Sorting out the Ruellieae Family Tree

Researching a diverse and widespread plant family, scientists at Rancho Santa Ana Botanic Garden and visiting scientists from Ethiopia are delving into the importance of biodiversity.

Erin Tripp, principal investigator and post-doctoral researcher at Rancho Santa Ana Botanic Garden (RSABG), along with co-principal investigator Lucinda McDade, Judith B. Friend Director of Research at RSABG, are reconstructing the phylogenetic tree (family tree) of the plant lineage Ruellieae to further scientific understanding of the diversity of life.

Focusing on Ruellieae—part of the family Acanthaceae—Tripp and McDade study evolutionary relationships and trait evolution of the largely tropical plant family.

Acanthaceae is part of the broader order Lamiales that includes familiar plants such as the snapdragon, mint and African violet, and is one of the top 12 most diverse families of flowering plants in the world. Despite the diversity and widespread distribution of the Acanthaceae, species-level and even generic-level diversity of the family is still poorly known in some groups—in part because of their tropical habitats that sometimes occur in difficult to access geographical regions.

As part of her three-year, NSF-funded research project, Tripp traveled to Namibia and Ethiopia this spring to conduct field research on the plant group. During the six weeks in the field, she collected fresh samples of plants for herbaria, flowers for dissection and microscopy study and genetic material. Ensermu Kelbessa, curator at the Ethiopian National Herbarium, professor at Addis Ababa University and Acanthaceae specialist, joined Tripp during the second half of her fieldwork.

The research continues back in Claremont

Kelbessa and his student Mekbib Fekadu will spend a month at RSABG this August. Fekadu, an undergraduate student at Addis Ababa University, will take part in an NSF-funded, 10-day undergraduate workshop “Plant Systematics and Evolutionary Biology,” held at RSABG.

During the visit, Kelbessa, McDade and Tripp will collaborate to document the pollen diversity of African Ruellieae by utilizing samples collected on the Ethiopian and Namibian fieldtrips. Pollen is important because its structure or morphology helps to identify genera and species in the Acanthaceae. After finishing the workshop, Fekadu will assist Tripp generating molecular sequence data for the project.

The findings of Tripp and her colleagues from the African and RSABG work will ultimately be used to create a worldwide synthesis of evolutionary relationships and diversification in Ruellieae. This is helpful because a well-sampled study of the genera and of evolutionary relationships among them can shed light on the mechanics of the evolution of certain plant traits and plant symbioses—such as pollinator relationships. It also provides baseline information on standing taxonomic diversity.

The Acanthaceae family is a rich source of pollination systems, and a more robust understanding of Ruellieae could answer important questions about the evolution of one of the key ecological interactions in the world.

Read more about Erin Tripp's research on her personal page.