Scales Jeffrey A, King Aaron A, Butler Marguerite A
Department of Zoology, University of Hawaii at Manoa, Honolulu, Hawaii 96822, USA.
Am Nat. 2009 May;173(5):543-53. doi: 10.1086/597613.
Despite its role in whole-animal performance, the adaptation of muscle physiology related to terrestrial locomotion remains underexplored. We tested evolutionary models based on predator escape and foraging strategies of lizards to assess whether fiber-type composition of a leg muscle is adaptive for behavior. The best-fitting model for fast-twitch fiber-type evolution was one based on predator-escape strategy, while the foraging-mode model fared poorly (Akaike Information Criterion with small sample size correction; DeltaAICc=29.7). According to the predator-escape model, lizards relying on sprints to avoid predators are predicted to have relatively higher proportions of fast glycolytic (FG) fibers (70%), while cryptic lizards are predicted to have relatively higher fast oxidative glycolytic (FOG) fiber proportions (77%). This pattern suggests an evolutionary trend toward greater FG (FOG) fiber composition among lizards that specialize in sprinting (crypsis). The best-fitting model for slow-twitch fibers had a single optimum, suggesting a common selective pressure across these lizards. The second-best model explaining slow-twitch fiber-type evolution was Brownian motion (DeltaAICc=0.80), indicating some support for neutral evolution. We find evidence suggesting that different fiber types occurring in the same muscle can evolve under different evolutionary pressures.
尽管肌肉生理学在动物整体表现中发挥着作用，但与陆地运动相关的肌肉生理学适应性仍未得到充分探索。我们基于蜥蜴的捕食者逃避和觅食策略测试了进化模型，以评估腿部肌肉的纤维类型组成是否适应行为。快速抽搐纤维类型进化的最佳拟合模型是基于捕食者逃避策略的模型，而觅食模式模型表现不佳（采用小样本量校正的赤池信息准则；DeltaAICc = 29.7）。根据捕食者逃避模型，预计依靠冲刺来躲避捕食者的蜥蜴具有相对较高比例的快速糖酵解（FG）纤维（70%），而隐蔽型蜥蜴预计具有相对较高比例的快速氧化糖酵解（FOG）纤维（77%）。这种模式表明，在专门进行冲刺（隐蔽）的蜥蜴中，FG（FOG）纤维组成有增加的进化趋势。慢抽搐纤维的最佳拟合模型有一个单一的最优值，表明这些蜥蜴受到共同的选择压力。解释慢抽搐纤维类型进化的第二佳模型是布朗运动（DeltaAICc = 0.80），这表明对中性进化有一定支持。我们发现有证据表明，同一肌肉中不同的纤维类型可以在不同的进化压力下进化。
