Department of Biology, University of Massachusetts, Boston, MA, USA.
Ashoka Trust for Research in Ecology and the Environment, Bangalore, India.
Ann Bot. 2019 Jan 1;123(1):181-190. doi: 10.1093/aob/mcy154.
Kin selection theory predicts that a parent may minimize deleterious effects of competition among seeds developing within ovaries by increasing the genetic relatedness of seeds within an ovary. Alternatively, the number of developing seeds could be reduced to one or a few. It has also been suggested that single or few seeded fruits may be correlated with small flowers, and multi-ovulate ovaries or many seeded fruits may be associated with large flowers with specialized pollination mechanisms. We examined the correlation between flower size and seed number in 69 families of monocotyledons to assess if correlations are significant and independent of phylogeny.
We first examined the effect of phylogenetic history on the evolution of these two traits, flower size and seed number, and then mapped correlations between them on the latest phylogenetic tree of monocotyledons.
The results provide phylogenetically robust evidence of strong correlated evolution between flower size and seed number and show that correlated evolution of traits is not constrained by phylogenetic history of taxa. Moreover, the two character combinations, small flowers and a single or few seeds per fruit, and large flowers and many seeded fruits, have persisted in monocotyledons longer than other trait combinations.
The analyses support the suggestion that most angiosperms may fall into two categories, one with large flowers and many seeded fruits and the other with small flowers and single or few seeded fruits, and kin selection within ovaries may explain the observed patterns.
亲缘选择理论预测，父母可能通过增加卵巢内种子间的遗传相关性，从而最小化种子在卵巢内竞争的有害影响。或者，可以将发育中的种子数量减少到一个或几个。也有人提出，单种子或少数种子的果实可能与小花有关，而多胚珠的卵巢或多种子的果实可能与具有特殊传粉机制的大花朵有关。我们检查了单子叶植物 69 科中花大小与种子数量之间的相关性，以评估相关性是否与系统发育无关且具有统计学意义。
我们首先检验了系统发育历史对这两个特征（花大小和种子数量）的进化的影响，然后在单子叶植物的最新系统发育树上绘制了它们之间的相关性。
结果提供了强有力的系统发育证据，证明花大小和种子数量之间存在强烈的相关进化，并表明特征的相关进化不受分类群的系统发育历史的限制。此外，小花和每果实一个或少数种子，以及大花和多种子果实这两种特征组合，在单子叶植物中比其他特征组合更持久。
分析结果支持这样一种观点，即大多数被子植物可能分为两类，一类是大花和多种子果实，另一类是小花和单种子或少数种子果实，而卵巢内的亲缘选择可能解释了观察到的模式。
