Abstract Detail


Hinojosa-Espinosa, Oscar [1], Potter, Daniel [2].

Phylogeny of the marigold composites, the Tageteae sensu lato (Asteraceae).

The Tageteae is a New World tribe within the Heliantheae alliance (Asteraceae). As currently circumscribed (i.e., sensu lato), it is composed of 32 genera and 270 species. Most of the diversity and endemism in the tribe is found in North America, especially in Mexico. The tribe includes garden plants, such as the marigolds (e.g. Tagetes spp.) and Dahlberg daisies (Thymophylla spp.), as well as several species that have been used locally as medicines (e.g., Chrysactinia mexicana), spices (e.g., T. micrantha), leaf vegetables (Porophyllum spp.), and in rituals (e.g., T. erecta, used in the Day of Dead, and T. lucida, used in the festivity of Saint Michael the Archangel). Members of this tribe are annuals or perennials, sometimes shrubby or succulent, terrestrial or occasionally aquatic, with mostly opposite leaves that are often pinnatisect and usually have schizogenous secretory cavities. The capitula are mostly radiate, epaleate, with the involucre often connate and mostly bearing secretory cavities, and the cypselae are blackish at maturity and usually crowned by a pappus of scales, bristles, or scales divided into bristles. The secretory cavities found in the leaves and/or bracts are filled with terpenoid essential oils and when they are ruptured, a sweet fragrance or pungent odor is emitted. Within Asteraceae, this type of secretory cavity is found exclusively in the tribe Tageteae, and as traditionally defined (i.e. sensu stricto) the tribe only included taxa with secretory cavities. However, phylogenetic analyses based on molecular data have shown that some genera previously classified in the tribe Helenieae that lack the secretory cavities are nested within the traditional Tageteae. As a result, a broader circumscription of the tribe (Tageteae sensu lato) that includes genera with secretory cavities as well as genera lacking them has been broadly accepted. In addition, it has been noticed that the strongly lignified anther appendages might be one of the unifying features of the Tageteae sensu lato. With the objective of further investigating the evolution of the Tageteae, we conducted phylogenetic analyses based on nuclear and plastid DNA sequences and more extensive taxon sampling than in previous studies. We also performed morphological studies of the anther appendages in almost all genera of the Tageteae sensu lato and in a few taxa outside the tribe for comparison. Our analyses agree with previous phylogenetic studies in resolving some genera lacking secretory cavities as nested within the traditional Tageteae. Most clades representing genera are strongly supported, but the relationships among genera or at the subtribal level are mostly unresolved or weakly supported. We also found that most taxa have strongly lignified anther appendages, but the lignification is also found in other tribes of the Heliantheae alliance. Further phylogenetic analyses based on larger data sets may provide more phylogenetic resolution above the genera level within the tribe. Moreover, sampling the few genera of Tageteae, unavailable for this study, and several additional species of related tribes are needed for a more comprehensive study of the phylogeny of the marigold composites.

1 - 3009 Mercedes Av, Davis, CA, 95616, United States
2 - DEPARTMENT OF PLANT SCIENCES MAIL STOP 2, One Shields Avenue, Davis, CA, 95616, United States

Heliantheae alliance
Secretory cavities
Marigold tribe

Presentation Type: Oral Paper
Number: SYST III010
Abstract ID:370
Candidate for Awards:None

Copyright © 2000-2022, Botanical Society of America. All rights reserved