Population- and sex-specific divergence in growth patterns between two ninespine stickleback (Pungitius pungitius L) populations

Abstract

Background: Growth rate is an important life-history trait that often shows sex- and population-specific differentiation in many organisms. Yet the relative contributions of additive genetic, non-additive genetic, environmental, and maternal effects underlying these differences remain largely unknown, especially in wild animal populations. Goal: To determine the relative contributions of additive genetic, non-additive genetic, and environmental effects underlying population differences in growth rate between two stickleback populations differing markedly in their body size. Organism: Ninespine stickleback (Pungitius pungitius). Methods: We crossed two phenotypically and genetically distinct populations to produce 'pure' marine (Hel-Hel; small sized), 'pure' pond (Pyö-Py ö; large sized), and 'hybrid' (Hel-Pyö and Pyö-Hel) offspring. We reared them in standardized common garden settings until maturation. Results: Analyses of Von Bertalanffy growth curve parameters revealed that sexes and crosstypes differed in their intrinsic growth rates (k) and asymptotic sizes (L∞8). In general, males and marine fish (Hel-Hel) had higher k and smaller L∞8?than females and fish from the pond (Pyö-Pyö). Fish from 'hybrid' crosses exhibited k and L∞8?intermediate to the 'pure' crosses, but were more similar in both respects to the pure marine than to the pure pond fish. Thus population differentiation in k and L∞8?has a genetic basis, but additive genetic effects do not explain all the observed differences. k and L∞8?were negatively correlated within three cross-types (both 'hybrids' and Pyö-Pyö): low intrinsic growth rates were associated with increased asymptotic size. k and L∞8?were not correlated within the Hel-Hel cross: high intrinsic growth rate was not directly associated with reduced asymptotic size. Neither k nor L ∞8?predicted the age at maturation in Hel-Hel fish, and only poorly so in Pyö-Pyö fish. Conclusion: We discovered genetically based population differentiation in key growth-related life-history traits, but little or no evidence for a role of intrinsic growth rate or asymptotic size in determining the timing of maturation in ninespine stickleback. © 2013 Nurul Izza Ab Ghani.