The behavioral processes at the basis of hybridization and introgression are understudied in terrestrial mammals. We use a unique model to test the role of sexual signals as a reproductive barrier to introgression by investigating behavioral responses to male sexual calls in estrous females of two naturally allopatric but reproductively compatible deer species, red deer and sika deer. Previous studies demonstrated asymmetries in acoustic species discrimination between these species: most but not all female red deer prefer conspecific over sika deer male calls while female sika deer exhibit no preference differences. Here, we extend this examination of acoustic species discrimination to the role of male sexual calls in introgression between parent species and hybrids. Using two-speaker playback experiments, we compared the preference responses of estrous female red and sika deer to male sexual calls from conspecifics versus red × sika hybrids. These playbacks simulate early secondary contact between previously allopatric species after hybridization has occurred. Based on previous conspecific versus heterospecific playbacks, we predicted that most female red deer would prefer conspecific calls while female sika deer would show no difference in their preference behaviors toward conspecific and hybrid calls. However, results show that previous asymmetries did not persist as neither species exhibited more preferences for conspecific over hybrid calls. Thus, vocal behavior is not likely to deter introgression between these species during the early stages of sympatry. On a wider scale, weak discrimination against hybrid sexual signals could substantially contribute to this important evolutionary process in mammals and other taxa.

中文翻译：

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雌雄对两种雌雄同体杂种鹿（鹿）和日本对虾的交配和杂交雄性交配的偏好。

在杂交和渗入基础上的行为过程在陆生哺乳动物中被研究不足。我们使用独特的模型，通过调查两种自然变体但具有生殖相容性的鹿种（马鹿和梅花鹿）的发情雌性对雄性性行为的行为反应，来测试性信号作为渗入繁殖的生殖屏障的作用。先前的研究表明，这些物种之间在声学物种识别上存在不对称性：大多数但不是全部雌性马鹿都比同花公鹿更喜欢同种，而雌性梅花鹿没有偏好差异。在这里，我们将对声学物种歧视的研究扩展到男性性电话在亲本和杂种之间渗入中的作用。通过使用两个扬声器的播放实验，我们比较了发情的雌性红和梅花鹿对同种与红色×梅花杂种的雄性性唤起的偏好反应。这些回放模拟了杂交后先前异源菌种之间的早期次级接触。根据先前的特定种与异种种回放，我们预测大多数雌性马鹿会偏爱特定种的调用，而雌性梅花鹿对特定种和杂种调用的偏好行为没有差异。然而，结果表明，先前的不对称性并没有持续存在，因为这两个物种都没有显示出对同种异性的更多偏好。因此，在交感神经的早期阶段，声音行为不可能阻止这些物种之间的渗入。在更大范围内