Sympatric Divergence and Performance Trade-Offs of Bluegill Ecomorphs

Abstract

Phenotypic plasticity in response to environmental cues can create distinct morphological types within populations. This variation in form, and potentially function, may be a factor in initiating population divergence and the formation of new species. Here we show the translation of sympatric, habitat-specific morphological divergence into performance differences in energy economy, maneuverability and steady-state locomotion. Littoral and pelagic bluegill sunfish ecomorphs show differences in performance that appear adaptive within their respective habitats: greater maneuverability in the heavily vegetated littoral; greater steady-state swimming speed and economy in the open-water pelagic. This represents a trade-off in unsteady versus steady swimming performance, likely because morphological features associated with maximizing maneuverability are incompatible with enhancing steady-swimming performance. This may constrain the direction of adaptive change, maintaining the divergence created by phenotypic plasticity. The combination of habitat specific sympatric adaptation and constraints imposed by performance trade-offs may be an important factor underlying the high rate of speciation in freshwater fishes from post-glacial lakes.

Field swimming behavior in largemouth bass deviates from predictions based on economy and propulsive efficiency

“…Accelerations, decelerations and turning rates (Fig. 1C,D) fell within the range measured during sustained flume swimming at an applied average velocity (Plew et al, 2007;Thiem et al, 2015), and were low in comparison to maximal accelerations and angular velocities during maneuvers, which approach 30 m s −2 and 1000 deg s , respectively, in juvenile bass and other centrarchids of similar body mass (Webb, 1978(Webb, , 1986Ellerby and Gerry, 2011). The fish also followed relatively straight paths as indicated by a mean (±s.d.)…”

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)

“…As such, the observed intraspecific variation in pectoral fin use, swimming cost and U crit could have implications for habitat use in individual fish. For example, Ellerby and Gerry showed that habitat use varies with individual differences in energy economy, steady-state swimming and manoeuvrability in bluegill sunfish (Lepomis macrochirus) (Ellerby and Gerry, 2011). Although P. reticulata often occupy distinct pools in rivers, it remains to be tested whether intraspecific variation in pectoral fin use, swimming cost and U crit influence habitat use within pools and to what degree such relationships (or lack of) affect daily energy expenditures (Careau and Garland, 2012).…”

Streamwise vortices destabilize swimming bluegill sunfish (Lepomis macrochirus)

“…We have data on the contributions of each fin to the wake structure during steady swimming locomotion (Drucker and Lauder, 2001;Tytell, 2006). This species has also been used in studies that examined maneuvering behaviors such as escape responses, maneuvering through complex habitats, braking and accelerating, as well as responses to small hydrodynamic perturbations (Drucker and Lauder, 2001;Ellerby and Gerry, 2011;Lauder, 2009, 2013;Higham, 2007;Standen, 2010;Standen and Lauder, 2005;Tytell and Lauder, 2008). The cost of transport for this species has also been show to increase with the gait transition from pectoral fin to caudal fin locomotion (Kendall et al, 2007).…”