Can Sexual Selection Cause Divergence in Mating System–Related Floral Traits?

Abstract

Premise of the Research. The wide diversity of floral traits seen among plants is shaped by neutral and selective evolutionary processes. In outcrossing species, sexual selection from competing pollen donors is expected to be important for shaping mating system-related traits but empirical evidence is scarce. In a previous evaluation of experimental evolution lines crossed with either one or two pollen donors (monogamous, M, or polyandrous, P, lines) at early floral stages in mixed-mating Collinsia heterophylla (Plantaginaceae), P showed enhanced pollen competitive ability and reduced maternal seed set compared to M, in accordance with sexually antagonistic evolution of pollen. Here, we asked whether the presence of sexual selection during pollen competition affect mating system-related floral traits in the same lines.Methodology. We compared flowering start, timing of anther-stigma contact (as an indication of timing of self-pollination), timing of stigma receptivity and first seed set between M and P, and with a source line, S (starting material). The former three traits are later in outcrossers than in selfers of Collinsia. The latter trait was expected to be earlier in P than in M because of sexual selection for early seed siring of pollen.

Softness of selection and mating system interact to shape trait evolution under sexual conflict

“… 2015 ) and the plant Collinsia heterophylla (Lankinen et al. 2017 ; Lankinen and Strandh 2019 ), have been widely used to study the effect of sexual selection and sexual conflict in experimental evolution studies, we need to develop theoretical predictions for these systems.…”