Co-existence between potentially competing newt species can lead to niche differentiation (e.g., in terms of diet shifts). This may cause adaptive responses involving changes in head shape. Here, we tested the hypothesis: the head shape of Lissotriton montandoni is different in conditions of co-occurrence with Ichthyosaura alpestris than in conditions in which other newt species are absent. We analysed images depicting head shape of specimens of I. alpestris and L. montandoni from a museum collection. All specimens of I. alpestris originated in a habitat where L. montandoni also occurred, whereas specimens of L. montandoni derived from populations that cohabited with I. alpestris and populations in which the presence of another newt species was not recorded. In each image, landmarks and semilandmarks were digitised. Females of L. montandoni from the population where I. alpestris also occurred were characterised by more massive heads and longer mouths in lateral views than females from sites where no other newt species occurred. Significant differences in head shape were also found when analysing ventral views between these species when they occupied the same habitat. We confirmed that the head shape of female L. montandoni differs between conditions of co-occurrence and absence of I. alpestris; no differences were found for males. A differently shaped head may be an adaptation to diet; L. montandoni females with longer mouths and more robust basal parts of the head can feed on larger invertebrates and compete more effectively with I. alpestris. The co-existence of newt species should be taken into account in future ecomorphological studies.

中文翻译：

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共存条件下蝾螈头部的稳健性：喀尔巴阡蝾螈和高山蝾螈的案例

潜在竞争蝾螈物种之间的共存可导致生态位分化（例如，在饮食转变方面）。这可能会导致涉及头部形状变化的适应性反应。在这里，我们检验了这个假设：在与山蝾螈共生的条件下，与没有其他蝾螈物种的条件下，蒙丹多尼蝾螈的头部形状是不同的。我们分析了描绘来自博物馆收藏的 I. alpestris 和 L. montandoni 标本头部形状的图像。I. alpestris 的所有标本都起源于 L. montandoni 也发生的栖息地，而 L. montandoni 的标本来自与 I. alpestris 共存的种群以及未记录到其他蝾螈物种存在的种群。在每幅图像中，地标和半地标都被数字化。L的女性 与来自没有其他蝾螈物种发生的地点的雌性相比，来自 I. alpestris 也出现的种群的 montandoni 的特征是从侧面看，头部更大，嘴更长。在分析这些物种占据相同栖息地时的腹侧视图时，还发现它们的头部形状存在显着差异。我们证实雌性 L. montandoni 的头部形状在 I. alpestris 共生和不存在的情况下有所不同；男性没有发现差异。不同形状的头部可能是对饮食的一种适应；L. montandoni 雌性嘴巴更长，头部基部更强壮，可以以更大的无脊椎动物为食，并更有效地与 I. alpestris 竞争。在未来的生态形态研究中应考虑蝾螈物种的共存。也出现的 alpestris 的特征是在侧视图中比来自没有其他蝾螈物种的地点的雌性更大的头部和更长的嘴巴。在分析这些物种占据相同栖息地时的腹侧视图时，还发现它们的头部形状存在显着差异。我们证实雌性 L. montandoni 的头部形状在 I. alpestris 共生和不存在的情况下有所不同；男性没有发现差异。不同形状的头部可能是对饮食的一种适应；L. montandoni 雌性嘴巴更长，头部基部更强壮，可以以更大的无脊椎动物为食，并更有效地与 I. alpestris 竞争。在未来的生态形态研究中应考虑蝾螈物种的共存。也出现的 alpestris 的特征是在侧视图中比来自没有其他蝾螈物种的地点的雌性更大的头部和更长的嘴巴。在分析这些物种占据相同栖息地时的腹侧视图时，还发现它们的头部形状存在显着差异。我们证实雌性 L. montandoni 的头部形状在 I. alpestris 共生和不存在的情况下有所不同；男性没有发现差异。不同形状的头部可能是对饮食的一种适应；L. montandoni 雌性嘴巴更长，头部基部更强壮，可以以更大的无脊椎动物为食，并更有效地与 I. alpestris 竞争。在未来的生态形态研究中应考虑蝾螈物种的共存。