November 17, 2013
Went to Willcox and then around the Dos Cabezas Mts. to Chiricahua National Monument. We hiked the Echo Canyon Loop Trail and on the way back took the road past Fort Bowie to I-10 and home. Saw Arctostaphylos pungens at the Texas Canyon Rest Stop in the Little Dragoon Mts.
and in the Dos Cabezas Mts at the town of Dos Cabezas, AZ, all through Chiricahua National Monument and around Fort Bowie. Found A. pringlei only one place, on Sugarloaf Mt. in Chiricahua National Monument. This A. pringlei was not sticky at all although it had the correct leaf color and young twig color and was in sympatry with A. pungens. In this thicket of plants there were for the first time what could be hybrids. Hard to tell as the variation in A. pringlei is large.
The Chiricahua Mts. contain botanical elements from the Sonoran Desert to the west, the Chihuahuan Desert to the east, the Rocky Mts. to the north and the Madrean highlands to the south. Found Arizona Madrone (Arbutus arizonica) in several places throughout the monument and one tree had berries, much juicier than manzanita berries.
The eroded towers and balanced rocks were caused by a massive period of volcanism some 25 – 30 million years ago. Vast quantities of volcanic ash were deposited to form a 2000 ft layer of pumice. This pumice is either hard or soft depending on the original temperature of the fallen ash. Hot ash crystallizes into hard pumice while cooler ash makes a softer pumice. Shrinkage cracked the layer and water seepage washed away the softer pumice creating what we see today (Chronic, 1983).
Burnt regions from recent fire have been a constant companion this summer and Ciricahua National Monument has not been spared. On the return trip up to the top we passed through a heavily burned canyon. All the manzanita in the canyon had their leaves covered with red galls.
I’ve seen this type of gall before on both species of Arctostaphylos here in Arizona. This gall is on many plants in the Arctostaphylos genus and is caused by an aphid of the genus Tamalia. There are five described species and two undescribed species in this genus and all species use Arctostaphylos as a host along with two other known hosts in the closely related Arbutus xalapensis (Texas or Mexican madrone) and Comarostaphylis diversifolia (summer holly). One of the species of Tamalia is an inquiline, a related gall parasite that doesn’t form a gall but uses all the protection and resources of the gall (Miller, Sharkey, 2000). Aphid galls attract predators, most importantly the larvae of Syrphidae and other flower flies (Elisabeth C. Miller Library, 2013). These aphids form galls on the leaf margins but they can also form galls on the leaf veins and the flowers. It is unusual for a gall aphid to have this much variety in gall formation (Miller, 2005). Several species of manzanita can defend themselves from aphids by growing dense hairs and by being glandular, secreting a sticky sap (Andres, Connor, 2003). A. pringlei var. drupaceae in California is extremely glandular and is know to be used by a single species of gall aphid, Tamalia dickensoni. This aphid has much longer legs and mouth parts than other species in the genus (Miller, 2005). As usual, there is nothing about A. pringlei in Arizona. I am wondering if the variability in glandularity that I have found here has something to do with these aphids. Arbutus xalapensis is also known for it’s great variability in hairiness and glandularity (Ezcurra, Gomez, Becerra, 1987). I am probably seeing all these galls in the burn area because the burn creates a lot of new growth.