Biotic and abiotic drivers of species loss rate in isolated lakes

1. Today, anthropogenic impacts are causing a serious crisis for global biodiversity, with rates of extinction increasing at an unprecedented rate. Extinctions typically occur after a certain delay and understanding the mechanisms causing delays is a key challenge for both fundamental and applied perspectives. 2. Here, we make use of natural experiments, the isolation of lakes by land up-lift in Northern Scandinavia, to examine how yearly extinction rates are affected by time since isolation and a range of abiotic and biotic factors. 3. In this aim, we adapted a model of delayed species loss within isolated communities to test the effects of time since isolation, area, pH, depth and presence/absence of piscivores on extinction rates. 4. As expected, we found that small and/or young lakes experience a higher annual rate of extinctions per species than larger and/or older ones. Compared to previous studies that were conducted for either young (few thousand years ago) or very old (>10 000 years ago) isolates, we demonstrated over a large and continuous temporal scales (50-5000 yr), similar relationship between extinction rates and age. We also show that extinction rates are modified by local environmental factors such as a strong negative effect of increasing pH. 5. Our results urge for the need to consider the time since critical environmental changes occurred when studying extinction rates. In a wider perspective our study demonstrates the need to consider extinction debts when modeling future effects of climate change, land-use changes, or biological invasions on biodiversity.

1. 当今，人为活动正给全球生物多样性带来严重危机，物种灭绝速率正以前所未有的速度攀升。物种灭绝通常存在一定时滞，阐明引发该时滞的内在机制，无论是从基础研究还是应用研究视角而言，都是一项关键挑战。
2. 本研究借助北欧北部陆地抬升致使湖泊隔离这一天然实验，探究隔离时长以及一系列非生物、生物因子对年度灭绝速率的影响。
3. 为此，我们针对隔离群落内物种延迟消失的模型进行改良，以检验隔离时长、湖泊面积、pH值、水深以及捕食性鱼类存在与否对灭绝速率的影响。
4. 正如预期，我们发现小型湖泊或年轻湖泊的单位物种年灭绝速率，高于大型湖泊或成熟湖泊。相较于此前仅针对年轻（距今数千年）或极古老（距今超1万年）隔离湖泊开展的研究，我们在跨度为50至5000年的大范围连续时间尺度上，证实了灭绝速率与湖泊年龄间存在类似关联。此外，我们还发现局部环境因子会改变灭绝速率，例如pH值升高会产生显著的负向影响。
5. 本研究结果提示，在探究灭绝速率时，需考虑临界环境变化发生后的时长。从更宏观的视角来看，我们的研究表明，在模拟气候变化、土地利用变化或生物入侵对生物多样性的未来影响时，需纳入灭绝债（extinction debt）这一因素。