Abstract：
Islands are biodiversity hotspots that host unique assemblages. However, a substantial proportion of island species are threatened and their long-term survival is uncertain. Identifying and preserving vulnerable species has become a priority, but it is also essential to combine this information with other facets of biodiversity like functional diversity, to understand how future extinctions might affect ecosystem stability and functioning. Focusing on mammals, we (i) assessed how much functional space would be lost if threatened species go extinct, (ii) determined the minimum number of extinctions that would cause a significant functional loss, (iii) identified the characteristics (e.g., biotic, climatic, geographic, or orographic) of the islands most vulnerable to future changes in the functional space, and (iv) quantified how much of that potential functional loss would be offset by introduced species. Using trait information for 1474 mammal species occurring in 318 islands worldwide, we built trait probability density functions to quantify changes in functional richness and functional redundancy in each island if the mammals categorized by IUCN as threatened disappeared. We found that the extinction of threatened mammals would reduce the functional space in 63% of the assessed islands, although these extinctions in general would cause a reduction of less than 15% of their overall functional space. Also, on most islands, the extinction of just a few species would be sufficient to cause a significant loss of functional diversity. The potential functional loss would be higher on small, isolated, and/or species-rich islands, and, in general, the functional space lost would not be offset by introduced species. Our results show that the preservation of native species and their ecological roles remains crucial for maintaining the current functioning of island ecosystems. Therefore, conservation measures considering functional diversity are imperative to safeguard the unique functional roles of threatened mammal species on islands.
摘要：
岛屿是生物多样性的热点地区，拥有独特的组合。然而,相当比例的岛屿物种受到威胁，它们的长期生存是不确定的。识别和保护脆弱物种已成为当务之急，但也必须将这些信息与生物多样性的其他方面结合起来，比如功能多样性，了解未来的灭绝可能如何影响生态系统的稳定性和功能。专注于哺乳动物，我们（i）评估了如果受威胁物种灭绝将失去多少功能空间，（ii）确定会导致重大功能损失的最小灭绝次数，(iii)确定的特征(例如，生物，气候,地理,或地形)最容易受到功能空间未来变化的岛屿，（iv）量化了引入的物种将抵消多少潜在的功能损失。使用全球318个岛屿中1474种哺乳动物的性状信息，我们建立了性状概率密度函数，以量化每个岛屿中功能丰富度和功能冗余的变化，如果IUCN分类为威胁的哺乳动物消失了。我们发现受威胁的哺乳动物的灭绝将减少63%的评估岛屿的功能空间，尽管这些灭绝通常会导致其整体功能空间的减少不到15％。此外，在大多数岛屿上，仅少数物种的灭绝就足以导致功能多样性的重大损失。潜在的功能损失会更小，孤立的,和/或物种丰富的岛屿，and,总的来说,失去的功能空间不会被引入的物种所抵消。我们的结果表明，保护本地物种及其生态作用对于维持岛屿生态系统的当前功能仍然至关重要。因此,考虑功能多样性的保护措施对于保护岛屿上受威胁哺乳动物物种的独特功能作用至关重要。
