2019 Volume 94 Issue 6 Pages 342-353
To understand floral and reproductive nature of Guettarda speciosa L. (Rubiaceae) occurring in Taiwan and Japan, we investigated variation of stigma and anther heights, pollen stainability and size, compatibility system by artificial pollination experiments, and reproductive outputs in natural populations. Stigma and anther heights continuously varied among the individuals and did not show a bimodal distribution known in the typically distylous species. However, the separation between the stigma and anther heights and their orders indicated that this species was morphologically distylous with L- and S-styled morphs, although its stigma and anther heights were not reciprocal between the two morphs. These two morphs occurred in even ratio and set fruits with seeds equally in natural pollinations. Moreover, hand pollination experiments indicated that both morphs had self- and intramorphic incompatibilities, suggesting that cross-pollination between different morphs was significant for setting seeds. These results indicate that the examined populations of G. speciosa are also morphologically and functionally distylous and that the pollen flow is almost equal between the two morphs, irrespective of the fact that their stigma and anther heights lack the precise reciprocity.
