Reports of sexual lability in the 22 species with well-described sex chromosomes. from Labile sex expression in angiosperm species with sex chromosomes

Here, we review the literature on sexual lability in dioecious angiosperm species with well-studied sex chromosomes. We distinguish three types of departures from strict dioecy, concerning either a minority of flowers in some individuals (leakiness) or the entire individual, which can constantly be bisexual or change sex. We found that for only four of the 22 species studied, reports of lability are lacking. The occurrence of lability is only weakly related to sex chromosome characteristics (number of sex-linked genes, age of the non-recombining region). These results contradict the naive idea that lability is an indication of the absence or the recent evolution of sex chromosomes, and thereby contribute to a growing consensus that sex chromosomes do not necessarily fix sex determination once and for all. We discuss some implications of these findings for the evolution of sex chromosomes, and suggest that more species with well-characterized lability should be studied with genomic data and tools.This article is part of the theme issue ‘Sex determination, sex chromosome evolution, and the role of sexual differentiation in land plants’.

本综述针对已被深入研究性染色体的雌雄异株被子植物（dioecious angiosperm）的性别可塑性（sexual lability）相关文献展开系统梳理。我们将其划分为三类偏离严格雌雄异株的情形：其一仅涉及部分个体上的少数花朵（即渗漏现象（leakiness））；其二关乎整个植株——这类植株可始终保持两性特征，或发生性别转换。经统计，在所研究的22个物种中，仅4个物种未出现性别可塑性相关报道。性别可塑性的出现仅与性染色体特征（性连锁基因数量、非重组区域的演化年龄）呈弱相关。上述结果与“性别可塑性是性染色体缺失或新近演化的标志”这一直觉性观点相悖，同时进一步佐证了日益形成的学术共识：性染色体并非一经演化形成便会永久固定性别决定机制。我们探讨了本研究结果对于性染色体演化的若干启示，并提出应借助基因组学数据与研究工具，对更多具有明确性别可塑性特征的物种展开深入探究。本文隶属于“陆地植物的性别决定、性染色体演化及性别分化作用”专题栏目（theme issue）。