For instance, Trinidadian guppies ( Poecilia reticulata) from high-predation populations have evolved differences in coloration ( Houde, 1997 Magurran, 2005), life histories ( Reznick et al., 1990 Reznick and Bryga, 1996) and morphology ( Hendry et al., 2006) that are closely connected to aspects of Darwinian fitness compared with low-predation populations. The effects of predators have been documented to lead to phenotypic and (or) genetic changes in a wide array of traits at the whole- and sub-organismal levels ( Langerhans, 2006 Domenici et al., 2008 Langerhans, 2009 Oufiero et al., 2011).
NODUS SHARK TANK DRIVER
As an important driver of DNS, predation has attracted considerable attention ( Blumstein and Daniel, 2005 Domenici et al., 2008 Langerhans, 2009 Oufiero et al., 2011). Specifically, divergent natural selection (DNS) is generally believed to represent the primary mechanism that generates and maintains phenotypic diversity ( Rice and Hostert, 1993 Orr and Smith, 1998 Langerhans, 2009).
locomotion, behaviour and life history) of populations from different habitats toward different adaptive peaks. Natural selection promotes the traits (e.g. Inhabited environmental conditions vary greatly, and habitat conditions are generally believed to be of major evolutionary significance ( Langerhans, 2009). It was interesting to find that the high-predation fish showed an unexpected lower velocity preference, which might represent a compromise between predation avoidance, foraging and energy saving. Thus, the cost of this strategy is an elevated RMR, and no trade-off between unsteady and steady swimming performance was observed in the pale chub population under various predation stresses. The fish from the high-predation populations may improve their predator avoidance capacity primarily through an elevated routine metabolism and shorter response latency to achieve advanced warning and escape, rather than an improved fast-start swimming speed or acceleration. Neither of the kinematic parameters fast-start and critical swimming speed ( U crit) showed a significant difference between the high- and low-predation populations. The fish from the high-predation populations showed a shorter response latency, elevated routine metabolism, lower swimming efficiency at low swimming speed and lower water velocity preference compared with those from the low-predation populations. We also measured the routine metabolic rate (RMR), maximum metabolic rate (MMR) and cost of transport (COT) and calculated the optimal swimming speed ( U opt). To test whether there is predator-driven intra-species variation in the locomotion, metabolism and water velocity preference of pale chub ( Zacco platypus) along a river, we measured unsteady and steady swimming and water velocity preference among fish collected from both high- and low-predation habitats in the Wujiang River.
Fish inhabit environments that vary greatly in terms of predation intensity, and these predation regimes are generally expected to be a major driver of divergent natural selection.
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