Evolution: Have wings come, gone and come again?

摘要

Can complex traits be re-evolved by lineages that have lost them? Phylogenetic study now suggests that wings may indeed have reappeared several times within the ancestrally wingless stick insects. The evolution of wings is widely regarded as a major contributing factor in the evolutionary success of the insects, providing abundant new possibilities for dispersal, prey capture and predator avoidance. Insect wings (like eyes) are an example of the complex structures whose evolution so troubled Darwin, and which remain important foci for work on the evolution of development. A major question for these structural adaptations -- and for other complex traits, such as sexual reproduction -- is whether lineages that lose them can ever regain them. The prevailing view is that such re-evolution is unlikely because, after their loss, the genes required for their development should be free to accumulate mutations and so become non-functional. This issue is examined directly in a recent paper by Whiting et al. on the evolution of wings in stick insects (Phasmatodea).