Thursday, July 20, 2023

[Botany • 2023] Homalomena perplexa (Araceae: Homalomeneae) • A New Species of Homalomena from Con Dao National Park, Vietnam


Homalomena perplexa K.Z.Hein, Vuong, Bao & V.S.Dang, 

in Dang, Truong, Nguyen, Pham, Nguyen, Le, Nguyen, Bustamante et Hein, 2023. 

Abstract
Homalomena perplexa K.Z.Hein, Vuong, Bao & V.S.Dang from Ba Ria Vung Tau province, Vietnam, is described and illustrated as a species new to science. Description, color plates, discussion of similar taxa, phenology, distribution, and a preliminary conservation status assessment are provided. Homalomena philippinensis Engl. is lectotypified.

Keyword: Aroideae, Con Dao Island, Homalomena perplexa, Homalomena philippinensis, Southeast region


Homalomena perplexa sp. nov.
A. Plants in habitat, B. Flowering plant.
Photo by: Ba Vuong Truong.

Homalomena perplexa sp. nov.
 A. Excavated plant, B. Leaf (left showing abaxial surface; right showing adaxial surface), C. Detail of abaxial surface of leaf blade, D. Detail of emerging blooms each subtended by prophyll, E. Bloom at pistillate anthesis (right showing artificially removed spathe), F. Spadix at pistillate anthesis, spathe artificially removed, G. Pistillate flower zone. H. Staminate flower zone.
 Photos by: Ba Vuong Truong.

Homalomena perplexa K.Z.Hein, Vuong, Bao & V.S.Dang, sp. nov. 

Diagnosis: This new species is distinguished from all other Vietnamese Homalomena species by the combination of triangular-sagittate to cordato-sagittate leaf blades lacking broken pellucid veins abaxially, a synflorescence with up to 5 blooms, slightly falcate and subcylindric-tapering spathe with ca. 1 mm long mucro, lageniform ovaries with capitate stigma, and cylindrical staminate flower zone which is contiguous with pistillate flower zone. Homalomena perplexa is most similar to H. philippinensis but readily distinguished by longer peduncle (up to 20 cm vs. ca. 8 cm), slenderer spadix (spadix width: length ratio 1:8 vs. 1:4.5) and stigma nearly equaling the ovary in width (stigma about half as wide as the ovary).

Distribution and habitat: The new species is currently known only from the type locality in Con Dao National Park (Con Dao Island), Vietnam. It grows under the shade of the evergreen forest at an elevation between 100–350 m. 

 Etymology: The specific epithet alludes to the taxonomic confusion made by Engler and Hong Thien Van by misidentifying it as Homalomena philippinensis and H. occulta. 
Vernacular name: Thiên niên kiện nhầm. 

Uses: Rhizome is used to treat joint pains and aches by local people.


Van Son Dang, Ba Vuong Truong, Quoc Bao Nguyen, Quoc Trong Pham, Van Tu Nguyen, Hong Son Le, Van Nga Nguyen, Rene Alfred Anton Bustamante and Khant Zaw Hein. 2023. A New Species of Homalomena (Araceae: Homalomeneae) from Con Dao National Park, Vietnam, with lectotypification of Homalomena philippinensisTaiwania. 68(3); 269-274. DOI: 10.6165/tai.2023.68.269