Diversity and evolution of the vascular system in Nyctaginaceae

Abstract

Cambial variants represent alternative forms of secondary growth that generates great anatomical diversity. Studies on species containing cambial variants have been increasingly common in the literature. However, studies integrating information on stem anatomy and ontogeny within a phylogenetic framework are scarce and the study of plants with cambial variants in the context of evolutionary developmental biology remains underexplored. Therefore, the goal of this project is to understand the development, diversity, distribution and evolution of the cambial variants, secondary xylem and phloem in the stems of Nyctaginaceae, a family with ample occurrence in the Neotropics, ample diversity of habits (e.g., herbs, subshrubs, shrubs, trees and lianas) and types of cambial variants (i.e., successive cambia and interxylary phloem). For this, samples will be collected in natural populations, living collections or wood collections, in order to sample all the anatomical diversity found in the family. Standard methods in plant anatomy will be used to obtain anatomical characters and ontogenetic information. Adult samples from representatives of the main clades within the phylogeny of Nyctaginaceae will be sampled, including six of the seven tribes, and 26 genera a priori. Among the genera, some species will be selected for the ontogenetic study, according to the diversity found within the family. Based on the information of ontogeny, types of cambial variants and secondary xylem and phloem, characters will be delimited and reconstructed onto a time-calibrated and robust phylogeny in order to understand how the vascular system has evolved in Nyctaginaceae, and the possible developmental mechanisms that can be involved across the time which may have contributed to the diversification of the group. (AU)