Phylogenetic signal in growth and reproductive traits and in their plasticity: the Descurainia radiation in the Canary Islands
Abstract
Despite the extensive use of phylogenetic methods in comparative plant biology, there is little information on how traits and their plastic responses can be affected by phylogenetic constraints (i.e. limitations in phenotypic expression resulting from the phylogenetic history of a lineage), particularly in plant radiations that may have occurred over a relatively short time period. In this study, we examined phylogenetic constraints in a monophyletic group of species of Descurainia (Brassicaceae) endemic to the Canary Islands.
We measured growth and reproductive traits in a glasshouse experiment representing 17 populations of eight taxa previously analysed in a phylogenetic context. Two water availability treatments were used to assess the plasticity of the examined traits.
Most of the traits did not show strong phylogenetic signal; only weak evidence for phylogenetic constraint was found in traits related to reproduction (total number of flowers, onset of flowering) and biomass allocation to roots. Substantial levels of plasticity were observed in all the examined traits, but plasticity showed little interaction between treatment and taxon, suggesting little divergence among taxa.
Our study provides evidence that phylogenetic constraints in these quantitative traits, including their plastic expression, have not played a significant role in the pattern of phenotypic diversification of this island plant group. Phenotypic plasticity may thus have favoured adjustment to the habitats occupied by each species during the radiation process. (c) 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 174, 384-398.