Effects of temperature and salinity on juveniles of two ascidians, one native and one invasive, and their hybrids
Effects of temperature and salinity on juveniles of two ascidians, one native and one invasive, and their hybrids
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DOI：
10.1016/j.jembe.2017.09.019
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发表时间：
2017-12-01
影响因子：
2
通讯作者：
Viard, Frederique
中科院分区：
文献类型：
--
作者：
Malfant, Marine;Coudret, Jerome;Viard, Frederique
人类介导的物种运输，即生物引进，促进先前空间隔离的物种之间的二次接触。当物种没有生殖隔离时，杂交是这些二次接触的一个重要的可能结果，影响着本地和非本地物种的命运。这种情况的一个例子是，将原产于亚洲的暖温带被囊类玻璃海鞘引入其冷温带同源玻璃海鞘的欧洲原产地。尽管有一个古老的分歧（约。4 Mya），这两个物种缺乏生殖隔离，在实验室产生的可育F1杂种。然而，最近的一项种群基因组研究表明，杂交种在野生环境中极为罕见，回交个体也不存在，这表明自然界中两个物种之间存在生殖障碍。因此，人们假设了合子后机制，如环境对杂种的选择。由于这两个物种最近才被重新分类，因此缺乏关于它们各自生态和杂交后代的数据。为了研究这些环境效应，我们进行了21个试验杂交，并检查了ca的存活率和个体生长率。1900个F1-通过种内和种间杂交产生的幼仔。四个处理结合两个温度（12摄氏度和17摄氏度）和两个盐度水平（25和35），代表在自然界中发现的条件，适用于一个星期大的少年。28天后，在三个F1类别中观察到高存活率，杂交种和亲本种之间没有差异。根据对两种虫态的地理学研究和野外监测，结果表明：robusta在温暖的温度和标准盐度条件下表现特别好。F1-杂种没有表现出远交衰退，生长速率类似于或高于F1-C。好吧总之，这两个物种在测试的环境条件下表现良好，单独的合子后生态效应不太可能有效地对抗本地和非本地物种之间的杂交。
Human-mediated transports of species, i.e. biological introductions, promote secondary contacts between previously spatially isolated species. When the species are not reproductively isolated, hybridization is an important possible outcome of these secondary contacts, influencing the fate of both the native and non-native species. Such a situation is exemplified by the introduction of the warm-temperate tunicate Ciona robusta, native to Asia, into the European native range of its cold-temperate congener Ciona intestinalis. Despite an old divergence (ca. 4 Mya), the two species lack reproductive isolation with fertile F1-hybrids produced in laboratory. However, a recent population genomic study showed that hybrids are extremely rare in the wild and back-crossed individuals are absent, suggesting the existence of reproductive barriers between the two species in nature. Post zygotic mechanisms like selection against hybrids by the environment were thus hypothesized. Because the two species have only been recently reclassified, data on their respective ecology and their hybrids are lacking. To investigate these environmental effects, we carried out 21 experimental crosses and examined survival and individual growth rate of ca. 1900 F1-juveniles produced with intra- and inter-specific crosses. Four treatments combining two temperatures (12 degrees C and 17 degrees C) and two salinity levels (25 and 35), representative of conditions found in nature, were applied to one-week old juveniles. After 28 days, a high survival rate was observed in the three F1 categories, with no difference between hybrids and parental species. As expected based on biogeography studies and field monitoring of the two species, the results showed that C. robusta performed particularly well in warm temperature with standard salinity condition. F1-hybrids did not show outbreeding depression, with growth rates similar to or higher than F1-C. intestinalis. Altogether the two species performed well under the tested environmental conditions, and post-zygotic ecological effects alone are unlikely to be effective against hybridization between the native and non-native species.