10/7/2003

A. Joseph Pollard

(Plant Ecology/Evolution: Plant-Herbivore Interactions)

“Evolutionary ecology of metal hyperaccumulation by Thlaspi caerulescens”

Plants differ in both their tolerance of heavy metals and in their ability to accumulate metals from the environment. These differences exist at both a between-species and within-species scale. By examination of within-species variation in metal tolerance and accumulation, we can gain an understanding of the evolutionary dynamics and ecological significance of these characters. This understanding is very relevant to current attempts to exploit metal accumulation as a tool for bioremediation of contaminated sites. We will study Thlaspi caerulescens, a remarkable European plant know to accumulate huge quantities of zinc, cadmium, and nickel. During my recent sabbatical year in England, I began studies of this species, and made collections from localities in Britain and Spain. We will grow plants hydroponically in growth chambers, and examine variation, using quantitative genetics techniques such as heritability analysis, in ability to accumulate metals. We will attempt to relate these variations to differences in metal availability at the sites where plants were collected: Zn/Pb/Cd-rich calamine soils, Ni/Co/Cr-rich serpentine soils, and non-mineralized soils. We will also examine the hypothesis that metal hyperaccumulation represents a defense against herbivores, and investigate the consequences of hyperaccumulation for mobilization of metals into ecosystem food chains.