Research uncovers varying evolution of venom
14 Jan 2016 by qmwwwtqmqt.d qmwwwtqmqt.d
Chemical compounds of venom evolve at different speeds depending on an animal’s evolutionary age and the varying natural selection forces acting upon them, researchers in Israel have found.
Chemical compounds of venom evolve at different speeds depending on an animal’s evolutionary age and the varying natural selection forces acting upon them, researchers in Israel have found.
Research led by Dr Yehu Moran from the Ecology, Evolution and Behaviour Department at the Hebrew University of Jerusalem compared the evolutionary patterns of over 3,500 toxin sequences from 85 gene families spanning the breadth of the animal kingdom. Using both evolutionarily ancient – spiders and centipedes - and “young” – snakes and cone snails - animal groups a new “two-speed” mode of venom evolution was proposed.
Dr Moran, said: “Our research shows while the venoms of ancient lineages evolve more slowly through purifying selection, the venoms in more recent lineages diversify rapidly under the influence of positive selection.”
Before this study, positive selection – the increase in allele frequencies within a population - was recognised as the primary driving force behind venomous evolution, whereas purifying selection – the deletion of alleles within a population – had seldom been acknowledged as a significant factor.
According to Dr Moran and guest scientist Dr Kartik Sungar, the difference lies with how suitable an animal is in their ecological niche. Ancient venomous groups are highly established within their niche; therefore the rate of accumulating variations of toxins slows. However, “young” groups entering a novel ecological niche experience strong positive pressures that diversify their toxins, increasing their variations and efficiency in debilitating respective predators or prey.
Dr. Moran and Dr. Sungar, said: “While positive selection increases the diversity of venom proteins, purifying selection probably aids in preserving the potency of the venom by filtering out mutations that negatively affect toxin efficiency. However, species that have entered the stage of purification and fixation may re-enter the period of expansion if they experience a major shift in ecology and/or environment.”
This study reveals information on the evolutionary chemical arms race between predatory venomous animals, however whether the same theory can be applied to non-predatory venomous animals remains to be seen.
The research was published in PLOS Genetics.
Charlotte Allum
