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.

本研究针对墨西哥夸特罗锡内加斯（Cuatro Ciénegas）盆地丘林西河（Rio Churince）系统中，黑鳍鲤齿鳉（Cyprinodon atrorus）与双带鲤齿鳉（Cyprinodon bifasciatus）这两种鲤齿鳉之间的自然杂交带（natural hybrid zone），通过连续三年冬、春、夏三季的环境与遗传变化时空分析，检验了外源选择（exogenous selection）在该杂交带中的重要性。在该系统中，环境因子（盐度与温度）与遗传变异（3个诊断性核DNA位点（diagnostic nuDNA loci））在空间和季节维度上存在显著相关关系，这一结果证实了外源选择对杂交带维持的关键调控作用。在环境特征更接近亲本生境的样点，杂交种群的遗传组成保持稳定，且与本土亲本物种相似；而在中间环境样点，杂交种群则呈现亲本与杂交基因型类别的复杂混合，且该区域的等位基因与基因型频率在不同季节间的变化幅度也最大。对丘林西河系统内全部杂交种群的分析显示，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）的结果一致：当双带鲤齿鳉暴露于黑鳍鲤齿鳉的生境时，冬季（极端低温与温度波动）和夏季（盐度骤变及极端低温与温度波动）的死亡率高达75%。尽管尚未得到实证，但黑鳍鲤齿鳉及其类杂交种群的分布上限似乎受到类似的生态约束（捕食或种间竞争）。本研究还建立了该物种间杂交带的当代外源选择，与此前证实的环境变异与渐渗（introgression）对夸特罗锡内加斯盆地鲤齿鳉属物种的表型分化具有长期进化意义这一结论之间的关键关联。