Many of you are well versed in the collection, processing, and curation of herbarium specimens, but just in case here is a quick look at one of the cornerstones of botanical research. In the simplest sense an herbarium specimen is a piece of a plant (or sometimes a whole plant or several whole plants) collected in the field, placed in a plant press, and dried. Pressed plants 2-dimesional versions of their former living 3-dimensional selves, mounted on archival paper, and then stored in museum for centuries (or longer??).
Wish I had photos of this cute little thing in the wild, but here it is, a specimen of the Tejon Heterotheca
Herbarium specimens are mounted with labels that contain location, habitat, and ecological and descriptive information that can be helpful in determining a plants identification. These specimens, handled carefully, can be examined over and over again, and serve as the physical proof of a plant’s presence at a specific location at a specific point in time. For example, the herbarium at RSABG houses a specimen from Cook’s voyage in the 18th century! Herbaria often contain many specimens from locations that have been developed, and where natural vegetation no longer occurs. Historical specimens can help researchers track changes in vegetation over time. For example, one could track the spread of an invasive plant species by examining the frequency and location of where and when said invasive plant has been collected. Now, let’s take a look at an example of how herbarium specimens have been useful so far in my work on Tejon Ranch!
Back in the summer and fall of last year I collected a number of plants that were not easily identifiable in the field (see this post on the Tejon Streptanthus). One of these specimens was a small perennial member of the sunflower family (Asteraceae) found growing on an open limestone ridge with the beautiful Tejon buckwheat (Eriogonum callistum). Attempts to key pressed specimens of the plant helped me and several botanists/friends determine that this plant was likely a Heterotheca (goldenaster). Since I was not satisfied with our ability to identify this plant to species, I decided to send a few pictures of the plant to the world’s Heterotheca expert, Dr. John Semple, at the University of Waterloo. Dr. Semple originally thought that the plant might be Heterotheca villosa var. minor, a common species not previously collected from Tejon Ranch, and recommended that I send him a specimen for verification.
So, I decided to package up one of my specimens and send it up to the cold north for Dr. Semple to examine. After a review of my specimen from Dr. Semple concluded that it is, “similar to H. villosa var. minor, but the hairs on the corolla lobes are long for that taxon. It did not jump at me as something new like H. monarchensis did and that has longer corolla lobe hairs than in Heterotheca except for the H. sessiliflora complex. So, maybe this is something new after all, but it would be close to H. monarchensis.”
Further communication with Dr. Semple concluded that one of the next steps that necessary to determine if the Tejon Heterotheca is indeed a new species will be for me to collect more herbarium specimens of these plants in order to take detailed morphological measurements. I will also be collecting seeds to send to Dr. Semple, so that he can make a count of the plants’ chromosome numbers (a useful cellular character in determining the identification of some plant species).
The discovery of a potentially new species of Heterotheca, possibly related to H. monarchensis would be a significant botanical discovery. Heterotheca monarchensis is an extremely rare species known from only 2 locations on carbonate rock outcrops in Kings Canyon National Park, some 200 miles to the north of Tejon Ranch. One striking similarity is that the plants on Tejon Ranch also grow on soils originating from carbonate rocks! The location of the Tejon Heterotheca has been subject to very little botanical exploration. In fact, I located these plants at a newly documented location of Tejon Buckwheat discovered by Neal Kramer last summer. Heterotheca monarchensis was discovered in a remote area of Kings Canyon NP in 1996 by intrepid botanist Dana York. Heterotheca monarchensis and the Tejon Heterotheca certainly share at least two things in common: 1. They both grow on a harsh substrate often home to rare plants of restricted habitats, and 2. They occur in areas with little history of botanical exploration.
Much work is still needed to determine if the Tejon Heterotheca is indeed a new species, or if it represents a new population of a species that is already known to science. Searching for new populations and making more herbarium collections of the Tejon Heterotheca will be a major priority during my fieldwork this summer.
The contribution of herbarium specimens toward scientific progress, and our understanding of biodiversity cannot be underestimated. They play a central role in the discovery of species, and our understanding of diversity in this changing world.
This is where I am headed this weekend! Yeah for the start of the field season!