College of Science and Engineering, Flinders University, GPO Box 2100, Adelaide, South Australia 5001, Australia.
School of Agriculture, Food and Wine, The University of Adelaide, Waite Campus, Urrbrae, Adelaide, South Australia 5064, Australia.
Proc Biol Sci. 2020 Apr 29;287(1925):20200045. doi: 10.1098/rspb.2020.0045. Epub 2020 Apr 15.
Island biogeography explores how biodiversity in island ecosystems arises and is maintained. The topographical complexity of islands can drive speciation by providing a diversity of niches that promote adaptive radiation and speciation. However, recent studies have argued that phylogenetic niche conservatism, combined with topographical complexity and climate change, could also promote speciation if populations are episodically fragmented into climate refugia that enable allopatric speciation. Adaptive radiation and phylogenetic niche conservatism therefore both predict that topographical complexity should encourage speciation, but they differ strongly in their inferred mechanisms. Using genetic (mitochondrial DNA (mtDNA) and single-nucleotide polymorphism (SNP)) and morphological data, we show high species diversity (22 species) in an endemic clade of Fijian bees, with most species restricted to highlands and frequently exhibiting narrow geographical ranges. Our results indicate that elevational niches have been conserved across most speciation events, contradicting expectations from an adaptive radiation model but concordant with phylogenetic niche conservatism. Climate cycles, topographical complexity, and niche conservatism could interact to shape island biodiversity. We argue that phylogenetic niche conservatism is an important driver of tropical island bee biodiversity but that this phylogenetic inertia also leads to major extinction risks for tropical ectotherms under future warming climates.
岛屿生物地理学探讨了岛屿生态系统中的生物多样性是如何产生和维持的。岛屿的地形复杂性可以通过提供促进适应性辐射和物种形成的多种生态位来驱动物种形成。然而，最近的研究认为，如果种群偶尔分裂成气候避难所，使异域物种形成成为可能，那么系统发育生态位保守性与地形复杂性和气候变化相结合，也可能促进物种形成。因此，适应性辐射和系统发育生态位保守性都预测地形复杂性应该鼓励物种形成，但它们在推断机制上有很大的不同。我们使用遗传（线粒体 DNA（mtDNA）和单核苷酸多态性（SNP））和形态学数据，展示了斐济蜜蜂一个特有分支的高物种多样性（22 个物种），大多数物种局限于高地，并且经常表现出狭窄的地理范围。我们的结果表明，大多数物种形成事件中，海拔生态位都得到了保守，这与适应性辐射模型的预期相矛盾，但与系统发育生态位保守性一致。气候循环、地形复杂性和生态位保守性可能相互作用，塑造岛屿生物多样性。我们认为，系统发育生态位保守性是热带岛屿蜜蜂生物多样性的一个重要驱动因素，但这种系统发育惯性也会导致热带外温动物在未来气候变暖下面临重大灭绝风险。
