Abstract
Extensions of species’ geographical distributions, or range extensions, are among the primary ecological responses to climate change in the oceans. Considerable variation across the rates at which species’ ranges change with temperature hinders our ability to forecast range extensions based on climate data alone. To better manage the consequences of ongoing and future range extensions for global marine biodiversity, more information is needed on the biological mechanisms that link temperatures to range limits. This is especially important at understudied, low relative temperatures relevant to poleward range extensions, which appear to outpace warm range edge contractions four times over. Here, we capitalized on the ongoing range extension of a teleost predator, the Australasian snapper Chrysophrys auratus, to examine multiple measures of ecologically relevant physiological performance at the population’s poleward range extension front. Swim tunnel respirometry was used to determine how mid-range and poleward range edge winter acclimation temperatures affect metabolic rate, aerobic scope, swimming performance and efficiency and recovery from exercise. Relative to ‘optimal’ mid-range temperature acclimation, subsequent range edge minimum temperature acclimation resulted in absolute aerobic scope decreasing while factorial aerobic scope increased; efficiency of swimming increased while maximum sustainable swimming speed decreased; and recovery from exercise required a longer duration despite lower oxygen payback. Cold-acclimated swimming faster than 0.9 body lengths sec−1 required a greater proportion of aerobic scope despite decreased cost of transport. Reduced aerobic scope did not account for declines in recovery and lower maximum sustainable swimming speed. These results suggest that while performances decline at range edge minimum temperatures, cold-acclimated snapper are optimized for energy savings and range edge limitation may arise from suboptimal temperature exposure throughout the year rather than acute minimum temperature exposure. We propose incorporating performance data with in situ behaviour and environmental data in bioenergetic models to better understand how thermal tolerance determines range limits.
Highlights
Among the most pervasive consequences of climate change are species redistributions
Relative to ‘optimal’mid-range temperature acclimation, subsequent range edge minimum temperature acclimation resulted in absolute aerobic scope decreasing while factorial aerobic scope increased; efficiency of swimming increased while maximum sustainable swimming speed decreased; and recovery from exercise required a longer duration despite lower oxygen payback
This study presents the first examination of swimming and metabolic performance of a marine fish from the ‘leading edge’ of a climate-driven range extension
Summary
Among the most pervasive consequences of climate change are species redistributions. Globally, species geographic range limits are shifting in latitude, elevation or depth, typically in the direction of the movement of local climate conditions (Chen et al, 2011; Brito-Morales et al, 2018). Much of the efforts to date towards understanding effects of climate on marine species and ecosystems, and especially marine species redistributions, have used statistical approaches, correlating historical ecological data (e.g. distribution, abundance or phenology) to environmental data to identify the factors driving observed trends (Perry et al, 2005; Sunday et al, 2012; Brodie et al, 2015; Hill et al, 2015; Pacifici et al, 2015) These statistical relationships can be extrapolated with forecasted environmental conditions to predict future species distributions (García Molinos et al, 2015; Champion et al, 2019). There is substantial variation in the rate and direction of species redistributions not explained by climate alone that depends at least partially on species-specific biology (Sunday et al, 2015)
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