The hyperaccumulation of metals by a rare class of plants is a fascinating and little understood phenomenon. No genetic analysis has been possible since no intraspeci¢c variation is known for this character. Here, we report on crosses between the zinc-hyperaccumulating and -tolerant species Arabidopsis halleri and the non-hyperaccumulating, non-tolerant species Arabidopsis petraea. The F 2 segregates for both characters and it appears that the two characters are genetically independent. The data for tolerance are consistent with a single major gene for this character (although the number of genes for hyperaccumulation cannot be determined), and is probably not very large.

Summary• Hyperaccumulation of metals has been proposed to be a defence against herbivores. Here we investigated whether snails discriminated between plants of Arabidopsis halleri , and the F2 of the cross between A. halleri and A. petraea , on the basis of their internal Zn concentration • A. halleri and F2 plants were grown in four different Zn concentrations. Snails preferred F2 plants to A. halleri plants, and preferred plants that had been grown under low external Zn concentrations, but there was no evidence that they discriminated on the basis of internal Zn concentration • F2 plants were germinated on Zn contaminated soil and snails were allowed to eat the seedlings for a range of different time periods. The survivors were grown on, and tested for, Zn accumulation under standard conditions. No difference was found between the different time periods, indicating that the snails had eaten seedlings randomly • The results do not support a hypothesis that high internal Zn concentration protects seedlings from predation or herbivory by snails