Slowing taxon cycle can explain biodiversity patterns on islands: Insights into the biogeography of the tropical South Pacific from molecular data,Journal of Systematics and Evolution

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Slowing taxon cycle can explain biodiversity patterns on islands: Insights into the biogeography of the tropical South Pacific from molecular data
Journal of Systematics and Evolution ( IF 3.4 ) Pub Date : 2023-11-06 , DOI: 10.1111/jse.13026
Gunnar Keppel _{1,

2} , Francis J. Nge _{3,

4} , Thomas Ibanez ₂

Affiliation

Islands in the tropical Pacific Ocean are renowned for high biodiversity and endemism despite having relatively small landmasses. However, our knowledge of how this biodiversity is formed remains limited. The taxon cycle, where well-dispersed, earlier colonizers become displaced from coastal to inland habitats by new waves of colonizers, producing isolated, range-restricted species, has been proposed to explain current biodiversity patterns. Here, we integrate the outcomes of phylogenetic studies in the region to investigate the sources, age, number of colonizations, and diversification of 16 archipelagos in the tropical and subtropical South Pacific. We then evaluate whether the results support the taxon cycle as a plausible mechanism for these observations. We find that most species in the Pacific arrived less than 5 Mya from geographically close sources, suggesting that colonization by new taxa is a frequent and ongoing process. Therefore, our findings are broadly consistent with the theory of the Taxon Cycle, which posits that ongoing colonization results in the gradual displacement of established lineages. Only the oldest archipelagos, New Caledonia and Fiji, do not conform to this trend, having proportionally less recent colonization events, suggesting that the taxon cycle may slow on older islands. This conclusion is further validated by New Caledonia having lower diversification rate estimates than younger islands. We found that diversification rates across archipelagos are negatively correlated with area and age. Therefore, a taxon cycle that slows with island age appears to be a suitable concept for understanding the dynamic nature and biodiversity patterns of the Pacific Islands.

中文翻译：

减缓分类单元周期可以解释岛屿上的生物多样性模式：从分子数据洞察热带南太平洋的生物地理学

热带太平洋岛屿尽管陆地面积相对较小，但仍以高度生物多样性和特有性而闻名。然而，我们对这种生物多样性如何形成的了解仍然有限。分类单元周期，即分散的早期殖民者被新一波殖民者从沿海栖息地转移到内陆栖息地，产生孤立的、范围有限的物种，有人提出解释当前的生物多样性模式。在这里，我们整合了该地区系统发育研究的成果，调查了南太平洋热带和亚热带 16 个群岛的来源、年龄、殖民数量和多样性。然后，我们评估结果是否支持分类单元循环作为这些观察的合理机制。我们发现太平洋上的大多数物种从地理位置相近的来源抵达的数量少于 5 Mya，这表明新类群的殖民是一个频繁且持续的过程。因此，我们的研究结果与分类单元循环理论大致一致，该理论认为持续的殖民化会导致已建立的谱系逐渐移位。只有最古老的群岛新喀里多尼亚和斐济不符合这一趋势，它们最近的殖民事件相对较少，这表明较古老岛屿上的分类单元周期可能会减慢。新喀里多尼亚的多样化率估计值低于年轻岛屿，进一步验证了这一结论。我们发现群岛的多样化率与面积和年龄呈负相关。因此，随着岛屿年龄的增长而减慢的分类单元周期似乎是理解太平洋岛屿动态性质和生物多样性模式的合适概念。

更新日期：2023-11-06

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