Abstract
The ability to adapt to changing environments is fundamental for species persistence. Both plasticity and genetic selection are potential drivers that allow for traits to be advantageous, thus leading to increases in survival or fitness. Identifying phenotypic plasticity in life history traits of long-lived organisms can be difficult owing to high survival, long generation times, and few studies at sufficient spatial and temporal scales to elicit a plastic response within a population. To begin to understand phenotypic plasticity of a long-lived freshwater fish in response to environmental conditions, we used a long-term data set consisting of over 1,200 mark-recapture events to inform our understanding of dynamic rate functions and life history attributes. Furthermore, we used a common garden experimental approach to confirm whether changes in life history traits are in response to plasticity in the reaction norm or are genetically derived. Using these approaches, we demonstrated differences in life history traits among Pallid Sturgeon (Scaphirhynchus albus) occupying river segments of varying physical and hydrological stress. The common garden experiment corroborated plastic phenotypic expression in reaction norms for age at first maturity, longevity, fecundity, and maximum size. These growth-mediated attributes resulted in differences in overall fitness traits, where Pallid Sturgeon fecundity was greater than a tenfold difference and 3–6 times the number of life-time spawning events. Anthropogenic modifications to river form and function are likely responsible for the variation in life history attributes resulting from an increased metabolic demand for maintaining station, foraging, and migration. Collectively, our approach provided surprising insight into the capabilities of a centenarian fish to dramatically respond to a changing environment.
Highlights
Pallid sturgeon life history.Pallid Sturgeon is a long-lived periodic-strategist that delays maturation and reproduction for several years—in some cases 10–20 years
Phenotypic plasticity was evident in reaction norms for age at first maturity, longevity, fecundity, and maximum size (Fig. 3)
These growth-mediated attributes resulted in differences in overall fitness traits, where differences in Pallid Sturgeon fecundity was greater than a tenfold difference and many more life-time spawning events
Summary
Pallid Sturgeon is a long-lived periodic-strategist that delays maturation and reproduction for several years—in some cases 10–20 years. Literature suggests that Pallid Sturgeon live to 41 y of age 31, but those estimates are based off age assignments from annuli deposition on pectoral fin rays which have been shown to provide inaccurate r esults[32,33]. Recent analyses utilizing bomb radiocarbon has indicated that Pallid Sturgeon from the upper Missouri River obtain an age of at least 65 years[34]. Pallid Sturgeon are estimated to become sexually mature from 10 to 17 years for females and 7 to 10 years for males and both sexes display an intermittent spawning cycle[35]
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