Facultad de Artes Liberales, Departamento de Ciencias, Universidad Adolfo Ibáñez, Santiago & Viña del Mar, Chile.
Instituto Milenio de Socio-Ecología Costera 'SECOS', Santiago, Chile.
J Anim Ecol. 2021 Aug;90(8):1961-1972. doi: 10.1111/1365-2656.13514. Epub 2021 May 21.
Our understanding of the plastic and evolutionary potential of ectothermic organisms and their populational impacts in the face of rapid global change remains limited. Studies attempting on the relationship between the magnitude of thermal variability across latitude and the degree of phenotypic plasticity exhibited by marine ectotherms are inconclusive. We state that the latter arises from the narrow range of thermal variability captured by the limited span of the latitudinal gradients studied to date. Using a mechanistic ecophysiological approach and a satellite-based assessment of the relevant environmental variables (i.e. temperature and food availability), we studied individuals of the intertidal barnacle Jehlius cirratus from seven local populations widely spread along the Humboldt current system that spanning two biogeographic regions. At the same time, we synthesized published information on the local abundance of our study species across a total of 76 sites representing 20° of latitude, and spanning from 18 to 42°S. We examined the effects of latitude and environmental variability on metabolic rate plasticity, thermal tolerance (thermal breadth and thermal safety margins) and their impacts on the abundance of this widespread marine invertebrate. We demonstrate that the phenotypic plasticity of metabolic rate in J. cirratus populations is not related to latitude. In turn, thermal breadth is explained by the temperature variability each population experiences. Furthermore, we found clinal variation with a poleward decrease of the critical thermal minimum, suggesting that episodic extreme low temperatures represent a ubiquitous selective force on the lower thermal limit for ectotherms. Across our study gradient, plasticity patterns indicate that populations at the equatorial extreme are more vulnerable to a warming climate, while populations located in the biogeographic transitional zone (i.e. high environmental heterogeneity), on the centre of the gradient, display higher levels of phenotypic plasticity and may represent a genetic buffer for the effects of ocean warming. Together, our results suggest the existence of a fitness trade-off involving the metabolic cost of plasticity and population density that is evident only across the vast latitudinal gradient examined.
我们对变温动物的可塑性和进化潜力及其在快速全球变化面前对种群的影响的理解仍然有限。研究试图确定跨纬度的热变异性幅度与海洋变温动物表现出的表型可塑性程度之间的关系，但结果尚无定论。我们认为，这是由于迄今为止研究的纬度梯度跨度有限，只能捕捉到狭窄的热变异性范围。我们使用一种基于机制的生理生态学方法和基于卫星的相关环境变量（即温度和食物供应）评估，研究了分布在 Humboldt 海流系统的七个当地种群的潮间带藤壶 Jehlius cirratus 的个体，这些种群分布在两个生物地理区域。同时，我们综合了我们研究物种在总共 76 个地点的当地丰度的已发表信息，这些地点代表了 20°的纬度，范围从 18°到 42°S。我们检验了纬度和环境变异性对代谢率可塑性、热耐受性（热幅宽和热安全边际）的影响，以及它们对这种广泛分布的海洋无脊椎动物丰度的影响。我们证明，J. cirratus 种群代谢率的表型可塑性与纬度无关。相反，热幅宽由每个种群经历的温度变异性来解释。此外，我们发现了随着极向变窄的临界热最小值的渐变变化，这表明偶发性的极端低温是对变温动物下限的普遍选择压力。在我们的研究梯度中，可塑性模式表明，处于赤道极端的种群对气候变暖更为脆弱，而位于生物地理过渡区（即高环境异质性）、梯度中心的种群则表现出更高水平的表型可塑性，可能代表了海洋变暖影响的遗传缓冲。总之，我们的研究结果表明，存在一种涉及代谢可塑性成本和种群密度的适应权衡，这种权衡只有在我们研究的广阔纬度梯度上才能显现出来。
