Pollination of enigmatic mauritian endemic roussea simplex (rousseaceae) : birds or geckos?

Roussea simplex (Rousseaceae) is an enigmatic Mauritian endemic plant whose biogeography and taxonomic position has puzzled botanists for many years. Recent molecular work has assigned it to a monotypic endemic genus in the family Rousseaceae, occupying a basal position within the Asterales (Lundberg 2001). It was once a common and widespread plant in wet high-altitude forests in Mauritius, but it is now critically endangered and confined to small, isolated patches (Friedmann 1988, Scott 1997, pers. obs.). Evidence of its former abundance is given by Vaughan and Wiehe (1937, p. 314), who remarked that, “In other places an extremely thick canopy of woody lianes (Roussea simplex Sm.) develops about 4–6 m. above ground level, causing such dense shade that both terrestrial and epiphytic plants are practically excluded”. The plants have large, robust and slightly serrated leaves (7–12 × 3–5.5 cm), and the yellow flowers are also large and robust, measuring approximately 2.5 cm in both length and diameter (Scott 1997). The flowers are 4or most commonly 5-meric, with a weak, sweet, almost yeasty smell. The 4–5 large anthers face outwards, away from the stigma, and pollen is secreted in a wet, very sticky, yellowish substance, which readily adheres to any surface (Fig. 1). Despite the former widespread occurrence of R. simplex in Mauritius, very little is known about its ecology. Preliminary observations of a nectar-feeding bird, the Mascarene Grey White-eye Zosterops borbonicus mauritianus, at R. simplex suggested that it may be a pollinator. When nectar-feeding at R. simplex, all Grey White-eyes enter the flowers from the front, pressing their beak and lower forehead between anthers and corolla, Thus the birds certainly visit the flowers in a way that would suggest them to be poten-