EPOW - Ecology Picture of the Week

Explanation:  This modest little plant is na'ena'e, a native of the high country of Maui, one of the major Hawaiian islands.  It grows as a branching shrub with small succulent leaves that resist drying in the often arid lava environment of Haleakala Crater and on the slopes of this volcano.  Na'ena'e is a perennial that produces many flowering heads of orange-yellow flowers.   

Typical spreading growth pattern
of Dubautia menziesii

Along with two other native plant genera of Hawai'i (Argyroxiphium and Wilkesia), plants of this genus (Dubautia) show a remarkable degree of evolutionary specialization on Hawai'i, also called "adaptive radiation."  This occurs when some original species colonizes a distant environment and then evolves into an array of new species that each specializes in using resources in a unique way.  The original colonizer that evolved into these three plant genera and all their Hawaiian species (and also others in California) was probably most similar to a species of a tarweed shrub (Adenothamus validus) found in Baja California.  Somehow, the tarweed dispersed to Hawai'i long ago and then began its remarkable adaptive radiation. 

Dubautia menziesii growing among lava
rocks on the slopes of Haleakala volcano, Maui

Just among the Hawaiian Dubautia are species evolved to specialize as mat-like clumps in lava fields on the Big Island of Hawai'i (D. scabra) ... as larger shrubby species found in dry areas of Big Island and Maui (D. linearis, D. ciliolata, and D. menziesii) ... as tree-like species found in dry to moist forests, including one (D. waialealae) found in the wettest parts of Hawai'i ... and even as a vine adapted to wet forests (D. latifolia).  

The related genus Argyroxiphium constitute the silverswords, and occasionally na'ena'e, pictured here, will hybridize with the Haleakala silversword.   

In all, there are some 23 recognized species of Dubautia and at least 6 congeneric (and more cross-generic) hybrids!  And you thought Darwin's finches on the Galapagos Islands were remarkable for their adaptive radiation!  

Reference:  Sohmer, S. H., and R. Gustafson. 1987. Plants and flowers of Hawai'i. University of Hawaii Press, Honolulu, Hawaii. 160 pp.
     One reference suggests there are 21 endemic species of Dubautia in the Hawaiian Islands.  Regardless of exact numbers and taxonomy, this is still one diverse genus!

Previous EPOW links on Hawai'i:
     Kipukas: Islands Within Islands 
     Stilt Palm, Pandanus tectorius