Interspecific competition affects population dynamics, distributional ranges, and evolution of competing species. The competitive exclusion principle states that ecologically similar species cannot coexist unless they exhibit niche segregation. Herein, we assess whether niche segregation allows the coexistence of Crocidura russula and C. suaveolens in southwestern Iberia and whether segregation is the result of current (ecological effect) or past (evolutionary effect) competition. We performed an annual live-trapping cycle in the two main habitats of the Odiel Marshes Natural Reserve (OMNR), the tidal marsh and the Mediterranean forest, both in syntopic (i.e., where both species co-occur) and allotopic (where only one of the two species occurs) sites within this Reserve. We modeled the presence–absence of each species in both habitats and sites by generalized linear mixed models. The coexistence of both species was favored by spatial and temporal niche segregation. Crocidura suaveolens was restricted to tidal marsh and did not occupy Mediterranean forest, even when C. russula was absent. We interpret this to be the result of competition in the past triggering an evolutionary response in C. suaveolens towards its specialization in tidal marsh. Moreover, the specialist C. suaveolens currently is outcompeting C. russula in tidal marshes, reversing the dominance pattern observed elsewhere. The degree of co-occurrence between both species in syntopic sites was low, as they showed inverse dynamics of seasonal abundances. Interspecific competition leading to habitat specialization favors the coexistence of these ecologically similar species.

中文翻译：

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本地栖息地专业化作为对两个同域鼩之间种间竞争的进化反应

种间竞争影响种群动态、分布范围和竞争物种的进化。竞争排斥原则指出生态相似的物种不能共存，除非它们表现出生态位隔离。在此，我们评估生态位隔离是否允许在伊比利亚西南部的 Crocidura russula 和 C. suaveolens 共存，以及隔离是当前（生态效应）还是过去（进化效应）竞争的结果。我们在 Odiel 沼泽自然保护区 (OMNR)、潮汐沼泽和地中海森林的两个主要栖息地中进行了一次年度活捕循环，均在同位（即，两种物种共同出现的地方）和异位（其中只有一个两个物种中出现）该保护区内的地点。我们通过广义线性混合模型对每个物种在栖息地和地点的存在与否进行建模。空间和时间生态位隔离有利于两种物种的共存。Crocidura suaveolens 仅限于潮汐沼泽，不占据地中海森林，即使 C. russula 不存在。我们将此解释为过去竞争的结果，触发了 C. suaveolens 对潮汐沼泽专业化的进化反应。此外，专家 C. suaveolens 目前正在潮汐沼泽中击败 C. russula，扭转了在其他地方观察到的优势模式。同位点中两种物种之间的共现程度较低，因为它们显示出季节性丰度的反向动态。