The goal of phylogenetic studies is to yield more information about how the characteristics of organisms have evolved, not just how the species in a group are related to each other. Current best practice allows for uncertainty in the phylogeny when taking the analysis further, into the comparative analysis, whereas earlier approaches took the phylogenetic tree as a given even if there was considerable uncertainty in it. Professor Ross Crozier's research group in the School of Tropical Biology at James Cook University have used the Bayesian Markov Chain Monte Carlo approach to derive the tree under a simulated annealing approach, and then used the final set of "post burn-in" trees to simulate character evolution and thus derive not only estimates of the uncertainty of the tree but also of the comparative analysis. Their computations typically use runs of 4,000,000 generations in the BMCMC process.
Evolution of weaver ant sociality
Weaver ants of the genus Polyrhachis are well developed in Australia and present a valuable system for studying the evolution of social characteristics. In some species nests are prepared by gluing together leaves using the silk extruded by the larvae. Originally, this was thought to be a derived trait in this genus, but the group's comparative analysis showed that in fact the ancestral species would have been a weaver. In the figure below, the use of silk in nests is shown by an open circle, and it can be clearly seen that the ancestral species in this genus was indeed a weaver.
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Phylogenetic tree of the genus Polyrhachis |
Contacts
Prof. Ross Crozier
and colleagues
School of Tropical Biology,
James Cook University
Publications
Steiner FM et al. 2006. 'No sympatric speciation here: multiple data sources show that the ant Myrmica microrubra is not a separate species but an alternate reproductive morph of Myrmica rubra'. J. Evol. Biol. 19:777-787.
Hasegawa E, Crozier RH. 2006. 'Phylogenetic relationships among species groups of the ant genus Myrmecia'. Mol. Phylog. Evol. 38:575-582
Written by R. Crozier, August 2006