San Jacinto, Friday June 29, 2007

These are notes from Tom Chester's hike on Friday June 29, 2007.  He, Dave Stith and I hiked from Humber Park to Caramba Overlook and back, with particular attention to the bit from Law's Jct to the overlook, which Tom was interested in taking notes on for a trail guide.  Tom's write-up has full (and often interesting) details. 

The much-vaunted view from Caramba Overlook.  (Would someone chop that stupid pine down? :)

Sunset from Devil's Slide Trail.

Flowers 

These are just highlights. There were dozens of species in bloom, some quite spectacular.  Tom covers this in detail. 

Amorpha californica var. californica 

This shrub seems to take the place of Prunus emarginata to the east of the creek at Law's Jct, with P. emarginata appearing immediately to the westward and A. californica appearing in all the subsequent drainages to the east.  Interestingly the two seem to be 100% mutually exclusive, at least along the trail.

Boschniakia strobilacea 

I was very excited to see this plant thriving and in full bloom  though you wouldn't know it unless you stick your nose right in it!  I can scarcely imagine a better-named plant (ground cone), as they look exactly like a bunch of old pine cones tossed to the side of the trail.  Good eye, whoever first spotted this one! 

Calochortus invenustus 

I have a soft spot for Mariposa lilies, even ratty ones like number two. 

Datisca glomerata 

The Jepson Manual claims this is one of only four species in the Datiscaceae family  a family which I had never even suspected the existence of until yesterday.  And furthermore, it is only one of two species in the genus, the other belonging to Asia.  (Thanks, JM, that really narrows it down!) The other two genera are apparently both monotypic. 

This, the Durango root, is not a spectacular flower, to be sure, but interesting nonetheless. 

Gilia splendens ssp. splendens 

Lilium parryi 

Veratrum californicum var. californicum 

Fungi 

There were very few fungi present: a single old dried Coprinus (inky cap), and quite a number of the following veiled polypore:

Cryptoporus volvatus 

Sorry, I took no pictures, but see this page and google images.  They look much like some sort of plastic goo oozing out of the pine, but upon closer inspection prove to be shelf fungi.  They are interesting ones, because very few polypores have veils (whence "volvatus").  This one in particular dries as hard as a rock, making one wonder how they ever expect to expel their spores if the veil seals them in so tightly that you practically need a hammer to break it open!

Lichens 

I was interested in seeing how rich the epiphytic lichen community was.  I figured 8000 feet would be sufficiently high to be above most of LA's pollution, permitting a nice flora.  However, I was struck by the paucity.  Except for a few firs sporting a healthy growth of Letharia (wolf lichens), there was nary a single epiphytic species to be seen on either conifer or hardwood. 

Ironically, there were more epiphytic lichens down lower on the western slope near Humber Park where pollution levels would presumably be higher.  It was either this or it was low for Letharia, because the first specimens I saw were scanty 1-2 cm scattered tufts near the top of Devil's Slide.  However, lower down two species of Xanthoria (sunburst lichens, the more common one sterile, the other fertile) thrived on the underside of slightly leaning hardwoods.  I also saw a few Physcia (rosette lichens) and a truly valiant Melanelia (aptly-named camouflage lichen) in the same microhabitat.  Except for the Melanelia, these species are all pollution-tolerant (zone 4-5 on the Hawksworth Rose scale, if I remember right).  In particular, they actually require the extra "nutrients" provided by the nitrous and sulphurous oxides in smog.  (These or related species, for example, will apparently grow in profusion on "pee-trees" or down-wind of feedlots.)

I was a bit rushed, but I'm pretty sure they grew best near trails, especially the extremely dusty and steep approach "trail" climbers use to reach the base of Tahquitz.  This is also to be expected, as the dust will cover the nearby trees and help provide the requisite nutrients.  Rain will subsequently wash most of the dust off, of course, but only from vertical surfaces and the upper side of leaning trees.  Thus trees that lean slightly receive optimal dust enrichment: lean less and water washes more off, lean more and less dust sticks to the underside. 

Back on top, rocks seemed to be better endowed, growing a nice collection of crustose microlichens.  Among the more striking species were the brilliant yellow map and red-orange fire dot lichens  Rhizocarpon and Caloplaca, respectively.  But there were dozens of other species, most of which I was entirely ill-prepared to identify, even to genus level.  There were also a few macrolichens, predominantly rock posies (Rhizoplaca), rock tripe (Umbilicaria phaea), and various rock shields (Xanthoparmelia). 

All of these  both micro and macro  are typical desert rock lichen flora.  One can find essentially the same stuff growing in mountains throughout the Mojave.  While at first glance it did not appear to be the case, it would be interesting to see if the relatively high elevation selected for different related species within each category.  The only anomalous finding (in my limited experience) was the abundance of Rhizoplaca.  It is not unusual to find them, but I rarely see them as one of the dominant species, as I did near Caramba Overlook (where the rock lichen flora was best developed). 

A few rock faces bore extraordinarily happy and colorful communities.  At first glance it made no sense why certain faces would be so much more successful than immediately adjacent faces, so I asked Trevor Goward.  He suggested that winter snow cover was likely an important factor in these high-elevation lichen communities.  Apparently most lichens don't tolerate prolonged snow-cover. 

To the best of my understanding, the snow acts as an insulator, keeping the lichen ever so slightly above freezing, while at the same time providing high moisture.  This causes the fungal parter in the fungus-alga symbiosis to continue to metabolize throughout the winter, while the alga remains dormant.  (Give a fungus water, as house owners know only too well, and it will grow.) The fungus thus depletes the lichen's store of carbohydrates, which the alga is unable to replenish.  This condition is fatal for both parties.  Crustose species would presumably be particularly affected as they have such thin thalli (indeed some  the endolithic lichens  are restricted to scattered hyphae growing within the structure of the rock itself), and thus have very small carbohydrate stores.  Normally this is not a problem because crustose rock lichens are fully exposed to the sun, and are thus limited by moisture, i.e.  limited by the fungal metabolism not photosynthesis, making carbohydrate stores unnecessary. 

Most boulders along the trail are low, and probably suffer snow coverage for weeks if not months at a time.  There are, however, crags that tower above even the deepest snow level.  For whatever reason, it seemed to me that most crags up there are well weathered (Tom mentions that this is a "remnant landscape", presumably indicating significant age), making them sort of mounded and convex.  To reliably escape snow coverage requires very steep or leaning faces, or better yet, faces protected by overhangs.  The two abnormally exuberant faces I remember were both formed by large slabs calving off leaving a steep face protected by a small overhang. 

Letharia vulpina 

The bright yellowish green "moss" growing on one side of the firs on the steep decline just before (west of) Tahquitz Meadow[NOTE] is a lichen, wolf lichen in particular.  While there are no pictures from this trip, I took the following two on top of Pine Mountain out in Los Padres National Forest.

The ones we saw yesterday all seemed to be sterile (Letharia vulpina).  The fertile version (L. columbiana) should theoretically also be common in these mountains.  Look for the brown "eyes" (apothecia).  To see the difference, see these pictures of the sterile versus fertile species, or see this page. 

Xanthoparmelia mexicana and X. lineola 

The picture at right was taken in the Great Smokies, but it shows a typical representative of this ubiquitous and difficult genus.  While the genus might be easy to identify (greenish flat-lobed splats on rocks throughout the world), distinguishing between the many species (over 600 are known at present[1]) can only be done confidently in a lab, often requiring thin-layer chromatography (TLC) to tease out the exact varieties of acids present in the medulla.  You may rightly ask why two otherwise identical lichens would be given species status based on obscure chemistry.  Good question!

I collected a tiny bit of several specimens of rock shield lichens from near Caramba Overlook just to get some idea of the diversity present on San Jacinto of this difficult genus.  It seems the dominant species is the fertile X. lineola, with the isidiate (nonfertile) X. mexicana appearing occasionally. 

Interestingly, both species are characterized by a) pale lower surface, b) broad adnate lobes, and c) strong presence of salazinic acid in the medulla.  It could, of course, be a coincidence, but it does make one wonder what it is about salazinic acid, for example, that is advantageous in this habitat.

The photo shows the striking  and quite satisfying!  spot test that identifies salazinic acid.  Application of lye (NaOH or KOH) reacts instantaneously vivid yellow, then over the period of about 5 seconds advances through orange and red to a deep brownish blood-red.  Unfortunately, my photography skills are insufficient to catch the initial beautiful yellow. 

I found it interesting that X. lineola rarely showed apothecia (the structures that bear sexual spores).  However even the youngest specimens displayed copious pycnidia (structures that bear asexual spores called conidia).  (It seems that no one quite knows how they actually work, or even definitively if they do aid in propogation at all!) Apparently it takes many years before even a fertile species will begin to reproduce sexually.  That said, the one sample I took which I thought lacked apothecia, when examined under 30x scope, turned out to have many minute ones budding near the center of the thallus.

The following pictures are all taken at 30x magnification under a dissecting scope.  Scale still varies due to some "digital zoom".  These are just to illustrate qualitatively the various structures discussed above.  Click on any of them to see higher resolution image. 

Spot test in medulla.  Isidia seen on top.	The green is algae just inside the cortex.	Section of thallus showing pycnidia.
Typical apothecia.	"Hidden" apothecia.	Pycnidia.

Fertile -vs- Sterile 

The lichens we encountered on this walk illustrate what seems to be a recurring phenomenon.  Both the Xanthoria and Xanthoparmelia we saw came in pairs (the Letharia probably did as well, had I had time to examine the healthy population near Tahquitz Meadow).  There were in each case one fertile and one sterile species.  The Xanthoparmelia were especially gratifying because the two species I saw happened to be identical except for the sexuality.  This certainly did not have to be the case, as there appear to be as many as 8 other species listed in Nash et al that have dots in the San Jacinto area, some quite common such as X. cumberlandia (stictic instead of salazinic acid) and X. coloradoensis (lobulate). Letharia only has the two species worldwide, making it a perfect example, at least in theory. [NOTE]

The point is one often finds this pairing of sexual with asexual species.  To understand why this should be the case, consider how lichens establish.  The spore must land not only in a suitable location with the proper aspect, moisture, pH, temperature, exposure, etc.  (many lichens are spectacularly sensitive to subtle microhabitat differences), but the nascent fungus that grows from this spore must soon encounter an appropriate alga before a symbiosis will form, triggering the growth of the lichen thallus we see.  As one would expect, this must be an extremely rare event.

Thus lichens reproduce asexually quite frequently.  Soredia and isidia are the most common mechanisms.  Both are tiny outgrowths that break off very easily during rains and heavy winds, and possibly even hitch rides on birds or other animals.  Isidia have a shiny cortex, while soredia are just a tangle of medulla and algae.  In both cases the fragments carry both the fungul and algal partners together, thereby guaranteeing that if they land in a favorable spot they will be able to immediately grow a new thallus.

Apparently it has been shown[NOTE] that the unlichenized fungus growing from a spore can associate with algae carried by a closely-related species's soredia or isidia.  This is tremendously important, because it establishes a non-trivial relationship between sterile and fertile species of similar lichens.  Depending on how picky lichenized fungi are about which strains of algae they will associate with, I would expect this to create tight groups of species, the members of each group possessing similar morphological and chemical characters, and each group containing one or a few each of fertile and sterile species.  The sterile species broadcast literally thousands to millions of bits of algae over the neighborhood which the fertile species in turn may freely take advantage of to ensure their spores fall near a suitable alga.

Furthermore, it raises an obvious question (at least to me) about what the optimal ratio of fertile to sterile species is.  Asexual propogation is more efficient, yet sexual reproduction gives species an advantage whenever they are forced to adapt to new conditions.  If you think in terms of these groups, perhaps the group benefits from both forms of reproduction.  The asexual members prospering during static times, while sexual members saving the group from extinction during sudden changes in the environment.  Once the sexual members have successfully adapted to new conditions, they apparently promptly speciate into sterile and fertile forms again.  I say apparently, because I can think of no genera[NOTE] of macrolichens off the top of my head that contain exclusively fertile species, so it must happen fairly quickly.

If this is the case, one might expect to find the intermediate stages: species that have both fertile and sterile forms, but which have not diverged sufficiently to be considered separate species.  This is a bit tricky to test because, by definition almost, lichenologists have historically considered the bearing of apothecia versus soredia/isidia sufficient grounds to separate the taxa at species level.  However one does find species that produce both.  A well-known example is the ubiquitous oldgrowth forest indicator species, lungwort (Lobaria pulmonaria), which is always sorediate, but which produces apothecia as well about 3% of the time[3].  As it turns out, according to Nash et al., even Xanthoparmelia mexicana rarely has apothecia (whatever "rare" means!), presumably in addition to the abundant isidia.  My favorite example of this is a leprose species, Chrysothrix candelaris (gold dust), which had to wait until 1981 before anyone was lucky enough to find a thallus with apothecia. [4] Up until that time no one even knew which family it belonged to!