Divergence in floral morphology and pollinator interactions in two sympatric Australian pea plants

Abstract

The diversification of flowering plants is often attributed to plant-pollinator interactions. Plants often evolve combinations of traits (collectively termed ‘pollinator syndromes’) which attract and utilise specific groups of insects. Oxylobium ellipticum (Vent, R.Br) and Hovea montana (Hook.f.) J.H.Ross are two Australian pea plants found in sympatry in Kosciuszko National Park. These plants differ in floral colour, but exhibit what appear to be identical mechanisms for accepting and depositing pollen from/to a pollinator. Through the analysis of floral morphology and pollinator activity it was found that these species have diverged in floral traits further than previously thought. Oxylobium ellipticum has larger keel petals resulting in a requirement for greater force to open flowers and the pressure point is found further from the base of the flower. These differences may be the result of reproductive competition leading to differential pollinator filtering systems or potentially divergent exploitation of the same pollinators.