Abstract
Mate choice in plants is poorly understood, in particular its indirect genetic benefits, but also the direct benefits of avoiding harmful matings. In the herb Collinsia heterophylla, delayed stigma receptivity has been suggested to enhance pollen competition, potentially functioning as a female mate choice trait. Previous studies show that this trait can mitigate the cost of early fertilization caused by pollen, thus providing a direct benefit. We performed two‐donor pollinations during successive floral stages to assess how this stigma receptivity trait and two pollen traits known to affect siring success influence indirect benefits in terms of offspring performance. We also investigated differential resource allocation by studying the influence of sibling performance in the same capsule. Offspring performance in terms of flower number was mainly affected by parental identities and differential resource allocation. Offspring seed production showed some influence of resource allocation, but was also affected by pollen donor identity and varied positively with late stigma receptivity. However, the effect of late stigma receptivity on offspring seed production was weakened in matings with pollen that advanced stigma receptivity. In conclusion, delayed stigma receptivity may be selected through both direct and indirect fitness effects in C. heterophylla, where pollen‐based delay on stigma receptivity might act as a cue for mate choice. However, selection may also be counteracted by antagonistic selection on pollen to advance stigma receptivity. Our results highlight the challenges of studying indirect genetic benefits and other factors that influence mate choice in plants.
Highlights
Mate choice, a process that generates nonrandom variation in partner mating success, is common in many species and a central tenet of sexual selection (Andersson, 1994; Darwin, 1871; Hosken & House, 2011)
There is an opportunity for female mate choice if pistil traits favour some pollen over others by enhancing pollen competition (Wilson & Burley, 1983; e.g. long style, Ramesha et al, 2011; large stigmatic area, Armbruster, 1996; and delayed stigma receptivity, Galen, Schykoff, & Plowright, 1986) or by chemical signalling in the stigma and style (Bhattacharya & Baldwin, 2012)
Previous studies have found a positive link between enhanced pollen competition and high offspring fitness (e.g. Mulcahy, 1971; Quesada et al, 2001), we know little about the underlying mechanisms, regarding the influence of sexual selection
Summary
A process that generates nonrandom variation in partner mating success, is common in many species and a central tenet of sexual selection (Andersson, 1994; Darwin, 1871; Hosken & House, 2011). Enhanced pollen competition induced by females can improve mean offspring quality (Labouche, Richards, & Pannell, 2017; Marshall & Whittaker, 1989; Mulcahy, 1971; Quesada, Fuchs, & Lobo, 2001; Skogsmyr & Lankinen, 2000) It remains unclear whether superior offspring results from mate choice for indirect genetic benefits or from other possible indirect genetic benefits of sorting among pollen, for example increased mate compatibility or paternal diversity (Bernasconi et al, 2004; Lyons, Ware, Price, Antonovis, & Motten, 1989; Moore & Pannell, 2011; Pélabon, Albertsen, Falahati-Anbaran, Wright, & Armbruster, 2015; Skogsmyr & Lankinen, 2002) or avoidance of pistil contact or fertilization by pollen that causes female reproductive costs, that is sexual conflict We explored effects of resource allocation on offspring performance
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