Abstract
Evolutionary lag-the difference between mean and optimal phenotype in the current environment-is of keen interest in light of rapid environmental change. Many ecologically important organisms have life histories that include stage structure and both sexual and clonal reproduction, yet how stage structure and clonality interplay to govern a population's rate of evolution and evolutionary lag is unknown. Effects of clonal reproduction on mean phenotype partition into two portions: one that is phenotype dependent, and another that is genotype dependent. This partitioning is governed by the association between the nonadditive genetic plus random environmental component of phenotype of clonal offspring and their parents. While clonality slows phenotypic evolution toward an optimum, it can dramatically increase population survival after a sudden step change in optimal phenotype. Increased adult survival slows phenotypic evolution but facilitates population survival after a step change; this positive effect can, however, be lost given survival-fecundity trade-offs. Simulations indicate that the benefits of increased clonality under environmental change greatly depend on the nature of that change: increasing population persistence under a step change while decreasing population persistence under a continuous linear change requiring de novo variation. The impact of clonality on the probability of persistence for species in a changing world is thus inexorably linked to the temporal texture of the change they experience.
Highlights
In a rapidly changing environment, organisms must constantly evolve to maintain fitness and persist
Simulations indicate that the benefits of increased clonality under environmental change greatly depend on the nature of that change: increasing population persistence under a step change while decreasing population persistence under a continuous linear change requiring de novo variation
To determine how clonal reproduction and stage structure jointly impact evolutionary lag and the probability of evolutionary rescue, we develop a general model for phenotypic evolution with both sexual and clonal reproduction
Summary
In a rapidly changing environment, organisms must constantly evolve to maintain fitness and persist. Tion (and with costly offspring), there was an increase in the probability of population persistence after a step change in the optimal phenotype as the association parameter between the parent and clonal offspring environmental component (r) was increased 8), including adult survival and stage structure greatly increased the probability of population persistence for all values of the relative amount of clonal reproduction (rc) and the clonal offspring association parameter (r); all of the curves in figure 8 are shifted to the right compared with the corresponding curves in figure 4 (note the difference in scale for the abscissa). If populations are able to keep their numbers near carrying capacity (as commonly observed in the simulations with a linear change except when populations approached extinction; results not shown), having adults that survive into the time step automatically reduces the number of juveniles (from both sexual and clonal reproduction) that can establish. An example for which fecundity ( f ) was decreased as adult survival (t22) was increased so as to keep the initial decline at the stable stage distribution (l) constant is shown in figure 10
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