Phylogenetic distribution of regeneration and asexual reproduction in Annelida: regeneration is ancestral and fission evolves in regenerative clades

We describe a Bayesian method for investigating correlated evolution of discrete binary traits on phylogenetic trees. The method fits a continuous-time Markov model to a pair of traits, seeking the best fitting models that describe their joint evolution on a phylogeny. We employ the methodology of reversible-jump (RJ) Markov chain Monte Carlo to search among the large number of possible models, some of which conform to independent evolution of the two traits, others to correlated evolution. The RJ Markov chain visits these models in proportion to their posterior probabilities, thereby directly estimating the support for the hypothesis of correlated evolution. In addition, the RJ Markov chain simultaneously estimates the posterior distributions of the rate parameters of the model of trait evolution. These posterior distributions can be used to test among alternative evolutionary scenarios to explain the observed data. All results are integrated over a sample of phylogenetic trees to account for phylogenetic uncertainty. We implement the method in a program called RJ Discrete and illustrate it by analyzing the question of whether mating system and advertisement of estrus by females have coevolved in the Old World monkeys and great apes. Show more

Regeneration, the replacement of lost body parts, is widespread yet highly variable among animals. Explaining this variation remains a major challenge in biology. Great strides have been made in understanding the phylogenetic distribution, ecological context and developmental basis of regeneration, and these new data are yielding novel insights into why and how regeneration evolves. Here, we review the phylogenetic distribution of regeneration and discuss how the origin, maintenance and loss of regeneration can each be driven by distinct factors. As the complexity of factors affecting regeneration evolution is increasingly appreciated, and as explicitly evolutionary studies of regeneration become more common, the coming years promise exciting progress in revealing the underlying mechanisms that have shaped animal regeneration. Show more