Herkogamy but not reciprocity is a better predictor of legitimate pollen transfer and fruit set in Jasminum malabaricum, a self-compatible species with stigma-height dimorphism.

Abstract

Premise Reciprocity and herkogamy, morphological traits that define style length polymorphisms, are thought to be critical in determining legitimate inter-morph pollen transfer in plants with style length polymorphism. However, the consequences of individual-level variation in these traits for pollen transfer and reproductive success have rarely been examined, and the relationship between these two fundamental traits remains unexplored.Methods We quantified individual-level estimates of herkogamy and reciprocity and tested the assumption that higher herkogamy and reciprocity result in higher legitimate pollen transfer and reproductive success in natural populations of Jasminum malabaricum, a species that exhibits stigma-height dimorphism. Additionally, we examined the relationship between herkogamy and reciprocity to understand potential consequences for avoiding self-pollination and encouraging legitimate pollen deposition.Results Surprisingly, reciprocity was not related to pollen load, legitimate pollen fraction or reproductive success. In contrast, herkogamy was positively associated with legitimate pollen fraction and fruit set in the long-styled morph. Interestingly, we observed a negative relationship between herkogamy and reciprocity in the long-styled morph.Conclusions Herkogamy was more important than reciprocity in increasing legitimate pollen transfer and reproductive success in J. malabaricum. Herkogamy might be particularly important in stabilising species with stigma-height dimorphism and other such polymorphic intermediates with low reciprocity, and this may allow the evolution of reciprocal arrangement of sex organs at a later stage in the pathway towards distyly. The negative relationship between herkogamy and reciprocity suggests a trade-off between avoidance of self-pollen deposition and promotion of legitimate pollen deposition.Competing Interest StatementThe authors have declared no competing interest.View Full Text