Correlates of prolonged swimming performance in F2 hybrids of migratory and non-migratory threespine stickleback ecotypes

Abstract

SUMMARYDetermining which underlying traits contribute to differences in whole-animal performance can be difficult when many traits differ between individuals with high and low capacities. We have previously found that migratory (anadromous marine) and nonmigratory (stream-resident) threespine stickleback (Gasterosteus aculeatus) populations have genetically based differences in prolonged swimming performance (U crit ) that are associated with divergence of a number of candidate morphological and physiological traits (pectoral fin size and shape, body shape, pectoral muscle and heart size, and pectoral muscle metabolic enzyme activities). Here, we use F2 hybrid crosses to determine which traits are correlated with U crit when expressed in a largely randomized genetic background and a range of trait values for other divergent traits. We found that four of our 12 candidate traits were positively correlated with U crit in F2 hybrids and that the combined effects of ventricle mass, pectoral adductor mass and adductor citrate synthase activity accounted for 17.9% of the variation in U crit . These data provide additional support for a causal role of muscle and heart size in mediating intraspecific differences in U crit , but indicate that many candidate morphological and biochemical traits do not have a strong effect on U crit when disassociated from other divergent traits. However, the limited variation in U crit in our F2 hybrid families may have decreased our ability to detect correlations among these candidate traits and U crit . These data suggest that many traits, interactions among traits and traits not measured in this study affect prolonged swimming performance in threespine stickleback. Supplementary material available online at

Effects of intraspecific variation in reproductive traits, pectoral fin use and burst swimming on metabolic rates and swimming performance: a study on the Trinidadian guppy (Poecilia reticulataPeters)

“…Recently, studies have started to examine U crit in ecological and evolutionary contexts (Claireaux et al, 2007;Oufiero et al, 2011;Dalziel and Schulte, 2012;Dalziel et al, 2012a;Dalziel et al, 2012b). Using individual fish, the present study demonstrated a relationship between pectoral fin use, steady swimming cost and U crit .…”

Body Fineness Ratio as a Predictor of Maximum Prolonged-Swimming Speed in Coral Reef Fishes

“…Conversely, Dalziel et al [74] found evidence for a positive association between fineness and endurance performance within only one of two populations. When adjusting for multiple factors that might regulate endurance-swimming performance, however, Dalziel et al [97] found very small effect sizes at the inter-individual level.…”

“…This pattern suggests, not surprisingly, that U max is determined by multiple underlying factors, including unmeasured traits such as cardiac ventricle size, gill surface area, and various properties of the pectoral fin muscle including gearing, size, and enzyme activities [97]. If many factors affect function and these factors are not highly correlated with each other then the standardized effect size of most of these factors must be small (<0.1).…”

Mechanical Transgressive Segregation and the Rapid Origin of Trophic Novelty

“…Like the mechanical systems examined here, most functional systems are complex, vary quantitatively, and are composed of a number of components. Performance abilities as diverse as fish swimming61, damselfly escape performance62, shrew and bat bite force6364, and turtle shell hydrodynamics65 are just a few of the complex phenotypes that are known to exhibit non-additive relationships between component structures, functional, and ecological adaptations. As our understanding of the mechanistic basis of organismal abilities increases, especially in organisms that are known to exhibit porous species boundaries, it will expand our ability to quantitatively assess the myriad functional consequences of hybridization.…”