Resupinate Dimorphy, a novel pollination strategy in two-lipped flowers of Eplingiella (Lamiaceae)

ABSTRACT This work provides a summary of the typical floral structure of subtribe Hyptidinae (Lamiaceae), in which both style and stamens are declinate within or near the concave anterior corolla lobe. Cross-pollination is facilitated by protandry, acting in conjunction with the explosive release of the stamens and pollen. In contrast, we report that in the three species of the genus Eplingiella we found individuals with either resupinate or non-resupinate flowers, which represents a novel floral dimorphism. In these species of Eplingiella, the style occupies a position towards the posterior corolla lip and opposes the declinate stamens. Thus, in non-resupinate flowers the pollinating bee receives pollen on its ventral side and makes contact with the style on its dorsal side, whereas in resupinate flowers, the bee receives pollen on its dorsal side, and contacts the style on its ventral side. Both floral morphs seem to be required to achieve cross-pollination. In the two populations studied, each of the two morphs is present and in similar proportions, providing a novel means of promoting cross-pollination and reducing selfing. The situation in Eplingiella is compared to some other examples of floral polymorphism, but appears to be a unique pollination strategy, here termed Resupinate Dimorphy