Beetle DNA holds key to evolutionary puzzle

Researchers at The University of Western Australia have moved a step closer to understanding the fundamental evolutionary question of variation within a species by studying the genetics of a small brown beetle.

Led by Dr Joseph Tomkins from the UWA Centre for Evolutionary Biology, the research team’s discovery, published in Science, answers a basic question about the origins of genetic variation.

The team studied the cowpea weevil Callosobruchus maculatus using a pedigree, such as that used for breeding dogs or agricultural animals, to show that beetles that were smaller and used their food source less efficiently were from parents that carried more mutations throughout their genome.

Dr Tomkins said the finding that numerous mutations of small effect added up to generate much of the variation between individuals in a population had important implications for understanding evolution.

“Here we have been able to show that a significant proportion of the genetic variation between individuals comes from damaged DNA rather than from other sources - such as the specialisation of different genetic types to different environmental circumstances,” he said.

The research has particular importance for the study of evolution through sexual selection, “Sexual selection, when males compete for access to females or when females are choosy about the males with which they mate, means that some males will not produce offspring.

“A key hypothesis for why females are choosy about the males with which they mate is that they are choosing males with ‘good genes’. Our research suggests that the nature of these good genes is to a large extent simply an absence of mutations.”

Dr Tomkins said the research showed that these unsuccessful males were likely to be the ones with the most mutations and that these males would take their mutations with them when they died, rather than passing them on to the next generation.

The research may have potential applications in the fields of food production, human health and conservation.

“The method used by our researchers has potential to be used in captive breeding programs to identify lineages that have fewer partially recessive mutations. This could facilitate the creation of founding populations with much better long-term prospects.

“Our result suggests that the method we employed could be used to investigate ways of using selective breeding to improve plants and animals for food production.”