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Hellhole Canyon spermolepis | 
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| Fig. 1. Spermolepis infernensis, Hellhole Canyon spermolepis, in Yaqui Meadow on 31 March 2016. Photos of the same plant from the side (left) and from the top (right), with a dime for scale in both linked pictures and a thumb for scale in the right picture. Note that this plant is just twice as long as the small grains of sand in the picture, with the lower part of the dime between two grains of sand.
Click on the pictures for larger versions. See Fred Melgert and Carla Hoegen's Anza-Borrego Desert Wildflowers page on Spermolepis infernensis, and Keir Morse's Calphotos photographs for a number of additional pictures. | ||
Table of Contents
Introduction
Habitat
Geographic Distribution
Photographs of Flowers and Fruit
Comparison to Apiastrum angustifolium
Introduction
Prior to our discovery of a thriving population of this species in the Borrego Valley in 2016, many of the authors of this page doubted that Spermolepis infernensis was a real species. Nesom described this species in 2012 (Phytoneuron 87: 1–49: 6.6 MB PDF or read online page by page) from a total of just nine plants in the two sheets of a single voucher collected in 1932! Nesom wrote:
Similar to Spermolepis lateriflora in its epedunculate (sessile) umbels but different in its sparse fruit vestiture of apically straight, blunt-tipped hairs.Spermolepis infernensis and S. lateriflora perhaps are sister species, in view of their similarity in inflorescence structure and distribution in the western USA. It is possible that S. infernensis is a recent derivative of S. lateriflora, with a reduction in the density of the fruit vestiture and a developmental change that results in truncation of the hairs. The difference in appearance is striking, however, and the effect on dispersal potential surely must be significant.
S. lateriflora is also a new species defined by Nesom in 2012, split out of S. echinata, with all the plants in Arizona, California and New Mexico now being S. lateriflora.
We agreed with Nesom's comment in his paper that S. lateriflora (a new species also defined by Nesom in 2012, split out of S. echinata) is probably a waif sporadically introduced in California from its main population in central and southeastern Arizona. There are only three collections of that species in California, from 1877, 1941 and 1952, two of them from places along the main travel corridor between Arizona and California, Lower Box Canyon and the Vallecito Stage Station. The third voucher location is reported as the Oakland Hills in the San Francisco Bay area, which would be a bizarre location if it was correct. Dean Taylor has pointed out that this "Oakland" location is almost surely a digitizing error, of giving an "Oakland" location to a Lemmon Herbarium voucher that has no label and no collecting information.
There are only three collections of S. infernensis as well, from 1932, 1979 and 2009, all from locations with abundant traffic from Arizona: the ABDSP Visitor Center; Hellhole Canyon near the Visitor Center (not the Hellhole Preserve near Valley Center that is 30 miles west of Borrego Springs as given in Nesom), and a location just west of Yaqui Pass. It seemed likely to us that those were waifs as well of a variant plant of S. lateriflora that had a mutation resulting in the loss of most of its fruit hairs. After all, the Visitor Center and the nearby Hellhole Canyon are immensely-popular locations among botanists, and it was inconceivable to us that there could only be two collections from that area in 84 years. Furthermore, some of the authors have done numerous surveys in those two areas, including three targeted searches for Spermolepis there, and we had never seen it.
Fortunately, Steve Schoenig scheduled a CNPS Rare Plant Treasure Hunt for Spermolepis on 31 March 2016, and four of the authors participated in that full-day search even though we thought it was going to be a wild goose chase. We first surveyed the area south of the Visitor Center, again with no luck. We then went to the area of the latest voucher collection area, west of Yaqui Pass, and found a thriving population of hundreds of plants of S. infernensis! Two additional full-day surveys were quickly done by different groups of the authors, finding a fairly widespread population in an area that has received very little botanical attention and very little traffic from botanists. Mary Jo Churchwell will voucher the western portion of this population, inside the boundaries of ABDSP, in the near future.
What was striking about the plants we saw was how tiny they were. The voucher specimens analyzed by Nesom were 7-13 cm tall, and the specimens collected in 1979 were 4-9 cm tall. Photographs of those large plants in the voucher analyzed by Nesom (photograph is given in his paper) were the only search images we had. Coupled with our previous experience in seeing plants of Apiastrum angustifolium, we thought the plants would be fairly easy to find in the field, which turned out to be incorrect, at least in the low rainfall year of 2016.
We were surprised that the specimens we saw in the field were just ~2-5 cm tall, and would be utterly inconspicuous to most botanists unless they were specifically looking for such tiny plants. Furthermore, they have the same color and size as depauperate plants of Cryptantha micrantha and Schismus barbatus, and could easily be mistaken as one of those plants at a glance. Even once we knew what to look for, we often had to kneel down and look closely at the plants to distinguish these three species.
Further surveys in the Borrego Valley will be needed to better characterize the full extent of the population.
Habitat
In our surveys so far, S. infernensis lives only in relatively-old undisturbed alluvium that frequently supports large populations of jumping cholla, Cylindropuntia bigelovii, and Eschscholzia minutiflora, with scattered plants of Ferocactus cylindraceus and Ambrosia dumosa. The jumping cholla was especially problematic during all of our surveys where S. infernensis was found, attaching itself to our boots regularly.
In most of the places we have seen it, there are no apparent erosional channels at all; one example is shown in Fig. 2; see also another example showing a view to the south. In some places, there are very gentle little washlets. It often grows in the undisturbed habitat between washes that has not yet been dissected by current washes.
Keir Morse is pointing to a group of S. infernensis plants found in one of the open spaces in this area (the tiny plants are not visible in this picture). Most of the open areas in this picture do not contain S. infernensis; the populations are widely scattered in the area shown in the picture.
Click on the picture for a larger version.
Within this larger habitat, so far S. infernensis is found in two quite different small-scale habitats. It often occurs completely out in the open, as shown in Fig. 3. Or, oddly, it can frequently occur on the northwest side of a shrub that shades its location during most of its growing season until the afternoon, as shown in Fig. 4. See also plants growing in the shade of galleta grass, Hilaria rigida, and plants snuggled under a Cylindropuntia ganderi.
Click on the picture for a larger version.
Click on the picture for a larger version.
Geographic Distribution
Fig. 5 shows a Google Earth view of the geographic distribution in the part of Yaqui Meadows that is in Anza Borrego Desert State Park from a survey on 9 April 2016 by Tom Chester, Keir Morse, Carla Hoegen and Fred Melgert. See also Google Earth view looking to the southwest.
In Fig. 5, the light blue solid line paths are the gps tracks recorded separately by Fred, Keir and Tom. The blue balls are where we GPS'd Spermolepis; most of these locations were found by Keir and Carla, who really had an eye for spotting the tiny little plants in that survey. One of the locations had 27 plants at the gps points, but most points had 4-5 plants.
Fred and Carla counted a total of 254 plants at the 54 GPS points they recorded, an average of 4.7 plants per GPS point. We estimate there were roughly 45 plants at the additional 10 GPS points that Keir and Tom recorded, assuming 4.5 plants at each point. The total number of plants we saw on this survey in the Park was thus close to 300.
The hotbed of Spermolepis in this older alluvial fan appears to be along its middle ridge. However, we would need a follow-up survey with a number of east-west transects through that area to really characterize the population.
There are a number of similar older alluvial fans that ring the southwest end of the Borrego Valley that are prime targets for future searches. Fig. 6 shows some areas that might contain Spermolepis.
Click on the picture for a larger version with more readable text; you may have to click again on the linked picture to see it full-size.
Photographs of Flowers and Fruit
Photographs of flowers are shown in Fig. 7, and fruit in Figs. 8 and 9.
Apiaceae are generally most-reliably determined to species using their fruit. We were surprised at the lack of hairs in the younger fruit seen on 31 March 2016, but on 9 April 2016 the fruit was much more similar to the one shown in Nesom. It appears that the hairs grow as the fruit matures, and/or become more prominent as the fruit dries.
For many more high-quality pictures of the plants, flowers and fruit, see Fred Melgert and Carla Hoegen's Anza-Borrego Desert Wildflowers page on Spermolepis infernensis, and Keir Morse's Calphotos photographs.
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| Fig. 7. Photographs of flowers of S. infernensis. Top row: photographs by Keir Morse. Bottom row: left by Jim Roberts; right by Tom Chester. Click on the pictures for larger versions. | |
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| Fig. 8. Photographs of fruit of S. infernensis, along with one fruit of Apiastrum angustifolium.
Top row: Close-up photographs of immature fruit of S. infernensis by Fred Melgert. Second row: photograph of immature fruit by Jim Roberts. Third row: Left photograph by Keir Morse; Right photograph by Tom Chester. Bottom row: Left: fruit of the type specimen of S. infernensis from Nesom 2012. Right: fruit of Apiastrum angustifolium from Nesom 2012. Click on the pictures for larger versions. | |
Comparison to Apiastrum angustifolium
Apiastrum angustifolium is very similar to Spermolepis when it is young. Once it starts producing a stem, it can be easily distinguished by its apparently-opposite leaves, compared to the alternate leaves of Spermolepis; see picture of Apiastrum angustifolium from ABDSP from Kate Harper. Its fruit is distinctive, lacking the hairs of S. infernensis, and with a different shape, wider than tall compared to roughly equal lengths for S. infernensis; see Fig. 8 above.
Of course, most frequently we come across young plants of Apiastrum angustifolium that cannot be reliably determined yet, and for years, we wondered whether those plants could actually be Spermolepis, and had to return to them to definitively get their determinations.
It was with great relief that we finally realized that the habitat of the two species was completely different. Apiastrum angustifolium is primarily a coastal species that infrequently reaches close to the desert floor. It grows in heavily shaded areas, often in the shade of boulders, and only in canyons when it grows near the desert floor, such as the mouths of Flat Cat and Hellhole Canyons. As mentioned above, the habitat of Spermolepis is the open desert, albeit sometimes in the shade of other plants.
Yabea microcarpa is similar to both species, but it is not found in the Borrego Desert except at the highest elevations on the western edge of ABDSP near Ranchita.
Photographs by Tom Chester except as indicated.