LOCATING EVOLUTIONARY PRECURSORS ON A PHYLOGENETIC TREE
Article first published online: 6 AUG 2012
© 2012 The Author(s). Evolution© 2012 The Society for the Study of Evolution.
Volume 66, Issue 12, pages 3918–3930, December 2012
How to Cite
Marazzi, B., Ané, C., Simon, M. F., Delgado-Salinas, A., Luckow, M. and Sanderson, M. J. (2012), LOCATING EVOLUTIONARY PRECURSORS ON A PHYLOGENETIC TREE. Evolution, 66: 3918–3930. doi: 10.1111/j.1558-5646.2012.01720.x
- Issue published online: 3 DEC 2012
- Article first published online: 6 AUG 2012
- Accepted manuscript online: 25 JUN 2012 09:02AM EST
- Received March 7, 2012 Accepted June 4, 2012
- Deep homology;
- extra-floral nectary;
- trait evolution
Conspicuous innovations in the history of life are often preceded by more cryptic genetic and developmental precursors. In many cases, these appear to be associated with recurring origins of very similar traits in close relatives (parallelisms) or striking convergences separated by deep time (deep homologies). Although the phylogenetic distribution of gain and loss of traits hints strongly at the existence of such precursors, no models of trait evolution currently permit inference about their location on a tree. Here we develop a new stochastic model, which explicitly captures the dependency implied by a precursor and permits estimation of precursor locations. We apply it to the evolution of extrafloral nectaries (EFNs), an ecologically significant trait mediating a widespread mutualism between plants and ants. In legumes, a species-rich clade with morphologically diverse EFNs, the precursor model fits the data on EFN occurrences significantly better than conventional models. The model generates explicit hypotheses about the phylogenetic location of hypothetical precursors, which may help guide future studies of molecular genetic pathways underlying nectary position, development, and function.