Data from: Relationships between spatio-temporal environmental and genetic variation reveal an important influence of exogenous selection in a pupfish hybrid zone

The importance of exogenous selection in a natural hybrid zone between the pupfishes Cyprinodon atrorus and C. bifasciatus was tested via spatio-temporal analyses of environmental and genetic change over winter, spring, and summer for three consecutive years. A critical influence of exogenous selection on hybrid zone regulation was demonstrated by a significant relationship between environmental (salinity and temperature) and genetic (three diagnostic nuDNA loci) variation over space and time (seasons) in the Rio Churince system, Cuatro Ciénegas, Mexico. At sites environmentally more similar to parental habitats, the genetic composition of hybrids was stable and similar to the resident parental species, whereas complex admixtures of parental and hybrid genotypic classes characterized intermediate environments, as did the greatest change in allelic and genotypic frequencies across seasons. Within hybrids across the entire Rio Churince system, seasonal changes in allelic and genotypic frequencies were consistent with results from previous reciprocal transplant experiments, which showed C. bifasciatus to suffer high mortality (75%) when exposed to the habitat of C. atrorus in winter (extreme temperature lows and variability) and summer (abrupt salinity change and extreme temperature lows and variability). Though unconfirmed, the distributional limits of C. atrorus and C. atrorus-like hybrids appear to be governed by similar constraints (predation or competition). A crucial link was also established between contemporary exogenous selection in a hybrid zone between these species and previous demonstration of long-term evolutionary significance of environmental variation and introgression on the phenotypic diversification Cuatro Ciénegas Cyprinodon.

针对墨西哥夸特罗谢内加斯（Cuatro Ciénegas）地区奇林塞河（Rio Churince）水系中鲤齿鳉（pupfishes）属的黑纹鲤齿鳉（Cyprinodon atrorus）与双带鲤齿鳉（C. bifasciatus）之间的自然杂交带，本研究通过连续三年冬、春、夏三季的环境与遗传变化时空分析，验证了外源性选择（exogenous selection）的重要性。研究证实外源性选择对杂交带调控具有关键影响：该水系内环境因子（盐度与温度）与遗传变异（3个诊断性核DNA（nuDNA）位点）在空间和季节维度上存在显著关联。在与亲本栖息地环境更为相似的位点，杂交种群的遗传组成保持稳定，且与定居的亲本物种一致；而在中等环境条件的位点，则呈现出亲本与杂交基因型类别的复杂混合，同时该区域的等位基因频率与基因型频率在各季节间的变化幅度也最大。针对奇林塞河全水系的杂交种群而言，其等位基因与基因型频率的季节变化模式，与此前互易移植实验（reciprocal transplant experiments）的结果相符：该实验显示，当双带鲤齿鳉暴露于黑纹鲤齿鳉的栖息地时，在冬季（极端低温与温度波动）和夏季（盐度骤变与极端低温及温度波动）环境下的死亡率高达75%。尽管尚未得到证实，但黑纹鲤齿鳉及其黑纹鲤齿鳉型杂交个体的分布边界似乎受到类似约束（捕食或竞争作用）。本研究还建立了该物种间杂交带的当代外源性选择，与此前证实的环境变异与基因渐渗（introgression）对夸特罗谢内加斯鲤齿鳉表型分化的长期演化意义之间的关键关联。