A second view on the evolution of flight in stick and leaf insects (Phasmatodea)

Area of Science:

• Evolutionary Biology
• Zoology

Background:

• Dollo's law posits that complex traits, once lost, cannot be re-evolved.
• Recent studies suggest phenotypic reversals, or trait reacquisition, may violate this law.
• The independent re-evolution of wings in stick and leaf insects (Phasmatodea) is a debated example.

Purpose of the Study:

• To investigate the evolutionary history of wings in Phasmatodea.
• To test the hypothesis of multiple independent wing re-evolution events.
• To examine the role of ocelli in understanding flight evolution in these insects.

Main Methods:

• Phylogenetic reconstruction using a comprehensive sample of over 500 phasmatodean species.
• Analysis of wing presence/absence across the reconstructed phylogeny.
• Comparative study of ocelli distribution in relation to wing evolution.

Main Results:

• The study supports an ancestral loss of wings in Phasmatodea, with most lineages originating as wingless.
• Evidence suggests multiple independent re-evolution events of wings within the group.
• Ocelli, though dependent on wings for evolution, are absent in most winged species, supporting the regain hypothesis.

Conclusions:

• The evolutionary history of wings in Phasmatodea demonstrates trait reacquisition and phenotypic reversals.
• The distribution of ocelli provides strong support for the hypothesis of wing regain.
• Further research, including fossil evidence and genetic studies, is needed to fully understand these evolutionary processes.