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 play 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 to 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中发挥关键作用。不过，当前针对霍尔丹法则的研究大多聚焦于具备常规性别决定系统（XY型与ZW型）的物种，该法则的例外情形尚未得到充分探讨。本研究以两种田野蟋蟀姊妹种——海洋蟋蟀（Teleogryllus oceanicus）与普通蟋蟀（T. commodus）——中霍尔丹法则关于雌性不育的罕见例外情形为研究对象，检验X连锁不相容性所扮演的角色。二者均采用XO型性别决定系统。研究通过三代杂交实验，将每个物种的X染色体渐渗至不同的混合基因组背景中，以此验证各类杂交组合的育性与存活能力相关预测。我们曾提出假设：相较于携带两条亲本X染色体的雌性个体，携带两条不同物种X染色体的雌性个体，其育性与存活能力会出现下降。然而，本研究未发现此类X连锁不相容性的有力证据。研究结果排除了X-X不相容性的可能性，转而支持杂交雌性不育的染色体间上位性基础。最后，我们讨论了本研究发现的广泛意义，重点探讨了在不具有二态性性染色体的物种中，偏离霍尔丹法则的情形是否会更为普遍。