McCourt is a professor in the Department of Biodiversity, Earth and Environmental Science and associate curator of botany at the Academy.
Jillian Adair has a strong interest in the restoration and preservation of the natural ecosystems in the world. It’s an effort, she says, that starts at the lowest rung of the natural world: algae.
“Plants and green algae represent the base of the food chain in many ecosystems. I believe that studying botany—and more specifically phycology (the study of algae)—will help me learn how to understand and eventually repair ecosystems starting from the base of the food chain and working up,” Adair says.
Adair is pursuing undergraduate and graduate degrees in environmental science. She began working in the Botany Department with Richard McCourt, a professor in the Department of Biodiversity, Earth and Environmental Science (BEES) and associate curator of botany, and John Hall, a postdoctoral research associate, as a freshman. Last year, she presented her research at a national meeting of the Phycological Society of America. Her research was supported by a National Science Foundation grant called “Research Experiences for Undergraduates.”
“Green algae are evolutionarily fascinating—some are closely related to land plants—and we continue to study this aspect of their evolutionary history in our lab,” explains Hall. “We do not know how many species exist. Many new species are discovered every year. We do not understand how most species are related to each other or how their unusual life histories and structural characteristics have evolved.”
Their research has zeroed in on saccoderm desmids, a group of green algae that falls under the class Zygnematophyceae, alias “conjugating green algae.” Saccoderm desmids are known to undergo sexual reproduction in order to further their generations. During conjugation, two cells line up and a tube forms between them. Their cellular components migrate to the middle of the tube and merge to form a zygospore, which eventually germinates and grows into a green algal cell.
Although the relationship between saccoderm desmids and land plants are not conclusive, it is believed that the Zygnematophyceae may be the class of algae most closely related to land plants, Adair says. This means that saccoderm desmids and other conjugating green algae may share a more recent common ancestor with land plants than to most other green algae.
To explore this possibility, Adair and Hall have cultured green algae. By doing so, they grow a green algal strain in a defined medium under controlled conditions. Cells are cultured in order to get enough tissue material for DNA sequencing. Through this process, as well as the commonly used method of DNA extraction, they were able to collect and compare the DNA sequences of many green algal strains with others.
Specifically, Adair sequenced the DNA of many strains that fall under a genus of saccoderm desmids, called Cylindrocystis.
“I discovered that this genus is polyphyletic [character states that have converged or reverted to appear to be the same but have not been inherited from a common ancestor],” Adair says. “Therefore, more research needs to be done in order to properly label the two separate clades [groups consisting of an ancestor and all of its descendants, a single branch on the tree of life].”
She continued: “Both of these clades contain morphologically similar taxa (a group(s) of one or more populations of organisms) and each clade appears to undergo conjugation and develop zygospores. One clade contains primarily circular cells compared to the other clade, which has cells of the cylindrical nature, hence the name Cylindrocystis. I also found that one particular Cylindrocystis strain produced zygospores which had three rings around the cell similar to another unrelated genus of green algae, Debarya.”
Currently, Adair is comparing the degree of competition of closely related green algal taxa to that of unrelated green algal taxa. This experiment may provide support for current competitive hypotheses that describe the distribution of species within a freshwater ecosystem.
“We are now trying to correlate the structural and reproductive characteristics to evolutionary history,” says Hall. “This will help us better understand how these reproductive strategies evolved, which characteristics are phylogenetically informative, and how we can improve our classification of Cylindrocystis and other conjugating green algae to better reflect their evolutionary history.”