Island environments are known to involve dramatic changes in breeding system and pollination ecology. Species of Trochetia (Malvaceae), a genus endemic to the Mascarenes (Indian Ocean), present uncommon floral features among angiosperms suggesting a vertebrate pollination. In Mauritius, recent studies have demonstrated that T. blackburniana is mainly pollinated by the Mauritian day gecko, Phelsuma cepediana. While these interactions between vertebrates and T. blackburniana have been investigated, little is known about the pollination ecology of the sister species T. granulata, species endemic to Réunion.
In collaboration with the Université of La Réunion, the Conservatoire Botanique National de Mascarins, and Nature Océan Indien, the research group led by Prof. GAO Xinfen and Prof.ZHANG Libin from Chengdu Institute of Biology, Chinese Academy of Sciences, has recently worked on the breeding system and the pollination ecology of T. granulata in Réunion through compatibility studies and video recordings of flower visits.
The results from the hand-cross experiments showed that T. granulata is self-compatible but cannot produce fruit without the visit of a pollen vector. During surveys, four different visitors were reported: the introduced honey bee (Apis mellifera), two endemic species of white-eye (Zosterops borbonicus borbonicus and Z. olivaceus) and the endemic Réunion day gecko (Phelsuma borbonica).
Mutually beneficial lizard-plant interaction is typical island phenomena and our study is the first well-documented case of potential lizard pollination in Réunion. In addition to Trochetia, several taxa endemic to the Mascarenes (e.g. Roussea, Nesocodon, Heterochaenia) show similar floral pattern and reproductive system. Such floral characters and reproductive features might be linked to the specific interactions with endemic fauna of the Mascarenes. In Mauritius and Réunion, the lineage including Trochetia, presents a striking diversity in species richness and in floral morphology. This diversity in the Dombeyoideae might be the results of an adaptive radiation mediated by pollinator interactions.
This work was published on Journal of Tropical Ecology, 29, 353(2013). It was financially supported by the Young International Fellowship of the Chinese Academy of Sciences(No. 2011Y1SB10) and the National Natural Science Foundation of China (No. 31150110463).