Introgression threatens the survival of the critically endangered freshwater crayfish Cherax tenuimanus (Decapoda : Parastacidae) in the wild

Hybridization and genetic introgression following the introduction of exotic species can pose a significant threat to the survival of geographically restricted species. A remnant population of the critically endangered freshwater crayfish Cherax tenuimanus in the upper reaches of the Margaret River in southwestern Australia is under threat following the introduction and spread of its congener Cherax cainii. Here, we examine the extent of hybridization and introgression between the two species using twelve polymorphic microsatellite loci. Our study reveals there are three times more C. cainii than C. tenuimanus at our study site in the upper reaches of the Margaret River. There is also evidence of hybridization and introgression between C. tenuimanus and C. cainii at this site, with F1, F2 and backcrossed individuals identified. While interbreeding was confirmed in this study, our simulations suggest that the levels of introgression are much lower than would be expected under random mating, indicating partial reproductive barriers exist. Nevertheless, it is apparent that hybridization and introgression with C. cainii pose a serious threat to C. tenuimanus and their survival in the wild will require active adaptive management and continued genetic monitoring to evaluate management effectiveness.

外来物种引入后引发的杂交与基因渐渗，会对狭域分布物种的存续构成显著威胁。栖息于澳大利亚西南部玛格丽特河上游的极危淡水螯虾塔曼马努斯螯虾（Cherax tenuimanus）残存种群，正面临其同属物种凯恩氏螯虾（Cherax cainii）引入并扩散带来的生存威胁。本研究采用12个多态性微卫星位点（microsatellite loci），对这两个物种间的杂交与基因渐渗程度展开分析。结果显示，玛格丽特河上游研究样地内凯恩氏螯虾的种群丰度为塔曼马努斯螯虾的三倍。同时，本研究在该样地中发现了两种螯虾间存在杂交与基因渐渗的明确证据，已鉴定出子一代（F1）、子二代（F2）及回交（backcrossed）个体。尽管本研究证实了二者存在杂交行为，但模拟分析表明，当前的基因渐渗水平远低于随机交配情境下的预期水平，暗示二者之间存在部分生殖隔离。尽管如此，与凯恩氏螯虾的杂交及基因渐渗仍对塔曼马努斯螯虾构成了严重的生存威胁，该物种的野外存续需要开展主动适应性管理，并持续进行遗传监测以评估管理措施的实施成效。