Sexual selection in plants: the process, components and significance

Abstract

Darwin (1859) proposed the theory of sexual selection to explain the evolution of sexually dimorphic characters in animals. He observed that in animals the bulk of the reproductive investments in to the offspring are made by females. This, he suggested results in (a) female choice-where females choose the best fit males and, (b) male competition-where males compete among themselves to mate with the females. In the late 1980s a few laboratories including ours have attempted to extend the theory of sexual selection to plants. These attempts have shown that though plants 'neither sing nor dance', they do exhibit female choice and male competition as intensely as animals do. In this paper we review the conceptual developments in the area of sexual selection in plants with an emphasis on the work carried out at our laboratory over the last two decades. These studies have shown that a number of plant reproductive features, such as the pollen-ovule ratios, floral sex ratio, evolution of polyads etc., that hitherto have been treated as "sterile" botanical issues may indeed have evolved as a consequence of intense sexual selection in plants.