Clay Cressler will talk on
Adaptive genome evolution in salamanders: a phylogenetic perspective
at 12:30 in the EEB lounge (BioSciences 4338)
Salamanders have the largest and most variable genome sizes of all of the vertebrates, and the largest among all animals other than lungfishes. Additionally, there is a wide range of metamorphic strategies across the order, from the standard metamorphosis characteristic of frogs, to neoteny, where somatic development is slowed to the point that individuals sexually mature with most juvenile morphological traits intact, to direct development, where individuals bypass the larval stage and hatch as fully-formed, miniature adults. Among the direct-developing salamanders (plethodontids), there has been a subsequent regaining of metamorphosis. Because of the negative correlation between genome size and development rate (because cell division is slower the larger the genome), we expect that metamorphosis imposes constraints on genome size evolution. The variation in metamorphic strategies coupled with variation in genome sizes in salamanders provides an excellent opportunity to test this hypothesis. I briefly discuss the importance of incorporating phylogenetic information into such a test, and describe a method of phylogenetic comparative analysis that allows users to compare the strength of evidence for several competing adaptive and non-adaptive hypotheses. I apply that method to the salamander genome size dataset and find evidence for adaptive evolution of genome size, with smaller genomes associated with metamorphosis compared to direct development and neoteny. These results suggest that adaptive evolution may play an important role in limiting genome size in salamanders, even as non-adaptive processes (mutation and drift) may play a role in expanding genome size upper bounds.
Dr. Clay Cressler is an NSF Postdoctoral Fellow in the department of Biology at Queen’s University. For his PhD, Clay examined how behavioral and life-history traits are expected to evolve under the joint selection pressures of predation and starvation; this work was done with Dr. Aaron King at the University of Michigan. Clay’s current research investigates host-parasite interactions and how differential investment, by the host, into resource acquisition and allocation can shape ecological and evolutionary dynamics of host-parasite systems. This is an exciting approach because it incorporates energetics into our understanding of host-parasite dynamics and because it has important implications to understanding the evolution of and managing for diseases.
Everyone is welcome to attend
Coffee and treats available at the seminar