San Diego Natural History Museum--Your Nature ConnectionSDNHM Biodiversity Research Center of the Californias
Binational Multidisciplinary Expeditions
Agua Verde-Punta
  Mechudo 2003

Isla Guadalupe 2000
Lindblad Binational 1997
On Collecting and
  Expeditions: A Botanical
Why do we go on natural history expeditions?

Natural History Expeditions to Northern Baja California Sur:
A Botanical Perspective

By Jon Rebman, Curator of Botany

Why do we go on natural history expeditions?
Why do we collect and make scientific specimens?
Why are we exploring northern Baja California Sur?
What is the next step after collecting?
What about future expeditions?

The primary emphases of any expedition are to observe, record, and collect natural history information on the biodiversity and geology of the study sites.

The Baja California peninsula still contains some of the least botanically explored areas in North America. As a result of its topography, geological history, and floristic influences this arid land supports a wealth of plant diversity. It is estimated that the flora consists of more than 4,000 plant taxa with a rate of endemism close to 30%. This means that approximately 1200 different kinds of plants are unique to Lower California and can only be found there. However, as new and remote areas are scientifically explored, and with existing plant groups studied in more detail, new plant species are constantly being discovered and some species that have been lost to science for many years are finally being found again. For example, as a result of our Museum's renewed efforts on field research projects in Lower California such as the two recent trips mentioned earlier, two little-known plant species are rediscovered and now, better understood.

The endemic leguminous shrub, Eysenhardtia peninsularis (Fabaceae), was originally named by T. S. Brandegee on the basis of a single specimen collected near El Paraíso, Baja California in 1889. For over a century afterward, it was not collected or reported by any botanists. This plant species was presumed extinct until recently, when I found it in the Sierra San Francisco of northern Baja California Sur. When first re-encountered, only a few small shrubs, severely browsed by livestock, were found and vouchered. Subsequent visits and knowledge from local ranchers have turned up small populations of the species on rocky flats and low hills near the ranch community. However, heavy livestock grazing in this region may be contributing to the scarcity of this species and endangering its future existence, so it is hoped that conservation efforts will be considered in order to protect it from extinction.

Ambrosia acuminata, photo by Jon Rebman, 1998 Another plant species, Ambrosia acuminata (Asteraceae), collected by T. S. Brandegee in 1889, has only been known from the type locality at La Purísima in Baja California Sur—until our 1997 expedition. On the Museum's most recent natural history expedition, this endemic, shrubby ragweed was found in three different populations on the western slopes of the Sierra Guadalupe, north of its previously known locality. It is not known yet if other herbarium vouchers of this species, other than the type material from 1889, exist. In any case, these new herbarium specimens and population records of its new distribution will aid future researchers in better understanding this little-known species.

Not only have our recent expeditions yielded the rediscovery of some plant species, but the discovery of others. Since the study areas have had little or no historical scientific exploration they have always been gap of biological knowledge, devoid of scientific documentation. Therefore, every collection from the region provides us with proof of what species occur there. Some collections represent new distributional records for species on the peninsula. That is, species found in the center of the peninsula that were formerly only known from the more tropical Cape Region in the south or from the more temperate north. Other collected specimens serve as new records for the peninsula. That is, species previously known only from mainland Mexico or from the United States, or else species that have been reported from the peninsula but never collected, have now been definitively documented with museum specimens to occur on the peninsula.

Nopal tree (Opunita sp.)

Even more exciting, some of our collections may represent possible species which are new to science. That is, organisms found that don't seem to correspond to any species that has been previously described. It will take much further study and analysis to discover whether they are actually new species. One possible new species encountered on the expeditions is a Prickly-pear Cactus/Nopal tree (Opuntia sp.; Cactaceae) that grows up to 4.5 m (14.8 ft) tall in the higher parts of the Sierra Guadalupe. With further taxonomic investigation, this cactus may turn out to be a new endemic plant species for Lower California.

Natural history expeditions not only provide the scientific community with specimen documentation for species and basic data essential for testing hypotheses, they also allow for an excellent opportunity for scientists from different backgrounds and countries to come together and work, compare ideas, foster good relations, and promote future collaborative efforts and research. In the field of botany, the binational aspect of our expeditions has permitted three scientists from different areas (La Paz, Ensenada, and San Diego) with different expertise (in floristics, ecology, phytosociology, and systematics) to work together and share knowledge which benefits all. For example, the Sierra Guadalupe has a mosaic of plant species from many directions and habitats, so it is very productive to have botanists who are familiar with the flora in different regions.

Multidisciplinary expeditions also have their advantages. Since most scientists are very specialized within their own discipline, it is difficult to thoroughly understand natural history aspects and processes that cross the boundaries between fields of study. For instance, flower-pollinator or plant-herbivore associations can be enigmatic. However, with a botanist and an entomologist working side by side, each scientist views the process differently and open communication can substantially improve our understanding of the complete process or relationship.

Ambrosia acuminata and Nopal tree (Opuntia sp.) Photos by Jon Rebman. 1977.