Delimitation of Ericaceae
|Previous studies of the limits of Ericaceae (Anderberg, 1992, 1993; Judd & Kron, 1993; Kron, 1996; Kron & Chase, 1993) have indicated that Epacridaceae and Empetraceae are nested within the traditionally defined Ericaceae. A large scale study that addressed the monophyly of Ebenales using rbcL sequences (Morton, et al., 1996) supports this hypothesis. The sister relationship of Enkianthus to the remaining Ericaceae s.l. was also indicated by rbcL data (Morton et al., 1996). The combined analysis of 18s, rbcL, and matK data in this study indicates that there is strong support for the inclusion of Epacridaceae and Empetraceae within an expanded Ericaceae.|
Relationships within Ericaceae
|Pyroloideae branch after
Enkianthus, making the herbaceous
green (and by extension the non-green) taxa an early branch in the evolution
of Ericaceae. Arbutoideae branch next and
are sister to a clade that contains the remaining Ericaceae.
Morphological support for the sister relationship of Arbutoideae to the remaining Ericaceae includes leaves scattered along the stem (char. #12), pedicel with two bracteoles (char. #35), loss (or reduction of) an endothecium (char. #66), and pollen shed in tetrahedral tetrads (char. #68). Bracteole number, however, is rather homoplasious (Fig. 8). A fibrous endothecium has also been lost in many non-photosynthetic Pyroloideae, and is present in Bejaria. It is noteworthy that tetrads also occur in Moneses and Pyrola (both within Pyroloideae); the presence of tetrads in these taxa is most parsimoniously interpreted as a parallelism (Fig. 9). However, if tetrads are considered to have evolved only once, then the feature becomes synapomorphic for all Ericaceae except Enkianthus.
The monophyly of the remaining Ericaceae (not including Arbutoideae, Pyroloideae, or Enkianthus) is supported by the morphological feature of anthers inverting early in development (char. #56, see Fig. 10). Once this feature evolved in Ericaceae, it has apparently never been lost. Early anther inversion is a remarkable morphological feature (Matthews & Knox, 1926), although not unique to Ericaceae, and correlates with a grouping strongly supported in the molecular analyses (see Kron et al., 2002, Botanical Review, for more details).
Within the early anther inversion clade there are two large clades. One large clade comprises Vaccinioideae + Styphelioideae + Harrimanella. The second clade is composed of Ericoideae + Cassiope. Morphological support for either of these large clades apparently is lacking, although the Ericoideae + Cassiope clade could be supported by the presence of leaves revolute in the bud (char # 10) (see Fig. 11) depending on how the character is optimized. This lack of morphological support argues against the formal recognition (i.e, naming) of either of these large clades.
Ericaceae Durande, Notions Elém. Bot. 270. 1782. (as Ericae) nom. cons.
Andromedaceae DC. ex Schnizl., Iconogr. Fam. Regni Veg.
2:[iv], ad t. 161c. 1834-1870.
Arbutaceae (Meissn.) Bromhead, Mag. Nat. Hist., n.s., 4:
337, 338. 1840 (as Arbuteae)
Arctostaphylaceae J. Agardh, Theoria Syst. Pl.: 106. 1858
Azaleaceae Vest, Anleit. Stud. Bot.: 272, 294. 1818 (as
Diplarchaceae Klotzsch, Monatsber. Königl. Preuss. Akad.
Wiss. Berlin 1859.: 15. 1860.
Empetraceae Bercht. & J. Presl, Prir. Rostlin: 251. 1820
(as Empetreae), nom. cons.
Epacridaceae R. Br., Prodr.: 535. 1810, nom. cons.
Hypopityaceae Link, Handbuch 2: 403. 1831 (as
Kalmiaceae Durande, Notions Elém. Bot.: 271. 1782. (as
Ledaceae J. F. Gmel., Allg. Gesch. Pflanzengifte, ed. 2:
Menziesiaceae Klotzsch, Linnaea 24: 11. 1851.
Monotropaceae Nutt., Gen. N. Amer. Pl. 1: 272. 1818 (as
Oxycoccaceae A. Kern., Pflanzenleben 2: 713, 714. 1891.
Prionotaceae Hutch., Evol. Phylog. Fl. Pl.: 306. 1969.
Pyrolaceae Lindl., Syn. Brit. Fl.: 175. 1829 (as Pyroleae),
Rhododendraceae Juss., Gen. Pl.: 158. 1789 (as
Rhodoraceae Vent., Tabl. Règne Vég. 2: 449. 1799.
Salaxidaceae J. Agardh, Theoria Syst. Pl.: 104. 1858 (as
Stypheliaceae Horan., Prim. Lin. Syst. Nat.: 72. 1834.
Vacciniaceae Adans., Fam. Pl. 2: 160. 1763 (as Vaccinia),
Evergreen or deciduous shrubs, lianas, trees, or herbs (and these sometimes
lacking chlorophyll), sometimes epiphytic; leaves alternate, decussate,
or whorled, sometimes in a basal rosette or distally clustered on shoots,
entire to serrate, and often with margins strongly revolute and leaves
needle-like (i.e., ericoid); stipules lacking; leaf epidermal cells lignified
or not, and hypodermal cells often present; stomata usually anomocytic
or paracytic; vascular bundles frequently associated with a fiber-sheath;
nodes usually unilacunar; buds protected by 2 to numerous scales or naked.
Indumentum a mixture of unicellular and multicellular hairs, or sometimes
only unicellular-pubescent, the multicellular hairs extremely various,
glandular or non-glandular, unbranched and short to elongate, variously
branched, or peltate. Inflorescences terminal or axillary, usually indeterminate
and often racemose, with variously developed bracts and usually a pair
of bracteoles, these sometimes recaulescent, replacing calyx lobes; flowers
pendulous to erectly held, articulated with pedicel or not. Flowers
showy to inconspicuous, perfect to imperfect, usually 4- or 5-merous,
actinomorphic to zygomorphic. Sepals (1-) 4-5 (-9), usually connate, persistent
or deciduous, occasionally colorful and fleshy; petals (3-) 4-5 (-9),
usually connate and typically campanulate, cylindrical, or urceolate,
occasionally rotate, deciduous or persistent. Stamens (2-) 5-10 (-16),
free from the corolla or adnate, sometimes connate, included or exserted,
the filaments straight to variously curved, unicellular-pubescent or glabrous;
anthers tetrasporangiate or bisporangiate, inverting (late, or more commonly
early) in development, with 2 or 4 apparently terminal or dorsal appendages
(awns, spurs) or these sometimes on the filaments, opening by pores or
short to long slits, sometimes through narrowed tubules, an endothecium
usually lacking. Pollen usually tricolpate to tricolporate, in tetrahedral
tetrads, but these sometimes reduced, or occasionally in monads, sometimes
associated with viscin threads. Nectary present or absent. Ovary (2-)
4-5 (-14) carpellate, superior to inferior, with usually axile to intruded
parietal placentation, rarely apical or basal; ovules 1-many per carpel,
anatropous to nearly campylotropous, unitegmic, tenuinucellate, the embryo
sac usually of the Polygonum type; style short to long, hollow,
sometimes expanded apically; stigma truncate to capitate or slightly to
strongly lobed, sometimes cup-shaped, funnel-shaped, or flabellate to
pinnatifid. Fruits loculicidal to septicidal capsules, berries, drupes
(with one or several pits), or occasionally dry and indehiscent; seeds
small, seeds without vascular bundle in raphe, testa usually single-layered,
with cells isodiametric to strongly elongated, sometimes winged or tailed,
sometimes mucilaginous on wetting. Embryo fusiform or spatulate, white
or less commonly green, with 2 cotyledons, to extremely reduced and undifferentiated;
endosperm cellular, well developed, with haustoria at both ends; germination