Latta, Robert G.
Permanent URI for this collectionhttps://hdl.handle.net/10222/22305
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Item Open Access Conservation genetics as applied evolution: from genetic pattern to evolutionary process(2008-02) Latta, Robert G.Conservation genetics can be seen as the effort to influence the evolutionary process in ways that enhance the persistence of populations. Much published research in the field applies genetic sampling techniques to infer population parameters from the patterns of variation in threatened populations. The limited resolution of these inferences seems to yield limited confidence which results in conservative policy recommendations. As an alternative, I suggest that conservation genetics focus on the relationships between those variables conservationists can control, and the probability of desirable evolutionary outcomes. This research would involve three phases - a greater use of existing evolutionary theory; testing management options using experimental evolution; and 'field trials' under an adaptive management framework. It would take a probabilistic approach that recognizes the stochasticity inherent in evolutionary change. This would allow a more nuanced approach to conservation policy than rule of thumb guidelines. Moreover, it would capitalize on the fact that evolution is a unifying theory in biology and draw on the substantial body of evolutionary knowledge that has been built up over the last half a century.Item Open Access Natural Selection, Variation, Adaptation, and Evolution: a Primer of Interrelated Concepts(2010-11) Latta, Robert G.Natural selection is an elegantly simple concept but one that can manifest in complex ways. I review how the basic model of single-trait viability selection has been extended to more complex forms of selection on multiple traits and on reaction norms. Fitness is defined as the expected lifetime reproductive success for individuals with a given genotype or phenotype over a given range of environments. Since the reproductive success realized by any individual will include a stochastic departure from this expectation, selection is therefore a consistent difference in fitness between organisms with different characteristics. A clear distinction is drawn between selection, which can act on any phenotypic difference, and the response to selection, which can occur only if phenotypic differences are heritable. This distinction separates the action of natural selection in filtering variation from the origin of the novel variants on which selection acts. Since selection frequently acts on standing genetic variation or on conditionally neutral variation, both of which accumulate in populations before the imposition of selection, such variation accumulates independently of its fitness effects under the subsequent selection regime. Recent discussions of "Lamarckian" inheritance must be carefully circumscribed to avoid the implication of directed mutation, for which there is no evidence.Item Open Access Adaptive Value and Costs of Physiological Plasticity to Soil Moisture Limitation in Recombinant Inbred Lines of Avena barbata(2010-02) Maherali, Hafiz; Caruso, Christina M.; Sherrard, Mark E.; Latta, Robert G.Costs are hypothesized to constrain the evolution of adaptive phenotypic plasticity, but they have been difficult to quantify because strong selection should eliminate costly genotypes from natural populations. However, recent studies suggest that crosses between natural populations can recover these genotypes. We determined the adaptive value and costs of, as well as the genetic variation for, physiological and morphological plasticity to soil water limitation in Avena barbata recombinant inbred lines (RILs) created by crossing mesic and xeric ecotypes. All traits were plastic, and plasticity in stomatal limitation of photosynthesis and photosynthetic rate before and at reproduction was adaptive. However, we detected a significant cost of plasticity only for stomatal conductance at reproduction, and the mean cost for all traits of A. barbata RILs was at least 50% smaller than costs previously estimated using RILs. In addition, heritabilities for plasticity were <0.1 and were significant only for photosynthesis at reproduction and leaf mass per unit area. Our results suggest that costs are less likely to constrain the evolution of adaptive plasticity in A. barbata than genetic variation for plasticity.