When may green plants be aposematic?

During the long, dry summers, the deserts of the Middle East are almost devoid of green plants. In the summer, most annuals, geophytes and hemicryptophytes either are dormant in the soil or have already been eaten by the grazing flocks. Many shrubs are summer deciduous or enter summer dormancy with minimal green canopy. However, there are several common plants that, contrary to the general phenology, are conspicuously green during summer, when all the surroundings are yellow. In such conditions, green is conspicuous and contrasts with the background, as do yellow, red and black in 'greener' ecosystems. The summer-green plants are also characterized by being poisonous or thorny as protection against herbivory. During winter and spring, when there are plenty of other green, more palatable annual plants, herbivory pressure is much lower and they need less protection. We propose that during summer in the dry desert, when most other plants are dry or indistinctive, a vivid green colour can be aposematic.  © 2004 The Linnean Society of London, Biological Journal of the Linnean Society , 2004, 81 , 413–416.