 A trade-off, moreover, exists between fruit size, leaf color, and aphids resistance as varieties with red leaves have smaller fruits, suggesting a cost to the production of red leaves linked to a greater need for reduced aphid infestation.Consistent with red-leaved trees providing reduced survival for aphids, tree species with bright leaves tend to select for more specialist aphid pests than do trees lacking bright leaves (autumn colors are useful only in those species coevolving with insect pests in autumn).The coevolution theory of autumn colors was proposed by W. D. Hamilton in 2001 as an example of evolutionary signalling theory.