Data from: Male-driven reproductive and agonistic character displacement in darters and its implications for speciation in allopatry

Selection against hybridization can cause mating traits to diverge between species in sympatry via reproductive character displacement (RCD). Additionally, selection against interspecific fighting can cause aggressive traits to diverge between sympatric species via agonistic character displacement (ACD). By directly affecting conspecific recognition traits, RCD and ACD between species can also incidentally cause divergence in mating and fighting traits among populations within a species (termed cascade RCD and cascade ACD). Here, we demonstrate patterns consistent with male-driven RCD and ACD in two groups of darters (orangethroat darter clade Ceasia and rainbow darter Etheostoma caeruleum). In both groups, males that occur in sympatry (between Ceasia and E. caeruleum) have higher levels of preference for mating and fighting with conspecifics over heterospecifics than do males from allopatry. This is consistent with RCD and ACD. We also found patterns consistent with cascade RCD and cascade ACD among species of Ceasia. Ceasia males that are sympatric to E. caeruleum (but allopatric to one another) also have heightened preferences for mating and fighting with conspecific versus heterospecific Ceasia. In contrast, Ceasia males that are allopatric to E. caeruleum readily mate and fight with heterospecific Ceasia. We suggest that RCD and ACD between Ceasia and E. caeruleum has incidentally led to divergence in mating and fighting traits among Ceasia species. This study is unique in that male preferences evolve via both RCD (male preference for conspecific females) and ACD (male preference to fight conspecific males) which leads to subsequent divergence among allopatric lineages.针对杂交的选择压力可通过生殖特征置换（reproductive character displacement, RCD），促使同域分布的物种种群间产生交配性状的分化。此外，针对种间争斗的选择压力可通过竞争特征置换（agonistic character displacement, ACD），导致同域分布物种间的攻击性状发生分化。由于RCD与ACD会直接作用于同种识别性状，物种间的这类置换过程还可附带引发同一物种种群内交配与争斗性状的分化，即级联生殖特征置换（cascade RCD）与级联竞争特征置换（cascade ACD）。本研究在两类镖鲈——橙喉镖鲈Ceasia支系与虹镖鲈*Etheostoma caeruleum*——中，发现了符合雄性驱动RCD与ACD的性状分化模式。在两类类群中，与异域分布的雄性相比，于Ceasia支系与*E. caeruleum*同域分布的雄性，对同种个体的交配与争斗偏好程度显著更高，这与RCD及ACD的理论预期一致。我们同时在Ceasia支系的物种种群中，发现了符合级联RCD与级联ACD的性状模式：与*E. caeruleum*同域分布但彼此间呈异域分布的Ceasia雄性，对同种Ceasia个体的交配与争斗偏好同样显著高于对异种Ceasia个体的偏好；与之相反，与*E. caeruleum*呈异域分布的Ceasia雄性，则易于与异种Ceasia个体完成交配与争斗行为。我们推测，Ceasia支系与*E. caeruleum*之间的RCD与ACD过程，附带引发了Ceasia各物种种群间交配与争斗性状的分化。本研究的独特之处在于，雄性偏好可通过RCD（雄性对同种雌性的交配偏好）与ACD（雄性对同种雄性的争斗偏好）共同演化，进而推动后续异域支系间的性状分化。