Department of Biology, The University of Oklahoma, Norman, OK 73019.
Universidad Nacional de Colombia sede Caribe, Centro de Estudios en Ciencias del Mar (CECIMAR), Santa Marta, Magdalena, Colombia.
Proc Natl Acad Sci U S A. 2020 Dec 29;117(52):33396-33403. doi: 10.1073/pnas.2006511117. Epub 2020 Dec 16.
Repeatable, convergent outcomes are prima facie evidence for determinism in evolutionary processes. Among fishes, well-known examples include microevolutionary habitat transitions into the water column, where freshwater populations (e.g., sticklebacks, cichlids, and whitefishes) recurrently diverge toward slender-bodied pelagic forms and deep-bodied benthic forms. However, the consequences of such processes at deeper macroevolutionary scales in the marine environment are less clear. We applied a phylogenomics-based integrative, comparative approach to test hypotheses about the scope and strength of convergence in a marine fish clade with a worldwide distribution (snappers and fusiliers, family Lutjanidae) featuring multiple water-column transitions over the past 45 million years. We collected genome-wide exon data for 110 (∼80%) species in the group and aggregated data layers for body shape, habitat occupancy, geographic distribution, and paleontological and geological information. We also implemented approaches using genomic subsets to account for phylogenetic uncertainty in comparative analyses. Our results show independent incursions into the water column by ancestral benthic lineages in all major oceanic basins. These evolutionary transitions are persistently associated with convergent phenotypes, where deep-bodied benthic forms with truncate caudal fins repeatedly evolve into slender midwater species with furcate caudal fins. Lineage diversification and transition dynamics vary asymmetrically between habitats, with benthic lineages diversifying faster and colonizing midwater habitats more often than the reverse. Convergent ecological and functional phenotypes along the benthic-pelagic axis are pervasive among different lineages and across vastly different evolutionary scales, achieving predictable high-fitness solutions for similar environmental challenges, ultimately demonstrating strong determinism in fish body-shape evolution.
可重复、趋同的结果是进化过程中决定论的初步证据。在鱼类中，众所周知的例子包括微进化过程中从淡水栖息地向水层的过渡，其中淡水种群（如棘鱼、慈鲷和白鲑）反复向细长的浮游体型和深体型底栖型分化。然而，在海洋环境中更深层次的宏观进化尺度上，这些过程的后果并不清楚。我们应用了一种基于系统发生基因组学的综合比较方法，来检验关于一个具有全球分布的海洋鱼类进化枝（鲷科的笛鲷和金线鱼）中趋同范围和强度的假说，该进化枝在过去 4500 万年中经历了多次向水层的过渡。我们收集了该组 110 种（约 80%）物种的全基因组外显子数据，并汇总了体型、栖息地占有、地理分布以及古生物学和地质学信息的数据层。我们还使用基因组子集实施了方法，以在比较分析中考虑系统发生不确定性。我们的结果表明，所有主要海洋盆地中的祖先底栖谱系都独立地进入水层。这些进化过渡始终与趋同表型相关联，具有截断尾鳍的深体型底栖形式反复进化为具有叉形尾鳍的细长中层物种。谱系多样化和过渡动态在栖息地之间不对称，底栖谱系的多样化速度更快，并且更频繁地占据中层栖息地，而不是相反。沿底栖-上层过渡轴的趋同生态和功能表型在不同谱系中普遍存在，跨越了极其不同的进化尺度，为类似的环境挑战实现了可预测的高适应性解决方案，最终证明了鱼类体型进化中的强决定论。
