3 4
Dubautia arborea	Natural Hybrid	D. ciliolata

Biosystematic and cytogenetic analyses indicate that hybrids among the group of Dubautia species with 13 pairs of chromosomes are essentially fully fertile and exhibit normal chromosome pairing. Thus, where such species are sympatric, it is common to find evidence of hybridization, sometimes resulting in spectacular swarms of recombinant types representing every conceivable intermediate between the parental types. One superb example of this type involves D. arborea and D. ciliolata in a small area of sympatry in Waipahoehoe Gulch on Mauna Kea, Hawaii. Interestingly, a form that is very similar to D. menziesii, otherwise known only from Maui, has apparently become reproductively stabilized in the lower part of this gulch and in at least one other area of sympatry on Mauna Kea (first 2 hybrid images). The other 2 hybrid illustrations show an array of shoots (3) and leaves (4), each taken from from a different individual growing in the narrow zone of sympatry in this gulch.  Asa Gray cited collections of this hybrid combination from Hawaii along with Maui specimens when he described D. menziesii.  The formal names Raillardia struthioloides A. Gray and Railliardia ciliolata var. trinervia Hillebrand also have been applied to elements of this hybrid combination.

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