Mountain Science Center, Faculty of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8577, Japan.
Evolutionary and Population Biology-IBED, University of Amsterdam, P.O. Box 94240, 1090GE, Amsterdam, The Netherlands.
Exp Appl Acarol. 2020 May;81(1):59-74. doi: 10.1007/s10493-020-00492-4. Epub 2020 Apr 19.
Competitive interaction between sister species can be affected by reproductive interference (RI) depending on the ability of males to discriminate conspecific from heterospecific mates. We study such interactions in Tetranychus evansi and T. urticae. These spider mites co-occur on solanaceous plants in Southern Europe, and cause important yield losses in tomato crops. Previous studies using Spanish populations found that T. evansi outcompetes T. urticae, and that this is due to unidirectional RI of T. evansi males with T. urticae females. The unidirectional RI is attributed to differences in male mate preference for conspecific females between the two species. Also, differences in the propensity of interspecific web sharing in females plays a role. To investigate proximate mechanisms of this RI, here we study the role of female pheromones on male mate preference and female web sharing. We extracted pheromones from females of the two species, and investigated if males and females were arrested by the pheromone extractions in various concentrations. We observed that T. urticae males were more sensitive to the pheromone extractions and able to discriminate conspecific from heterospecific ones. Tetranychus evansi males, on the other hand, were less sensitive. Females from both species were arrested by conspecific pheromone extraction in lower concentrations. In conclusion, heterospecific mating by T. evansi males, which results in RI, can be explained by their lack of discrimination between female pheromones of the two species. Differences in the propensity of interspecific web sharing in females might not be explained by the pheromones that we investigated.
姐妹种间的竞争相互作用可能会受到生殖干扰（RI）的影响，这取决于雄性区分同种和异种种群的能力。我们在 Tetranychus evansi 和 T. urticae 中研究了这种相互作用。这些叶螨在欧洲南部的茄科植物上共同出现，会导致番茄作物的重大产量损失。之前使用西班牙种群的研究发现，T. evansi 会胜过 T. urticae，这是由于 T. evansi 雄虫对 T. urticae 雌虫的单向 RI 所致。单向 RI 归因于两种物种雄性对同种雌性的交配偏好的差异。此外，种间共享蛛网的倾向差异也起作用。为了研究这种 RI 的直接机制，我们在这里研究了雌性信息素对雄性交配偏好和雌性蛛网共享的作用。我们从这两个物种的雌性中提取了信息素，并研究了雄性和雌性是否会在不同浓度下被信息素提取物捕获。我们观察到，T. urticae 雄虫对信息素提取物更敏感，能够区分同种和异种种群。相比之下，T. evansi 雄虫则不那么敏感。两种物种的雌性都能在较低浓度的同种信息素提取物中被捕。总之，T. evansi 雄虫进行的异种种群交配，导致了 RI，这可以通过它们缺乏对两种物种雌性信息素的辨别能力来解释。我们研究的信息素可能无法解释种间蛛网共享倾向的差异。
