Studying Evolution From Different Angles

Alan doing fieldwork in Apalachicola National Forest, Florida

Alan Lemmon and Emily Moriarty Lemmon are senior graduate students in evolutionary biology. Their main research focus is studying how new species form.  Alan is a theoretician who uses computer simulations and mathematical models to study evolutionary processes.  Emily is an empirical biologist who studies speciation in North American chorus frogs.  As a married couple, the two collaborate on a number of projects. These include examining the accuracy of models of sequence evolution, estimating historical patterns of migration, identifying abiotic factors driving species divergence, and studying the evolution of reproductive isolation.

As part of his dissertation research, Alan has used analytic models and simulations of hybrid zones to answer two questions:

1) Does sex linkage promote speciation?

and

2) What is the relative role of selection and drift in speciation?

Hybrid crosses and their genotypes (from Alan's thesis).

In addition to doing purely theoretical research, Alan is also working with empiricists to develop statistical tools for data analysis.

One of his current projects is to develop a Bayesian statistical framework for estimating hybrid fitness components, which can be used to study how pre- and postzygotic isolation evolve in natural systems.

He is also working on developing methods for estimating historical patterns of dispersal, which can be used to study how geological and climatic factors drive speciation in different taxa.

Emily looking for frogs in Colonial National Park, Virginia

For her thesis research, Emily studies species formation from the broad to fine scale in chorus frogs (Pseudacris). On the broad end of the spectrum, she has used DNA sequence data to construct phylogenies and correlated speciation events with abiotic factors promoting diversification. She has also examined how components of acoustic signals of frogs evolve and diverge to reduce competition for acoustic space among species.

On the fine scale, Emily has done extensive work at a contact zone between two incipient chorus frog species, where she discovered that selection against hybridization has led to the divergence of reproductive behaviors in sympatry, resulting in the completion of the speciation process.

Although Alan and Emily approach the study of evolution from very different angles, they find that these different approaches lead to fruitful collaborations.

Spotted Chorus Frog <a href="spot/frogs.mp3">listen</a>

Theoretical models provide the substrate for building hypotheses, which can then be tested on real organisms. Experiments and observations in natural systems indicate what is actually happening in the field, and these data, in turn, can inform the theory.

Alan finds that collaborating with Emily on field projects gives him a “reality check” with regard to what organisms are actually doing, and this knowledge helps him to build more realistic biological models and develop more useful statistical tools.  Emily finds that Alan’s theoretical background brings novel ideas and direction to empirical projects. The pair plans to continue collaborating throughout their careers.