Tuesday, February 28, 2017

[Botany • 2017] Begonia elachista Moonlight & Tebbitt sp. nov. • An Enigmatic New Species and A New Section of Begonia (Begoniaceae) from Peru


Begonia elachista 
Moonlight & Tebbitt


Abstract

The world’s smallest BegoniaBegonia elachista Moonlight & Tebbitt sp. nov., is described and illustrated from a limestone outcrop in the Amazonian lowlands of Pasco Region, Peru. It is placed within the newly described, monotypic Begonia sect. Microtuberosa Moonlight & Tebbitt sect. nov. and the phylogenetic affinities of the section are examined. Begonia elachista sp. nov. is considered Critically Endangered under the International Union for the Conservation of Nature (IUCN) criteria.

Keywords: Begonia; sectional classification; limestone endemics; Peru; Amazonia


Fig 3. Begonia elachista Moonlight & Tebbitt sp. nov. 
[Begonia sect. Microtuberosa Moonlight & Tebbitt sect. nov.]A. Whole plant. B. Male and female flower, front view. C. Female flower, side view. D. Habit and associated vegetation. EF. Habitat and wild population.
Scale bars: A = 1 cm; B = 5 mm; C = 2 mm; D = 2 cm; E–F = 10 cm.
Photographed by Peter Moonlight. All from P. Moonlight & A. Daza 318 (E). 


Taxonomic Treatment

Class Equisetopsida C.Agardh (Agardh et al. 1825)
Subclass Magnoliidae Novák ex Takht. (Takhtajan 1967)
Superorder Rosanae Takht. (Takhtajan 1967)
Order Cucurbitales Juss. ex Bercht. & J.Presl (von Berchtold & Presl 1820)

Family Begoniaceae C.Agardh (Agardh 1824)

Genus Begonia L. (Linnaeus 1753)

Begonia sect. Microtuberosa Moonlight & Tebbitt sect. nov.

 Diagnosis: Begonia sect. Microtuberosa sect. nov. is most closely related to B. sect. Trachelocarpus and three species of B. sect. Gaerdtia. Both of these sections are endemic to eastern Brazil and differ markedly from sect. Microtuberosa sect. nov. in both their habit and floral characteristics (see Table 1). However, all three sections share their filaments fused at least at the base and B. sect. Microtuberosa sect. nov. further shares its androecium morphology with B. sect. Pereira and its lack of bracteoles with B. sect. Trachelocarpus. The majority of both floral and vegetative characters are, however, markedly different among the three sections.

Begonia sect. Microtuberosa sect. nov. is readily identified as the only Neotropical section of Begonia with male flowers with four or fewer stamens, and the combination of ovaries with two or three locules and entire placentas, and a tuberous habit.

Etymology: The name ‘Microtuberosa’ emphasises the diminutive and tuberous habit of the type species. 

Type species: Begonia elachista Moonlight & Tebbitt sp. nov. 

Distribution: On a limestone outcrop in lowland Amazonian Peru to the east of the Chemillén Cordillera at an altitude of 430 m.




Begonia elachista Moonlight & Tebbitt sp. nov. sect. Microtuberosa

Diagnosis: Begonia elachista sp. nov. is a highly distinct species with an unusual combination of features that is easily recognized as the only Peruvian species of Begonia that reaches maturity at fewer than 5 cm in height. It is also unique within Peru in having ovate leaves smaller than 3 × 3 cm and a combination of entire placentae and a tuberous habit.

Etymology: The epithet ‘elachista’ comes from the Greek for ‘least’ and emphasizes the diminutive size of this species, which is the smallest known species of Begonia.

Distribution and habitat: Begonia elachista sp. nov. is known only from the type locality in the Peruvian region of Pasco (Oxapampa Province) and has been collected on calcareous rocks by the entrance to a cave within primary lowland Amazonian forest, at an altitude of 430 m. It was observed growing on rocks free from other vascular plants in association with various bryophyte species in the almost continual shade of the surrounding forest.

.....

Peter Watson Moonlight, Carlos Reynel and Mark Tebbitt. 2017.  Begonia elachista Moonlight & Tebbitt sp. nov., An Enigmatic New Species and A New Section of Begonia (Begoniaceae) from Peru. European Journal of Taxonomy.  281: 1–13.  DOI: 10.5852/ejt.2017.281

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