The formerly recognized family Epacridaceae includes small to large shrubs and small trees of about 37 genera and more than 450 species. Most representatives occur in Australia, especially in the south-west, west and south-east, and in Tasmania. Non-Australian species range from Indo-Malaysia to South America, New Zealand, New Caledonia and Hawaii. The epacrids grow in a wide variety of habitats ranging from Mediterranean and temperate to (sub)tropical climates, covering coastal dunes, lowland forests, sandy heaths, upland areas and even montane to (sub)alpine regions (Burrows et al., 1979; George et al., 1979; Specht 1979a, b; Specht and Womersley, 1979).
Until recently, this plant group was recognized at family level and most taxonomists considered it to be the Australian counterpart of Ericaceae. Epacridaceae were separated from Ericaceae on the basis of their distribution pattern, parallel leaf venation, presence of unicellular hairs, number of stamens and anther dehiscence by slits (Stevens, 1971). However, owing to a high degree of variation in both families, these so-called distinguishing characters have never maintained the two families as distinct entities. Indeed, some botanists had already merged epacrids in Ericaceae over 150 years ago (e.g. Don, 1834). Recently, DNA-sequence data have again supported this view showing that epacrids, although strongly supported as a monophyletic group, are sister to the subfamily Vaccinioideae within Ericaceae s.l. (Kron, 1996; Kron et al., 1999, 2002). In the most recent classification of Ericaceae, epacrids are given subfamilial rank. Due to nomenclatural rules, the group should now be called Styphelioideae (Kron et al., 2002).
The taxonomic position of the epacrid genera according to several classification systems is shown in Table 1. On the basis of ovary and fruit characters, Bentham and Hooker (1876) and Drude (1889) provided the first major classifications within the epacrids. Based on leaf fibre patterns, stomata, nodal anatomy and pith structure, Watson (1967) erected the subfamily Richeoideae and the tribe Cosmelieae, which are now considered as two tribes. A cladistic analysis of morphological characters presented further support for three monophyletic subgroups (Cosmelieae, Richeeae and Styphelieae including Need hamiella and Oligarrhena), but the other representatives were clustered in an unnatural assemblage (Powell et al., 1996). The classification system within epacrids was further refined using rbcL-data, resulting in seven tribes (Crayn et al., 1998). Although tribal relationships and affinities within Styphelieae remain uncertain, additional atpß-rbcL intergeneric spacer data concurred with this classification (Crayn and Quinn, 2000). However, matK data contradict the proposed tribal relationships based on rbcL data, although these relationships are not strongly supported either (Kron et al., 2002).
There is still an under-representation of shrubs and subshrubs in wood anatomical descriptions (e.g.
Dickison, 1999), as illustrated by, for example, our fragmentary knowledge of the wood structure of epacrids and Ericaceae in general.
Etienne (1919) was one of the first botanists who paid attention to the general anatomy of epacrids. Although his sampling was outstanding (31 genera), his work focused on a limited number of wood anatomical characters of mostly juvenile wood samples. The best overall summary of the wood anatomy is given by
Metcalfe and Chalk (1950). There are several other publications that deal with the wood anatomy of one or more epacrid species, such as the work of
Carlquist (1977a) including remarks on the ecological wood anatomy of five epacrid genera,
Meylan and Butterfield (1978) investigating three epacrid genera with SEM,
Ilic (1991) showing pictures of two genera,
Schweingruber (1992) discussing growth rings and growth zones of 43 epacrid samples, and
Bell and Pate (1996) and
Bell et al. (1996) commenting on various characteristics related to fire response mechanisms within epacrids.
This work presents a detailed wood anatomical overview of the epacrids. Special emphasis is paid to a comparison of the wood anatomical variation with recent molecular phylogenies to reveal possible evolutionary patterns and to comment on the intrafamilial classification. Moreover, ecological conditions are taken into consideration to better interpret the anatomical variation observed.
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