Protective mechanisms in insects: rates of molecular and phenotypical evolution

Abstract

Rates of molecular evolution of insect protective mechanisms were considered using primary structure modification of defensins, invertebrate antimicrobial peptides as a model. Analysis of 484 pairs of amino acid sequences shows that one amino acid replacement takes in average 10-12 million years. Conservative nature of defensins variability dramatically contrast with fast phenotypical adaptation to environmental alterations occupying usually in insects a period from several to several dozens years.

It is supposed that protective proteins and peptides evolution includes two steps: step of adaptive evolution (from gene duplication to the forming of new protein function) where positive natural selection is a major driving force, and step of postadaptive (neutral) evolution where stabilizing selection and gene drift predominate.