Patterns of Hybrid Seed Inviability in the Mimulus guttatus sp. Complex Reveal a Potential Role of Parental Conflict in Reproductive Isolation

First author: Jenn M. Coughlan; Affiliations: Duke University (杜克大学): Durham, USA

Corresponding author: Jenn M. Coughlan

Genomic conflicts may play a central role in the evolution of reproductive barriers. Theory predicts that early-onset hybrid inviability may stem from conflict between parents for resource allocation to offspring. Here, we describe M. decorus: a group of cryptic species within the M. guttatus species complex that are largely reproductively isolated by hybrid seed inviability (HSI). HSI between M. guttatus and M. decorus is common and strong, but populations of M. decorus vary in the magnitude and directionality of HSI with M. guttatus. Patterns of HSI between M. guttatus and M. decorus, as well as within M. decorus, conform to the predictions of parental conflict: first, reciprocal F1s exhibit size differences and parent-of-origin-specific endosperm defects; second, the extent of asymmetry between reciprocal F1 seed size is correlated with asymmetry in HSI; and third, inferred differences in the extent of conflict predict the extent of HSI between populations. We also find that HSI is rapidly evolving, as populations that exhibit the most HSI are each others’ closest relative. Lastly, although all populations appear largely outcrossing, we find that the differences in the inferred strength of conflict scale positively with π, suggesting that demographic or life history factors other than transitions to self-fertilization may influence the rate of parental-conflict-driven evolution. Overall, these patterns suggest the rapid evolution of parent-of-origin-specific resource allocation alleles coincident with HSI within and between M. guttatus and M. decorus.Parental conflict may therefore be an important evolutionary driver of reproductive isolation.

基因组冲突可能在生殖障碍的演化中发挥着核心作用。理论预测显示，早发型杂交弱势可能源于父母之间在遗传给后代时的资源分配发生冲突。本文中，作者描述了猴面花Mimulus guttatus复合群体中一种隐藏的物种M. decorus，通过杂交种子弱势来形成生殖隔离。M. guttatus与M. decorus之间的杂交种子弱势是普遍的，且强烈，但M. decorus群体与M. guttatus的杂交种子弱势在强弱和方向性上有所变异。 M. decorus与M. guttatus的杂交种子弱势的模式以及M. decorus群体内，符合亲代基因组冲突的预测：首先，正反交F1表现出大小差异和起源亲本特定的胚乳缺陷；其次，正反交F1种子大小之间的不对称程度与杂交种子弱势中的不对称相关；第三，冲突程度的推断差异可以预测群体之间的杂交种子弱势程度。作者还发现，杂交种子弱势的演化迅速，存在最高杂交种子弱势的群体是彼此的近亲。最后，尽管所有群体都呈现出高度异交，作者发现推断的冲突强度的差异与π成正比，这表明群体特征或生活史因素，而非向自我受精的过渡，影响着由亲本基因组冲突驱动的演化速率。总体而言，这些模式表明与起源亲本特定的资源分配等位基因的快速演化与M. decorus和M. guttatus之间的杂交种子弱势相吻合。所以说，亲本的基因组冲突可能是生殖隔离演化的一个重要驱动因子。

通讯：Jenn M. Coughlan (https://jenncoughlan.weebly.com)

个人简介：2006-2010年，特伦特大学，学士；2010-2012年，多伦多大学，硕士；2012-2018年，杜克大学，博士；2018年-至今，北卡罗来纳大学教堂山分校，博士后。

研究方向：沟酸浆属植物杂交种子弱势的演化。

doi: https://doi.org/10.1016/j.cub.2019.11.023

Journal: Current Biology

Published date: December 26, 2019