The Flowering Plants of Hawaii
Part 16 Elaeocarpaceae - Epacridaceae - Ericaceae
This family occurs in tropical and subtropical regions of the World but not in Africa. Authors of the Manual state that there are about 10 genera in the family with some 400 species. By Mabberley’s (p. 300) reckoning the numbers should be 12 and 600. The largest genus, Elaeocarpus, contains about 360 species. A single species is found in the Hawaiian Islands. Elaeocarpus bifidus (see image), kalia in Hawaiian, can be found in bog margins and wet forests on Kaua`i and O`ahu.
Some current authorities (Mabberley, p. 308) include Epacridaceae in the blueberry family, Ericaceae, at the subfamily level (Styphelioideae). We follow the Manual, however, in talking about Epacridaceae as a family in their own right. The family consists of about 30 genera and perhaps as many as 400 species. The only representative of this primarily southern Hemisphere family on the Hawaiian Islands is Styphelia tameiameiae (see image) most commonly known as pükiawe (various spellings) and `a`ali`i mähu, among others less frequently used.
The most common use for this plant involved smudging a high ranking priest with smoke from burning pükiawe wood, along with the appropriate prayer, before mixing with people of lesser standing. A somewhat less restrictive use involved lei making.
Many people find it strange that such a familiar fruit as the blueberry actually grows on the Hawaiian Islands, and moreover that the islands’ three species are endemics. There seems to be some feeling that the blueberries and their relatives are northern plants and just shouldn’t occur on tropical islands.
This view may be attributable to a North American chauvinism but more likely to the fact that most visitors do not realize just how widespread and ecologically diverse the family Ericaceae are in the world. A brief look at some numbers (Mabberley, pp. 313-314) may be instructive. The family, including Empetraceae, Epacridaceae (dealt with above), Pyrolaceae, and Monotropaceae, comprises 3,850 species arrayed in 117 genera. The family is cosmopolitan with significant species diversity in southern Africa and Asia. For example, the type genus Erica consists of 860 species in South Africa. The Cape floristic province alone has 658 species of Erica of which 635 are endemic to that small area. The common decorative genus Rhododendron, now taken to include Ledum, consists of at least 1,000 species with 650 in China and 155 endemic to the mountains of New Guinea. Vaccinium consists of 140 circumpolar and northern temperate species of which 65 occur in North America. The widespread occurrence of blueberry species in the Northern hemisphere is typical of the challenge of determining where the ancestor of Hawaiian species came from. We’ll address that question after first getting acquainted with the island species.
Three species of Vaccinium make their home in the islands: V. calycinum (see images ), V. dentatum (see image). And V. reticulatum (see images). Four examples of Vaccinium reticulatum are included to give some idea of the range of variation in the species. Vaccinium reticulatum is common on the Big Island and on Maui, rarer on the other islands. It grows widely on new lava, cinder fields, and open areas at higher elevation. It is one of the first flowering plants to colonize new lava fields as can be seen in the Devastation Trail area of Volcano National Park. Cracks in lava beds provide anchor points, protection from the wind, and adequate water for the establishment of new plant communities. A typical example is illustrated (see image) with a tiny blueberry plant—already bearing fruit—nestled between two clumps of the gold-back fern Pityrogramma. Plants can also be found growing in piles of clinker lava (see image below).
Vaccinium calycinum occurs on all of the main islands preferring a wetter habitat than its lava-colonizing cousin. This is a larger species often attaining heights of two meters. Visitors to the Big Island will undoubtedly wish to spend time in and around Kilauea Iki—an easily accessible volcanic crater—where they would find V. calycinum lining the access trail and V. reticulatum growing on the crater floor. Vaccinium dentatum is also a plant of wetter habitats, including bogs. It also can be found on all of the main islands but some experience is needed to distinguish it from V. reticulatum. I have often found V. dentatum growing along sections of the Pihea Trail in Koke`e Park (Kaua`i).
The Hawaiian names for these species are based upon the word `öhelo, which the Hawaiian Dictionary (Pukui and Elbert, p. 277) simply define as V. reticulatum. A modifier of `öhelo is used to define this species in the Manual, however, namely, `öhelo `ai, which means ‘edible’ `öhelo. This infers that the other two species are not edible, which is not the case. Vaccinium dentatum yields a tasty enough berry; the yield isn’t as rich as with V. reticulatum so more work is necessary in order to get an equal amount.
In the case of V. calycinum, which is known in Hawaiian as `öhelo lau lä`au, (lit., `öhelo upon a tree) the fruit is rather pulpy and not particularly tasty, certainly not choice. This is also a much larger plant, a shrub that can grow to two meters, which is reflected in its name. Visitors shouldn’t be put off by finding that Hawaii’s blueberries are in fact red; Vaccinium parvifolium, the red huckleberry, which grows in my home area, the Pacific Northwest, sports that color.
Botanists with field experience in the Hawaiian Islands are well acquainted with the considerable level of variation that many native species exhibit in size, structure, and ecological tolerance throughout their ranges. It should not be surprising, then, that differences in opinion exist with regard to what constitutes a species in many of these cases.
The islands’ blueberries serve as a realistic case in point. The usual format in floristic manuals shows the currently accepted species name followed by a list of synonyms, that is, names by which the plant in question have been described in earlier works. Thus, under V. calycinum are listed 17 synonyms, under V. dentatum 11, and under V. reticulatum 9. Many of these synonyms are at lower taxonomic levels, varieties or even forms, but full species recognition has been suggested for several.
This issue was examined in detail by a colleague of mine, Dr. Sam Vander Kloet from Acadia University in Nova Scotia, a noted specialist in Ericaceae with a particular interest in the blueberries (and author of the section on Vaccinium in the Manual; see also Vander Kloet 1988; Prof. Vander Kloet died January 2011). He collected specimens of most of the naturally occurring forms from Nature on the islands and reared them in controlled conditions in a common garden. This is the approach used in an attempt to cancel out the effects of different environmental conditions that the individual plants experience in their native habitats. The premise is that when environmental effects have been ‘neutralized’ the resulting variation will be a reflection of genetic factors alone. In the case of these growth experiments, the Hawaiian plants sorted themselves out into three discrete groups, a result reflected in the recognition of the three species about which we have been talking.
As I noted above, a plant’s name is really a matter of opinion subject to challenge by anyone who wishes to re-examine the situation at hand. Although it is generally accepted that the patterns of variation within Hawaiian Vaccinium can be reasonably accommodated by the three-species concept, I have met people with field experience in the islands who do not agree, but that’s botany. Let’s move on to the next challenge, where did the islands’ blueberries come from?
Vaccinium is a moderately large genus—about 140 species as noted above—with a circumpolar and North Temperate distribution. Mabberley (p. 889) informs us that there are eight species in Europe, 22 in Japan, and 65 in North America. Identifying the source of the Hawaiian colonists becomes even more challenging since Vaccinium species also occur in the mountains of central and southeastern mountains of Africa and in Madagascar as well as in tropical America. DNA-Based studies of the relationships among the many members of Vaccinium were described by Drs. E. A. Powell and K. A. Kron of Wake Forest University in 2002.
Their data led to three conclusions: (1) The Hawaiian species are not related to a species from southern Polynesia (V. cereum) originally thought to belong, along with the Hawaiian species, to a unique group within the genus; (2) The Hawaiian species are most closely related to a group of species that occur along the Pacific Rim from Japan to Mexico; and (3) The Hawaiian species are extremely closely related to one another suggesting that the triad is the result of a single colonization followed by differentiation. The data did not identify the original colonizer.