Evolution of anterior patterning in Diptera

In the fruit fly, Drosophila, the gene bicoid governs the gene network responsible for the development of the head and thorax in the early fly embryo. Even though it is essential for the proper development of the embryo, bicoid is an evolutionary novelty, present only in a subset of higher flies. Thus, a very intriguing question arises: How did the transition between systems lacking bicoid and systems completely dependent on bicoid occur? To answer this question it is necessary to study how anterior development is coded for in flies that do not have bicoid and how this transition could have happened without fatal consequences.

For this purpose, I am studying anterior embryonic development in two non-model organisms: the hover fly Episyrphus balteatus, for which a bicoid homologue has not been found, and Megaselia abdita, a species where bicoid is present. For the analysis of this system, I decided to clone genes know to be involved in anterior-posterior axis specification such as nanos and orthodenticle. Subsequently, I performed whole mount in situ hybridization to understand the expression of these genes.

I am also studying the function of nanos and orthodenticle by double stranded RNA interference (RNAi), which will ultimately provide us with information on the way anterior patterning operates in both species.

The study of the development of anterior structures in this system should provide valuable information on the way developmental gene networks evolve. I am working on this project under the supervision of Dr. Schmidt-Ott and Dr. Lemke at the University of Chicago.

If you want to know more about this and other research in the Schmidt-Ott lab go to Links

Sexual selection and immune response in Tits (Parus major and Parus caeruleus).

It is now well established that carotenoid based sexual signals are costly to maintain because of their parallel use by the immune system and their role as antioxidants. This multiplicity of functions results in a trade-off between irreversible deposition in feathers and use in physiological processes. Quantifying the effects of antibiotics, as well as antigens on growth and secondary sexual signals, may allow us to better understand the relationships between immune processes and carotenoid based sexual signals. The objectives of this study were twofold: We first intended to compare the effects of a non-replicating (LPS) and a multigenic (SRBC) antigen on the growth of Parus major and Parus caeruleus chicks. Second, we assessed the effects of both an antigen and an antibiotic on growth, circulating plasma carotenoid concentrations and feather coloration (plumage characteristics such as brightness, chroma and UV reflectance) in both species. Our first results show that LPS, contrary to SRBC, had a significant impact on chick's growth even if all chicks had the same weight by fledging. Further, the second phase of this experiment, confirmed the weight loss caused by LPS and that chicks are capable of recovering from it. Interestingly, we observed that the reaction to treatments does not depend on the genetic background of chicks, as they all reacted the same way to antigens and antibiotics. Furthermore, we observed that chicks treated with LPS had significantly less circulating plasma carotenoid than control chicks. However, contrary to our expectation neither antibiotics or LPS caused differences in plumage coloration. I worked on this project for my Master's thesis under the supervision of Dr. Gabriele Sorci.

If you want to know more about this and other research in the Gabriele Sorci's current lab go to Links

Ecology, evolution and performance in Anolis carolinensis

I spent a semester in Dr. Duncan Irschick's laboratory at Tulane University, where we focused on the divergence between isolated populations of Anolis carolinensis lizards occupying different habitats in south-eastern Louisiana. We studied how different selective pressures in each habitat drive divergence between populations in ecological characteristics such as behavior, morphology and performance. During the time I spent at Dr. Irschick's lab, I conducted several projects along this research axis:

1. Inter-population comparison of display behavior

Factors such as habitat visibility and distribution, male competition and predation risk can profoundly affect the evolution of visual displays. Dr Irschick and I compared the field display behavior of Anolis carolinensis in both an urban environment (New Orleans), and an undisturbed, high-predation environment (a Louisiana swamp). We were interested in estimating the relative importance of sexual and natural selection and its consequences on display behavior of green anoles. In order to do this, we quantified variations in the display characteristics, dewlap size and display rates between both populations. We found dramatic differences in the display rates and use of display modifiers between both populations, but no differences in the dewlap size or use of stereotyped display types. This work resulted in a first-authored publication (Bloch, N. & Irschick, D. 2006. An analysis of inter-population divergence in visual display behavior in the green anole. Ethology 112, 370-378).

2. Shrinking dewlap

Elaborate sexual ornaments are a product of sexual selection, and play an essential role in male competition, female attraction and ultimately, reproductive success. The Anolis dewlap is a perfect example of such elaborate male ornaments, used in territorial defense, species recognition, and predator-prey interactions. With Dr. Irschick and other collaborators, we showed that dewlap size drastically changes across seasons in several Louisiana populations. Additionally we kept lizards from these populations in the laboratory to find out if these variations exhibit an endogenous rhythm. A paper with our suggested explanations to the observed seasonal variation in dewlap size resulted from this project (Irschick DJ, Ramos M, Buckley C, Elstrott J, Carlisle E, Lailvaux S, Bloch N, Herrel A, Vanhooydonck B. 2006. Are morphology performance relationships invariant across different seasons? A test with the green anole lizard (Anolis carolinensis). Oikos 14, 49-59).

3. Toe clipping project

Many long term evolutionary studies of lizards use toe-clipping as an easy and permanent method of marking individual animals. Although several previous studies have reported that toe clipping does not affect the performance of terrestrial lizards, little is known of the effects of toe-clipping on performance in arboreal lizards. I used a force platform to compare the clinging performance of green anoles (Anolis carolinensis) before and after toe-clipping. I showed, under the supervision of Dr. Irschick, that toe-clipping drastically reduces the clinging ability of these lizards. This result suggests that researchers should exercise caution when using toe-clipping on arboreal lizards. A first-authored manuscript resulted from this study (Journal of Herpetology 39(2), 288-293).

If you want to know more about this and other research in the Duncan Irschick's current lab go to Links