Evolution of divaricating plants in New Zealand in relation to moa browsing.

New Zealand appears to be the only country where spineless, small-leaved divaricating plants make up nearly 10% of the woody flora. Climatic explanations have been advanced to account for the origin of these divaricating plants. We suggest that the divergent and interlaced branching, the woody exterior and the tough stems of these plants are adaptations evolved in response to browsing by moas. Together with a few species of much smaller birds, moas were the only browsing vertebrates in New Zealand prior to the arrival of man. The divaricate habit is probably only one of several strategies evolved by plants in response to moa browsing. However, because moas fed in a different way from mammals there is little to support the idea that introduced browsing mammals have merely replaced moas as all ecological factor in New Zealand