60. DNA Evolution Rates

Organised by Andrew Allen, Macquarie University, to be held at Network Headquarters, Sydney. First meeting 18-22 May 2009	PARTICIPANTS INCLUDE Andrew Allen (Leader) - Macquarie U, ecological theory Jonathan Davies -NCEAS, USA, phylogenetics James Gillooly - U Florida, USA, physiological ecology Simon Ho - Australian National U, Canberra, bioinformatics Angela Moles - U NSW, plant ecology Rob Lanfear - ANU, molecular evolution rates
May 09>

GOAL

This working group aims to achieve a better understanding of the mechanisms responsible for heterogeneity in rates of molecular evolution among plant taxa. This goal will achieved by tackling two specific tasks during the course of a five-day meeting: (1) compiling data that can be used to assess the magnitudes of changes in rates of molecular evolution with respect to plant size and environmental variables; (2) formulating and testing a range of alternative hypotheses that may account for rate heterogeneity among taxa and environments.

BACKGROUND

Rates of molecular evolution are known to vary substantially among species and environments for both plants and animals, but the driving mechanisms are poorly understood. The mechanisms responsible for rate heterogeneity is currently a topic of intense interest and debate because of its importance for inferring evolutionary relationships among lineages, for dating evolutionary events using DNA-sequence data, and more generally, for understanding what controls evolutionary rates at the level of genotype.

As a first step towards quantifying such heterogeneity in a theoretical framework, Gillooly et al. (2005) proposed a model that yields predictions on rates of molecular evolution in animals based on the two primary determinants of metabolic rate – body size and temperature. The model is derived by combining the neutrality assumption of Kimura’s (1983) theory with the assumption that metabolic rate largely controls mutation rates. Gillooly et al. (2005) demonstrated that the model can account for the higher rates of molecular evolution observed for warm-blooded animals than for ectotherms, and for the higher rates of molecular evolution observed for rodents than for larger-bodied mammals. Allen et al. (2006) subsequently demonstrated that model can also account for differences in rates of molecular evolution among species of planktonic foraminifera along the polar-to-tropical gradient in ocean temperatures.

Preliminary evidence indicates that rates of molecular evolution exhibit similar heterogeneity with respect to plant size (Gaut et al. 1996) and environmental temperature (Davies et al. 2004; Wright et al. 2006). These findings suggest that a model similar in form to that of Gillooly et al. (2005) may predict heterogeneity in rates of molecular evolution among plant species. Importantly, however, the model of Gillooly et al. (2005) is not applicable to plants, as currently formulated, because plants do not have a sequestered germline and their rates of metabolism are controlled by photosynthesis, which exhibits weaker temperature than animal respiration (Allen et al. 2005). Thus, new hypotheses, theoretical models, and empirical analyses are needed to understand the controls on rates of plant evolution at the level of genotype.

Last Updated April 2009