Ontogenetic colour changes in an insular tree species: signalling to extinct browsing birds?
* Animals often use colours to hide from predators (crypsis) or advertise defences (aposematism), but there is little evidence for colour-based defence in plants. * Here, we test whether ontogenetic changes in leaf colour of lancewood (Pseudopanax crassifolius) may have been part of a defensive strategy against flightless browsing birds called moa, which were once the only large herbivores in New Zealand. We tested this hypothesis by conducting spectrographic measurements on different-sized plants grown in a common garden. We also compared these results with observations on a closely related, derived species that evolved in the absence of moa on the Chatham Islands. * Spectrographic analyses showed that birds would have difficulty distinguishing seedling leaves against a background of leaf litter. Conversely, brightly coloured tissues flanking spines on sapling leaves are highly conspicuous to birds. Once above the reach of the tallest known moa, adults produce leaves that are typical in appearance to adult leaves. The Chatham Island species lacks ontogenetic colour changes entirely. * Overall, the results indicate that P. crassifolius goes through a remarkable series of colour changes during development, from cryptically coloured seedlings to aposematically coloured saplings, which may have formed a defensive strategy to protect against giant browsing birds.
Fadzly
Nik
N
School of Biological Sciences, Victoria University of Wellington, PO Box 600, Wellington 6140, New Zealand.
Jack
Cameron
C
School of Biological Sciences, Victoria University of Wellington, PO Box 600, Wellington 6140, New Zealand.
Schaefer
H Martin
HM
Faculty of Biology, Department of Evolutionary Biology and Animal Ecology, University of Freiburg, Hauptstr. 1, 79104 Freiburg, Germany.
Burns
K C
KC
School of Biological Sciences, Victoria University of Wellington, PO Box 600, Wellington 6140, New Zealand.
D000818:Animals; D027481:Araliaceae / Q000254:growth & development / Q000502:physiology*; D005075:Biological Evolution; D001717:Birds; D003116:Color; D005247:Feeding Behavior; D009520:New Zealand; D010858:Pigmentation / Q000502:physiology; D018515:Plant Leaves / Q000254:growth & development / Q000502:physiology*; D014197:Trees / Q000254:growth & development / Q000502:physiology*
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