Institute of Molecular
Evolutionary Genetics
















FALL 2012


Previous IMEG Seminars and Abstracts:

Fall 2013

Spring 2013

Fall 2012


Spring 2012

Fall 2011

Fall 2010


Spring 2010
Fall 2009

Spring 2009

Fall 2008

Spring 2008

Fall 2007
Spring 2007
Fall 2006

Spring 2006
Fall 2005
Spring 2005

Fall 2004

Spring 2004

Fall 2003

Spring 2003
Fall 2002





12:10 PM

317 Mueller Lab.

Speaker: Dr. Sayaka Miura - Penn State University - Dept. of Biology


Title: Natural selection and the frequency distributions of mutant nucleotides in human populations


Abstract: Mutation is the ultimate source of genetic variation upon which natural selection operates. There are many different kinds of selection that have been suggested to control the evolutionary change of populations. One of them is to emphasize the importance of temporal fluctuation of selection coefficients in different generations. An extensive theoretical study of this type of selection was conducted in the 1970s and 1980s, but there were no empirical data that could be used for testing the importance of the fluctuating selection models. However, recent genomic data on DNA polymorphism can now be used for testing this type of selection and many investigators have shown a renewal of interest in this issue. I have therefore conducted both theoretical and empirical studies to resolve some persistent controversies over the models to be used. In this study, I focused on the controversy between Gillespie’s model of stabilizing selection effect and Nei and Yokoyama’s competitive selection model. My theoretical study has shown that the frequency distribution of mutant nucleotides can be substantially different between the two models. I then analyzed the frequency distribution of SNP mutant nucleotides obtained from the Central African population (about 1,500,000 SNP sites from about 300 individuals) and those obtained from the genome sequence data from African American populations in the US (about 500,000 single nucleotide polymorphic sites from 2,300 individuals; protein-coding regions only). Interestingly, my analysis of SNP data showed that the effect of fluctuating selection is very small in both models and the distribution of mutant frequencies followed more or less the neutral distribution. By contrast, the genome sequence data showed that the model with competitive selection fits the data better than the neutral mutation or the fluctuating model with the stabilizing selection effect but the estimated variance of selection coefficient was quite small.


1. Bell G. 2010. Fluctuating selection: the perpetual renewal of adaptation in variable environments. Philos Trans R Soc Lond B Biol Sci. 365:87-97.

2. Ana L. Caicedo, Scott H. Williamson, Ryan D. Hernandez, et al. 2007. Genome-wide patterns of nucleotide polymorphism in domesticated rice. Plos Genetics 3(9): e163. Doi:10.1371/journal.pgen.0030163




100 Life Sciences

MARKER LECTURE - Postponed until the Spring 2013 semester


Speaker: Dr. Jonathan Losos - Harvard University - Dept. of Organismic and Evolutionary Biology


Title: Lizards in an Evolutionary Tree: Ecology and Adaptive Radiation of Anoles






100 Life Sciences

MARKER LECTURE - Postponed until the Spring 2013 semester


Speaker: Dr. Jonathan Losos - Harvard University - Dept. of Organismic and Evolutionary Biology


Title: Experimental Studies of Evolution in Nature






107 Forest Resources


Speaker: Dr. Michael Goodisman - Georgia Tech - Dept. of Biology


Title: Molecular Evolution and Sociality in Insects





4:00 PM

100 Life Sciences


Speaker: Dr. Paul Keim - Northern Arizona University - Dept. of Biological Sciences

Title: The Molecular Epidemiology and Forensics of Bacterial Pathogens - Whole Genome Analysis Leads Great Resolution





4:00 PM

100 Life Sciences


Speaker: Dr. Scott Edwards - Harvard University - Dept. of Organismic and Evolutionary Biology

Title: Molecular Ecology in the 21st Century: Genomic Foundations of an Integrative Science






317 Mueller Lab


Speaker: Dr. Iliana Baums - Penn State University - Dept. of Biology


Title: Adaptation to Climate Change in Coral-Algal Symbioses


Abstract: Evolutionary adaptation can be rapid, allowing species to survive climate change. The challenge is to predict which species have or lack adaptive capacity. Ocean warming impacts corals and their narrow thermal tolerance raises questions about their ability to adapt. This is of concern because corals build the physical structure of reefs. Without corals, one of the most diverse ecosystems on earth would cease to exist. Changes in the association between coral hosts and their photosynthetic symbionts can quickly improve temperature tolerance but such changes are often temporary, perhaps because temperature-tolerant symbionts do not transfer as many resources to their hosts compared to temperature-sensitive symbionts. The alternative, evolution of de novo host adaptations is thought to be too slow to keep pace with climate change given the coral’s long generation times, large population sizes and ongoing gene flow. This assumption underlies models predicting the demise of reefs. However, gene flow does not always prevent local adaptation. Further, evolution can be rapid if selection pressure is strong and if the species harbor genetic variability in the trait that is subject to selection. We have gathered data on asexual reproduction, gene flow and functional genetic variation in corals and their symbionts. These data indicate that gene flow among coral and symbiont populations is limited. Further, even within coral populations there is functional genetic variation: symbiont-free coral larvae derived from different parents vary in their response to temperature stress despite ongoing gene flow.  Together, these discoveries changed understanding of dispersal in corals and necessitate a re-evaluation of the capacity of corals to adapt to climate change.