incompatibility (between plants genetically homogeneous within the same population) and the absence of efficient pollinators. Self‐incompatibility can be partly overcome by repeated self‐pollination. Thermogenesis was studied on a large sample of inflorescences and little variation concerning the thermogenic potential was observed. Our results showed that, despite optimal flowering conditions (concerning pollen fertility, stigma receptivity, and thermogenic potential), propagation of wild Alocasia macrorrhizos populations in Vanuatu was mainly vegetative. Giant taro plants might have been carried beyond the range of their most effective pollinators. Other factors were considered: the presence of numerous earwigs (Labidura truncata) insects within inflorescences, which could have a competing effect with the usual pollinators of giant taro, and the long distances between genetically homogeneous populations.