Journal Article

Inflorescence architecture affects pollinator behaviour and mating success in Spiranthes sinensis (Orchidaceae)

Tatsunori Iwata, Atushi Ushimaru, Hiroshi S. Ishii, Osamu Nagasaki

2012

Overview

Despite the wide inflorescence diversity among angiosperms, the effects of inflorescence architecture (three-dimensional flower arrangement) on pollinator behaviour and mating success have not been sufficiently studied in natural plant populations. Here, we investigated how inflorescence architecture affected inter- and intra-plant pollinator movements and consequent mating success in a field population of Spiranthes sinensis var. amoena (S. sinensis). In this species, the flowers are helically arranged around the stem, and the degree of twisting varies greatly among individuals. The large variation in inflorescence architecture in S. sinensis results from variation in a single structural parameter, the helical angle (the angular distance between neighbour-flower directions). The numbers of visits per inflorescence and successive probes per visit by leaf-cutting bees decreased with helical angle, indicating that individual flowers of tightly twisted inflorescences received less visitations. As expected from pollinator behaviour, pollinia removal and fruit set of individual flowers decreased with helical angle. Meanwhile, geitonogamy decreased in tightly twisted inflorescences. Our novel findings demonstrate that natural variation in inflorescence architecture significantly affects pollinator behaviour and reproductive success, suggesting that inflorescence architecture can evolve under pollinator-mediated natural selection in plant populations. We also discuss how diverse inflorescence architectures may have been maintained in S. sinensis populations.

• Publisher: New Phytologist Trust,Blackwell Publishing Ltd,Wiley Subscription Services, Inc
• Subject: anatomy & histology / Angiosperms / Animal reproduction / Animals / Apoidea / Architecture / Bees / Bees - physiology / Breeding success / Flowers / Flowers & plants / Fruit / Fruit - growth & development / fruit production / Fruit set / growth & development / Helical flow / Inflorescence / Inflorescence - anatomy & histology / Inflorescence - physiology / inflorescence architecture / Inflorescences / Insect pollination / Japan / Mating / Mating behavior / Models, Biological / Natural selection / orchid / Orchidaceae / Orchidaceae - anatomy & histology / Orchidaceae - growth & development / Orchidaceae - physiology / physiology / Plant population / Plant populations / Plants / Pollen / Pollen - physiology / Pollinating insects / Pollination / Pollination - physiology / pollinator attraction / Pollinators / Pollinia / pollinia removal / Populations / Reproduction / Reproduction - physiology / Reproductive behavior / Reproductive behaviour / Reproductive success / Sexual Behavior, Animal / Sexual Behavior, Animal - physiology / Spiranthes / stems / Success / successive probes / Variation