Data from: Does reproductive isolation reflect the segregation of color forms in Spiranthes sinensis (Pers.) Ames complex (Orchidaceae) in the Chinese Himalayas?

Isolation between species, or taxa sharing a common lineage, depends
primarily on the relative strengths of various reproductive barriers.
Previous studies on reproductive isolation between orchids emphasized
mechanical and ethological barriers in flowers of species showing food
and/or sexual mimicry. In this study, we investigated and quantified a
series of pre- and post-pollination barriers between pink and white forms
of Spiranthes sinensis sl, a nectar-secreting complex. We generated ML
trees based on trnS-G and matK to explore phylogenetic relationships in
this species complex. Spiranthes sinensis sl segregated from some other
congeners but the white form constituted a distinct clade in relation to
the pink form. The white form secreted 2-Phenylethanol as its single scent
compound and was pollinated almost exclusively by native, large-bodied
Apis cerana and Bombus species (Apidae). Apis cerana showed a high floral
constancy to this form. The scentless, pink form was pollinated primarily
by smaller bees in the genera Ceratina (Apidae), and members of the family
Halictidae, with infrequent visits by A. cerana and Bombus species. Fruit
set and the production of large embryos following inter-form pollination
treatments were significantly lower compared to intra-form pollination
results for the white form. Our results suggested that pollinator
isolation, based on color and scent cues, may result in greater floral
constancy in white populations when both forms are sympatric as two
different, guilds of pollinators forage selectively preventing or reducing
prospective gene flow. Post-pollination barriers appear weaker than
pre-pollination barriers but they also play a role in inter-form
isolation, especially in the white form. Our findings suggest that floral
color forms in S. sinensis do not represent an unbalanced polymorphism.
Interpretations of the evolutionary status of these forms are discussed.