Among the coastal scrublands covering the hills of Tijuana and Playas de Rosarito, there are small populations of Otay Tarplant (Deinandra conjugens), an endemic flower of the southern California Floristic Province. Thanks to the field work of Baja Rare, a binational group in which Pronatura Noroeste participates, we know more and more about this rare floral species and, most importantly, how to conserve it.
Belonging to the tribe Madiinae, of the family Asteraceae —to which sunflowers belong—, little was known in Mexico about this annual species that flowers during the summer season. From studies in the United States, we knew that its range extends from southern California to northwestern Baja California, within the critical ecoregion of the California Floristic Province. It is fair to say that because of its restricted habitat, it is considered a rare species of high vulnerability.
To determine the status of the floral species and promote strategies for its conservation, since 2022 we have been working, in collaboration with the San Diego Zoo and Expediciones Botanicas, to increase knowledge of Deinandra conjugens in Mexico. Three objectives drive the effort: identify new populations of Deinandra conjugens in Baja California, assess the status and conservation potential of each known population, and collaborate with the Mexican government and other organizations on conservation actions.
Led by Dr. Sula Vanderplank, an expert collaborator in regional flora at Pronatura Noroeste, the team undertook the task of finding, corroborating and generating a map of existing populations of Otay Tarplant in Baja California. Such mapping will help to outline future conservation strategies for the species and its habitats. The challenge was anything but simple.
There are currently 6 species of Deinandra found in Baja California. All of them share similarities, such as the distinctive canary yellow of their radial flowers and the particularity of growing exclusively in clay soils. However, to differentiate Deinandra conjugens from a Deinandra paniculata, skill is required to detect the tiny details that separate one from the other, such as the number of radial flowers, which is no more than 8 in D. conjugens, and the glands on the external part of the flower, being heterogeneous in size those of the Otay Tarplant.
Like many species of flora and fauna that inhabit the Pacific coastal areas of Baja California, habitat loss due to land use change, which has been accelerated by the real estate boom in this region, is their main threat.
“The conservation of Deinandra conjugens is important, like other endemic species of clay soils, because they are part of microhabitats that are very scarce in Baja California. It is one of 65 endangered species that we are working with on both sides of the border,” explains Dr. Sula Vanderplank.
According to the work plan, it is intended to submit a comprehensive report on the Otay Tarplant to the Ministry of Environment and Natural Resources (SEMARNAT) with the goal of having it listed as a threatened species under NOM-059.
**In addition to the San Diego Zoo, this conservation effort was supported by the San Diego Natural History Museum, U.S. Fish & Wildlife Service, SUVA Research and Expediciones Botanicas.
