Data from: Sleeping with the ‘enemy’ - Hybridization of an endangered tree weta

While hybridization is an important part of the evolutionary process, for rare species mating with more common species hybridization can increase the risks of extinction. By mating with heterospecifics rare species waste valuable reproductive resources and as a result population sizes may decline. If introgression occurs, the rare species can become genetically swamped by alleles from the more common species, rendering it effectively extinct. As a consequence of these risks, hybridization with the more common species Hemideina femorata (Canterbury tree weta) may lead to the extinction of the range restricted species H. ricta (Banks Peninsula tree weta) on Banks Peninsula. The current study uses spatial interpolation to model the distribution of each species and the potential sympatric zone to guide sampling efforts. Polymorphic microsatellite markers and mitochondrial sequence data were used to determine the extent of hybridization between H. ricta and H. femorata. The results confirm that hybridization is possible between these species. However, hybrids and introgression appear to be very rare, suggesting that reproductive isolating barriers are present but incomplete. The threat of extinction to H. ricta via hybridization with H. femorata is low but extreme loss of habitat may cause changes to population densities that could increase the risks of hybridization. Therefore, landowners should be encouraged to conserve native bush.

尽管杂交是演化过程中的重要环节，但对于稀有物种而言，与常见物种杂交会提升其灭绝风险。稀有物种与异种个体交配时会浪费宝贵的繁殖资源，进而可能导致种群规模下降。若发生基因渐渗，稀有物种的基因组会被常见物种的等位基因所淹没，实质上等同于灭绝。鉴于此类风险，与常见物种坎特伯雷树沙螽（Hemideina femorata）杂交，可能会导致分布范围受限的班克斯半岛树沙螽（H. ricta）在班克斯半岛上走向灭绝。本研究采用空间插值法对两个物种的分布区以及潜在同域分布区进行建模，以指导采样工作。研究使用多态性微卫星标记与线粒体序列数据，分析了H. ricta与H. femorata之间的杂交程度。研究结果证实，这两个物种之间确实可以发生杂交。然而，杂交个体与基因渐渗现象均极为罕见，表明二者之间存在但尚未完全形成生殖隔离屏障。尽管H. ricta通过与H. femorata杂交面临的灭绝威胁较低，但栖息地大幅丧失可能会改变种群密度，进而提升杂交风险。因此，应鼓励土地所有者保护本土灌丛。