Department of Environmental Science, Policy, and Management, University of California, Berkeley, CA, USA.
Museum of Vertebrate Zoology, University of California, Berkeley, CA, USA.
Glob Chang Biol. 2020 Jun;26(6):3268-3284. doi: 10.1111/gcb.15030. Epub 2020 Apr 5.
Transition zones between biomes, also known as ecotones, are areas of pronounced ecological change. They are primarily maintained by abiotic factors and disturbance regimes that could hinder or promote species range shifts in response to climate change. We evaluated how climate change has affected metacommunity dynamics in two adjacent biomes and across their ecotone by resurveying 106 sites that were originally surveyed for avian diversity in the early 20th century by Joseph Grinnell and colleagues. The Mojave, a warm desert, and the Great Basin, a cold desert, have distinct assemblages and meet along a contiguous, east-west boundary. Both deserts substantially warmed over the past century, but the Mojave dried while the Great Basin became wetter. We examined whether the distinctiveness and composition of desert avifaunas have changed, if species distributions shifted, and how the transition zone impacted turnover patterns. Avifauna change was characterized by (a) reduced occupancy, range contractions, and idiosyncratic species redistributions; (b) degradation of historic community structure, and increased taxonomic and climatic differentiation of the species inhabiting the two deserts; and (c) high levels of turnover at the transition zone but little range expansion of species from the warm, dry Mojave into the cooler, wetter Great Basin. Although both deserts now support more drier and warmer tolerant species, their bird communities still occupy distinct climatological space and differ significantly in climatic composition. Our results suggest a persistent transition zone between biomes contributes to limiting the redistribution of birds, and highlight the importance of understanding how transition zone dynamics impact responses to climate change.
生物群落过渡带，也称为生态交错带，是生态变化显著的区域。它们主要由非生物因素和干扰机制维持，这些因素可能会阻碍或促进物种因气候变化而发生的分布范围转移。我们通过重新调查在 20 世纪初由约瑟夫·格里诺尔（Joseph Grinnell）及其同事对鸟类多样性进行调查的 106 个地点，评估了气候变化如何影响两个相邻生物群落及其交错带的后生动物群落动态。莫哈韦沙漠是一个温暖的沙漠，大盆地是一个寒冷的沙漠，它们具有独特的组合，并沿着连续的东西边界相遇。两个沙漠在过去一个世纪都大幅升温，但莫哈韦沙漠变干燥，而大盆地变得更湿润。我们研究了沙漠鸟类区系的独特性和组成是否发生了变化，物种分布是否发生了转移，以及过渡带如何影响周转率模式。鸟类变化的特点是：（a） 占有度降低，分布范围收缩，特有种重新分布；（b） 历史群落结构退化，以及栖息在两个沙漠中的物种的分类和气候分化增加；（c） 过渡带的周转率很高，但从温暖干燥的莫哈韦沙漠向较凉爽湿润的大盆地扩张的物种很少。尽管两个沙漠现在都支持更多耐旱和耐高温的物种，但它们的鸟类群落仍然占据着独特的气候空间，在气候组成上有显著差异。我们的研究结果表明，生物群落之间的持久过渡带有助于限制鸟类的重新分布，并强调了了解过渡带动态如何影响对气候变化的响应的重要性。
