Edwina Dowle
Doctor of Philosophy, (Zoology)
Study Completed: 2014
College of Sciences
Citation
Thesis Title
Rates of Molecular Evolution and Gene Flow
Read article at Massey Research Online: 
The latitudinal biodiversity gradient (LBG) describes the pattern of higher species diversity in tropical compared to temperate regions. The evolutionary speed hypothesis suggests that species in tropical regions evolve faster than those in temperate regions. Ms Dowle demonstrated that the most popular method for determining variation in the rate of molecular evolution among taxa is seriously flawed. The LBG may result from variations in rates of speciation derived from small-scale population level processes. As species are sometimes defined as reproductively isolated units, it has been hypothesised that hybridisation results in gene flow and the merging of taxa. However, results showed that morphologically distinct taxa were maintained despite high levels of ongoing gene flow. Ms Dowle’s research supports an emerging model that speciation is not limited by the genomic rate of molecular evolution, but that it is frequently driven by natural selection, even in instances of ongoing gene flow.
Supervisors
Professor Steven Trewick
Professor Mary Morgan-Richards