Data from: MHC-similarity and sexual selection: different doesn't always mean attractive

dataset: Please see paper for details on data collection, experimental design and data analysis.

aligned sequences: MHC aligned sequences.

MHC: Raw data (1st sheet) and band sharing-similarity (2nd sheet).

Microsatellites data: raw data (1st sheet) and genalex summary-similarity (2nd sheet).

Females that mate multiply have the possibility to exert postcopulatory choice and select more compatible sperm to fertilize eggs. Prior work suggests that dissimilarity in major histocompatibility complex (MHC) plays an important role in determining genetic compatibility between partners. Favouring a partner with dissimilar MHC alleles would result in offspring with high MHC diversity and therefore with enhanced survival thanks to increased resistance to pathogens and parasites. The high variability of MHC genes may further allow discrimination against the sperm from related males, reducing offspring homozygosity and inbreeding risk. Despite the large body of work conducted at precopulatory level, the role of MHC similarity between partners at postcopulatory level has been rarely investigated. We used an internal fertilizing fish with high level of multiple matings (Poecilia reticulata) to study whether MHC similarity plays a role in determining the outcome of fertilization when sperm from two males compete for the same set of eggs. We also controlled for genomewide similarity by determining similarity at 10 microsatellite loci. Contrary to prediction, we found that the more MHC-similar male sired more offspring while similarity at the microsatellite loci did not predict the outcome of sperm competition. Our results suggest that MHC discrimination may be involved in avoidance of hybridization or outbreeding rather than inbreeding avoidance. This, coupled with similar findings in salmon, suggests that the preference for MHC-dissimilar mates is far from being unanimous and that pre- and postcopulatory episodes of sexual selection can indeed act in opposite directions.

数据集：有关数据采集、实验设计与数据分析的详细内容，请参阅相关论文。
比对序列：主要组织相容性复合体（major histocompatibility complex, MHC）比对序列。
MHC相关数据：原始数据（第1工作表）及条带共享相似性（band sharing-similarity，第2工作表）。
微卫星（microsatellite）数据：原始数据（第1工作表）及GenALex相似性汇总结果（第2工作表）。

雌性多次交配时，可实施交配后选择（postcopulatory choice），筛选相容性更佳的精子以完成卵子受精。既往研究表明，主要组织相容性复合体（MHC）的基因差异在决定伴侣间遗传相容性方面发挥关键作用。选择MHC等位基因差异较大的伴侣，可使后代获得更高的MHC多样性，进而通过增强对病原体与寄生虫的抵抗力提升生存能力。MHC基因的高度多态性还可帮助雌性区分亲缘雄性的精子，降低后代的纯合性与近交风险。尽管学界已在交配前选择层面（precopulatory level）开展了大量研究，但针对伴侣间MHC相似性在交配后过程中的作用，相关探讨仍较为匮乏。
本研究以一种普遍存在多次交配行为的体内受精鱼类——孔雀鱼（Poecilia reticulata）为研究对象，探究当两份雄性精子竞争同一组卵子时，MHC相似性是否会影响受精结果。同时，我们通过检测10个微卫星位点的基因组相似性，对全基因组相似性进行了控制。
研究结果与预期相悖：MHC相似性更高的雄性成功繁育了更多后代，而微卫星位点的相似性则无法预测精子竞争（sperm competition）的结果。本研究结果提示，MHC识别机制或更多用于避免杂交或远交，而非规避近交。这一发现与鲑鱼中的同类研究结果相呼应，表明对MHC差异伴侣的偏好并非普遍存在，且性选择的交配前（precopulatory）与交配后（postcopulatory）环节可能确实会朝着相反方向发挥作用。