Evo-Devo Discussion Group
Department of Ecology & Evolutionary Biology
University of Connecticut
Evolution of slender salamanders (Plethodontidae: Batrachoseps)
Elizabeth Jockusch and
The slender salamanders, genus Batrachoseps, are the most diverse salamander clade in western North America.
These lungless salamanders are endemic to California, southern Oregon and Baja California. The taxonomy of the group is still largely unresolved due to extreme morphological similarity between genetically well-differentiated species. Our aim is to compile a multilocus dataset including mitochondrial and nuclear DNA sequence data from a geographically comprehensive set of samples to 1) aid in problems of species delineation, 2) identify contact zones between species and characterize potential instances of gene flow between well-differentiated taxa, 3) recover their phylogenetic relationships, and 4) reconstruct the biogeographic history of the group.
We are also using these data to examine hypotheses for an evolutionary history involving isolation, secondary contact, and differential movement of males and females in this group.
Antenna patterning mechanisms in morphologically distinct Tribolium flour beetle species (Tenebrionidae)
Dave Angelini and Moto Kikuchi
Describing the mechanisms through which animal morphology evolves is a major goal of modern biology.
Adult morphology is produced through the processes and genetic networks that comprise development.
However, most comparative developmental studies have focused on widely divergent taxa, obscuring
morphologically significant molecular differences with those incurred over time by genetic drift.
To more directly investigate the evolution of developmental mechanisms underlying morphological
diversification, I am exploring developmental genetic networks responsible for patterning the antennae in closely related species of Tribolium flour beetles. Tribolium castaneum is a species often used in genetic and developmental studies. Its genome has recently been sequenced, and it is amenable to functional analyses using transgenics and RNA interference.
Congenic species have also been used in genetic studies, but provide distinct, fixed antennal phenotypes. My work aims to identify the ontogenetic and molecular changes involved in these divergent paths of morphological evolution.
The evolution of developmental plasticity in salamanders
Tobias Landberg (co-advised by Kurt Schwenk and Carl Schlichting)
My dissertation research focuses on the evolution of developmental plasticity in salamanders. Raising larval salamanders in the lab under a variety of experimental conditions, I compare the developmental trajectories of several ambystomatid species. The goal is to understand how ontogenetic, ecological and phylogenetic sources of phenotypic variation affect critical factors such as swimming performance, the ability to evade predators, developmental rates and size at metamorphosis. This integrative approach is designed to forge explicit links between morphology, organismal performance and fitness in the context of the different environments that species experience.
Diversification of insect appendages
Brigid is broadly interested in the evolution of development of invertebrates. The fantastic morphological differentation across invertebrate taxa is amazing, and how development has been modified to produce these phenotypes is of particular interest. The evo-devo field is an exciting place to be working today, with the advent of molecular techniques that allow us to visualize how genes are patterning organisms through their development. One component of her doctoral thesis focuses upon uncovering the mechanistic basis of gill differentiation in several species of mayflies that encompass some of the key disparities in gill morphology. Her work involves the characterization of several key "appendage" genes in mayflies to document and describe the roles of these genes in the formation of these homologous, yet highly differentiated structures. Since mayflies are not model organisms for developmental work, much of Brigid's field work in the summer is spent collecting fertilized eggs from female mayflies and subsequently rearing the hatchlings. Along with her developmental work, Brigid is also constructing a molecular phylogeny of the Leptophlebiidae family of mayflies to investigate patterns of gill evolution. Leptophlebiids (the "prong-gill" mayflies) are a highly speciose family, with much of the diversity concentrated in the Southern Hemisphere. She will explore gill morphological evolution with this tree, and test explicit hypotheses of gill evolution relating to gill morph and habitat type.
Speciation in skinks of the Plestiodon skiltonianus complex
Jonathan Q. Richmond
Phyletic diversification in North American scincid lizards of the skiltonianus species group is consistent with a model of ecological speciation. The association of certain morphotypes with different environmental conditions suggests that phenotypic divergence is the result of adaptation to contrasting selection regimes. Several lines of evidence suggest that body size was likely the target of natural selection, and that divergences in color pattern and mate recognition are probable secondary consequences of evolving large body size. I am testing these hypotheses using nuclear genetic markers to evaluate levels of gene flow within and among morphotypes.
The evolution of insect wings
Elizabeth Jockusch and Karen Ober
Insect wings are a classic example of an evolutionary innovation whose origin remains obscure. There are two major competing hypotheses for their origin: wings may have arisen de novo from lateral expansions of the dorsal thorax or they may be derived from a branch of the ancestral arthropod leg. Recently, two kinds of developmental data have been used to support the latter hypothesis, that wings are homologous to a branch of crustacean legs. This support rests on the assumption that wing development in Drosophila follows the ancestral pattern in particular respects. We are testing this assumption by using a variety of developmental techniques to investigate wing development in more basal insect lineages.