Northern Distributional Limits Of The Mexican Willow Oak (Quercus Viminea) In Arizona, Sonora, And Chihuahua

Observations of the Sierra Madrean oak Quercus viminea in ten Sky Island mountain ranges 15 to 85 km south of the Arizona and New Mexico border in Sonora and Chihuahua help define the northern and western limits of its distribution. We also discovered it in the Patagonia Mountains of southern Arizona as far north as 15.3 km from Sonora. It is sympatric with the closely related Q. emoryi, with which it introgresses.

Quercus viminea

Willow-leaf oak is closely related to emory oak, but in some areas they appear to intergrade. Its leaves are generally shinier, slimmer, longer, and brighter green. Branch tips are generally less robust than emory oak. There is overlap in range of the two species in Sonora, but generally as one heads south Q. emoryi fades out as Q. viminea becomes more common. in areas of overlap they can grow at different elevations with emory oak at the lower end of the oak zone, often with or just above blue oak.