No Effect of Selective Maturation on Fruit Traits for a Bird-Dispersed Species, Sambucus racemosa.

Kohei Koyama,Mayu Tashiro

doi:10.3390/plants10020376

Kohei Koyama, Mayu Tashiro

Open Access

https://doi.org/10.3390/plants10020376

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Abstract

Selective abortion, also called selective maturation, is a phenomenon wherein maternal plants selectively mature ovules that have the potential to grow into higher-quality fruits, such as those that contain more seeds. We hypothesized that the effects of selective maturation on fruit traits could be influenced by the dispersal mechanism. However, to date, limited studies have been conducted on selective maturation in bird-dispersed fruits. Unlike self- or wind-dispersed species, bird-dispersed species would not selectively mature fruits that contain more seeds because they are not preferred by birds. Here, we investigated the effect of selective abortion on the fruit traits of a bird-dispersed species, elderberry (Sambucus racemosa L. subsp. kamtschatica). We performed a flower-removal experiment. Half of the inflorescences on each individual tree were removed for the treatment group, whereas the control group was not manipulated. We found that the flower-removed trees showed higher fruit sets, suggesting the existence of resource limitation. The number of seeds per fruit did not increase by the experimental treatment. Additionally, the control individuals did not produce larger fruits. The lack of effects on fruit traits supported our hypothesis that the effect of selective maturation on fruit traits may differ among species with different dispersal mechanisms.

Highlights

IntroductionSelective abortion is a phenomenon wherein maternal plants selectively abort lowerquality ovules or immature fruits before fruit maturation to mature only those fruits or seeds that are of a higher quality [1,2,3,4,5,6,7] and thereby save resources [3], though resource limitation is not the sole factor that controls abortion in plants [7,8,9,10,11,12,13,14,15]
This hypothesis states that maternal plants that do not undergo hand-thinning have a wider choice of high-quality zygotes or embryos for selective maturation than plants that have experienced the artificial random removal of flowers [18,31,32]
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Summary

Introduction

Selective abortion is a phenomenon wherein maternal plants selectively abort lowerquality ovules or immature fruits before fruit maturation to mature only those fruits or seeds that are of a higher quality [1,2,3,4,5,6,7] and thereby save resources [3], though resource limitation is not the sole factor that controls abortion in plants [7,8,9,10,11,12,13,14,15]. The existence of selective maturation has been confirmed via hand-thinning experiments (i.e., random removal of flowers, ovules, or immature fruits [18,30]), which are based on the wider-choice hypothesis. This hypothesis states that maternal plants that do not undergo hand-thinning have a wider choice of high-quality zygotes or embryos for selective maturation than plants that have experienced the artificial random removal of flowers [18,31,32]. The widerchoice hypothesis predicts that fruits that escape self-thinning (i.e., spontaneous thinning by maternal plants [18,30]) are of higher quality than those escaped artificial random thinning [18]

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