In collaboration with Prof. V.M. Eckhart, I examined the water relations of Clarkia xantiana ssp. xantiana across its geographic range in California, in an effort to understand the environmental factors that constrain species range expansion. Our work is published in the article referenced below:
Eckhart VM, Singh I, Louthan AM, Keledjian AJ, Chu A, Moeller DM, Geber MA (2010) Plant-soil water relations and the species border of Clarkia xantiana ssp. xantiana (Onagraceae). International Journal of Plant Sciences 171:749-760. pdf from JSTOR