Wiens Kirsten E, Crispo Erika, Chapman Lauren J
Department of Pathology, New York University School of Medicine, New York, NY, USA.
Integr Zool. 2014 Jan;9(1):85-96. doi: 10.1111/1749-4877.12029.
Gene flow among populations in different selective environments should favor the evolution of phenotypic plasticity over local adaptation. Plasticity in development is a common response to long-term hypoxia in some widespread African fishes, including Pseudocrenilabrus multicolor, a cichlid that exploits both normoxic (high oxygen) rivers/lakes and hypoxic (low oxygen) swamps. Previous studies have shown that fish from normoxic and hypoxic sites differ in many traits, including gill size, brain size and body shape, and that much of this variation reflects developmental plasticity. However, these earlier studies focused on areas in Uganda where gene flow between swamp and river or lake populations is high. In this study we tested the hypothesis that P. multicolor from a relatively isolated lake population (Lake Saka, Uganda) exhibit low levels of plasticity in traits related to oxygen uptake. Multiple broods of P. multicolor from Lake Saka were reared under low and high dissolved oxygen, and traits related to gill size, brain mass and body shape were quantified. Surprisingly, both gill size and brain mass showed high levels of developmental plasticity. We suggest that high levels of plasticity, particularly in the gill size of P. multicolor, reflects low costs of maintaining the plastic response, even in relatively isolated populations.
在不同选择环境中的种群间基因流动，应更有利于表型可塑性的进化而非局部适应性。在一些分布广泛的非洲鱼类中，发育可塑性是对长期低氧的常见反应，包括多色假丽鱼，一种丽鱼科鱼类，它既利用常氧（高氧）的河流/湖泊，也利用低氧（缺氧）的沼泽。先前的研究表明，来自常氧和低氧区域的鱼类在许多性状上存在差异，包括鳃的大小、脑容量和体型，并且这种差异很大程度上反映了发育可塑性。然而，这些早期研究集中在乌干达的一些地区，那里沼泽与河流或湖泊种群之间的基因流动很高。在本研究中，我们检验了这样一个假设：来自相对隔离的湖泊种群（乌干达萨卡湖）的多色假丽鱼在与氧气摄取相关的性状上表现出较低水平的可塑性。将来自萨卡湖的多色假丽鱼的多个亲代群体在低溶解氧和高溶解氧条件下饲养，并对与鳃大小、脑质量和体型相关的性状进行量化。令人惊讶的是，鳃大小和脑质量都表现出高水平的发育可塑性。我们认为，高水平的可塑性，特别是在多色假丽鱼的鳃大小方面，反映了维持可塑性反应的成本较低，即使在相对隔离的种群中也是如此。
