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.

中文翻译：

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两种草食螨的雄性和雌性对雌性信息素的生殖干扰和敏感性。

繁殖干扰（RI）可能会影响姐妹物种之间的竞争性相互作用，具体取决于雄性将同种与异种配偶区分开的能力。我们研究了Tetranychus evansi和T. urticae中的这种相互作用。这些叶螨共存于南欧的茄科植物上，并导致番茄作物的重要减产。使用西班牙语的人群以往的研究发现，T.伊氏outcompetes T.螨，并认为这是由于单向RI吨伊氏男性与T.螨女性。单向RI归因于两个物种之间雄性对同种雌性的偏好。另外，女性种间网络共享倾向的差异也起作用。要研究此RI的邻近机制，在这里我们研究女性信息素对男性伴侣偏好和女性网络共享的作用。我们从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被各种浓度的信息素提取物所捕获。我们观察到荨麻锥虫雄性对信息素的提取更加敏感，能够区分异种同种。埃文氏螨另一方面，男性则较不敏感。来自这两个物种的雌性都通过较低浓度的同种信息素提取而被捕。总之，伊万氏锥虫雄性的异种交配导致了RI，这可以用他们在两种雌性信息素之间缺乏区别的原因来解释。我们调查的信息素可能无法解释女性种间网络共享倾向的差异。