Friday, February 1, 2019

[Botany • 2019] Gravesia serratifolia (Melastomataceae: Sonerileae) • A New Species from Marojejy National Park, Madagascar


Gravesia serratifolia Almeda & H. Ranariv.

in Almeda & Ranarivelo, 2019. 
Photo: Éric Mathieu

Abstract 
Gravesia serratifolia, a new species from upper elevations of Marojejy National Park in northeastern Madagascar, is herein described, illustrated, mapped, and compared with similar species. It is readily characterized by its sparingly branched habit, leaf blades coarsely serrate with a moderate to sparse lepidote indumentum on both surfaces, inflorescence of few-flowered dichasia, calyx obsolete or evident as depressed truncate undulations with prominent calyx teeth that are laterally compressed when fresh, filaments with rusty-brown glandlike indumentum, and dorso-basal staminal appendages linear-oblong and widely spreading to coiled. A conservation assessment of Vulnerable is recommended for this species based on IUCN Red List Categories and Criteria. 

 Keywords: Sonerileae, conservation, new species, paleotropics, Madagascar


Gravesia serratifolia Almeda & H. Ranariv., sp. nov.

Diagnosis: Distinguished from all Gravesia species by a combination of small (1−3.3 × 0.7−2.7 cm) coarsely serrate leaf blades that are moderately lepidote on both surfaces like young vegetative buds, calyx tube well-developed and flangelike, 1.5 mm long; calyx lobes obsolete or evident as depressed truncate undulations, calyx teeth 5, 0.75−1 × 0.5−0.75 mm, prominent and prolonged beyond calyx tube, laterally compressed when fresh but appearing knobby and callose-thickened when dry; filaments sparsely to moderately beset with rufescent simple (rarely branched) glandlike trichomes mostly less than 0.25 mm long that are commonly clustered or fascicled, and anther connective conspicuously prolonged dorso-basally ca. 0.5 mm above the junction with the filament into a linear-oblong widely spreading or coiled appendage 0.5−0.75 mm long.

Figure 2. Gravesia serratifolia showing habit, leaves, inflorescence, and flower.
(Photo: Éric Mathieu)

Figure 1. Gravesia serratifolia. A. Habit. B. Representative leaf (abaxial surface) C. Representative leaf (adaxial surface). D. Enlargement of a portion of abaxial leaf surface showing serrate margin and scattered lepidote indumentum. E. Enlargement of abaxial leaf base showing acarodomatia where secondary veins diverge from primary vein. F. Petal (adaxial surface) G. Stamen (profile view). H. Enlargement of filament showing fascicled glandlike trichomes. I. Enlargement of filament showing solitary and branched glandlike trichomes. J. Hypanthium and style (at anthesis) with petals and stamens removed. K. Simple dichasium showing bracts and bracteoles.
Drawn from Ranarivelo & Ravelonarivo RHS 857.

Etymology:— The epithet for this species, serratifolia, highlights the conspicuous serrate foliar margins that extend for most of the length of each mature leaf blade.


 Frank Almeda and Heritiana Ranarivelo. 2019. Gravesia serratifolia (Melastomataceae: Sonerileae), A New Species from Marojejy National Park, Madagascar. Phytotaxa. 391(2); 115–121. DOI:  10.11646/phytotaxa.391.2.4

Résumé: Gravesia serratifolia, une nouvelle espèce originaire des hautes altitudes du Parc National de Marojejy, au Nord-Est de Madagascar, est décrite, illustrée, cartographiée, et comparée à des espèces qui lui ressemblent. Elle est caractérisée par son port peu ramifié; ses feuilles très serrulatées dont le recouvrement de l’indument en lépidote des deux côtés de leur surface varie de moderé à éparse; son inflorescence pauciflore et dichasiale; son calice floral essentiellement non-lobé mais fortement denté, les dents étant comprimées à l’état frais; l’indument de ses filaments pourvu de sorte de glandes roux-sombres; ses appendices staminaux au niveau de la base dorsale, oblongues, et qui varient de largement diffus à enroulés. Le statut de conservation «Vulnerable» est recommandé pour cette espèce, suivant les Catégories et les Critères de la Liste Rouge de l’UICN.

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