Data from: Reinforcement and a cline in mating behavior evolve in response to secondary contact and hybridization in shield-back katydids (Orthoptera: Tettigoniidae)

In a dispersal-limited species that has evolved reproductive character displacement at a contact zone, a cline in mating behavior may result if gene flow diffuses alleles out of the contact zone into allopatric populations. Prior work has found such a clinal pattern in the shield-back katydid Aglaothorax morsei, in which the male calling songs in a sympatric population have a displaced, short interpulse interval that increases in length with increasing distance from the contact zone. In this study, molecular phylogenetic and female preference data show that (1) sympatric populations result from secondary contact, (2) hybridization in sympatry has resulted in unidirectional mitochondrial introgression, and (3) female preferences are consistent with reproductive character displacement, and could generate a cline in mating behavior. These data together suggest a history of reinforcement, generally considered rare in acoustically communicating insects, thus Aglaothorax represents an important example of a rarely documented evolutionary process.针对一类在接触带（contact zone）演化出生殖特征位移（reproductive character displacement）的扩散受限物种，若基因流将等位基因从接触带扩散至异域种群，则可能形成交配行为的渐变群（cline）。既往研究在盾背螽斯（shield-back katydid）类群的莫氏盾背螽斯（Aglaothorax morsei）中发现了此类渐变群模式：该物种同域种群的雄性鸣唱信号具有位移后的短脉冲间隔，且脉冲间隔长度随距接触带距离的增加而逐渐延长。本研究通过分子系统发育（molecular phylogenetic）与雌性偏好数据，得到如下三项结论：（1）同域种群起源于次生接触（secondary contact）；（2）同域杂交引发了单向线粒体基因渐渗（unidirectional mitochondrial introgression）；（3）雌性偏好与生殖特征位移相符，且可驱动交配行为渐变群的形成。上述结果共同表明该类群存在强化选择（reinforcement）的演化历史——这一过程在声学通讯昆虫中通常极为罕见，因此盾背螽斯属（Aglaothorax）为这类鲜有报道的演化过程提供了重要研究范例。