Rhododendron subgenus Vireya

''Vireya'' rhododendron

''Rhododendron'' section ''Vireya'' (vireyas) is a tropical group of '' Rhododendron'' species, numbering about 300 in all. Vireyas are native to southeastern Asia and range from Thailand to Australia.

Description

''Vireya'' are morphologically diverse, and characterised by seeds with tailed appendages, the presence of leaf idioblasts and capsule valves which twist upon opening.

The formal description (Craven 2008) is: Scales sessile or sometimes stalked, lobed to deeply incised or sometimes entire; corolla campanulate, trumpet-like, salver-shaped, tubular or funnel-shaped; stamens (5–)10(–16), exserted to included, staminal filaments glabrous or hairy from the base; capsule valves twisting after dehiscence; seeds with a distinct tail at each end.

Taxonomy

''Vireya'' is the largest of the three sections constituting subgenus ''Rhododendron'', and includes about a third of all ''Rhododendron'' species. The exact classification has varied among various authors, some authors considering ''Vireya'' to be a separate subgenus rather than as here, a section of the subgenus ''Rhododendron''. It has been suggested that taxonomic nomenclatural correctness requires changing the name of the ''Vireya'' rhododendrons to ''Schistanthe''. Thus the term 'Vireya' has been used to refer to Section ''Vireya'' (Sleumer), Subgenus ''Vireya'', Section ''Schistanthe'', or the majority of the Malesian tropical rhododendrons. (Fayaz). Goetsch (2011) gives the number of species as 320, and the total taxa including subspecies, forms and varieties as 380.

Subdivision

The section has traditionally been considered to consist of seven subsections based on morphology, although Brown etal., using phylogenetic analysis, found a lack of support for monophyly of these subsections, and rather a series of clades based on geographical distribution:
* R. subsect. ''Albovireya'' Sleumer, type ''Rhododendron album'' Blume
* R. subsect. ''Euvireya'' Copel.f., type '' Rhododendron javanicum'' (Blume) Benn
* R. subsect. ''Malayovireya'' Sleumer, type '' Rhododendron malayanum'' Jack
* R. subsect. ''Phaeovireya'' Sleumer, type '' Rhododendron beyerinckianum'' Koord.
* R. subsect. ''Pseudovireya'' Clarke, type '' Rhododendron vaccinioides'' Hook.f.
* R. subsect. ''Siphonovireya'' Sleumer, type '' Rhododendron habbemae'' Koord
* R. subsect. ''Solenovireya'' Copel.f., type '' Rhododendron jasminiflorum'' Hook.

In Argent's (2006) treatment of Vireya as a subgenus, he included seven sections, with ''Euvireya'' consisting of five subsections, but this is not supported by phylogenetic analysis. These studies, for instance that of Hall (2006), suggested a very different approach. The Asian mainland species represented by ''Pseudovireya'' appear as a sister group to the other six subsections, while the Malesian species within ''Pseudovireya'' also formed an outgroup, resulting in three major clades. Thus Craven etal. proposed there be only two subsections of ''Vireya'', corresponding to the core species, ''Euvireya'' and the much smaller ''Malayovireya'' , while the other two groups formed out of ''Pseudovireya'' be raised to section rank, keeping the original name ''Pseudovireya'' for the mainland species, and using Argent's name, ''Discovireya'' for the Malesian species. For a comparison of the Sleumer, Argent and Craven schemata, see Craven (2008), Table1.

Thus the new subsection structure is:
* R. subsect. ''Euvireya'' Copel.f., type ''Rhododendron javanicum'' (Blume) Benn
* R. subsect. ''Malayovireya'' Sleumer, type '' Rhododendron malayanum'' Jack

Characteristics:(Craven 2008)
* ''Euvireya'' – Scales sessile or stalked, scattered or dense, not of two obviously different size classes, lobed to deeply incised (or sometimes entire) and the centre not dark-coloured.
* ''Malayovireya'' – Scales sessile, dense, of two obviously different size classes, lobed and the centre dark-coloured.

Distribution

Vireya are found throughout the Malesian Archipelago. Malesian species are found in all subsections, while species from other areas appear only in ''Euvvireya'', ''Malayovireya'' and ''Pseudovireya''.
Found in that area an outstanding specimen ''Rhododendron loranthiflorum'' has been named after the New York guru Sri Chinmoy

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