Phenotypic Evolution: The Ongoing Synthesis

I explore the proposition that evolutionary biology is currently in the midst of its greatest period of synthesis. This period, which I call the Ongoing Synthesis, began in 1963 and continues at the present time. I use analysis of citations, conduct, and content to compare the Ongoing Synthesis to widely recognized periods of synthesis in the nineteenth and twentieth centuries. To compare content, I focus on phenotypic evolution and compare current efforts with George Gaylord Simpson’s struggle to understand evolution in deep geological time. The essence of current effort is captured by the question, What is the best model for phenotypic evolution? Although many investigators are actively engaged in answering this question, I single out two examples of my own collaborative work for emphasis here. These two studies share three important characteristics: diagnosis of evolutionary pattern using massive data sets, validation of model parameter values using compilations of estimates (e.g., heritability, stabilizing selection, distance to an intermediate optimum), and identification of evolutionary process using alternative models of stochastic evolution. Our primary findings (discovery of the blunderbuss pattern and the result that rare bursts of evolution carry lineages out of established adaptive zones) compare favorably with important insights from the Modern Synthesis.This is the publisher’s final pdf. The published article is copyrighted by the University of Chicago Press and can be found at: http://www.press.uchicago.edu/ucp/journals/journal/an.html.Keywords: adaptive zone, adaptive radiation, blunderbuss pattern, quantum evolution, deep evolutionary tim

Stochastic population dynamics in populations of western terrestrial garter snakes with divergent life histories

Comparative evaluations of population dynamics in species with temporal and spatial variation in life-history traits are rare because they require long-term demographic time series from multiple populations. We present such an analysis using demographic data collected during the interval 1978–1996 for six populations of western terrestrial garter snakes (Thamnophis elegans) from two evolutionarily divergent ecotypes. Three replicate populations from a slow-living ecotype, found in mountain meadows of northeastern California, were characterized by individuals that develop slowly, mature late, reproduce infrequently with small reproductive effort, and live longer than individuals of three populations of a fast-living ecotype found at lakeshore locales. We constructed matrix population models for each of the populations based on 8–13 years of data per population and analyzed both deterministic dynamics based on mean annual vital rates and stochastic dynamics incorporating annual variation in vital rates. (1) Contributions of highly variable vital rates to fitness (λs) were buffered against the negative effects of stochastic variation, and this relationship was consistent with differences between the meadow (M-slow) and lakeshore (L-fast) ecotypes. (2) Annual variation in the proportion of gravid females had the greatest negative effect among all vital rates on λs. The magnitude of variation in the proportion of gravid females and its effect on λs was greater in M-slow than L-fast populations. (3) Variation in the proportion of gravid females, in turn, depended on annual variation in prey availability, and its effect on λs was 4–23 times greater in M-slow than L-fast populations. In addition to differences in stochastic dynamics between ecotypes, we also found higher mean mortality rates across all age classes in the L-fast populations. Our results suggest that both deterministic and stochastic selective forces have affected the evolution of divergent life-history traits in the two ecotypes, which, in turn, affect population dynamics. M-slow populations have evolved life-history traits that buffer fitness against direct effects of variation in reproduction and that spread lifetime reproduction across a greater number of reproductive bouts. These results highlight the importance of long-term demographic and environmental monitoring and of incorporating temporal dynamics into empirical studies of life-history evolution

Can the Fisher-Lande Process Account for Birds of Paradise and Other Sexual Radiations?

Models of the Fisher‐Lande process (FLP) have been used successfully to explore many aspects of evolution by sexual selection. Despite this success, quantitative tests of these models using data from sexual radiations are rare. Consequently, we do not know whether realistic versions of the FLP can account for the extent and the rate of evolution of sexually selected traits. To answer this question, we generalize the basic FLP model of sexual coevolution and compare predictions of that basic model with patterns observed in an iconic sexual radiation, birds of paradise. Our model tracks the coevolution of male and female traits (two in each sex) while relaxing some restrictive assumptions. Using computer simulations, we evaluate the behavior of the model and confirm that it is an Ornstein‐Uhlenbeck (OU) process. We also assess the ability of the FLP to account for the quantitative aspects of ornament evolution in the genus Paradisaea using published measurements of display traits and a phylogeny of the genus. Finally, we use the program OUwie to compare model fits to generic OU and Brownian motion processes and to estimate FLP parameters. We show that to explain the sexual radiation of the genus Paradisaea one must either invoke extremely weak stabilizing selection on female mating preferences or allow the preference optimum to undergo Brownian motion at a modest rate.Keywords: phenotypic tango, adaptive radiation, Brownian motion, Ornstein‐Uhlenbeck (OU) process, sexual coevolution

Epistasis and Natural Selection Shape the Mutational Architecture of Complex Traits

The evolutionary trajectories of complex traits are constrained by levels of genetic variation as well as genetic correlations among traits. Because the ultimate source of all genetic variation is mutation, the distribution of mutations entering populations profoundly affects standing variation and genetic correlations. Here, we use an individual-based simulation model to investigate how natural selection and gene interactions (i.e., epistasis) shape the evolution of mutational processes affecting complex traits. We find that the presence of epistasis allows natural selection to mold the distribution of mutations, such that mutational effects align with the selection surface. Consequently, novel mutations tend to be more compatible with the current forces of selection acting on the population. These results suggest that in many cases mutational effects should be seen as an outcome of natural selection rather than as an unbiased source of genetic variation that is independent of other evolutionary processes

Evolutionary biology for the 21st century

New theoretical and conceptual frameworks are required for evolutionary biology to capitalize on the wealth of data now becoming available from the study of genomes, phenotypes, and organisms - including humans - in their natural environments.Molecular and Cellular BiologyOrganismic and Evolutionary Biolog

Evolutionary Biology for the 21st Century

We live in an exciting time for biology. Technological advances have made data collection easier and cheaper than we could ever have imagined just 10 years ago. We can now synthesize and analyze large data sets containing genomes, transcriptomes, proteomes, and multivariate phenotypes. At the same time, society's need for the results of biological research has never been greater. Solutions to many of the world's most pressing problems—feeding a global population, coping with climate change, preserving ecosystems and biodiversity, curing and preventing genetically based diseases—will rely heavily on biologists, collaborating across disciplines

The Evolution Of Courtship Behavior In Salamanders. (volumes I And Ii).

PhDZoologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/180230/2/7311306.pd