Dr. Roshan Vijendravarma
I study evolution of life history traits, especially laying emphasis on how ecology contributes to it. The main focus of my research is on understanding how organisms evolve in response to unfavourable changes in biotic and abiotic factors (e.g. pathogens, parasites and nutrition) within its environment. What is the physiological, behavioural and morphological basis of such adaptations? What are the associated trade-offs? Another focus is on understanding the genetic basis of neglected intra-specific interactions (e.g. Cannibalism) and its contribution to the evolution of other life history traits. To address these questions, I use experimental evolution, artificial selection, molecular genetics, physiology, immunology and neurobiology in the well-studied model system, Drosophila melanogaster.
Adaptation to chronic malnutrition
Populations of diverse organisms periodically face chronic nutritional stress and may evolve adaptations that improve their tolerance to such stress. These adaptations could be physiological, behavioural or morphological, and to elucidate mechanisms of these adaptations and their associated tradeoffs, I use replicate Drosophila populations subjected to experimental evolution for over 150 generations under poor nutritional conditions. The evolved populations have higher fitness on poor diets, mediated through several morphological (e.g. smaller body size) and behavioural (e.g. sitter like foraging behaviour and higher propensity to cannibalise) adaptations. We now know that non-additive effects (epistasis and maternal effects) underlie the genetic architecture of at least some of these adaptive traits.
The vicious cycle of malnutrition and infection: an evolutionary perspective
The link between infection and malnutrition is intricate. Malnourishment is a common occurrence for most species, including our own and makes an individual susceptible to infection, and infection further contributes to malnutrition, thus causing a vicious cycle. Although ample on-going research is directed to understand the physiological basis of this interaction and mechanisms by which this cycle can be intervened, nothing is known about this crucial interaction from an evolutionary perspective. To address this question, I study susceptibility to infections, and other host-pathogen interactions among Drosophila populations adapted to chronic malnutrition.
Larval predatory cannibalism
For over a century, the cannibalistic nature of Drosophila larvae remained unknown to researchers, whilst studies on cannibalistic behaviour itself lacked a suitable model system all along. I described this behaviour recently, demonstrating that it involves active predation on conspecifics, involves sensory cues, has nutritional value, and can evolve rapidly in response to nutritional stress. I am currently investigating the sensory and genetic basis of this behaviour. In addition, I am attempting to understand the evolutionary costs of cannibalism (e.g. infections and inclusive fitness).
Evolution of resistance to intracellular microsporidian parasites
My doctoral research, investigated the host-pathogen interactions between Drosophila and its intracellular microsporidian parasite Tubulinosema kingi. At a physiological level I studied the within-host dynamics of this microsporidia and the host's immune response towards it. While at an evolutionary level, I used an experimental evolution approach, demonstrating that host populations can evolve resistance to microsporidia and that such increased resistance is costly.
Molecular sex-ratio estimation of Asian elephants using dung samples
Determining the sex of wild Asian elephants visually is far more elusive than imagined, often leading to biased sex ratios, when wild populations are censused. I worked on using a molecular sexing method to estimate sex-ratios of wild elephants from dung samples collected along transects. The method involved isolating DNA from the epithelial cells lining dung samples, PCR amplification and restriction site polymorphisms on zinc-finger gene to determine the sex.
Press coverage and interviews (selected):
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- “Cannibal fruit flies: Lab maggots hunt one another”, BBC, May 2013.
- “Mild-mannered flies turn cannibal when short of food”, New Scientist, April 2013.
- “Why do some animals turn cannibalistic?” , The Munich Eye, June 2013.
- “Maggots Observed Chasing, Attacking And Cannibalizing One Another”, Nature World News, May 2013.
- “Young fruit flies go cannibalistic”, Science News, August 2012.
Ph.D., (Sep 2004-Dec 2007):
NERC-Centre for Population Biology,
Imperial College, London, UK (Evolutionary Biology).
Thesis: Host-pathogen interactions in Drosophila-microsporidia model system.
Advisor: Prof. Charles Godfray (now Oxford).
Bangalore University, India (Biotechnology).
Thesis: Sex-ratio estimation of Asian elephant populations from dung (DNA).
Advisor: Prof. Raman Sukumar, Indian Institute of Science (IISc), Bangalore.
Bangalore University, India (Microbiology, Zoology & Chemistry).
B.Sc.-Hons, (1998-99): JIVS, Bangalore, India (Genetic Engineering).
2013 - current:
SNF Senior researcher, Department of Ecology & Evolution,
University of Lausanne, Switzerland.
2008 - 2013:
Post-doctoral research fellow, Department of Ecology & Evolution,
University of Lausanne, Switzerland.
2004 – 2007:
BP-NERC-DHPA-(Doctoral) fellow, NERC-Centre for Population Biology,
Imperial College London, UK.
Vijendravarma, R. K., Narasimha, S. & Kawecki, T. J. (2013) Predatory cannibalism in Drosophila melanogaster larvae. Nature Communications 4 p. 1789.
Vijendravarma, R. K., Narasimha, S. & Kawecki, T. J. (2012) Evolution of foraging behaviour in response to chronic malnutrition in Drosophila melanogaster. Proceedings of the Royal Society B 279(1742) pp. 3540-3546.
Vijendravarma, R. K., Narasimha, S. & Kawecki, T. J. (2012) Adaptation to abundant low quality food improves the ability to compete for limited rich food in Drosophila melanogaster. Plos One 7(1) pp. e30650.
Vijendravarma, R. K., Narasimha, S. & Kawecki, T. J. (2010) Effects of parental larval diet on egg size and offspring traits in Drosophila. Biology Letters 6, 238-241.
Vijendravarma, R. K., Kraaijeveld, A. R. & Godfray, H. C. J. (2009) Experimental evolution shows Drosophila melanogaster resistance to a microsporidian pathogen has fitness costs. Evolution 63, 104-114.
Kolss, M., Vijendravarma, R. K., Schwaller, G. & Kawecki, T. J. (2009) Life-history consequences of adaptation to larva nutritional stress in Drosophila. Evolution 63, 2389-2401.