The Kimberley, north-western Australia, as a cradle of evolution and endemic biodiversity: an example using Grunters (Terapontidae)

Aim: To test two prominent, alternate hypotheses that provide explanations for the great accumulation of endemic species in the Kimberley bioregion in north-western Australia, using an extensively sampled, region wide phylogeny of northern Australia’s most speciose freshwater fish family, Terapontidae. Specifically, we test whether the Kimberley may act as (1) a “museum” accumulating taxa and endemic species over time or (2) a “cradle” of more recent diversification and neoendemism. Location: The Australian monsoonal tropics
Taxon: Grunters (Terapontidae) Methods: We obtained a robust and well supported Bayesian phylogeny for the family using DNA sequences from mtDNA and nuclear gene regions. We performed molecular phylogenetic analyses using species tree methods including molecular dating analysis, ancestral range reconstruction, and diversification analysis. Results: Based on our phylogeny, the combined molecular clock estimates and likelihood-based historical biogeographic reconstructions suggest that terapontids recently transitioned into the Kimberley from the east during the late-Miocene. We found that 80% of Kimberley terapontids diversified within the Kimberley in the last 3 Ma. Further, diversification analyses identified a single significant shift in diversification rates ~1.4 Ma that corresponds with a change in global climate midway through the Pleistocene that was predominantly driven by speciation in the Kimberley. Main Conclusions: The weight of evidence suggests that the Kimberley has been a “cradle” of evolution for Terapontidae, rather than a “museum”. Our analysis provides strong evidence for a geologically recent transition of terapontids into the Kimberley from regions to the east during the late Miocene followed by a significant increase in speciation rates during the Pleistocene, driven by speciation in the Kimberley. The results provide important insight into the evolutionary and biogeographical processes that have shaped the regions unique biota, which will inform land managers working to protect and conserve both species and the processes responsible for generating and sustaining them.

研究目的：本研究旨在通过广域采样的澳大利亚北部物种最丰富的淡水鱼科——鼓鲷科（Terapontidae）的全区域系统发育数据集，检验两种主流替代性假说，以解释澳大利亚西北部金伯利生物区（Kimberley bioregion）特有物种大规模聚集的成因。具体而言，本研究将验证金伯利生物区是否兼具两种角色：(1) 随时间推移积累类群与特有物种的进化博物馆，或(2) 近期发生物种分化与新特有化的进化摇篮。
研究区域：澳大利亚季风热带区
研究类群：鼓鲷类（Grunters，Terapontidae）
研究方法：本研究通过线粒体DNA（mtDNA）与核基因区域的DNA序列，构建了该科的高支持度、稳健的贝叶斯系统发育树。我们采用物种树法开展分子系统发育分析，涵盖分子定年分析、祖先分布区重建以及物种分化速率分析。
研究结果：基于本研究构建的系统发育树，结合分子钟估算结果与基于似然法的历史生物地理学重建结果显示，鼓鲷科（Terapontidae）物种于晚中新世时期从东部区域新近迁入金伯利生物区。我们发现，金伯利地区80%的鼓鲷科物种均于过去3百万年前（Ma）在该区域内完成物种分化。进一步的物种分化速率分析显示，约1.4百万年前（Ma）存在一次显著的分化速率转变，该时间点与更新世中期的全球气候变化相吻合，且这一转变主要由金伯利地区的物种形成事件驱动。
主要结论：综合现有证据表明，金伯利生物区实为鼓鲷科（Terapontidae）的进化摇篮，而非进化博物馆。本研究分析为鼓鲷科于晚中新世从东部区域新近迁入金伯利、并在更新世时期因该区域内的物种形成事件驱动而出现物种分化速率显著提升提供了强有力的证据。本研究结果为塑造该区域独特生物区系的进化与生物地理学过程提供了重要见解，可为致力于保护物种及其产生与维持过程的土地管理者提供参考依据。