Sex conflict and separation: effects of herkogamy on the reproductive system of hermaphroditic plants

Spanish National Plan for R+D+i. (CGL2013-4503-P) PI: J. Arroyo. 2014 -2017.

Spatial separation between male and female organs commonly occurs in hermaphroditic flowers in angiosperms. This variation has been interpreted as a mechanism to avoid self-pollination as well as reducing the sexual interference between the male and the female function within flowers. Separation of sex organs, however, can bear high reproductive costs. This is essentially due to the lack of precision in pollination, which results in a reduction of the efficiency of pollen transfer and wastage of gametes. Natural selection has provided with several alternatives to this conflict, and these are function of the specific ecological and evolutionary context of plant species. In this project, these solutions will be studied at micro and macroevolutionary level, using different plant systems. Specifically, the following solutions will be assessed: (i) the relationship between an increase in style length and herkogamy in the evolution of angiosperms. In some groups, placing sex organs reciprocally in discrete morphs (heterostyly) solves the conflict; (ii) it will be assessed whether approach herkogamy is the ancestral condition in angiosperms, and specific analysis will be planned in Narcissus. At microevolutioary and ecological levels, the significance of the reciprocal placement between anthers and stigmas will be assessed to establish whether it favours pollen transfer between different morphs, using Narcissus and Linum species. (iii) Side monomorphic hercogamy will be also assessed as another solution to this conflict, using Centaurium in a macroevulutionary context. Finally, a test on the level of maladaptation in herkogamy will be conducted in two different and opposite frameworks: (iv) the loss of herkogamy as a mechanism to achieve reproductive assurance in species colonizing new habitats (e.g. populations of Datura stramonium) and, (v) separation of sexes in flowers and individual plants (transition from distyly to dioecy) linked to the colonization of islands and stressful environments (Erythroxylon lineages).