Rapid range expansion of a marine ectotherm reveals the demographic and ecological consequences of short-term variability in seawater temperature and dissolved oxygen

The distributions of marine ectotherms are governed by physiological sensitivities to long-term trends in seawater temperature and dissolved oxygen. Short-term variability in these parameters has the potential to facilitate rapid range expansions, and the resulting ecological and socioeconomic consequences may portend those of future marine communities. Here, we combine physiological experiments with ecological and demographic surveys to assess the causes and consequences of sudden but temporary poleward range expansions of a marine ectotherm with considerable life history plasticity (California market squid, Doryteuthis opalescens). We show that sequential factors related to resource accessibility in the core range may drive these expansions—the buildup of large populations due to competitive release, and climate-associated temperature increase and oxygen loss that constrain aerobic activity. We also reveal that poleward range expansion alters the body size—and therefore trophic role—of invading populations, with potential negative implications for socioeconomically valuable resident species. To help forecast rapid range expansions of marine ectotherms, we advocate that research efforts focus on factors impacting resource accessibility in core ranges. Determining how environmental conditions in receiving ecosystems affect body size, and how body size is related to trophic role, will help refine estimates of the impacts of future marine communities.

海洋外温动物（marine ectotherms）的分布格局，由其对海水温度与溶解氧长期变化的生理敏感性所决定。上述环境参数的短期波动，可推动物种快速扩张分布范围，由此产生的生态与社会经济后果，或可预示未来海洋群落的演变趋势。本研究结合生理实验、生态调查与种群统计调查，对一种具有显著生活史可塑性的海洋外温动物——加州市场乌贼（California market squid，学名Doryteuthis opalescens）——的突发性、暂时性向极分布扩张的成因与后果展开评估。研究表明，核心分布区内与资源可获得性相关的一系列连锁因素，或是此类扩张的驱动因子：一是因竞争释放形成大规模种群，二是气候驱动的海水升温与溶解氧流失会限制生物的有氧代谢活动。本研究同时发现，向极分布扩张会改变入侵种群的体型，进而影响其营养生态位，对具有社会经济价值的本地物种存在潜在负面影响。为助力预测海洋外温动物的快速分布扩张，我们倡议未来研究应聚焦核心分布区内影响资源可获得性的各类因素。明确接收生态系统的环境条件如何影响物种体型，以及体型与营养功能间的关联，将有助于更精准地评估未来海洋群落所产生的生态影响。