Plants from contrasting coastal (rocky headlands and sand dunes) and inland (dry sclerophyll woodland and moist subtropical rainforest) environments show strong differences in both leaf morphology and plant architecture (Figure 3 from Walter et al., © 2017 The University of Chicago Press, reproduced from Walter et al. (2016) with permission © 2016 The Author(s). Evolution © 2016 The Society for the Study of Evolution

A new University of Queensland-led evolutionary biology study has proposed how natural selection supports the evolution of differences between groups and leads to the formation of new species.

Dr Greg Walter, formerly with UQ’s School of Biological Sciences, said the results suggested that natural selection drives the evolution of small differences by focusing on genetic variation.

This occurs at an early stage of speciation when these differences are too few or too subtle to warrant an organism being classified as a sub-species.

Dr Walter said the study findings were important to expand knowledge of the biological mechanisms that informed adaptation and survival, and timely in the leadup to International Darwin Day 12 February, 2018.

“Using an Australian native wildflower as a model, we focused on understanding how genetic correlations between traits influenced rapid adaptation to new environments,” Dr Walter said.

For example, the genes controlling plant height could also determine plant width and create a strong genetic correlation where wider plants were also taller, while short, wide plants were never observed.

“Natural selection should then occur in directions determined by the availability of genetic variance, along the genetic correlation,” he said.

“However, if natural selection favours a trait combination because it lies away from this genetic correlation – for example, short, wide plant shapes – then adaptation towards this optimal phenotype would be difficult.”

Dr Walter said natural selection could favour certain combinations of traits, but not all trait combinations were possible.

He said the results suggested that that during the early stages of adaptive radiation, natural selection could focus genetic variation and promote rapid adaptive divergence of traits.

“Much research has been done on evolutionary genetics, but there’s still a lot we don’t know,” he said.  

Dr Walter, now of the University of Bristol based in Sicily, worked on the paper while completing his PhD at UQ this year, in the evolutionary genetics lab of School of Biological Sciences’ Associate Professor Daniel Ortiz-Barrientos, which studies the genetics of speciation and adaptation.

The research, Evolution of genetic variance during adaptive radiation, is published in The American Naturalist (doi 10.1086/696123) and was co-authored by UQ Pro Vice Chancellor (Research) Professor Mark Blows, Associate Professor Daniel Ortiz-Barrientos (UQ) and Dr J. David Aguirre (Massey University, NZ).

Media: Dr Greg Walter, Gregory.walter@uqconnect.edu.au, or Associate Professor Daniel Ortiz-Barrientos d.ortizbarrientos@uq.edu.au, +61 7 336 51767, twitter, @dortizba

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