|
The Santa Rosa Basalt Brodiaea | 
|
Press Release, Tuesday, 13 November 2007
This summary for the press was updated on 30 November 2007 with the discovery on 27 November 2007 that one population lives on basalt soil that might be derived only from the basalt of the Santiago Peak Volcanics instead of the Santa Rosa Basalt.
A new rare species of Brodiaea has been discovered that lives only on only on basalt soils in areas currently or recently covered by the Santa Rosa Basalt of southwest Riverside County and immediately-adjacent San Diego County. The association with the basalt makes it likely that this is an ancient species, perhaps five million years old, which is on the verge of natural extinction in the near-geologic future when the last of the basalt is eroded away.
Because this species lives only on that basalt, scientists have named the species Brodiaea santarosae, the Santa Rosa Basalt Brodiaea. It has beautiful blue-purple lily-like flowers as large as two inches across, and blooms in May and June when the landscape is parched and dry, and most other grassland species have faded away.
The past history of this species, gleaned from the association with the basalt, is fascinating.
Prior to about ten million years ago, southern California was flat, without the mountains and faults present today, with a relief similar to that of eastern Kansas today. About ten million years ago, the North American Plate overrode an oceanic spreading center. In its dying gasp, the spreading center broke through the continental crust and completely covered that flat landscape with a series of lava flows, the Santa Rosa Basalt.
That cap of lava kept the land over which it spread together as the surrounding landscape was greatly altered to produce the mountains present today. That land remained essentially level as it was elevated, and is today called the Santa Rosa Plateau.
Five million years ago is an important date in the evolution of southern California species. Prior to that time, southern California received summer rainfall, and the species found here were not very different from species found elsewhere in North America. After that time, due to changes in atmospheric circulation caused by the new mountains such as the Sierra Nevada, we lost our summer rainfall and the climate became Mediterranean.
Species had to gradually adapt to the lack of summer rainfall, and the new habitat of the basalt was available to plant species that could grow there. (Many plant species cannot grow on basalt, since it is missing many normal plant nutrients and is high in minerals that are toxic to many plants.) Brodiaea santarosae may be an ancient species which colonized the basalt perhaps five million years ago and has survived as a distinct species to the present time due to its confinement to the basalt.
As more of the basalt has eroded, the populations of Brodiaea santarosae have become isolated. Further studies may be able to pin down when these populations were last in breeding contact, and give a firm estimate of the minimum age of this species.
B. santarosae is doomed to go extinct in the wild in the near geologic future (~100,000 years or so) unless it can adapt to non-basaltic soils, or unless viable populations are found to be present on basalt soil not derived from the Santa Rosa Basalt. At least 97% of the basalt has been eroded in the 8-11 million years since it formed. It will take much less than another 300,000 years (3% of the previous erosion interval) to erode the remaining basalt since the basalt has now been broken up into small areas and is now being eroded on all sides.
The story of how this species was finally recognized is also amazing. This species had been "hidden in plain sight", seen and even collected by previous botanists. Its true identity had gone undiscovered because the flowers of most Brodiaea species look very similar, all having nearly identical petals. It takes detailed examination of small aspects of the inner parts of the flowers to discriminate the species. This species was especially cryptic, since it has some flowers that superficially resemble another Brodiaea species, B. orcuttii; other flowers that superficially resemble a different Brodiaea species, B. filifolia, and yet other flowers that appear to be a hybrid between those two species!
The uncovering of this masquerade came from a fortuitous coincidence of events. Tom Chester and Wayne Armstrong had been working on Brodiaeas since 2003, and had begun to work on hybrids in 2005. Kay Madore had spent two years with Tom on his intensive work on the Flora of the Santa Rosa Plateau, gaining much experience with other Brodiaea species there, including B. filifolia. When Kay was doing routine botanical work in May for the Nature Conservancy, she came across some plants that were different from the Brodiaeas she had previously seen, and brought them to the attention of Tom and Wayne.
Tom and Wayne immediately began an intensive program to study the new plants, along with B. filifolia and B. orcuttii, both in the field and in the collections of herbaria in southern California. Thanks to their extensive previous work on Brodiaeas it did not take long to establish that these plants were a distinct species.
Interestingly, while it was clear from the beginning that the vast majority of specimens of B. santarosae grew on basalt, it appeared initially that a small number of specimens grew just outside mapped basalt areas. A perceptive comment, from one of the Madroño reviewers of the scientific paper, led to further field work in 2007 that revealed that all specimens in fact grew only on soils derived from basalt.
Quotes from the authors:
- Tom Chester: "For most species, we have no idea when they originated and no idea when and why they might go extinct naturally. One of the things I love most about B. santarosae is that it seems quite likely that it is an ancient species, and that it may go extinct naturally in the next ~100,000 years when the last of its growing medium erodes away.
To put this in perspective, there have been 25 glacial cycles in the last 2.5 million years. If humans had waited one more glacial cycle to inhabit North America, we would never have laid eyes on B. santarosae, and might never even suspected it ever existed."
- Wayne Armstrong: "It is rare in one's lifetime to find a new, undescribed species as unique and distinct as this one. I have spent many years studying and photographing brodiaeas; the Santa Rosa Basalt Brodiaea is truly one of the most beautiful of all the brodiaeas, with its large showy flowers."
- Kay Madore: "I was amazed to come across a field of this Brodiaea in beautiful full bloom so late in the dry season of 2006. The flowers were monstrously-large compared to other species of Brodiaea we had studied! I was thrilled and excited when Tom and Wayne discovered that this Brodiaea was actually a new species."
Comments from people not associated with this work:
- Rob Preston, Senior Botanist with Jones & Stokes and an expert on northern California Brodiaeas: "I have found that each species of Brodiaea tends to be faithful to a particular soil type. B. santarosae follows this pattern; furthermore, it is the only one I know of that has an affinity for basalt soils."
- Beth Cobb, docent at the neighboring Santa Margarita Ecological Reserve: "I had no idea the new species is so beautiful! I pictured it as some small dried-up weedy-looking thing that had been overlooked before."
- Zach Principe, the local biologist for The Nature Conservancy and biologist at the Santa Rosa Plateau Ecological Reserve from 1998 to 2004: "The recognition of a new species on the Santa Rosa Plateau is exciting news. As this species is only found in a few small areas, we are fortunate that The Nature Conservancy and its partners recognized the importance of this special place and were able to protect much of the area and its many rare species."
- Santa Rosa Plateau Ecological Reserve Resource Manager Carole Bell: "The discovery of Brodiaea santarosae, 21 years after the initial protection of the Santa Rosa Plateau Ecological Reserve, shows how protecting landscapes for a diversity of species, provides protection for all the flora and fauna, even the ones we didn't know existed! If land managers focus on the protection of critical habitat in their multi-species plans, we might have the opportunity, in the future, to discover other unknown species in Riverside County."
- Santa Rosa Plateau Ecological Reserve Interpreter Rob Hicks: "The Plateau's Ecological Reserve and the community at large are fortunate to have dedicated volunteers like Tom, Wayne, and Kay, who participate in the stewardship of its natural resources. Their discovery adds to an appreciation of the region's natural heritage that international scientists and local outdoor recreationists continue to explore and enjoy. Their discovery contributes to the global catalogue of species, while reminding us all of the hidden and ever-expanding benefits of conservation."
This news release is based on a paper published in the latest issue of Madroño: A West American Journal of Botany 54:187-198 sent out in late October 2007. A 4 MB PDF copy of the article is available here.
More information about this species can be found at this website, which contains the figures from the paper, and most of the key points: http://tchester.org/plants/analysis/brodiaea/santarosae.html
Pictures of this species, which blooms in May and June, are available here: http://tchester.org/plants/analysis/brodiaea/bsr/pictures.html
Higher-resolution versions of almost all of the pictures are available on request.
Pictures of the Santa Rosa Basalt are here: http://tchester.org/srp/plants/communities/geo_2.html
Additional references on geological history and past climates of this area:
- Plant Guide to Vernal Pool Trail, Santa Rosa Plateau contains another brief summary of the recent geological history and past climates of this area.
- Santa Rosa Plateau Geology is a more detailed summary of the recent geological history here.
Brief biographies of authors:
- Tom Chester is an astrophysicist retired from Caltech and the Jet Propulsion Lab, who become a docent at the Santa Rosa Plateau Ecological Reserve in 2000 and then a botanist in 2001. He spent two years, 2005 and 2006, doing fieldwork on the flora of the Santa Rosa Plateau. He has produced plant trail guides to 116 trails across southern California, all available online. His southern California plants website is Native and Introduced Plants of Southern California at tchester.org/plants. Tom lives in Fallbrook, in north San Diego County.
- Wayne Armstrong is a botanist and biologist recently retired from a career of teaching at Palomar Community College. Wayne and Tom have been working on the Brodiaeas of southern California since 2003. Wayne is the author of the immensely-popular website Wayne's Word: An On-Line Textbook of Natural History at waynesword.palomar.edu. Wayne lives in San Marcos, in north San Diego County.
- Kay Madore has been a docent at the Santa Rosa Plateau Ecological Reserve since 2000, and has spent much time helping Tom with fieldwork at the Santa Rosa Plateau. She was employed by the Nature Conservancy to do botanical survey work at the Santa Rosa Plateau Ecological Reserve in 2006. Kay lives in Brea, in eastern Orange County.
Contact information for people mentioned above can be obtained from Tom Chester, tom@tchester.org, 760-723-0087.