Klobucar Stephen L, Rick Jessica A, Mandeville Elizabeth G, Wagner Catherine E, Budy Phaedra
Department of Watershed Sciences and the Ecology Center Utah State University Logan UT USA.
Present address: Institute of Arctic Biology University of Alaska Fairbanks Fairbanks AK USA.
Ecol Evol. 2021 Mar 5;11(7):3040-3057. doi: 10.1002/ece3.7211. eCollection 2021 Apr.
Polymorphism facilitates coexistence of divergent morphs (e.g., phenotypes) of the same species by minimizing intraspecific competition, especially when resources are limiting. Arctic char ( sp.) are a Holarctic fish often forming morphologically, and sometimes genetically, divergent morphs. In this study, we assessed the morphological and genetic diversity and divergence of 263 individuals from seven populations of arctic char with varying length-frequency distributions across two distinct groups of lakes in northern Alaska. Despite close geographic proximity, each lake group occurs on landscapes with different glacial ages and surface water connectivity, and thus was likely colonized by fishes at different times. Across lakes, a continuum of physical (e.g., lake area, maximum depth) and biological characteristics (e.g., primary productivity, fish density) exists, likely contributing to characteristics of present-day char populations. Although some lakes exhibit bimodal size distributions, using model-based clustering of morphometric traits corrected for allometry, we did not detect morphological differences within and across char populations. Genomic analyses using 15,934 SNPs obtained from genotyping by sequencing demonstrated differences among lake groups related to historical biogeography, but within lake groups and within individual lakes, genetic differentiation was not related to total body length. We used PERMANOVA to identify environmental and biological factors related to observed char size structure. Significant predictors included water transparency (i.e., a primary productivity proxy), char density (fish·ha), and lake group. Larger char occurred in lakes with greater primary production and lower char densities, suggesting less intraspecific competition and resource limitation. Thus, char populations in more productive and connected lakes may prove more stable to environmental changes, relative to food-limited and closed lakes, if lake productivity increases concomitantly. Our findings provide some of the first descriptions of genomic characteristics of char populations in arctic Alaska, and offer important consideration for the persistence of these populations for subsistence and conservation.
多态性通过最小化种内竞争促进同一物种不同形态（如表型）的共存，尤其是在资源有限时。北极红点鲑是一种环北极鱼类，常常形成形态上，有时在基因上也不同的形态。在本研究中，我们评估了来自阿拉斯加北部两个不同湖泊组中七个北极红点鲑种群的263个个体的形态和遗传多样性及差异，这些种群具有不同的长度频率分布。尽管地理距离很近，但每个湖泊组所在的地貌具有不同的冰川年龄和地表水连通性，因此可能在不同时间被鱼类殖民。在各个湖泊中，存在一系列物理（如湖泊面积、最大深度）和生物特征（如初级生产力、鱼类密度），这可能促成了现今红点鲑种群的特征。虽然一些湖泊呈现双峰大小分布，但通过对基于模型的形态测量特征聚类进行异速生长校正后，我们并未在红点鲑种群内部和种群之间检测到形态差异。使用通过测序基因分型获得的15,934个单核苷酸多态性（SNP）进行的基因组分析表明，湖泊组之间存在与历史生物地理学相关的差异，但在湖泊组内部和单个湖泊内部，遗传分化与全长无关。我们使用PERMANOVA来确定与观察到的红点鲑大小结构相关的环境和生物因素。重要的预测因素包括水透明度（即初级生产力的替代指标）、红点鲑密度（鱼·公顷）和湖泊组。较大的红点鲑出现在初级生产力较高且红点鲑密度较低的湖泊中，这表明种内竞争和资源限制较少。因此，如果湖泊生产力随之增加，相对于食物有限和封闭的湖泊，生产力更高且连通性更好的湖泊中的红点鲑种群可能对环境变化更具稳定性。我们的研究结果首次描述了阿拉斯加北极地区红点鲑种群的基因组特征，并为这些种群的生存和保护提供了重要考量。
