Graduate School of Science and Engineering, Ehime University, Matsuyama, Ehime, Japan.
Department of Biology, Faculty of Science, Ehime University, Matsuyama, Ehime, Japan.
PLoS One. 2019 Feb 14;14(2):e0212452. doi: 10.1371/journal.pone.0212452. eCollection 2019.
Artificial transplantation of organisms and consequent invasive hybridization can lead to the extinction of native species. In Matsuyama, Japan, a native bitterling fish, Tanakia lanceolata, is known to form hybrids with another bitterling species, T. limbata, which was recently introduced from western Kyushu, Japan. These bitterlings spawn in the gills of two freshwater unionid species, Pronodularia japanensis and Nodularia douglasiae nipponensis, which have rapidly declined on the Matsuyama Plain in the past 30 years. To gauge the effect of invasive hybridization, we determined the genetic introgression between T. lanceolata and T. limbata and analyzed the morphology of these species and their hybrids to infer their niche overlap. We collected adult individuals of Tanakia spp. and genotyped them based on six microsatellite loci and mitochondrial cytochrome b sequences. We analyzed their meristic characters and body shapes by geometric morphometrics. We found that 10.9% of all individuals collected were hybrids. Whereas T. lanceolata were more densely distributed downstream and T. limbata were distributed upstream, their hybrids were widely distributed, covering the entire range of native T. lanceolata. The body height and anal fin length of T. limbata were greater than those of T. lanceolata, but their hybrids were highly morphologically variable, covering both parental morphs, and were widely distributed in the habitats of both parental species. Hybridization has occurred in both directions, but introduced T. limbata females and native T. lanceolata males are more likely to have crossed. This study shows that invasive hybridization with the introduced T. limbata is a potential threat to the native population of T. lanceolata via genetic introgression and replacement of its niche in streams.
生物体的人工移植和随之而来的入侵杂交可能导致本地物种灭绝。在日本松山，有一种本地的苦鱼，即细鳞鱼（Tanakia lanceolata），已知与另一种苦鱼，即从日本九州西部引进的台湾苦鱼（T. limbata）形成杂交种。这些苦鱼在两种淡水贻贝类物种的鳃中产卵，即日本圆顶珠蚌（Pronodularia japanensis）和日本褶纹冠蚌（Nodularia douglasiae nipponensis），这两种贻贝类物种在过去 30 年里在松山平原迅速减少。为了评估入侵杂交的影响，我们确定了细鳞鱼和台湾苦鱼之间的遗传渗入，并分析了这些物种及其杂交种的形态，以推断它们的生态位重叠。我们收集了成年的 Tanakia 种个体，并基于 6 个微卫星位点和线粒体细胞色素 b 序列对它们进行了基因分型。我们通过几何形态测量学分析了它们的可数特征和体型。我们发现，收集的所有个体中有 10.9%是杂交种。虽然细鳞鱼更密集地分布在下游，而台湾苦鱼分布在上游，但它们的杂交种分布广泛，覆盖了本地细鳞鱼的整个分布范围。台湾苦鱼的身体高度和臀鳍长度大于细鳞鱼，但它们的杂交种形态高度多变，涵盖了双亲的形态，并广泛分布在双亲物种的栖息地中。杂交发生在两个方向，但引入的台湾苦鱼雌性和本地的细鳞鱼雄性更有可能杂交。本研究表明，与引入的台湾苦鱼的入侵杂交可能通过遗传渗入和替代溪流中的生态位，对本地细鳞鱼种群构成威胁。
