Many animal species such as snakes, insects and fish have evolved camouflage defences to deter attack from their predators. However research published in New Phytologist has discovered that trees in New Zealand have evolved a similar defence to protect themselves from extinct giant birds, providing the first evidence of this strategy in plant life.
"Plants are attacked by a bewildering array of herbivores and in response they have evolved a variety of defences to deter predators such as thorns and noxious chemicals," said lead researcher Dr Kevin Burns from Victoria University of Wellington, New Zealand. "In contrast animals often use colours to hide from predators or advertise defences, but until now there has been little evidence of colour based defences in plants."
Dr Burns' team studied the leaves of the Araliaceae tree (P. crassifolius) a heteroblastic species which is native to New Zealand. This species goes through several strange colour transitions during the process from germination to maturity and the reason for these changes is now thought to be a defence strategy from an extinct predator, the moa.
Before the arrival of humans New Zealand had no native land mammals, but was home to moa, giant flightless birds, closely related to the modern ostrich and the top herbivore predator in the food chain. However moa were hunted to extinction 750 years ago.
The Araliaceae tree has several defences which the team suggest are linked to the historic presence of moa. Seedlings produce small narrow leaves, which appear mottled to the human eye. Saplings meanwhile produce larger, more elongated leaves with thorn-like dentitions.
The mottled colours of seedling leaves are similar to the appearance of leaf litter, which would have made them difficult for a moa to distinguish. The unusual colouring may also reduce the probability of leaf outlines and help camouflage leaves against the sunlight-draped for
|Contact: Ben Norman|