Department of Ecology, Evolution, and Behavior & Bell Museum of Natural History, University of Minnesota, 140 Gortner Laboratory, 1479 Gortner Avenue, St. Paul, MN 55108, USA.
Field Museum of Natural History, 1400 S Lake Shore Drive, Chicago, IL 60605, USA.
Proc Biol Sci. 2020 Feb 26;287(1921):20192746. doi: 10.1098/rspb.2019.2746.
A lineage colonizing a geographic region with no competitors may exhibit rapid diversification due to greater ecological opportunity. The resultant species diversity of this primary-colonizing (incumbent) clade may limit subsequent lineages' ability to persist unless these non-incumbent lineages are ecologically distinct. We compare the diversity in diet-related mandibular morphology of two sympatric murid rodent clades endemic to Luzon Island, Philippines-incumbent Phloeomyini and secondary-colonizing Chrotomyini-to the mandibular morphological diversity of Sahul Hydromyini, the sister clade of Chrotomyini and the incumbent murid lineage on the supercontinent of Sahul. This three-clade comparison allows us to test the hypothesis that incumbent lineages can force persistent ecological distinction of subsequent colonists at the time of colonization and throughout the subsequent history of the two sympatric clades. We find that Chrotomyini forms a subset of the diversity of their clade plus Sahul Hydromyini that minimizes overlap with Phloeomyini. We also infer that this differentiation extends to the stem ancestor of Chrotomyini and Sahul Hydromyini, consistent with a biotic filter imposed by Phloeomyini. Our work illustrates that incumbency has the potential to have a profound influence on the ecomorphological diversity of colonizing lineages at the island scale even when the traits in question are evolving at similar rates among independently colonizing clades.
一个在没有竞争者的地理区域中殖民的谱系可能由于更大的生态机会而表现出快速的多样化。这种初次殖民（在位）分支的物种多样性可能会限制随后谱系的生存能力，除非这些非在位谱系在生态上有所区别。我们比较了菲律宾吕宋岛两个同域鼠科啮齿动物谱系——在位的 Phloeomyini 和次生殖民的 Chrotomyini——在饮食相关下颌形态多样性方面的差异，以及 Chrotomyini 的姐妹谱系 Sahul Hydromyini 的下颌形态多样性，Sahul Hydromyini 是 Chrotomyini 和萨赫尔超级大陆在位鼠科谱系的祖先。这三个谱系的比较使我们能够检验这样一个假设，即在殖民化和随后两个同域谱系的历史中，在位谱系可以迫使后续殖民者保持持久的生态区别。我们发现 Chrotomyini 形成了其谱系多样性的一个子集，加上 Sahul Hydromyini，最大限度地减少了与 Phloeomyini 的重叠。我们还推断这种分化扩展到了 Chrotomyini 和 Sahul Hydromyini 的祖先，这与 Phloeomyini 施加的生物过滤器一致。我们的工作表明，即使在涉及的特征在独立殖民谱系中以相似的速度进化的情况下，在位也有可能对岛屿尺度上的殖民谱系的生态形态多样性产生深远影响。
