Möhring Jan, Hüllen Sebastian, Martin Sebastian, Mokodongan Daniel F, Wowor Daisy, Schwarzer Julia, Herder Fabian
Museum Koenig Bonn, Leibniz Institute for the Analysis of Biodiversity Change, Adenauerallee 127, D- 53113, Bonn, Germany.
Research Center for Biosystematics and Evolution, Museum Zoologicum Bogoriense, National Research and Innovation Agency (BRIN), Jalan Raya Bogor Km 46, Cibinong, 16911, Indonesia.
BMC Ecol Evol. 2025 Mar 12;25(1):19. doi: 10.1186/s12862-025-02355-1.
Ecological opportunity is considered a main driver of adaptive diversification. Colonization of new areas and habitats provides novel opportunities, which may lead to phenotypic change and rapid diversification. The geographically isolated island Sulawesi in Indonesia hosts numerous endemic radiations. The ricefish family Adrianichthyidae is the most speciose of the few exclusively freshwater-dwelling fish lineages that colonized the tropical island. While the family's distribution includes large parts of Asia, the monophyletic lineage endemic to Sulawesi comprises more than half of all species described, with conspicuous morphological diversity. Using shape and size as proxies for phenotypic and ecological diversity, we first test the hypothesis that Sulawesi ricefishes are more diverse than non-Sulawesi species. We then ask if adaptation to alternative macrohabitats, namely rivers and lakes, can explain phenotypic diversification. We find that Sulawesi ricefishes exhibit greater disparity in body and head shape than non-Sulawesi ricefishes. By including phylogenomic data, we demonstrate that shape diversity in Sulawesi evolved along multiple trajectories, with reduced phylogenetic influence. Changes in body depth and head elongation are prominent, indicating distinct ecological drivers. In particular, body depth evolves along the river-lake axis, and lake species are more diverse compared to riverine ricefishes. In some lacustrine species, pronounced changes in head shape, a trait commonly associated with feeding in fishes, suggest trophic adaptation. Rates of phenotype evolution are higher in the Sulawesi lineages, in particular in lacustrine species. Lastly, we identified opposing trends in size evolution, with generally larger bodies in Sulawesi and repeated miniaturization in non-Sulawesi species. Our results indicate that ecological opportunity greatly influenced the observed phenotype diversity. Low diversity of freshwater fish lineages created environments with reduced competition, whereas additional factors, such as the island's complex geological history, created diverse habitats. As reflected in very localized endemism, species diversity is possibly also driven by long-term spatial isolation, which alone however offers insufficient explanation for the increase in phenotypic disparity. Taken together, ecological opportunity was a dominant driver of the phenotypic diversification of Sulawesi ricefishes, potentially complemented by past introgressive hybridization events and small-scale spatial isolation.
生态机遇被认为是适应性多样化的主要驱动因素。新区域和栖息地的定殖提供了新的机遇，这可能导致表型变化和快速多样化。印度尼西亚地理上孤立的苏拉威西岛拥有众多地方性辐射演化支。稻田鱼科是少数完全栖息于淡水的鱼类谱系中物种最为丰富的，这些鱼类谱系定殖于这个热带岛屿。虽然该科的分布包括亚洲大部分地区，但苏拉威西岛特有的单系谱系包含了已描述的所有物种的一半以上，具有显著的形态多样性。我们以形状和大小作为表型和生态多样性的指标，首先检验苏拉威西稻田鱼比非苏拉威西物种更多样化这一假设。然后我们探究对不同宏观栖息地（即河流和湖泊）的适应是否能解释表型多样化。我们发现苏拉威西稻田鱼在身体和头部形状上比非苏拉威西稻田鱼表现出更大的差异。通过纳入系统基因组数据，我们证明苏拉威西岛鱼类的形状多样性沿着多条轨迹演化，系统发育影响减弱。身体深度和头部伸长的变化很突出，表明存在不同的生态驱动因素。特别是，身体深度沿着河湖轴演化，与河流稻田鱼相比，湖泊物种更加多样。在一些湖泊物种中，头部形状的显著变化（这是一个通常与鱼类摄食相关的特征）表明存在营养适应。苏拉威西谱系的表型进化速率更高，特别是在湖泊物种中。最后，我们在大小进化中发现了相反的趋势，苏拉威西的鱼类通常体型更大，而非苏拉威西物种则反复出现小型化。我们的结果表明，生态机遇极大地影响了观察到的表型多样性。淡水鱼谱系的低多样性创造了竞争减少的环境，而其他因素，如该岛复杂的地质历史，创造了多样的栖息地。正如在非常局部的特有性中所反映的那样，物种多样性可能也受到长期空间隔离的驱动，但仅靠这一点对表型差异增加的解释并不充分。总之，生态机遇是苏拉威西稻田鱼表型多样化的主要驱动因素，过去的渐渗杂交事件和小规模空间隔离可能对其起到了补充作用。
