The Ericaceae, commonly known as the heath or heather family, is a group of flowering plants found most commonly in acid and infertile growing conditions. The family is large, with roughly 4000 species spread across 126 genera, making it the 14th most speciose family of flowering plants.^[1] There are many well-known and economically important members of the Ericaceae, including the cranberry, blueberry, huckleberry, azalea, rhododendron, and various common heaths and heathers (Erica, Cassiope, Daboecia, and Calluna for example).^[2]

Description [edit]

The Ericaceae contains a morphologically diverse range of taxa, including herbs, dwarf shrubs, shrubs and trees. The leaves are usually alternate or whorled, simple and without stipules, and hermaphrodite flowers. The flowers show considerable variability. The petals are often fused (sympetalous) with shapes ranging from narrowly tubular to funnelform or widely bowl-shaped. The corollas are usually radially symmetrical (actinomorphic) but many flowers of the genus Rhododendron are somewhat bilaterally symmetrical (zygomorphic).^[3]

Distribution and ecology [edit]

Ericads have a nearly worldwide distribution. They are absent from continental Antarctica, parts of the high Arctic, central Greenland, northern and central Australia, and much of the lowland tropics and neotropics.^[1]

The family is largely composed of plants that can tolerate acidic, infertile conditions. Like other stress-tolerant plants, many Ericaceae have mycorrhizal fungi to assist with extracting nutrients from infertile soils, as well as evergreen foliage in order to conserve nutrients that have been absorbed.^[4] This is a trait not found in the Clethraceae and Cyrillaceae, the two families most closely related to the Ericaceae. Most Ericaceae (excluding the Monotropoideae, Pyroloideae, and some Styphelioideae) form a distinctive mycorrhizae, where fungi grow in and around the roots and provide the plant with nutrients.^[5] The Pyroleae tribe are mixotrophic and gain sugars from the mycorrhizae as well as nutrients.^[6]

In many parts of the world, a "heath" or "heathland" is an environment characterised by an open dwarf-shrub community found on low quality acidic soils, generally dominated by plants in the Ericaceae. A common example is Erica tetralix. This plant family is also typical of peat bogs and blanket bogs; examples include Rhododendron groenlandicum and Kalmia polifolia. In eastern North America, members of this family often grow in association with an oak canopy, in a type of ecology known as an oak-heath forest.^[7][8]

There is some evidence that eutrophic rain water can convert ericoid heaths with species like Erica tetralix to grasslands.^[9] Nitrogen is particularly suspect in this regard, and may be causing measurable changes to the distribution and abundance of some Ericaceous species.

Systematics [edit]

In 2002 systematic research conducted by Kron et al.^[10] resulted in the inclusion of the formerly recognised families Empetraceae, Epacridaceae, Monotropaceae, Prionotaceae and Pyrolaceae into the Ericaceae. This was based on a combination of molecular, morphological, anatomical, and embryological data, analysed within a phylogenetic framework. The move significantly increased the morphological and geographical range found within the group. The resulting family now includes 9 subfamilies, 126 genera, and c. 4000 species:

1. Enkianthoideae Kron, Judd & Anderberg (1 genus, 16 species)
2. Pyroloideae Kosteltsky (4 genera, 40 species)
3. Monotropoideae Arnott (10 genera, 15 species)
4. Arbutoideae Niedenzu (5 genera, 80 species)
5. Cassiopoideae Kron & Judd (1 genus, 12 species)
6. Ericoideae Link (19 genera, 1790 species)
7. Harrimanelloideae Kron & Judd (1 genus, 2 species)
8. Styphelioideae Sweet (35 genera, 545 species)
9. Vaccinioideae Arnott (50 genera, 1580 species)

Etymology [edit]

The name Ericaceae comes from the type genus Erica, which appears derived from the Greek word ereike. The exact meaning is difficult to interpret, but some sources show it as simply meaning 'heather.'^[11] The name may have been used informally to refer to the plants in pre-Linnaean times, and was simply formalised when Linnaeus described Erica in 1753, and then when Jussieu described the Ericaceae in 1789.^[12]

Genera [edit]

See the full list at List of Ericaceae genera.

References [edit]