Budy Phaedra, Luecke Chris
U.S. Geological Survey, Utah Cooperative Fish and Wildlife Research Unit, Department of Watershed Sciences, and The Ecology Center, Utah State University, Logan, UT, 84322, USA,
Oecologia. 2014 Sep;176(1):81-94. doi: 10.1007/s00442-014-2993-8. Epub 2014 Jun 27.
Size dimorphism in fish populations, both its causes and consequences, has been an area of considerable focus; however, uncertainty remains whether size dimorphism is dynamic or stabilizing and about the role of exogenous factors. Here, we explored patterns among empirical vital rates, population structure, abundance and trend, and predicted the effects of climate change on populations of arctic char (Salvelinus alpinus) in two lakes. Both populations cycle dramatically between dominance by small (≤300 mm) and large (>300 mm) char. Apparent survival (Φ) and specific growth rates (SGR) were relatively high (40-96%; SGR range 0.03-1.5%) and comparable to those of conspecifics at lower latitudes. Climate change scenarios mimicked observed patterns of warming and resulted in temperatures closer to optimal for char growth (15.15 °C) and a longer growing season. An increase in consumption rates (28-34%) under climate change scenarios led to much greater growth rates (23-34%). Higher growth rates predicted under climate change resulted in an even greater predicted amplitude of cycles in population structure as well as an increase in reproductive output (Ro) and decrease in generation time (Go). Collectively, these results indicate arctic char populations (not just individuals) are extremely sensitive to small changes in the number of ice-free days. We hypothesize years with a longer growing season, predicted to occur more often under climate change, produce elevated growth rates of small char and act in a manner similar to a "resource pulse," allowing a sub-set of small char to "break through," thus setting the cycle in population structure.
鱼类种群中的体型二态性，包括其成因和后果，一直是备受关注的领域；然而，体型二态性是动态的还是稳定的，以及外源性因素的作用，仍存在不确定性。在此，我们探究了经验性生命率、种群结构、丰度和趋势之间的模式，并预测了气候变化对两个湖泊中北极红点鲑（Salvelinus alpinus）种群的影响。两个种群在小型（≤300毫米）和大型（>300毫米）红点鲑占主导之间剧烈循环。表观存活率（Φ）和特定生长率（SGR）相对较高（40 - 96%；SGR范围为0.03 - 1.5%），与低纬度地区同种鱼类相当。气候变化情景模拟了观测到的变暖模式，导致温度更接近红点鲑生长的最佳温度（15.15℃），生长季节更长。气候变化情景下摄食率的增加（28 - 34%）导致生长率大幅提高（23 - 34%）。气候变化下预测的更高生长率导致种群结构中预测的循环幅度更大，以及繁殖输出（Ro）增加和世代时间（Go）减少。总体而言，这些结果表明北极红点鲑种群（不仅仅是个体）对无冰天数的微小变化极其敏感。我们推测，在气候变化下预计更频繁出现的生长季节较长的年份，会使小型红点鲑的生长率提高，其作用方式类似于“资源脉冲”，使一部分小型红点鲑“突破”，从而设定种群结构的循环。
