General Information

Habitat Requirements

At Kaluakauila on Oahu, Euphorbia haeleeleana occurs in dry to mesic Sapindus oahuensis (lonomea)–Erythrina sandwicensis (wiliwili)–Polyscias sandwicensis (ohe ohe)–Diospyros sp. (lama) forest at 156 to 586 m (512 to 1,922 ft) with the associated native plant species Bidens torta (kookoolau), Bobea sandwicensis (ahakea), Bonamia menziesii, Charpentiera tomentosa (papala), Dodonaea viscosa (aalii), Eugenia reinwardtiana (nioi), Myoporum sandwicensis (naio), Nestegis sandwicensis (olopua), Nototrichium humile (kului), Peperomia tetraphylla (ala ala wai nui), Pittosporum glabrum (hoawa), Polyscias sandwicensis (ohe ohe), Pouteria sandwicensis (alaa), Psydrax odorata (alahee), Rauvolfia sandwicensis (hao), Sapindus oahuensis (lonomea), and Schiedea hookeri. On Kauai, Euphorbia haeleeleana occurs in lowland mixed mesic or dry Diospyros (lama)-Metrosideros (ohia)-Alphitonia (kauila) forest at 284 to 1,178 m (931 to 3,866 ft) with the associated native plant species including Acacia koa (koa), Alphitonia ponderosa, Alyxia stellata (maile), Antidesma platyphyllum (hame), Asplenium dielpallidum, Bidens cervicata (kookoolau), Bobea brevipes (ahakea lau lii), Bonamia menziesii, Carex meyenii, C. wahuensis, Charpentiera elliptica (papala), Cheirodendron trigynum (olapa), Claoxylon sandwicense (laukea), Cyrtandra kauaiensis (ulunahele), Delissea kauaiensis (oha), Dicranopteris linearis (uluhe), Diospyros hillebrandii (lama), D. sandwicensis, Diplazium sandwichianum (hoio), Dodonaea viscosa, Doodia kunthiana (okupukupu), Elaeocarpus bifidus (kalia), Euphorbia atrococca (akoko), E. halemanui (akoko), Flueggea neowawraea (mehamehame), Freycinetia arborea (ie ie), Gahnia beecheyi, Hibiscus waimeae ssp. waimeae (kokio keokeo), Hydrangea arguta (kanawao), Ilex anomala (kawau), Isodendrion laurifolium (aupaka), Kadua affinis (manono), Kokia kauaiensis (kokio), Leptecophylla tameiameiae (pukiawe), Lepisorus thunbergianus (pakahakaha), Lipochaeta fauriei (nehe), Lysimachia kalalauensis, Melicope anisata (mokihana), M. barbigera (alani), Metrosideros polymorpha, Morinda trimera (noni kuahiwi), Myrsine spp. (kolea), Neraudia kauaiensis, Nestegis sandwicensis, Nototrichium spp., Panicum nephelophilum (konakona), Peperomia kokeana (ala ala wai nui), Peucedanum sandwicense (makou), Pipturus kauaiensis (mamake), Pisonia wagneriana (papala kepau), Pittosporum kauaiensis (hoawa), Polypodium pellucidum (ae lau nui), Polyscias kavaiensis (ohe ohe), Pouteria sandwicensis, Pritchardia minor (loulu), Psychotria hobdyi (kopiko), Psydrax odorata, Pteralyxia kauaiensis (kaulu), Santalum freycinetianum var. pyrularium (iliahi), Scaevola procera (naupaka kuahiwi), Smilax melastomifolia (pi oi), Streblus pendulinus (aiai), Vaccinium dentatum (ohelo), Wikstroemia furcata (akia), Wilkesia gymnophixium (iliau), and Zanthoxylum dipetalum var. dipetalum (kawau).

Movement / Home Range

Euphorbia haeleeleana is known historically from northwestern Kauai and the Waianae mountains of Oahu. Currently, on Oahu this species occurs in the Waianae mountains at Kaluakauila and Kaimuhole gulch. On Kauai, there are occurrences at Kalalau, Kuia, Hipalau, Hanakapiai, and Poopooiki valley.

Reproductive Strategy

Euphorbia haeleeleana sets fruit between August and October. Euphorbia haeleeleana is dioecious (male and female flowers on separate trees) and must be cross-pollinated to produce viable seed. Some populations appear to have mostly male flowers and do not produce much seed. The capsules are explosively dehiscent so seed tends to be collected in the immature stage for genetic storage and propagation, as ripe seeds have already been dispersed. Seeds on the ground are often empty and non-viable. It is unclear if rats (Rattus spp.) eat viable seeds or if most seeds produced are not viable.

Other

Euphorbia haeleeleana is distinguished from others in the genus in that it is a tree, whereas most of the other species are herbs or shrubs, as well as by the large alternate leaves with prominent veins. 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 haeleeleana, that grow in mesic (rainier) habitats or have evolved into woody plants and trees, which is highly unusual for plants with C4 photosynthesis (Yang and Berry 2011).