Lucek K, Sivasundar A, Kristjánsson B K, Skúlason S, Seehausen O
Aquatic Ecology and Evolution, Institute of Ecology & Evolution, University of Bern, Bern, Switzerland; Department of Fish Ecology and Evolution, EAWAG Swiss Federal Institute of Aquatic Science and Technology, Center for Ecology, Evolution and Biogeochemistry, Kastanienbaum, Switzerland.
J Evol Biol. 2014 Sep;27(9):1878-92. doi: 10.1111/jeb.12439. Epub 2014 Jun 27.
When genetic constraints restrict phenotypic evolution, diversification can be predicted to evolve along so-called lines of least resistance. To address the importance of such constraints and their resolution, studies of parallel phenotypic divergence that differ in their age are valuable. Here, we investigate the parapatric evolution of six lake and stream threespine stickleback systems from Iceland and Switzerland, ranging in age from a few decades to several millennia. Using phenotypic data, we test for parallelism in ecotypic divergence between parapatric lake and stream populations and compare the observed patterns to an ancestral-like marine population. We find strong and consistent phenotypic divergence, both among lake and stream populations and between our freshwater populations and the marine population. Interestingly, ecotypic divergence in low-dimensional phenotype space (i.e. single traits) is rapid and seems to be often completed within 100 years. Yet, the dimensionality of ecotypic divergence was highest in our oldest systems and only there parallel evolution of unrelated ecotypes was strong enough to overwrite phylogenetic contingency. Moreover, the dimensionality of divergence in different systems varies between trait complexes, suggesting different constraints and evolutionary pathways to their resolution among freshwater systems.
当遗传限制制约表型进化时，可以预测多样化会沿着所谓的阻力最小的路线进化。为了探讨此类限制及其解除的重要性，对不同年代的平行表型分化进行研究很有价值。在此，我们调查了来自冰岛和瑞士的六个湖栖和溪流三刺鱼系统的邻域进化，其年代跨度从几十年到数千年不等。利用表型数据，我们检验了邻域湖栖和溪流种群之间生态型分化的平行性，并将观察到的模式与类似祖先的海洋种群进行比较。我们发现，无论是在湖栖和溪流种群之间，还是在我们的淡水种群与海洋种群之间，都存在强烈且一致的表型分化。有趣的是，低维表型空间（即单一性状）中的生态型分化迅速，似乎通常在100年内就能完成。然而，生态型分化的维度在我们最古老的系统中最高，只有在那里，不相关生态型的平行进化才足够强大，足以覆盖系统发育偶然性。此外，不同系统中分化的维度在性状复合体之间有所不同，这表明淡水系统在解决这些问题时存在不同的限制和进化途径。
