General Information

Habitat Requirements

Euphorbia kuwaleana occurs on basaltic rock, on arid, exposed volcanic cliffs, on dry or mesic rocky ridges, or on sparsely vegetated slopes between sea level and 596 m (0 to 1,955 ft). At Puu Kailio, Euphorbia kuwaleana occurs in lowland shrubland with the associated native species Artemisia sp. (ahinahina), Bidens torta (kookoolau), Carex meyenii, Dodonaea viscosa (aalii), Doryopteris sp., Eragrostis variabilis (kawelu), Heteropogon contortus (pili), Lobelia niihauensis, Panicum beecheyi, Schiedea ligustrina, Sida fallax (ilima), and Waltheria indica (uhaloa). In Kauaopuu, this species occurs in lowland shrubland with Artemisia sp., Bidens sp., Carex sp., Chamaesyce sp. (akoko), Dodonaea viscosa, Heteropogon contortus, and Plectranthus parviflorus (ala ala wai nui). On the west side of Kolekole Pass, E. kuwaleana occurs on vertical open basalt cliffs with lichens, Bidens torta, Carex wahuensis, Cyperus phleoides, Deschampsia nubigena (hairgrass), Euphorbia multiformis (akoko), Leptecophylla tameiameiae (pukiawe), and Metrosideros polymorpha (ohia).

Movement / Home Range

Historically known from the central Waianae mountains and Moku Manu Island off the eastern coast of Oahu, Euphorbia kuwaleana is currently known from Waianae Kai-Lualualei ridge in the Waianae mountains.

Reproductive Strategy

Euphorbia kuwaleana fruits in spring and early summer. Fruits in Euphorbieae subfamily are generally dry capsules, exploding their seed only a few meters from their source. However, there are a few cases of long-distance dispersal within Euphorbieae, which include the genus Euphoriba. Molecular evidence supports that this group probably originated in the New World. Because many Euphorbia species possess mucilaginous seeds, their long-distance dispersal may have been accomplished by adhering to animals. This helps to explain why Euphorbia is one of the few taxa within Euphorbieae that has transoceanic distribution.

Other

Euphorbia kuwaleana is distinguished from others of the genus by its stalked, oval to rounded leaves with untoothed margins. and the bent stalk supporting the small capsule. Phylogenetic analysis of nuclear and chloroplast DNA sequence data for species in the tribe Euphorbiaceae indicated that the genus Euphorbia was paraphyletic with Chamaesyce and other genera nested within it (Steinmann and Porter 2002; Yang and Berry 2011). The recommendation that expanding Euphorbia to include Chamaesyce was accepted in the update to the Manual of Flowering Plants of Hawaii (Wagner et al. 2012), consequently, the scientific name of Chamaesyce kuwaleana is changed to Euphorbia kuwaleana. This taxonomic change does not affect the range or endangered status of this species. We recognized this taxonomic change in a technical correction published in 2015 that amended the list of endangered and threatened species in the Federal Regulations at section 17.l2 (USFWS 2015). A recent study has confirmed that the Hawaiian species of Euphorbia are a diverse and unique lineage. DNA analysis of Hawaiian Euphorbia suggests that extensive hybridization and a North American desert origin were involved in the evolution of native Hawaiian Euphorbia. Corresponding with originating from the desert, C4 photosynthesis is a physiological and anatomical system commonly associated with adaptations to warm, dry climates. However, in the Hawaiian Islands there are many Euphorbia that use the C4 system, including Euphorbia kuwaleana, that grow in wetter habitats or have evolved into woody plants and trees, which is highly unusual for plants with C4 photosynthesis (Yang and Berry 2011).