Tropicos | Name - !Schradera Vahl

!Schradera Vahl

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Project Name Data (Last Modified On 8/16/2017)

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Project Data (Last Modified On 4/9/2020)

Notes:

Schradera includes perhaps 40 Neotropical species of succulent, usually epiphytic shrubs and climbers found in wet forests (and numerous additional species in southeast Asia and Australasia). It is characterized by its climbing epiphytic habit; ligulate, often obtuse to rounded, deciduous stipules that are held flat together and erect in bud and are interpetiolar or shortly fused into a tube; terminal or rarely axillary capitate inflorescences or solitary flowers enclosed by a truncate involucre; 5-6(10)-merous distylous flowers without calycophylls; tubular truncate calyx limbs; well developed, notably fleshy white corollas with the lobes valvate in bud; and fleshy baccate fruits with numerous small angled seeds. The plants climb by adventitious roots. The flowers are grouped into subglobose heads, and in some species the flowers in a head are are partially to almost fully fused by their ovaries. The heads are subtended by a short to well developed involucre. The flowers are presumably nocturnal. The corolla lobes are so thickly fleshy they are sometimes triangular in cross-section, and characteristically have the tips adaxially galeate and abaxially prolonged into a conical top. The ovary is basically 2-locular in Schradera, but in some species it is have 3- or 4-locular (Steyermark, 1963; Puff et al. 1998). This genus belongs to tribe Schradereae. The nomenclatural history of this genus is complicated and confused, and the name Schradera has been formally conserved.

Schradera was a Neotropical genus until Puff et al. (1993) reviewed the genera of the tribe Schradereae and concluded that the Paleotropical genus Lucinaea DC. was not distinct. They synonymized these, and studied the Paleotropical genus in some detail (Puff et al., 1998). They recognized 16 Paleotropical species from southeastern Asia and Malesia, but that region is poorly known botanically and certainly more Schradera species remain to be documented there. The web page here treats only the Neotropical species.

The habit of some or perhaps most Neotropical species of Schradera is unusual in Rubiaceae in having two heteromorphic stages: the juvenile plants are slender with the stems and soft leaves flatly appressed to the surface they climb, while the reproductive stems have larger leathery leaves and lack adventitious roots, and are often widely spreading or pendulous from their supporting structure. The juvenile plants of the species of Schradera are mostly all quite similar; taxonomic treatments of the species of this genus only the vegetative features of the reproductive stems. See Taylor et al. (2019) for a more detailed discussion of what is known about the habit of Neotropical Schradera. One species, Schradera subandina, is anomalous in this genus in its axillary fasciculate inflorescences that each comprise a single, shortly involucrate flower. The involucre is generally shortly developed, 3-10 mm long, but is reduced in Schradera stellata and so well developed it encloses the entire inflorescence in Schradera lehmannii.

Schradera was first reviewed comprehensively by Steyermark (1963), who knew it as a genus restricted to the Neotropics. He recognized and keyed 25 species based on survey of the specimens from three US herbaria, and described several of them there as new (his key has a typographical error, with lead 18' missing). Steyermark separated species based on various characters, including in particular number of peduncles, number of secondary leaf veins, details of vegetative pubescence, proportionaly length of the corolla lobes vs. the corolla tube, length of the filaments, and number of styles and locules. Plants of Schradera are often scattered and located high in the forest canopy, and difficult to collect so the amount of morphological variation found within local populations of these species is not yet well documented. In particular some other Rubiaceae show infraspecific variation in locule number, especially in the Antilles (e.g., Notopleura parastica), and some Antillean species that Steyermark separated based on this feature are synonymized here. The range of corolla size within an average Schradera species is unknown but many nocturnal, white-flowered Rubiaceae have rather wide variation in this. Schradera subandina may be a good study case to understand the variation within a species, because its inflorescence arrangement is unique and distinctive but its vegetative variation is rather broad.

Since Steyermark's study Schradera has been reviewed only floristically, with updated genus descriptions presented by Taylor (2003), Taylor et al. (2004, 2019), and Lorence et al. (2012).

Schradera is similar to and easily confused vegetatively with Hillia and Cosmibuena, which have corolla lobes that are imbricate or convolute in bud and dry capsular fruits with flattened winged seeds. Schradera is also frequently confused with Clusia (Clusiaceae), which lacks stipules and has copious sticky sap.

Author: C.M. Taylor; and Ms. Sabine Will of WU contributed in sched. to the taxonomic information here.
The content of this web page was last revised 7 April 2020.
Taylor web page: http://www.mobot.org/MOBOT/Research/curators/taylor.shtml

Distribution: Humid to very wet vegetation from lowlands to montane areas: in the Neotropics found throughout the Antilles and from southern Central America to Bolivia and eastern Brazil, in the Paleotropics found from New Guinea to southern Indonesia. In the Antilles, several species of Schradera are separable and mostly or perhaps completely allopatric.

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