The Incidence and Implications of Mate Diversity in Seed Plants
Date
2019-09-04
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Abstract
Multiple mating in outcrossing plant species is common. For seed plants, reliance on pollen vectors and mixed pollination resulting from pollen carryover among flowers and visits by multiple vectors to individual flowers generates inevitable polygamy and diverse paternity. Mate diversity can provide direct quantitative benefits when reproduction is limited by mating opportunities and indirect qualitative benefits associated with sampling alternative mates and offspring and spreading the risk of poor mates, offspring and offspring environments. Nevertheless, whether mate diversity is simply an emergent property of cross-pollination or an independent beneficial feature of plant mating systems subject to selection remains unclear. To investigate the influences on and consequences of a maternal plant’s male mate diversity among and within flowers I conducted a meta-analysis of 108 seed plant species and a field experiment with Alstroemeria aurea, an Argentine flowering plant. Analysis of variation in effective mate number, Ep, a Hill number, identified various morphological and ecological influences on maternal mate diversity, with associations differing for among- and within-fruit mate diversity. Most species exhibited a mean Ep of fewer than 10 mates. Larger bodies, abiotic pollination and separation of sex functions greatly increased Ep. Trait correlates of mate diversity were largely consistent with overall promotion of outcrossing but not phylogenetic relatedness. The meta-analysis also revealed novel implications of correlated traits for mate number and the evenness of plant mating portfolios. Specifically, separation of sexual functions within or among flowers seems to promote receipt of diverse compatible pollen. Abundant ovule number per flower increases evenness of mate contributions. Plant traits that influence mate diversity can also play a role in its optimization. Greater mate diversity is not universally advantageous, as illustrated by the field experiment with A. aurea. Effects of experimental pollination with 1, 2 or 4 mates applied separately among or together within flowers identified costs of progamic and offspring bias for fruit and seed production. These quantitative costs can offset the largely qualitative benefits of multiple mating. Thus, mate diversity in plants may often be optimized to maximize the benefit:cost ratio, depending on local conditions of the mating environment. Whether paternal mate diversity is subject to similar optimization remains to be assessed.
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Plant mating, Mate diversity, Pollination, Plant reproduction, Plant evolutionary ecology, Mating portfolios, Alstroemeria aurea, Correlated paternity, Effective mate number, Multiple mating
Citation
Regel, C. E. (2019). The Incidence and Implications of Mate Diversity in Seed Plants (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.