Geographic Locations of Arctostaphylos pringlei and A. pungens in the San Jacinto Mountain Area
While studying possible hybrids involving Arctostaphylos pringlei and A. pungens, I became curious about the geographic distribution of these two species in the San Jacinto Mountain area.
First, I downloaded the voucher data from the Consortium of California Herbaria, and digitized the locations of vouchers that were not georeferenced. I also corrected the locations for two vouchers with erroneous coordinates, and gave the corrected coordinates to the Consortium.
Second, on 14 March 2007, I GPS'd all manzanita locations along SR371, SR74, and SR243 between Anza and Humber Park in Idyllwild from a car survey. However, since there are four different species in the southwest portion of this area, including A. glauca and A. glandulosa, I cannot associate a definite species identification with each location in that southwest portion. Hence those locations are plotted just as A. species in the map. I did stop several times to get a definite determination; those determinations are plotted as the appropriate species.
In the northwest portion of the car survey, the A. pungens specimens could be identified from the car since they were in bloom, whereas the A. pringlei specimens were not in bloom. I was thus able to discriminate those two species from the car survey. Although it is possible that some of those plants may also be A. glauca or A. glandulosa, spot-checks showed that the vast majority of those specimens were not.
I previously had done GPS surveys in 2006 for A. pringlei along three hiking trails, the Deer Springs, Devils Slide and South Ridge Trails.
The following plot gives the geographic distribution of Arctostaphylos pringlei and A. pungens in the San Jacinto Mountain area from the vouchers and my observations.
I have made the symbol for A. pungens slightly larger than the one for A. pringlei so that one could more easily see the occasional specimens amidst large stands of A. pringlei. The bright pink symbol for the pink-bracted A. pringlei stands out even in dense areas of A. pungens symbols.
Although some areas are heavily dominated by just one of these two species, the two species intermix even in those areas. Two examples:
- The Idyllwild area is heavily dominated by A. pringlei, but there are a small number of A. pungens specimens there as well.
- There are a number of A. pungens specimens near the intersection of SR371 and SR74, but at least one specimen of A. pringlei is found at the north junction of SR371 with Burnt Valley Road. I verified that voucher specimen during my car survey since I found it surprising to have a A. pringlei at that location.
Note that most areas have not been surveyed for these two species, so one should not assume that blank areas in the map do not contain either species.
Remember that there are four other Arctostaphylos species in the area of this map. A. patula is confined to high elevations, primarily within the blue contour identified as the boundary of the SnJt high country, as well as at the highest elevations on the Santa Rosa Mountains. A. glauca is widespread in the Santa Rosa Mountains and probably elsewhere. A. parryana ssp. deserticum is found on the eastern portion of the San Jacinto Mountains and the north-facing slopes of the Santa Rosa Mountains. A. glandulosa is probably widespread on the south and west sides of the San Jacinto Mountains.
The two species are segregated mostly by elevation, which is presumably the main cause of the rough geographic separation seen in the map above. The following plot of latitude versus elevation is solely from voucher information, which is a more representative sample geographically than my surveys:
A. pungens is seen clearly to be at elevations mostly below 5500 feet, whereas A. pringlei is mostly above elevations of 5000 feet. The single A. pungens voucher at 7500 feet is at 1 mi se | Toro Peak Ridge | Santa Rosa Mts., which is a hotter, drier, non-forested location very different from all of the other voucher locations.
The next plot gives a histogram of the elevations for each species, which includes voucher specimens with only elevation information:
The following table summarizes the elevation information from vouchers:
| Species | Elevation (feet) | ||||
|---|---|---|---|---|---|
| Munz Min. | SnJt Vouchers | Munz Max | |||
| Min. | Typical | Max | |||
| A. pungens | 3000 | 3500 | 4500-5500 | 6600 | 7000 |
| A. pringlei | 4000 | 3500 | 5000-6000 | 7700 | 7500 |
The maximum elevation for A. pungens in the SnJt Vouchers column comes from a specimen I found on the South Ridge Trail, even though that is not a voucher. I didn't include the Toro Peak specimen in the table since it is not typical of most of this area.
Voucher data provided by the participants of the Consortium of California Herbaria (ucjeps.berkeley.edu/consortium/).