Data from: A rare exception to Haldane’s rule: Are X chromosomes key to hybrid incompatibilities?

The prevalence of Haldane’s rule suggests that sex chromosomes commonly have a key role in reproductive barriers and speciation. However, the majority of research on Haldane’s rule has been conducted in species with conventional sex determination systems (XY and ZW) and exceptions to the rule have been understudied. Here we test the role of X-linked incompatibilities in a rare exception to Haldane’s rule for female sterility in field cricket sister species (Teleogryllus oceanicus and T. commodus). Both have an XO sex determination system. Using three generations of crosses, we introgressed X chromosomes from each species onto different, mixed genomic backgrounds to test predictions about the fertility and viability of each cross type. We predicted that females with two different species X chromosomes would suffer reduced fertility and viability compared with females with two parental X chromosomes. However, we found no strong support for such X-linked incompatibilities. Our results preclude X–X incompatibilities and instead support an interchromosomal epistatic basis to hybrid female sterility. We discuss the broader implications of these findings, principally whether deviations from Haldane’s rule might be more prevalent in species without dimorphic sex chromosomes.

霍尔丹法则（Haldane’s rule）的普遍存在表明，性染色体通常在生殖隔离与物种形成过程中发挥关键作用。然而，目前针对该法则的研究大多集中在具有常规性别决定系统（XY型与ZW型）的物种上，而霍尔丹法则的例外情况尚未得到充分研究。本研究以蟋蟀近缘种——海洋蟋蟀（Teleogryllus oceanicus）和普通蟋蟀（T. commodus）——为研究对象，针对其雌性不育这一霍尔丹法则罕见例外的情形，检验X连锁不相容性（X-linked incompatibilities）的作用。两个物种均采用XO型性别决定系统。我们通过三代杂交实验，将来自各物种的X染色体渐渗导入至不同的混合基因组背景中，以验证各类杂交组合的育性与存活能力相关预测。我们曾预测，携带两条不同物种X染色体的雌性个体，其育性与存活能力相较于仅携带亲本物种X染色体的雌性个体会出现下降。但本研究并未发现此类X连锁不相容性的有力证据。研究结果排除了X-X不相容性的可能，转而支持杂交雌性不育的染色体间上位性遗传基础。我们还讨论了本研究发现的更广泛的研究意义，主要围绕无异形性染色体物种中霍尔丹法则偏离现象是否会更为普遍这一问题展开。