Local diversity in phenological responses of migratory lake sturgeon to warm winters

Rich intraspecific diversity in traits that shape responses to environmental conditions implies that effects of climate change will differ within species or even populations. Nevertheless, few studies investigate how different groups within species respond to climatic fluctuations, and most risk assessments rely upon species-wide generalizations. We studied effects of among-year variation in air temperature on the spring migratory phenology of a metapopulation of lake sturgeon Acipenser fulvescens within waters connecting Lake Huron and Lake Erie of the Laurentian Great Lakes. Sturgeon here express multiple migratory phenotypes that all spawn in either the St. Clair River or Detroit River but differ in their use after spawning of more than 86 000 km(2) of accessible lake and river habitat. Acoustic tracking over nine years (2012-2020) revealed mixed phenological responses to late-winter air temperatures, with three migratory groups arriving at rivers earlier during warm years and one whose arrival was consistent across years regardless of temperature. Notably, two groups that spawn in the same river but overwinter in different lakes entered the river with greater synchrony during warm years because one advanced its phenology while the other did not. The results indicated warm weather could alter the dynamics of the metapopulation and broader community, and exemplify the complexity hidden beneath broadscale generalizations of species' response to climate change.

Automated summary

The rich intraspecific diversity in traits of a metapopulation of lake sturgeon leads to differential responses to climate change within the species. This study focuses on the effects of interannual air temperature variations on the spring migratory phenology of different groups within the sturgeon population. The results show mixed phenological responses to warm temperatures, with some migratory groups arriving earlier during warm years and others showing consistent arrival regardless of temperature. The findings highlight the complexity and individual variation in species' responses to climate change.