Reaction norms of life history traits in response to zinc in Thlaspi caerulescens from metalliferous and nonmetalliferous sites

Abstract

• We examined phenotypic plasticity of fitness components in response to zinc (Zn) in the Zn hyperaccumulator, Thlaspi caerulescens. • Two populations from Zn-enriched soils (M) and two populations from normal soils (NM) were grown in pots at three Zn concentrations (0, 1000 and 8000 mg kg -1 Zn), for an entire life cycle. Growth, Zn accumulation and fitness components were assessed. • Based on vegetative growth, M and NM populations had similar Zn tolerance at 1000 mg kg-1 Zn. However, reproductive output was markedly decreased in NM at 1000 and 8000 mg kg -1 Zn. In M populations, Zn did not affect fitness. However, low Zn status enhanced reproductive output in year 1 compared with year 2 and decreased survival after the first flowering season. • M populations are able to achieve equal fitness across a broad range of Zn concentrations in soil by different combinations of fecundity and longevity. No cost of higher tolerance was demonstrated in M populations. Reproductive traits appeared to be a more sensitive indicator of tolerance than vegetative growth. © The Authors (2006).