Homalium dorrii Appleq., spec. nova
Creators: name: Wendy L. Applequist
Publisher: name: Zenodo
Year: 2016
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Magnoliopsida
Malpighiales
Salicaceae
Homalium
Homalium dorrii

description: 4. Homalium dorrii Appleq., spec. nova
(Fig. 1, 2 A).
Typus: Madagascar. Prov. Toamasina: Analalava, 2.8 km W of old fortress at Foulpointe, 3.XII.1985, fl., Dorr et al. 4432 (holo-: MO-3320333!; iso-, P [P04705567, P04705569]!).
Homalium dorrii Appleq. differs from H. maringitra H. Perrier in having narrowly obovate to narrowly elliptic leaves with cuneate to convex bases, subopposite or clustered near twig ends, and longer sepals.
Tree to 10-15 m tall, 6 cm dbh; large twigs dark or grayish brown; young twigs gray-brown to pale whitish gray, glabrous; stipules deltoid, 1 mm, glabrous. Leaves clustered at twig apices or on short branches or subopposite, leaf scars on older twigs occasionally whorled; petiole 5-11 mm, glabrous; blade narrowly obovate to narrowly elliptic or oblong-elliptic or obovate, 4.2-9 × 1.6-4 cm; base convex to cuneate; apex rounded; margins slightly revolute, shallowly and irregularly denticulate with few teeth, glands located in teeth; abaxial surface glabrous, drying brown; adaxial surface glabrous, drying dark brown. Inflorescences racemose, lateral, often clustered near twig apices, 4.5-9 cm, sparsely short-pubescent (to moderately pubescent distally); peduncle 0.3- 4 cm, moderately thick; pedicel 1-4 mm, short-pubescent; bracts very few, deltoid, 0.5-1 mm, minutely pubescent; bracteoles not seen (absent or caducous and not leaving obvious scars). Flowers sepals 4-5, broad-based obovate to nearly oblong with rounded apex, 3.7-4.6 mm, abaxial surface moderately (sparsely) shortpubescent on basal half, sparsely pubescent toward apical margin; calyx cup funnelform (becoming convex in fruit), ridged, shortpubescent; sepal glands roughly elliptical, 1-1.2 × 0.5-0.6 mm, upper surface densely short-pubescent; petals white or whitish-grey, obovate with rounded apex, 4.8-5.4 × 2-2.6 mm, moderately longer than sepals, abaxial surface short appressed-pubescent mostly at base and in center, adaxial surface glabrous; filaments ca. 1-1.5 mm, glabrous; anthers 0.3 mm; ovary conic (becoming hemispherical in fruit), short-pubescent; styles 4, ca. 1 mm, basally short-pubescent. Seeds 1 per fruit, subglobose, 2-2.5 mm.
Distribution, ecology and conservation status. – The two known collections of H. dorrii are from the forest of Analalava near Foulpointe, at a low elevation near the coast, on laterite. The small number of collections suggests that the species is rare, since the area around Foulpointe was repeatedly botanized over several decades. Though the location had until recently been subject to ongoing degradation, it is now effectively protected. Thus, given the lack of knowledge regarding this species, a preliminary conservation status of “Data Deficient” [DD] seems most appropriate.
Homalium dorrii is presumed to be most closely related to H. maringitra and the newly described H. ranomafanicum, which have generally similar floral morphology (small flowers with sparse sepal indument but dense sepal gland indument). Both of those species have usually broader, elliptic to broadly obovate or obovate, at least partly alternate leaves and short sepals (to 3.5 mm in H. maringitra) that are often barely more than half as long as the petals; both are native to mid-elevation humid forests. Homalium dorrii must also be distinguished from H. oppositifolium, which is found in eastern littoral forests and has often similarly shaped leaves and densely pubescent sepal glands. Homalium oppositifolium has a densely (to moderately) pubescent perianth, as well as denser and longer pubescence on the rachis and pedicels and sometimes on the petiole and leaf midrib; the sepals are 5-6 in number and often narrow, and the bracts and bracteoles more numerous and sometimes quite large.
Paratypus. – Madagascar. Prov. Toamasina: Fkt. Morarano, forêt d’Analalava, à 7 km du SW de Foulpointe, 17°42’32”S 49°27’33”E, 43 m, 8.III.2005, post-fl., Birkinshaw et al. 1434 (P [P04734868]).
description: Published as part of Wendy L. Applequist, 2016, Revision of the Malagasy species of Homalium sect. Eumyriantheia Warb. (Salicaceae), pp. 33-60 in Candollea 71 (1) on pages 39-41, DOI: 10.15553/c2016v711a7, http://zenodo.org/record/161516