Evolutionary developmental biology (evo-devo) involves the integration of developmental genetics, phylogenetics and morphology in order to understand how the diversity of life evolved. The origin of developmental processes and their subsequent modifications underlie the plasticity necessary to generate novel features and patterns, which in turn underpin species diversification. Interdisciplinary cohesion between systematic and developmental fields for the study of morphological evolution remains at best patchy. An integrated approach is necessary to understand the genetic basis of developmental traits and their evolutionary significance within a phylogenetic framework. The wealth of opportunity that NGS can provide for systematics and evo-devo offers a timely opportunity to further integrate these fields.
Here, we discuss how NGS can be utilized to address several aspects of plant biology, revolutionizing both the systematic study of species and the genetic basis of the developmental traits that they exhibit. We use the South African daisy Gorteria diffusa Thunb. (Asteraceae) to illustrate the potential of a systematic evo-devo approach to study petal spot development and also discuss the importance of considering homology when generating comparative sequence datasets, as well as related topics.
Integrating systematic and evo-devo studies using NGS
Evo-devo has much to offer systematics because it can provide developmental and functional contexts for traits whose homologies are difficult to assess on the basis of morphology. More fundamentally, it also provides a perspective for understanding evolutionary processes. Plant evo-devo should be a synthesis between developmental genetics, comparative morphology and phylogenetic systematics (Hawkins 2002). Such a synthesis of fields can provide a deeper understanding of traits, illuminating the genetic basis of development and morphology within an evolutionary framework. The data to reconstruct phylogenies have never been more readily available and will become increasingly so with the continuing development of NGS technologies.
However, in practical terms, systematic and developmental fields have not been widely integrated, particularly with regard to the use of phylogenetic estimates for evo-devo studies, which, by definition, should incorporate a phylogenetic context to address the formation and modification of developmental processes and networks. Phylogenetic systematics and comparative morphology provide an optimal basis for sampling strategies and the design of developmental genetic studies. Both broad sampling and rigorous testing of a phylogenetic framework are essential to identify gene sequence homology and reconstruct ancestral states.