Data from: Convergence in organ size but not energy metabolism enzyme activities among wild Lake Whitefish (Coregonus clupeaformis) species pairs

The repeated evolution of similar phenotypes by similar mechanisms can be indicative of local adaptation, constraints or biases in the evolutionary process. Little is known about the incidence of physiological convergence in natural populations, so here we test whether energy metabolism in ‘dwarf’ and ‘normal’ Lake Whitefish evolves by similar mechanisms. Prior genomic and transcriptomic studies have found that divergence in energy metabolism is key to local adaptation in whitefish species pairs, but that distinct genetic and transcriptomic changes often underlie phenotypic evolution among lakes. Here, we predicted that traits at higher levels of biological organization, including the activities of energy metabolism enzymes (the product of enzyme concentration and turnover rate) and the relative proportions of metabolically active tissues (heart, liver, skeletal muscle), would show greater convergence than genetic and transcriptomic variation. We compared four whitefish species pairs and found convergence in organ size whereby all dwarf whitefish populations have a higher proportion of red skeletal muscle, three have relatively larger livers and two have relatively larger ventricles than normal fish. On the other hand, hepatic and muscle enzyme activities showed little convergence and were largely dependent on lake of origin. Only the most genetically divergent species pair (Cliff Lake) displayed white muscle enzyme activities matching results from laboratory-reared normal and dwarf whitefish. Overall, these data show convergence in the evolution of organ size, but not in the activities of candidate enzymes of energy metabolism, which may have evolved mainly as a consequence of demographic or ecological differences among lakes.

相似机制驱动相似表型的反复演化，可反映演化进程中的局部适应、演化约束或演化偏向。目前学界对自然种群中生理趋同的发生情况尚知之甚少，因此本研究旨在探究“矮型”与“正常型”湖白鲑（Lake Whitefish）的能量代谢是否通过相似机制演化。此前的基因组与转录组研究已发现，能量代谢的分化是白鲑物种对局部环境适应的关键特征，但不同湖泊间的表型演化往往由迥异的遗传与转录组变化所驱动。本研究预测，处于更高生物学组织层级的性状——包括能量代谢酶活性（酶浓度与周转率的乘积）以及代谢活跃组织（心脏、肝脏、骨骼肌）的相对占比——会比遗传与转录组变异表现出更强的趋同性。我们对四组白鲑物种对进行了比较分析，结果发现器官大小存在趋同演化：所有矮型白鲑种群的红色骨骼肌占比均更高，其中3个种群的肝脏相对更大，2个种群的心室相对大于正常型个体。与之相对，肝脏与肌肉的酶活性则几乎未表现出趋同，且主要取决于其来源湖泊。仅遗传分化程度最高的物种对（克利夫湖种群），其白肌酶活性与实验室饲养的正常型、矮型白鲑的研究结果相符。综上，本研究数据表明，器官大小的演化存在趋同性，但能量代谢候选酶的活性并未表现出趋同——后者的演化可能主要源于不同湖泊间的种群统计或生态差异。