Evaluation and synthesis of the growth forms in the family Asteraceae

Background: Plant forms reflect the overall structure of plants and have been classified according to habit, growth or life forms. These terms have often been used interchangeably, making comparisons difficult. Asteraceae exhibits a wide diversity of plant forms, expressed in numerous terms. Questions: Is it possible to propose a classification that synthesizes the terms applied to plant forms in Asteraceae? How are these forms distributed among tribes? Data description: Information on plant form was compiled for 1,240 species representing the 50 recognized tribes and 16 subfamilies of Asteraceae. Study site: Worldwide. Methods: The terminology and morphological traits used to describe growth forms in Asteraceae were reviewed and summarized. Results: One hundred thirty-five terms were identified, several of them used as synonyms or combining morphological, ecological, and reproductive attributes. Based on five morphological criteria, habit, phyllotaxy, stem lignification, persistent underground organs, and life span, a classification composed of nine categories is proposed, and their synonyms are given. Seven tribes showed a great diversity of growth forms (six or more categories). Madieae showed the greatest diversity (eight categories), despite having a lower species richness compared to other tribes; suggesting that species richness is not associated with growth form diversity. Conclusions: The proposal synthesizes the diversity of terms used within Asteraceae based on five morphological criteria and allows the recognition of morphological distribution patterns in the family.