Print PageComparative studies on endangered species and their more common congeners can shade light on the mechanism of species rarity, and are helpful for conservationists to formulate effective management strategies. Understanding the reproductive biology of endangered species is critical in guiding and establishing successful in-situ and ex-situ conservation programs. Geodorum eulophioides is an endangered orchid distributed narrowly in the subtropical southwestern China. Its current distribution is confined on a highly disturbed, small hill along the Hongshui River near the Yachang Orchid Nature Preserve of Guangxi province. At this site it co-occurs with two other more widespread congeners, G. recurvum and G. densiflorum. To compare their pollination and mating systems, we carried out reproductive phenology and pollination observations, and hand-pollination treatments (self, outcross,hybrid and bagged) during flowering seasons in June to July in 2009 and 2010.
Results/Conclusions
We found that: (1) G. eulophioides and G. recurvum were self-compatible, but depended on bee pollinators for fruitset. In contrast, G. densiflorum was able to self without a vector. For all three species, fruitsets were not different statistically among the self and outcross pollination treatments. (2) G. eulophioides and G. recurvum flowered during the same period and shared the same pollinator (Ceratina cognata Smith.), but their flowering period overlapped little with that of G. densiflorum, pollinator of the latter was not certain. (4) Floral visitation frequencies were extremely low for all three species. (5) Natural fruit sets of G. eulophioides (average 0.0552 fruits/flower) and G. recurvum (0.0107) were not significantly different from one another, but both were lower than those of G. densiflorum (0.1393). (6) G. eulphioides could hybridize with G. recurvum via hand pollination and have the potential do so naturally. But this is not true with G. densiflorum. Coupled with the severe habitat loss and degradation, the extreme low natural fruit set of the rare G. eulophioides call for rapid establishment of ex-situ collection of the species using fruits from hand pollination while improving in-situ habitat. Molecular phylogenetic study is also needed to define species boundaries.
