Habitat and Habit
In the Neotropics, the Ericaceae are concentrated in northwestern South America, in cool, moist, montane forest habitats between 1500 to 3000 m of elevation. As a general rule, Ericaceae prefer acid soils and are closely associated with endotropic mycorrhiza (Setaro et. al, 2005). The family is most abundant and diverse in Colombia, Ecuador, Peru, and Venezuela, respectively, where nearly 50% of the species are epiphytes and approximately 94% are endemic.
Ericaceae are often a prominent feature, dominating a major vegetation type of tropical montane regions known as the “ericaceous belt,” and because they are sun-loving, Ericaceae are more easily spot in forest gaps or along the edges of primary or secondary vegetation. A few species are pioneers and in the páramo (the upper most vegetation type in the Neotropics), Pernettya resists trampling by cattle and is a successional species where grazing pressures increase; it is frequently a pioneer species in new habitats created by road building, landslides, man-made fires, or volcanic activity. Pernettya invades the páramo when the vegetation structure is low and open, but may remain when vegetation recovers. Fire does not affect it directly, but actually helps spread it indirectly because it opens the vegetation (Pels & Verweij, 1992).
Ericaceae are epiphytes, hemiepiphytes, or terrestrial; however, some terrestrial species often shift to epiphytic habit, or vice versa, under appropriated conditions. Although most neotropical Ericaceae, and especially the neotropical blueberries (Vaccinieae) have a high affinity for the cool and humid conditions of cloud forests, they are not absolutely restricted to montane environments. Several epiphytic Ericaceae are found in Pacific-coast mangroves of Colombia and Ecuador, while representatives of many genera are also found in lowland tropical rainforests. In Venezuelan Guayana, Notopora schomburgkiana and Vaccinium spp. are typical elements of the sandy savanna shrubberies. Whenever the habitat becomes drier and/or more seasonal superior-ovaried groups such as Gaultheria become more frequent.
Pollination of Ericacae in temperate and subtropical latitudes is primarily by bees, but in the Neotropics bird-pollination dominates, most prominently through hummingbirds. The flowers of many neotropical blueberries often display a number of morphological features associated with pollination by hummingbirds: the flowers are pendent or arching (suited to hummingbirds which feed in flight); the flowers are odorless (hummingbirds have no sense of smell); flowers are relatively showy with shades of red, violet, or orange and their parts often have contrasting colors (which attract hummingbirds and are not particularly alluring to insects); the corollas are regular, long, and tubular in shape, and have constricted throats and spreading lobes perhaps to exclude large insects; corolla tubes are thick and fleshy (to protect them from damage by a probing bill); and some have sugar concentrations in the nectar that fall into the range preferred by birds (see Luteyn & Sylva, 1999).
Not all neotropical blueberries have large showy flowers. Diverse genera such as Disterigma have small and often lightly colored flowers that seem to be better suited for insect pollination (e.g. corollas 7–10 mm long and white). Although bumblebees visit most of the species of Disterigma , pollination studies have shown that some species have mixed pollination, meaning that they are equally visited by insects and hummingbirds (Navarro et al., 2007, 2008; Pedraza-Peñalosa, 2010a). Plants with mixed pollination are being pollinated by trap-lining hummingbirds that are attracted by the large amount of dilute nectar that is produced by the flowers rather than by their appearance. Thus, pollination in neotropical Ericaceae is rather complex and more studies are needed.
In connection with hummingbird pollination, nectar-thieving mites (Rhinoseius spp.) spend virtually their entire life cycle within the flowers of certain ericaceous hummingbird plants. The mites depend not only upon the flowers as their source of nectar, but also upon the birds themselves, as their primary means of dispersal is on the bill or in the nasal cavities of hummingbirds. In turn, the hummingbirds receive protein from the mites as well as sugars from the flower nectar.
Dispersal of the small, light seeds in genera such as Bejaria, Lyonia, and Agarista, which have capsular fruits, is by wind. However, most neotropical genera are berry-fruited and birds or small mammals probably act as agents of dispersal as the berries are often juicy and sweet. Fruit dispersal in this group of plants needs to be explored yet.
Common Names and Uses
In temperate regions, the number of Ericaceae species used as ornamentals is inordinately large when compared with other plant groups of similar size. Many of the most beautiful and prized horticultural plants throughout temperate regions of the world are found in the Ericaceae, notable examples being azaleas, Rhododendrons, heaths, and heathers. Some of the most spectacular bursts of color in the Spring are produced by these shrubs, and they are widely used not only for the beauty of their blooms, but also for the value of the many evergreen species as effective background shrubs. Natural species are cultivated, and many hybrids have originated in cultivation (there are over 6000 cultivars of Rhododendrons and azaleas). Economically, in temperate regions, blueberries and cranberries are among the most important members of the family, being in constant demand. The cultivated “highbush” blueberry, developed primarily from Vaccinium corymbosum and V. austral from eastern North America, has been domesticated entirely in the twentieth century. Cranberries (Vaccinium macrocarpon) are a native North American plant that have been cultivated (in New England) since the early nineteenth century.
The major toxic substance in Ericaceae seems to be andromedotoxin. This compound is known to occur in temperate species of Rhododendron, Leucothoe, Menziesia, Ledum, and Kalmia, and is probably more widespread than is now known. The leaves, twigs, flowers, and pollen grains of these genera all contain andromedotoxin. The course of the poisoning includes watering of the mouth, eyes and nose, loss of energy, vomiting, slow pulse, low blood pressure, lack of coordination, convulsions, and slow and progressive paralysis of arms and legs until death; fatalities, however, are rare. Humans can be poisoned by chewing on leaves and twigs, brewing “tea” from the leaves, or by sucking nectar from the flowers of these plants. Poisonous honey, produced by bees after visiting large stands of Rhododendron, has been known for over twenty-four hundred years. The honey is normally so bitter to the taste, however, that very little of it can be eaten. Various species of Rhododendron and laurel (Kalmia) have long been known to be poisonous to domesticated animals (Luteyn, 1993). In the Neotropics, uses of native Ericaceae are not well documented. In spite of this, the best example of native use of Ericaceae is Vaccinium floribundum, one of the most widespread neotropical species. In Ecuador and Colombia the berries are made into jams, drinks, and occasionally pies; fruits can be found in markets or supermarkets. In almost all regions that we have visited we have gathered reports of several species having edible fruits; nevertheless, there are also reports of different species being toxic or having intoxicating and unpleasant effects on people and cattle. The causes of these reports remain to be studied yet. There are also mixed reports, both in the literature and orally, as to the edible nature of the fruits of Pernettya. These reports range from statements that the fruits are sweet or edible, although somewhat insipid, to claims of intoxication (the Peruvian vernacular name “macha-macha” means drunkenness; see Macbride, 1959; Sleumer, 1985) or hallucination after eating (see Luteyn, 1995). The nutritional and toxic aspects of the fruits of P. prostrata were reported by Gutiérrez (1989). The described symptoms of intoxication included salivation, vomiting, colic pains, depression of respiration, debility, collapse, and occasionally (reportedly) death.
Several species and several genera are used locally as ornamentals, most notably in western Colombia. The flowers of some of these plants are stunningly beautiful and are often cultivated (Cavendishia adenophora). Unfortunately, the entire plant is often harvested from the wild in large quantities and taken for sale in local markets. Rhododendron simsii, native to Asia, is often cultivated terrestrially or in hanging baskets in the montane regions of Central America and northwestern South America.
Local and indigenous uses of neotropical Ericaceae have been compiled from label data of herbarium sheets or from the literature and have been included in our database. In all likelihood variations in spellings and/or misspellings probably occur; however, the labels were copied as written.