I am interested in understanding how organisms adapt to environmental conditions that vary with space and time. This environmental heterogeneity leads to major evolutionary and ecological impacts on natural populations. Environmental parameters that vary predictably across spatial gradients can result in distinct selection regimes that produce phenotypic differentiation and local adaptation. With my work, I aim to characterize certain life history traits that vary in populations due to differential selection pressures acting on them and demonstrate how the phenotypic variation observed is evidence of local adaptation.
Doctoral Candidate, Department of Biology, University of Pennsylvania
Advisor: Dr. Paul Schmidt
1. What is the plastic stress response to long term exposure to certain environmental variables?
We look at the plasticity of response in two geographically varying natural populations of Drosophila melanogaster exposed to different temperature and photoperiod regimes. To observe the response, we measure three stress phenotypes – chill coma recovery, heat shock tolerance and starvation resistance, which act as proxies for fitness in the environment.
2. Does the response observed in the lab correspond to the response observed after exposure in a field setting?
The physiological and ecological responses usually investigated under controlled laboratory conditions may not capture the true complexity of the natural environment. In order to resolve this discrepancy, we compare laboratory and field results of environmental manipulations on D. melanogaster. Virgin D. melanogaster females are collected and placed in cages for a five day outdoor treatment in a common garden experiment. After the initial treatment, these flies are then assayed for heat shock resistance and chill coma recovery.
3. How do flies modify their genome transcriptomic levels upon exposure to certain temperature and photoperiod regimes?
We performed a whole genome expression screen for two natural populations of D. melanogaster derived from high and low latitude sources in eastern North America. Both populations were placed under four fully factorial variables:
hot (29 ºC) and cold (14 ºC) temperatures and long day (15 L : 9 D) and short day (9L : 15 D) photoperiod conditions and RNA-Seq was performed for samples from each treatment condition.
Research Assistant, Department of Ecology & Evolution University of Chicago Advisor: Dr. Trevor Price
Phylogeography and phylogenetics of Himalyan passerine bird species
We studied the phylogenetic diversification in several lineages of passerine birds to find a potential common timeframe in which genera split as well as, to test if this coincided with the drastic changes in the ecosystem in the Himalayan range occurring 8–10 million years ago (mya). Thirteen genera of passerine birds (Lanius, Pteruthius, Yuhina, Arachnothera, Phylloscopus, Certhia, Parus, Abroscopus, Alcippe, Stachyris, Ficedula, Copsychus and Turdus) were included in the study because they represent almost all the different niches occupied by passerines in the Himalayas.
For each Himalayan species in each of the 13 genera, sequences for two mitochondrial genes, cytochrome b and ND2, were downloaded from GenBank or generated by using standard or specific PCR conditions and primers from museum specimens. Calibrated phylogenies were calculated on the concatenated data set by applying BEAST software.
The node ages for the respective genus splits indicated that there was a pattern within the different clades, with the most splits occurring in the timeframe of 7–11 mya, which is significantly different from equal distribution of splitting events. The rapid rise of the Himalayan range, combined with strong evidence of global climate change and the development of the monsoon system within the south Asian subcontinent, may have led to such simultaneous speciation events.
Summer Intern, Center for Cellular and Molecular Biology (CCMB), India
Advisor: Dr. Ramesh Aggarwal
Molecular analysis for wildlife conservation: studies on marker development and molecular taxonomy
The project carried out under the short summer training program at CCMB comprised two independent tasks : ascertaining the species status of a venomous snake using molecular tools; and developing resource material in the form of SSR-enriched genomic library for development of new gharial-specific microsatellite markers.