Variation in sex organ dimensions across individuals morphs and species consequences for reciprocity herkogamy and reproductive success in species with style length polymorphism

Abstract

Style length polymorphism is a floral polymorphism characterised by the presence of two or three floral morphs in a population which differ in style length The positioning of anther and stigma within and between flowers of these morphs is one of the important drivers of inter morph pollen transfer and helps in avoiding self pollination Despite this general patterns of relative sex organ positions in these species are not understood Moreover the extent of intra population variation in sex organ positions which is known to reduce inter morph pollen transfer is not understood completely To understand the relative sex organ position and intra population variation in sex organ dimensions in naturally occurring populations I quantified a herkogamy the separation between anthers and stigmas within a flower which reduces self pollination and b reciprocity the match in height of complementary anthers and stigma between morphs which promotes inter morph pollination from data extracted that included 296 species from 25 families I also examined the relationship between herkogamy and reciprocity the fundamental features of species with style length polymorphism I found that the morphs differ significantly in herkogamy and a large range of intra population variation is present in sex organ dimensions in these species Both positive and negative relationships were observed between herkogamy and reciprocity This relationship has not been reported before and implies a trade off between avoidance of illegitimate self pollen deposition and legitimate inter morph pollen deposition This trade off is important for understanding the evolution of style length polymorphisms in the context of pollen limitation reproductive assurance inbreeding depression and self incompatibility To better understand the effect of intra population variation on reciprocity and consequently pollen transfer in these species I developed an index to quantify reciprocity which appropriately incorporates intra population variation in sex orga newline newline