Adaptive Gene Loss in Vertebrates: Photosensitivity as a Model Case

Abstract

Current evolutionary thinking aims to amalgamate the conjectures first set out in Darwin's The Origin of Species with modern genetics to form a unified theory of phylogenetic change that explains the mechanisms mediating the diversity of life. With the advent of molecular biology, it has been shown that the mechanics of evolution fundamentally exert their effect at the molecular level and any genetic modification ultimately becomes fixed in the host genome if the resultant phenotype allows an organism to become better adapted to its ecology. The vertebrate colour visual sensory system, and the photopigment genes that form the first step in light detection, represents an ideal model to illustrate the influence of evolution at a molecular level, which through gene loss, duplication and genome rearrangement may allow an organism to adapt to an ever changing (and spectrally unique) environment.

Key Concepts:

• Modern evolutionary thought seeks to amalgamate a multitude of scientific disciplines to produce a unified theory of phylogenesis.

• Evolution fundamentally exerts its influence at the molecular level of genomes, genes, RNAs and proteins.

• Evolutionary mechanic is a continuous process and specific genetic changes become selectively fixed if the resultant phenotype allows an organism to be better suited to a particular environment.

• Adaptive evolution is the result of an ongoing interaction between an organism's physiology, its drive to survive and reproduce and its immediate ecology.

• The mechanisms that mediate molecular adaptation have permitted the multiplicity of ecological niches to be colonised by a myriad of diverse life forms.

• Sophisticated sensory systems ultimately form the interface that mediates the complex interactions between organisms and varied environments.

• The vertebrate visual system is a model case for determining the mechanics of adaptive evolution.

• In addition to gene duplication, genome rearrangement and genetic drift, gene loss is a major player in shaping the genetic substrate on which molecular adaptation may act.