A phylogenetic reconstruction of the Compositae tribe Vernonieae, with a focus on the species rich genera Critoniopsis and Vernonanthura, will be used to trace pathways and timings of the radiation of the tribe in the Americas. The Compositae is the largest of all flowering plant families (23,000-30,000 species) and is distributed worldwide. However, the Vernonieae is the only tribe in the family with genera widely radiated in South, Central, and North America in both montane and lowland habitats. Critoniopsis and Vernonanthura have a number of attributes that make them excellent candidates for investigating the effects of the major climatic and geological events that have affected the distribution of many plants and animals in the New World. The radiation spans some of the most biologically significant geologic and climatic events in the region including the uplift of the Andes, the drying of eastern South America, the closure of the Isthmus of Panama (the Great American Interchange) and the formation of the modern West Indian islands. The proposed research will clarify the availability and timing of major dispersal routes between South and North America. DNA sequence data from nuclear and chloroplast genomes will be used to reconstruct the evolutionary histories of Vernonanthura and Critoniopsis. They will be placed within the phylogenetic framework of the tribe thus extending its systematic value. Biogeographical analyses will be conducted using DIVA and likelihood methods in order to explore a range of explanations for the patterns observed. These will be correlated with the phylogenetic position of species in both genera.
The research is highly collaborative and involves students and faculty from Brazil, Mexico, University of Hawaii at Manoa and colleagues at the Smithsonian Institution and the Fairchild Botanical Garden. Graduate and undergraduate students will have multiple opportunities to participate in research and data analyses and efforts will be made to reach out to native Hawaiian students. The Vernonieae are particularly well represented in Brazil and a mini-symposium at the University of Sao Paulo is specifically designed to promote collaborative activities of students who are actively working in Compositae systematics and who will be taking the lead in the not-to-distant future. Through the Encyclopedia of Life (EOL) project information will be shared with the wider scientific community.
The sunflower family, Compositae, is the largest family of flowering plants with 23,000-30,000 species worldwide. It is well represented in South America, where it originated, and North America, where there are hundreds of species, but little is known of pathways and timing of movements between them. The tribe Vernonieae (Iron Weeds) is unique in that it includes two genera (Critoniopsis, Vernonanthura) that extend across this range, have been present for the past 15 my, and are also found in two distinct habitat zones: high elevation, cool areas (8,000-13,000 ft) and low elevation (<5,000 ft) warm, seasonally dry habitats, respectively. Establishing the relationships of the species within these genera through time (their phylogeny) allows us to document major dispersal routes, timing of dispersals and to evaluate the effect of climate on species movement. Many tropical plant and animal groups also share a similar history and distribution making understanding the radiation of Vernonieae broadly applicable to a wide range of disciplines as different as climate modeling, biogeography and animal and plant taxonomy. A dated phylogeny was constructed using DNA sequence data from chloroplast and nuclear gene regions for over 400 species (>1000 sequences). Two major centers of speciation and radiation were found, Brazil, the ancestral home, and another in Mexico/northern Central America. Radiation of Critoniopsis followed the gradual rise of the Andes from central to northern South America 20-3 my ago, stopping in Colombia where mountain building ended. Mexican species previously classified as Critoniopsis were shown to be only distantly related as well as geographically distinct and were placed in a separate genus, Eremosis. There was limited geographic movement of Eremosis species likely due to the presence of the high peaks in the east-west trending Trans Volcanic range. Both of these high elevation genera responded similarly, however, with respect to maintaining their habitat preference over the past 15 million years. Neither was apparently able to adjust to new environments that became available and as a result will continue to be limited to high mountains in their native ranges. The low elevation Vernonanthura, on the other hand, has steadily increased in range, starting from its origin in the area of southern Mexico/northern Central America 15 my ago (rather than Brazil as previously thought) and is now widely distributed in North and South America and the West Indies. Dispersal to the Caribbean and S. America is primarily the result of long distance seed dispersal spanning large expanses of open ocean. Speciation has been rapid especially within the past 5 my and is continuing in areas where the climate has become warmer. Not withstanding its overall adaptation to tropical and subtropical climates, one branch of this genus has also made the transition to eastern North America, a region with a strong winter season and extended periods of frost. Most tropical plant groups are not frost tolerant and it is uncommon for them to develop this type of environmental tolerance. It is likely that Vernonanthura will continue to expand its range with increased global warming as it is both climate tolerant and has good dispersal abilities. The differing responses of these genera suggest that current habitat preferences will strongly influence the ability of different of plants and perhaps animals that depend on them, to adapt to changing environmental conditions. Those that cannot adapt are in danger of extinction. Broader Aspects: A major meeting to bring together students and established researchers from North and South America was hosted with follow up meetings later. The objective was to provide an environment that would promote multi-level intellectual exchange and set the groundwork for future collaborations. The South American Compositae Symposium and field trip held in Sao Paulo Brazil in 2011 was co-sponsored with the Universidade de São Paulo and FAPESP, the Brazilian equivalent of the US National Science, and this grant which also provided student subsidies to attend. Research is a highly collaborative effort in today’s world and it is both necessary and desirable to provide the environment that will foster joint efforts within and among different nations with a shared biota. Other researchers from Europe and Asia along with many from Latin America and the US came together at the meeting of The International Compositae Alliance in Montreal (2012). This latter was again a place for students to meet one another, discuss their research and develop collaborations with the financial support of this grant and collaborating institution. Additionally, research findings were communicated at annual meetings of the Botanical Society of America (2010-2014), and at the 7th Colombian Botanical Congress (2013). Sequences have been deposited in GenBank and publications have resulted from this work. Two graduate students and two undergraduates were trained in all aspects of preparation from DNA extraction through complex data analyses and preparation and submission of journal articles.
