Last Saturday, February 23, I stopped at the campsite in Cochise Stronghold and walked east along the road. it was pretty cold, around 65° F. There was little flying, I found only three species, Thrips, a fly and an Osmia Sp. bee. I was able to get good photos of all three and was able to get a good series showing at least two behaviors by the bee. None of the flowers had opened and there was damage by side holes which I decided last week that these were probably caused by thrips and damage to the flower openings, probably caused by bees forcing the opening. The bee was at both these locations, don’t know if this was a primary robbery or it just used an already forced opening but there was at least secondary nectar robbery in both cases. (Richardson, Bronstein, 2012) observed these behaviors in Osmia Sp. (ribifloris?) as well as “legitimate” mutualist nectar gathering behavior. The question is: How can the mutualist behavior survive with “cheating” going on? What benefit to the insect does legitimate pollination provide? Why a mixed set of behaviors instead of one or the other? Of the some 35 insect species that were found to visit manzanita, 4 provided 65% of mutualist behaviors and all 4 robbed nectar. (Richardson, Bronstein, 2012) data.
Arctostaphylos is a genus of the Heath family (Ericaceae), a large family of flowering plants. Arctostaphylos is a member of the subfamily Arbutoideae, which contains five other genera: Arbutus, Arctous, Comarostaphylis, Ornithostaphylos, and Xylococcus (Hileman, Vasey, Parker, 2010). Only the Arbutus species madrone (Arbutus arizonica) is found in Arizona. There are three Arctostaphylos species found in Arizona, A. pungens (pointleaf manzanita) and A. pringlei pringlei (Pringle manzanita) here in southern Arizona and A. patula (greenleaf manzanita) found at the north rim (USDA PLANTS database). The flowers of Arbutoideae and of most subfamilies of Ericaceae are sympetalous, meaning they have a fused corolla (Harris, Harris, 2001) which gives them a distinguishing bell shape (Key to Arbutoideae).
The biogeography of Arbutoideae is quite interesting with a circumpolar distribution and a large distribution down Pacific N. America and a Mediterranean-type climate origin. This has given rise to the Madrean-Tethyan hypothesis, the idea that this subfamily once shared a single climate and has migrated around the world when the northern continents were connected. (Hileman, Vasey, Parker, 2010) have tested this and have found that there was a major separation of North American and Eurasian species around 23 million years ago when the Atlantic Ocean started separating N. America and Europe. The story now is that Arbutoideae arose in California and spread into Eurasia and after separation the California species radiated during the uprising of the Rocky Mountains with some extinctions afterwards. Most species of Arctostaphylos occur in the so-call California Floral Zone which extends along the coast from central Oregon to Baja, Mexico (Hileman, Vasey, Parker, 2010).
Phylogenetic and character analysis show that A. pungens and A. pringlei pringlei are sister species with A. australis, a Baja species (Wahlert, 2005), (Keeley, Massihi, Rodriguez, Hirales, 1997). A. pungens and A. pringlei pringlei are sympatric in Arizona. I don’t know if they hybridize but another subspecies of A. pringlei is a hybrid (Wahlert, 2005) and there is talk of another hybrid here. I found little about the two species in Arizona. In fact, two images representing A. pungens and A. pringlei pringlei from the Arizona-Sonora Desert Museum collection are the same picture! The only information I could find about the two species together was from California information here.
As far as field marks, A. pungens has green and glabrous leaves while A. pringlei pringlei leaves are grey-green with glandular hairs. A. pringlei pringlei is a larger plant and seems to occur more readily at higher elevations. I have yet to identify A. pringlei pringlei in the field.