Abstract
The environment an organism experiences during early development can impact its physiology and survival later in life. The objective of this study was to determine if temperatures experienced at embryonic life stages of brook trout (Salvelinus fontinalis) affected mass and routine metabolic rate (RMR) of a subsequent life stage (free-swimming fry). As part of this, we assessed the contributions and importance of hierarchical levels of biological organization [ancestral type (native vs. hatchery-introgressed), population, and family] to variability in mass and RMR of fry. As embryos and alevin, individuals were reared at either natural environmental (5°C) or elevated (9°C) temperatures and then acclimated to either matched or mismatched temperature treatments once yolk sacs were resorbed. Mass differences among fry were strongly influenced by population of origin as well as initial rearing and final acclimation temperatures. Variation in mass-adjusted RMR of fry was also strongly accounted for by source population, acclimation temperature, and individual mass. A significant interaction between population RMR and final acclimation temperature indicated that not all brook trout populations responded the same way to temperature changes. In contrast to expectations, the highest ancestry category (native vs. introgressed) did not significantly influence mass or mass-adjusted RMR.
Highlights
Environmental temperature is a critical factor that contributes to species’ distributions and abundances, in large part due to its effect on physiological processes (Levins, 1968; Anguilleta, 2009; Schulte et al, 2011)
When accounting for population and final acclimation temperature, individuals initially reared at 9°C were heavier than their siblings initially reared at 5°C (LSM ± SE; 9°C: 380.24 ± 4.87 mg and 5°C: 195.49 ± 6.06 mg; solid symbols versus open symbols, Fig. 2A)
This was true for the final acclimation temperature, controlling for population and initial rearing temperature; fry tested at 9°C were heavier than their siblings tested in colder waters of 5°C (LSM ± SE; 9°C: 318.58 ± 5.01 mg and 5°C: 257.15 ± 5.87 mg)
Summary
Environmental temperature is a critical factor that contributes to species’ distributions and abundances, in large part due to its effect on physiological processes (Levins, 1968; Anguilleta, 2009; Schulte et al, 2011). Increasing global temperatures are contributing to concerns about the capacity for many species and populations to tolerate or adapt to rising. Temperatures, with resultant conservation implications (Carroll et al, 2014) This is true for freshwater species that are unable to relocate to more favourable environments without direct, suitable habitat connections (McCullough et al, 2009; Whitney et al, 2016). Assisted gene flow between populations with differing adaptations carries inherent risks, and should be evaluated thoroughly before adopting evolutionary rescue as a management tool (Garant et al, 2007)
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