Herbarium, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, China; Guangdong Ocean University, Zhanjiang 524088, China.
Herbarium, South China Botanical Garden, Chinese Academy of Sciences, Guangzhou 510650, China; State Academy of Forestry Administration, Beijing 102600, China.
Mol Phylogenet Evol. 2018 Jun;123:113-122. doi: 10.1016/j.ympev.2018.02.015. Epub 2018 Feb 15.
Dioecy is a rare sexual system that is thought to represent an "evolutionary dead end". While many studies have addressed the evolution of dioecy and/or its relationship with the evolution of the woody habit, few have explored the relationship between dioecy and climbing habit, and their effects on diversification rates. Here, we study the evolution of sexual systems and growth habit in Mussaenda (Rubiaceae) using a robust phylogeny of the genus based on eight plastid regions and a broad sampling of taxa (92 of the 132 species were sampled). A time-calibrated tree was constructed to estimate diversification rates in different clades and its correlates with focal characters. More specifically, we assess evolutionary correlations between dioecy and climbing habit and their respective influences on diversification rates. Ancestral character state reconstructions revealed that distyly is the most likely ancestral state in Mussaenda. Distyly has subsequently given rise to dioecy, short-styled floral monomorphism, and long-styled floral monomorphism. Dioecy has evolved independently at least four times from distyly, and has reversed to homostylous hermaphroditism at least twice, which does not support the "evolutionary dead end" hypothesis. A significant correlation between the evolution of dioecy and climbing growth form was found in Mussaenda. It is possible that a strong association between high net diversification rates and dioecy may exist in Mussaenda, but no association was found with climbing habit.
雌雄异株是一种罕见的性系统，被认为代表了“进化的死胡同”。虽然许多研究已经探讨了雌雄异株的进化及其与木本习性的关系，但很少有研究探索雌雄异株和攀援习性之间的关系，以及它们对多样化率的影响。在这里，我们使用基于八个质体区域和广泛的分类群采样（92 种中的 132 种被采样）的属的稳健系统发育来研究 Musaenda（茜草科）中的性系统和生长习性的进化。构建了一个时间校准的树来估计不同分支中的多样化率及其与焦点特征的相关性。更具体地说，我们评估了雌雄异株和攀援习性之间的进化相关性及其对多样化率的各自影响。祖先特征状态重建表明，二型性是 Musaenda 中最可能的祖先状态。二型性随后导致雌雄异株、短花柱花同形和长花柱花同形。雌雄异株至少从二型性独立进化了四次，并且至少有两次逆转为同型雌雄同体，这并不支持“进化的死胡同”假说。在 Musaenda 中发现了雌雄异株和攀援生长形式的进化之间存在显著的相关性。在 Musaenda 中，高净多样化率与雌雄异株之间可能存在很强的关联，但与攀援习性没有关联。
