Floral morphs of Justicia adhatoda L. differ in fruit and seed, but not floral, traits or pollinator visitation

Abstract

Pigment patterns in corollas are common, and act as nectar guides for pollinators. We discovered multiple floral morphs of Justicia adhatoda L. (Acanthaceae) with variable extents of corolla vein pigmentation in a population in Sariska, Rajasthan. Two floral morphs, one completely white and the other white with dark purple vein pigmentation, were compared in order to investigate any possible differences relating to: (a) corolla surface structure, (b) pollinator visitation, (c) reward for the pollinator, and (d) fitness parameters in the morphs. Both morphs showed similar UV reflectance, had distally located conical cells in petals, indicated similar pollinator visitation and had similar nectar content. Contrastingly, seed germination and seed weight were significantly higher in the purple-veined morph, while fruit set and seed set were higher in the white morph which also showed higher amounts of saturated fatty acids in the seeds. The results about aborted seeds differed inconsistently. Thus, variation in corolla pigmentation in J. adhatoda suggests fitness trade-off between the morphs with higher fruit and seed set, but lower seed germination and seed weight in the white morph compared to the purple-veined. We are led to the possibility of different selective pressures acting on the morphs and resulting in adaptive polymorphism.