Erratum: Revisiting the Dioecy-Polyploidy Association: Alternate Pathways and Research Opportunities

The evolutionary transition from hermaphroditism (combined sexes) to dioecy (separate sexes) is associated with whole genome duplication (polyploidy) in several flowering plant genera. Moreover, there is evidence for transitions in the opposite direction, i.e. a loss of dioecy with an increase in ploidy. Here, we review evidence for these associations, synthesize previous ideas on the mechanism underlying the patterns and explore alternative pathways. Specifically, we examine potential ecological and genetic mechanisms, differentiated by whether ploidy or gender (functional sex expression of the plant) changes are the primary cause and whether the effect is direct or indirect. An analysis of 22 genera variable for both ploidy and gender indicates that gender monomorphism (hermaphroditism, monoecy) is more common among diploid than polyploid species, whereas gender dimorphism (dioecy, gynodioecy, subdioecy) is more frequent among polyploid species. The transition from diploid hermaphroditic to polyploid gender-dimorphic taxa may arise directly through changes in gender as a result of genome duplication through genomic rearrangements or homeologous recombination, or changes in gender may result in increased unreduced gamete production leading to polyploid formation. Alternatively, the transition may occur through the indirect effects of genome duplication on mating system and inbreeding depression, which favor selection for unisexuality, or habitat shifts associated with unisexuality may simultaneously cause increased unreduced gamete production. Novel mechanisms for transitions in the opposite direction (from dioecy to hermaphroditism with increase in ploidy) include disruption of genetic sex determination and the benefits of reproductive assurance. We highlight key questions requiring further attention and promising approaches for answering them and better clarifying the genesis of sexual system polyploidy associations. See also the sister article focusing on animals by Wertheim et al. in this themed issue.在多个开花植物属中，从雌雄同体（hermaphroditism，兼具雌雄两性）到雌雄异株（dioecy，雌雄两性分离）的演化过渡，与全基因组复制（whole genome duplication，即多倍体化polyploidy）存在显著关联。此外，亦存在反向演化过渡的相关证据，即随着倍性升高，雌雄异株性状发生丢失的现象。 本文首先综述了上述两类关联的相关证据，整合了此前针对该模式背后机制的相关假说，并探讨了其他可能的演化路径。 具体而言，本文将从倍性改变或植物功能性别表达改变何者为核心诱因、效应为直接还是间接两个维度，剖析潜在的生态学与遗传学机制。 通过对22个兼具倍性与性别变异的开花植物属开展分析，结果显示：性别单态（雌雄同体（hermaphroditism）、雄花两性花同株（monoecy））在二倍体物种中的占比高于多倍体物种；而性别二态（雌雄异株（dioecy）、雌全异株（gynodioecy）、亚雌雄异株（subdioecy））在多倍体物种中更为常见。 从二倍体雌雄同体类群向多倍体性别二态类群的过渡，可通过两种直接路径实现：一是基因组复制通过基因组重排或部分同源重组（homeologous recombination）改变植物性别；二是性别改变引发不减数配子（unreduced gamete）产生量提升，进而促成多倍体形成。 此外，该过渡也可通过间接路径实现：一是基因组复制对交配系统与近交衰退（inbreeding depression）产生间接影响，进而推动单性性状的定向选择；二是与单性性状相关的生境转变，可同步提升不减数配子的产生量。 针对反向过渡（即倍性升高时从雌雄异株向雌雄同体转变）的新型机制，包括遗传性别决定（genetic sex determination）通路的破坏，以及繁殖保障（reproductive assurance）带来的演化优势。 本文还梳理了亟待进一步研究的关键科学问题，以及可用于解答这些问题、并进一步阐明性别系统与多倍体化关联起源的可行研究路径。另可参阅本期专题中Wertheim等人针对动物类群的姊妹综述文章。