Document Type
Article
Department/Program
Virginia Institute of Marine Science
Publication Date
2002
Journal
MARINE ECOLOGY PROGRESS SERIES
Volume
243
First Page
123
Last Page
131
Abstract
Growth rates in rocky intertidal snails can vary considerably across wave exposure gradients, and have both plastic and genetic bases. However, little is known regarding whether genetic and environmental influences on variation in growth act in the same (cogradient) or in an opposing (countergradient) direction. Determining how genetic and environmental influences on growth covary with one another may improve our understanding of how habitat-specific variation in growth emerges. This study utilized laboratory flumes to examine the effects of high and low water velocities on the growth of intertidal snails Littorina obtusata from a wave-exposed and a sheltered shore. Both flow velocity and source population significantly influenced all measures of growth (shell length, shell thickness, shell mass and tissue mass). Snails from both populations exhibited greater growth in low versus high flow velocity. In addition, snails from the wave-exposed population grew more than snails from the sheltered population regardless of flow treatment. This result yielded a pattern of countergradient variation in growth and suggests that genetic differentiation between the 2 populations was responsible for the more rapid growth of wave-exposed snails. This greater growth potential of wave-exposed snails was particularly evident when they were raised in an environment conducive to rapid growth (i.e. low flow velocity). Most examples of countergradient variation in the growth of intertidal gastropods have involved temperature effects on latitudinally separated populations. This study provides evidence that countergradient variation in growth can occur on localized spatial scales in response to environmental cues other than temperature. On rocky intertidal shores, countergradient variation in growth may reflect selection for fast-growing genotypes to offset limitations on foraging time imposed by increased hydrodynamic stress on wave-exposed shores.
DOI
10.3354/meps243123
Keywords
cogradient variation; countergradient variation; foraging; growth; natural selection; Littorina obtusata; plasticity; predation; wave energy
Recommended Citation
Trussell, GC, Evidence of countergradient variation in the growth of an intertidal snail in response to water velocity (2002). MARINE ECOLOGY PROGRESS SERIES, 243, 123-131.
10.3354/meps243123
