Department of Biological Sciences and Tropical Marine Science Institute, National University of Singapore, Singapore 117543, Singapore.
Department of Ecology, Evolution and Behavior, University of Minnesota, St. Paul, Minnesota 55108.
Evolution. 2018 Feb;72(2):288-302. doi: 10.1111/evo.13402. Epub 2017 Dec 12.
The Coral Triangle (CT) region of the Indo-Pacific realm harbors an extraordinary number of species, with richness decreasing away from this biodiversity hotspot. Despite multiple competing hypotheses, the dynamics underlying this regional diversity pattern remain poorly understood. Here, we use a time-calibrated evolutionary tree of living reef coral species, their current geographic ranges, and model-based estimates of regional rates of speciation, extinction, and geographic range shifts to show that origination rates within the CT are lower than in surrounding regions, a result inconsistent with the long-standing center of origin hypothesis. Furthermore, endemism of coral species in the CT is low, and the CT endemics are older than relatives found outside this region. Overall, our model results suggest that the high diversity of reef corals in the CT is largely due to range expansions into this region of species that evolved elsewhere. These findings strongly support the notion that geographic range shifts play a critical role in generating species diversity gradients. They also show that preserving the processes that gave rise to the striking diversity of corals in the CT requires protecting not just reefs within the hotspot, but also those in the surrounding areas.
印度洋-太平洋海域的珊瑚三角区拥有数量惊人的物种，而这些物种的丰富度从这个生物多样性热点地区向外逐渐减少。尽管有多种相互竞争的假说，但这一区域多样性模式背后的动态仍未被充分理解。在这里，我们利用活珊瑚物种的时间校准进化树、它们目前的地理范围以及基于模型的物种形成、灭绝和地理范围变化的区域速率估计，表明珊瑚三角区的起源率低于周围地区，这一结果与长期存在的起源中心假说不一致。此外，珊瑚三角区的珊瑚特有种的比例较低，而三角区的特有种比在该区域以外发现的亲缘种更为古老。总的来说，我们的模型结果表明，珊瑚三角区珊瑚的高多样性主要是由于在这个区域进化的物种向这个区域扩张的结果。这些发现强烈支持了这样一种观点，即地理范围的变化在产生物种多样性梯度方面起着关键作用。它们还表明，要保护珊瑚三角区引人注目的珊瑚多样性所产生的过程，不仅需要保护热点地区内的珊瑚礁，还需要保护周围地区的珊瑚礁。
