Plants of Southern California:
Arctostaphylos parryana ssp. desertica, and comparison to A. glandulosa ssp. adamsii

This page is currently just a shell to hold the maps of the geographic distribution of Arctostaphylos parryana ssp. desertica and A. glandulosa, with the rest of the page incomplete.


Table of Contents

Introduction
How To Recognize The Species (not supplied yet)
Geographic Distribution


Introduction

This page is currently just a shell to hold the maps of the geographic distribution of Arctostaphylos parryana ssp. desertica and A. glandulosa, with the rest of the page incomplete.

This page is primarily on Arctostaphylos parryana ssp. desertica. However, it is so similar to A. glandulosa ssp. adamsii that they need to be discussed together. In fact, prior to the 1997 recognition of A. parryana ssp. desertica, plants of that species were called A. glandulosa ssp. adamsii.

Geographic Distribution

The geographic distribution of these two species, from my GPS points, cleaned-up vouchers and verified iNat observations, is shown in Fig. 2.

Fig. 2. Geographic distribution of A. glandulosa adamsii (left) and A. parryana ssp. desertica (right), from my GPS points, cleaned-up vouchers, and verified iNat observations. See also expanded version of these plots for the Garner Valley area for A. glandulosa and A. parryana desertica. The blue horizontal line separates Riverside County on the north from San Diego County on the south.

Keeley, Boykin, and Massihi chose the subspecies name of desertica to recognize "the consistent tendency of this taxon to be restricted to the desert edge of chaparral" (Keeley, Boykin, and Massihi 1997).

Fig. 3 shows that A.p. desertica in the San Jacinto and Santa Rosa Mountains is found only on the desert side of those mountains, up to and including the Desert Divide.

Fig. 3. Google Earth view looking south/southeast from an elevation of 27,000 feet showing known locations of A. parryana desertica (red dots) and the Desert Divide, the mountain crest separating the desert side of San Jacinto Mountain from the coast side. Click on the pix for a view of a slightly-larger area.

Most of the desert side of San Jacinto Mountain is unexplored, due to very steep treacherous slopes, so there may be many more locations of A.p. desertica not shown in this map. On the other hand, A.p. desertica may prefer not to live on steep slopes. Fig. 4 shows where Mark Reese and I surveyed for A.p. desertica on 18 May 2022, and found it only on ridgetops and flattish areas.

Fig. 4. Google Earth view looking west showing A.p. desertica locations (red dots) on the PCT and the access road to the PCT from Goff Flat. The blue line shows the survey track. Note that plants of A.p. desertica are preferentially found on flattish ridge tops (top left) and flattish ridges on the desert side of the Desert Divide. Click on the picture for a slightly-larger version.

Even on the Desert Divide ridge itself, there are significant stretches where there are no or few plants of A.p. desertica. Fig. 5 shows one such stretch.

Fig. 5. Google Earth view looking southwest showing A.p. desertica locations (red dots) on the PCT in an area that has been surveyed for it. Note the large gap with no A.p. desertica locations at all. There are only small numbers of plants of that species at the locations of the three red dots on the right of this picture. Click on the picture for a version showing a larger stretch of the Desert Divide.

The plants in San Diego County inhabit a somewhat-similar desert side / mountain crest location, although some of the plants are found in a more coastal side location, such as the ones below Eagles Nest and in the Ranchita area, and they do not prefer ridgetop locations in general; see Fig. 6.

Fig. 6. Google Earth view looking almost due north from an elevation of 27,000 feet showing known locations of A. parryana desertica (red dots) in San Diego area. Click on the pix for a view of a slightly-larger area that shows part of the Santa Rosa Mountain population as well.

As shown in Fig. 2, there is a considerable distance gap between the population in the San Jacinto / Santa Rosa Mountains, and the population in San Diego County. Fig. 7 shows that plants in those two areas largely have significantly-different elevations, although many of the San Diego County plants have the same elevations as the Santa Rosa Mountain plants.

Fig. 7. Latitude vs. Elevation for specimens of A.p. desertica.

Fig. 8 gives the latitude vs. elevation plot for both species.

Fig. 8. Latitude vs. Elevation for specimens of A. glandulosa and A.p. desertica. The symbols for A.p. desertica were made slightly larger so they could be seen amidst some of the A. glandulosa symbols.

Page not revised past this point.

Considerable clean-up of the vouchers was needed to produce the maps shown in Fig. 2:


I thank Don Rideout for considerable assistance with field surveys for these two species; Mark Reese for assistance with the field survey on 18 May 2022; and Fred Melgert and Carla Hoegen for their survey work in the Ranchita Area and their iNat posts of those plants.

Voucher data provided by the participants of the Consortium of California Herbaria.


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Copyright © 2021-2022 by Tom Chester
Permission is freely granted to reproduce any or all of this page as long as credit is given to me at this source:
http://tchester.org/plants/analysis/arctostaphylos/parryana_desertica_glandulosa_adamsii.html
Comments and feedback: Tom Chester
Last update: 31 May 2022