Gutiérrez-Valencia Juanita, Chomicki Guillaume, Renner Susanne S
Systematic Botany and Mycology, University of Munich (LMU), Menzinger Str. 67, 80638 Munich, Germany.
Systematic Botany and Mycology, University of Munich (LMU), Menzinger Str. 67, 80638 Munich, Germany.
Mol Phylogenet Evol. 2017 Jun;111:196-205. doi: 10.1016/j.ympev.2017.04.009. Epub 2017 Apr 10.
Mutualisms could be evolutionarily unstable, with changes in partner abundances or in the spatial context of interactions potentially promoting their dissolution. We test this prediction using the defense mutualisms between species of the Neotropical genus Cecropia and Azteca ants. A new, multigene phylogeny with representatives of all five genera of Cecropieae (most of them from the Neotropics) and half of the 61 species of Cecropia shows the West African endemic Musanga (2spp.) as sister to Cecropia, implying dispersal from the Neotropics to Africa, with a molecular clock suggesting that this occurred about 23Mya. Cecropia, a genus of neotropical pioneer trees, started diversifying ca. 8Mya. We infer a single origin of specialized symbiosis with Azteca within Cecropia, eight complete losses of this symbiosis, and a potential partner shift involving the replacement of Azteca by Neoponera luteola ants. Niche space modeling based on geo-referenced occurrences of over 9000 collections representing 58 of the 61 species of Cecropia, together with several comparative analyses, implies that mutualism loss is concentrated at high altitudes and on Caribbean islands, with the surprisingly frequent breakdowns potentially facilitated by low species-specificity of interacting Cecropia and Azteca mutualists.
互利共生在进化上可能是不稳定的，伙伴数量的变化或相互作用的空间背景的变化可能会促使其瓦解。我们利用新热带界的蚁栖树属物种与阿兹特克蚁之间的防御互利共生关系来检验这一预测。一个新的多基因系统发育树，包含了蚁栖树科所有五个属的代表（其中大多数来自新热带界）以及61种蚁栖树中的一半，结果显示西非特有的非洲桐属（2个物种）是蚁栖树属的姐妹群，这意味着从新热带界扩散到了非洲，分子钟表明这一事件发生在大约2300万年前。蚁栖树属是新热带界的先锋树种，大约在800万年前开始多样化。我们推断在蚁栖树属中与阿兹特克蚁的特化共生关系有一个单一的起源，这种共生关系完全丧失了八次，并且存在一个潜在的伙伴转变，涉及到黄新庞蚁取代了阿兹特克蚁。基于代表61种蚁栖树中58种的9000多个地理参考标本的生态位空间建模，以及几项比较分析表明，互利共生关系的丧失集中在高海拔地区和加勒比岛屿，相互作用的蚁栖树和阿兹特克蚁共生者的物种特异性较低可能意外地促进了这种频繁的共生关系破裂。
