Variation in the spectral qualities of flowers in the Nymphoides indica complex (Menyanthaceae) and its possible adaptive significance

The Nymphoides indica complex is polymorphic in the spectral qualities of its flowers. Flowers of the circumtropical white-flowered race absorb ultraviolet light strongly. Flowers of yellow-flowered South African plants reflect almost uniformly, but those of yellow-flowered plants from the West Indies absorb more strongly in the center and reflect from the remaining portion of the petals. The evolution of these contrasting patterns is considered to represent an increasing specialization of pollinator–flower relationships because of the effect these patterns have in directing pollinating insects to the flowers and to the reproductive organs of the flower.