FAPESP gathering discusses the scientific importance of the largest family of plants

Distributed throughout every continent in different biomes, species of the family are an absolute evolutionary success, according to José Pirani of USP.

By Fábio de Castro

Agência FAPESP – From an evolutionary point of view, plants of the Compositae family are a complete success: they are predominant among plants worldwide, with almost 30,000 species distributed throughout every continent in the most variable of biomes. The family, also known as Asteraceae, includes species of known plants, such as the sunflower, lettuce, the daisy and the chrysanthemum.

The success of this family throughout the history of the planet has sparked enormous scientific interest, and with the molecular technology available in the last 15 years, the family has increasingly been studied, according to José Rubens Pirani of the Botany Department at the Biosciences Institute (IB) at the University of São Paulo (USP).

On December 5, 2011, Pirani presented work at a conference on the diversification of Compositae, opening the the South American Compositae Meeting, a three-day international gathering that reviewed the most recent developments on the systematics, biogeography, evolution and conservation of the Compositae in South America.

The event, organized by FAPESP in partnership with the National Science Foundation (NSF) and the USP, brought together seven scientists from several countries to share information and develop research collaboration on studies involving species of Compositae. Pirani coordinates the projects “Diversification of megadiverse genera in the Neotropical Region: systematics and evolution of Baccharis L. and Mikania Willd. (Asteraceae)” and “Floral evolution and systematics of Galipeinae (Ruaceae),” both of which are financed by FAPESP under the Regular Research Awards program.

According to Pirani, Compositae is the most successful as well as the largest family of plants in the angiosperm group. “It is the family with the most impressive success and many utilities. It includes very small plants and trees, which are on the top of mountains, seaside or in deserts. Its species have an important role in innumerous ecosystems and are utilized for production of foodstuff, oil, industrial, ornamental and medicine products,” he said in an interview with Agência FAPESP.

The Asteraceae family is special, beginning with its enormous diversity of forms. Within a single family, it is common to have some homogeneity regarding plant characteristics; however, in the case of Compositae, the only common element is that all of the species have an inflorescence that consists of a cluster of flowers around a common receptacle.

“When we look at a sunflower, we think it is a flow. But, it is an inflorescence formed by a set of flowers. The yellow petals are female flowers that the sunflower has on its periphery. The aspect is one of a petal, but there is an ovary below,” Pirani explained.

The immense diversity of the species, possibly associated with the reproductive success of the family, which spread throughout the planet, is accompanied by a large array of utilities, ranging from ornamental to pharmaceutical and industrial.

“These plants have every type of usage. Still, given the immense variety, they are still underexplored by humans. Today, with more access to chemical extractions, we are discovering new uses for the Asteraceae,” he noted.

The fact that the Compositae have many polyploids – an altered number of chromosomes – fascinates geneticists. “The scientific relevance of the family is immense,” Pirani said. “It is important to generate hypotheses to explain why these plants have reached so much diversity. The geneticists are studying the polyploidy and chromosomatic variations of Compositae.”

The diversity and adaptation capacity of the family have also raised many scientific questions for biologists. Pirani explained, “This family apparently emerged in the Cretaceous Period in South America. We ask what happened throughout history to give it such capacity to occupy new lands, generate groups and morphological formations, always surviving past climate changes, the splitting of the continents and the major extinctions before arriving at modern times as the predominant group on Earth.”

The characteristics of the Compositae family explain why many researchers dedicate their lives to study them. “The meeting at FAPESP’s headquarters brought together the scientific community that studies this very important family on which science needs to have more up-to-date data,” Pirani said.

The meeting’s objective is to foster an opportunity for researchers who study Compositae to become acquainted with one another in order to establish scientific collaborations.

“We don’t want to only exchange scientific ideas and disseminate novelties but principally to bring these people, who often only know each other through publications, closer together. On the last day, the conference has two workshops for proposals on collective works,” Pirani explained.

According to Pirani, the 1990s marked the beginning of the molecular age of science. Therefore, the issues debated at the meeting were not limited to the traditional scenario for Compositae but extended to a scientific context that has been updated with DNA.

“There was a revolution in which several groups that were traditionally known and accepted as such were reevaluated based on genetic data. Access to molecular systematics cleared showed the lineage, demanding a revision and a taxonomical rearrangement. We have to seek morphological characteristics that explain some of the relationships suggested by molecular studies,” Pirani said.

Advances in chemistry have facilitated studies of the relationship between plants and animals, which are important for research on Compositae, as another characteristic of the family is that it has a large number of predators and pollinators.

Before the meeting, Pirani noted that the topic would be covered in the meeting at FAPESP’s headquarters by researchers including Thomas Lewinsohn, professor of the Animal Biology Department at Universidade Estadual de Campinas (Unicamp). “They will present new interpretations of the evolution of the relationship between insects and Compositae, in light of this new phylogeny of the family that we have.”

Molecular phylogeny – which, compared with morphology alone, is more informative with respect to consolidated evolutionary relationships – and the techniques that uncover the ultrastructures of pollen in the phylogenetic field are other technologies that were successfully applied in the Asteraceae study.

Despite the utilization of new techniques, traditional biology remains important, according to Pirani. Even with the wealth of information on DNA that laboratories have access to, the efforts of field biologists remain fundamental.

Pirani noted, “The good botanist is not only confined to the chemistry labs, or anatomy or DNA. He or she will have a team, collaborations, or will personally go the field to seek new material. And not only biological material, but new sources of information as well. Many times, we got to a place to collect a certain plant and find another that no one knew existed there. We continue describing innumerous species of the Asteraceae all the time.”

With material continuously being acquired, Pirani affirmed that there is a need for more professionals dedicated to these studies.  He pointed out that there is a tendency for specialization in laboratories because refined techniques demand broader theoretical and methodological studies. However, it is impossible to consolidate all the current knowledge, and the researcher should master the ability to integrate several sources of data.

“We see the need to have a greater number of new students that learn one technique to the fullest and only minimally learn the others,” Pirani said. “The new researchers will need to seek out interdisciplinary interfaces and be capable of identifying, for example, what chemists have to offer of relevance to the biology of the species in nature.”