Hybridization is an evolutionary process with wide-ranging potential outcomes, from providing populations with important genetic variation for adaptation to being a substantial fitness cost leading to extinction. Here, we focussed on putative hybridization between two morphologically distinct species of New Zealand grasshopper. We collected Phaulacridium marginale and Phaulacridium otagoense specimens from a region where mitochondrial introgression had been detected and where their habitat has been modified by introduced mammals eating the natural vegetation and by the colonization of many non-native plant species. In contrast to observations in the 1970s, our sampling of wild pairs of grasshoppers in copula provided no evidence of assortative mating with respect to species. Geometric morphometrics on pronotum shape of individuals from areas of sympatry detected phenotypically intermediate specimens (putative hybrids), and the distribution of phenotypes in most areas of sympatry was found to be unimodal. These results suggest that hybridization associated with anthropogenic habitat changes has led to these closely related species forming a hybrid swarm, with random mating. Without evidence of hybrid disadvantage, we suggest a novel hybrid lineage might eventually result from the merging of these two species.

中文翻译：

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缺乏分类交配可能解释了两种蚱蜢相遇时表型分化减少的原因。

杂交是一个具有广泛潜在结果的进化过程，从为种群提供重要的遗传变异以进行适应，到成为导致灭绝的巨大适应成本。在这里，我们专注于两种形态不同的新西兰蚱蜢之间的假定杂交。我们从已检测到线粒体渐渗的地区收集了 Phaulacridium margine 和 Phaulacridium otagoense 标本，该地区的栖息地已被引入的哺乳动物吃掉天然植被和许多非本地植物物种的殖民化而改变。与 1970 年代的观察相比，我们对 copula 中的野生蚱蜢的采样没有提供关于物种分类交配的证据。来自同域区域的个体前背板形状的几何形态测量学检测到表型中间标本（假定的杂种），并且发现在大多数同域区域的表型分布是单峰的。这些结果表明，与人为栖息地变化相关的杂交导致这些密切相关的物种形成了一个杂交群，随机交配。在没有杂交劣势的证据的情况下，我们建议一个新的杂交谱系最终可能来自这两个物种的合并。与随机交配。在没有杂交劣势的证据的情况下，我们建议一个新的杂交谱系最终可能来自这两个物种的合并。与随机交配。在没有杂交劣势的证据的情况下，我们建议一个新的杂交谱系最终可能来自这两个物种的合并。