Biodiversity is declining worldwide. When species are physically active (i.e., their diel niche) may influence their risk of becoming functionally extinct. It may also affect how species losses affect ecosystems. For 5033 terrestrial mammals, we predict future changes to diel global and local functional diversity through a gradient of progressive functional extinction scenarios of threatened species. Across scenarios, diurnal species were at greater risk of becoming functionally extinct than nocturnal, crepuscular, and cathemeral species, resulting in deep functional losses in global diurnal trait space. Redundancy (species with similar roles) will buffer global nocturnal functional diversity; however, across the land surface, losses will mostly occur among functionally dispersed species (species with distinct roles). Functional extinctions will constrict boundaries of cathemeral trait space as megaherbivores, and arboreal foragers are lost. Variation in the erosion of functional diversity across the daily cycle will likely profoundly affect the partitioning of ecosystem functioning between night and day.

中文翻译：

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整个昼夜循环中哺乳动物功能多样性的全球和区域侵蚀

全球生物多样性正在下降。当物种身体活跃时（即它们的昼夜生态位）可能会影响它们功能性灭绝的风险。它还可能影响物种损失如何影响生态系统。对于 5033 种陆生哺乳动物，我们预测未来的变化会通过受威胁物种的渐进式功能性灭绝情景的梯度来消灭全球和当地的功能多样性。在各种情况下，昼夜物种比夜间、黄昏和气候物种更容易在功能上灭绝，从而导致全球昼夜特征空间的深度功能丧失。冗余（具有相似作用的物种）将缓冲全球夜间功能多样性；然而，在整个陆地表面，损失将主要发生在功能分散的物种（具有不同作用的物种）中。功能性灭绝将缩小作为大型食草动物的动物性状空间的边界，而树栖觅食者将消失。日常循环中功能多样性侵蚀的变化可能会深刻影响生态系统功能在昼夜之间的划分。