Boea

Boea

Full name and orig. publication: Boea Comm. ex Lam., Encycl. Méth., Bot. 1: 401, fr. Béole (1783), ed. nouv. Padua 1: 396 (1 Aug. 1785, "1784").

Etymology: Several explanations have been offered. The most probable ones are that Boea is named after M. le Beau, brother-in-law of Philibert Commerson (Clarke 1883) or, based on a handwritten note on an isotype at G, Mlle de Beau, the niece of a clergyman friend of Commerson and Commerson's later wife (Puglisi & Middleton 2017).

Synonyms: Chleterus Raf. (1814), nom. illeg.

Infrafamilial position: Didymocarpoideae-Trichosporeae-Loxocarpinae (Weber et al. 2013).

Description (from Puglisi & Middleton 2017: 5): Rhizomatous herbs, caulescent or rosulate; stem woody, if present, with glandular or eglandular indumentum. Leaves opposite or in whorls of 3 or 4, petiolate; petioles with glandular or eglandular indumentum; lamina surfaces with glandular or eglandular indumentum, margin entire to dentate. Inflorescence an axillary cyme, longer or shorter than the leaves, usually more or less compound, few- to many-flowered; peduncles always with an indumentum; bracts linear or lanceolate, hirsute on the abaxial surface, glabrous, with glands or with multicellular hairs on the adaxial surface. Calyx free or almost free to base, lobes sometimes slightly unequal in length, lanceolate or linear, outside glabrous or with an indumentum that covers them entirely or partially, glabrous inside. Corolla bilabiate, pink or violet to blue, often unevenly coloured and with a yellow throat; tube short; upper lip 2-lobed, lower lip 3-lobed. Stamens 2; filaments more or less bent, glabrous or with sessile glands; anthers dorsifixed, coherent, strongly divergent, dehiscing longitudinally; staminodes 3, sometimes extremely reduced or absent. Ovary bilocular, glabrous or with glandular or eglandular indumentum; placentation axile, ovules many; style more or less bent downwards; stigma capitate or dorsoventrally bifid, sometimes unequally so. Capsule 2-valved, more or less twisted, dehiscing longitudinally along the valves. Seeds elliptic, sometimes slightly twisted.

Chromosome number: 2n = 16, 32.

Species number: 11.

Species names (only given in case of few species).

Type species: Boea magellanica Lam.

Distribution: Indonesia (Waigeo Island), Papua New Guinea, Solomon Islands and Australia.

Notes:
(1) Taxonomic history: Over time, the taxonomic fate of Boea was eventful and intimately connected with the genera Dorcoceras and Paraboea. Specimens of the type species, Boea magellanica Lam., were first collected by Commerson and described by Lamarck (1783/85). Lamarck thought that the plant came from Chile, but later it was found that it was collected at or near "Port Praslin". Localities of that name occur both in the Bismarck Archipelago (Papua New Guinea) and the Solomon Islands, and it is unknown in which of the two localities B. magellanica was collected.
As Puglisi & Middleton (2017a) point out, the first important change in the circumscription of Boea was the inclusion of the Chinese genus Dorcoceras Bunge (also having a flat corolla, two fertile stamens and twisted fruits), and part of Didymocarpus Wall. (Brown 1840). This greatly expanded the morphological and geographical range of Boea. In the course of time, over 100 species were ascribed to that genus.
In 1905, Ridley raised Didymocarpus sect. Paraboea C.B.Clarke (Clarke 1883) to generic rank and created again a genus having a flat-faced or shallowly campanulate corolla and two fertile stamens, but differing in the straight fruits (with various modes of dehiscence) from Boea and believing that is to be restricted to the Malay Peninsula.
In 1984, Burtt analysed the relationships of Boea and Paraboea and reached the conclusion that the separation of the two genera on the basis of twisted vs. straight fruits was unnatural. He separated the two genera on grounds of indumentum characters. Simple, unbranched hairs were seen as typical of Boea, arachnoid-interwoven hairs typical of Paraboea. Burtt's revision fundamentally changed the content of the two genera, resulting in a relocation of the majority of species of Boea to Paraboea. A small number of species fitting in neither genus was later transferred to the newly established genera Emarhendia and Senyumia (Kiew et al. 1998) and Kaisupeea (Burtt 2001). The existence of straight and twisted-fruited genera side by side was accepted by later authors, e.g., Xu & Burtt (1991) and Xu et al. (2009) in their revision of Paraboea and applies for other genera too.
The (hitherto) last step in clearing the relationships between Boea, Paraboea, the reestablished Dorcoceras and other genera, was the molecular-phylogenetic/taxonomic work of Puglisi et al. (2011, 2016) and Puglisi & Middleton (2017a,b). Boea emerged as an essentially Australasian genus, comprising 11 species and with main distribution in the Bismarck Archipelago, the Solomon Islands and (2 spp.) Australia.
(2) Boea hygroscopica and probably other species of Boea belong to the remarkable ecological group of resurrection plants. They can dry out and completely recover when water is available. Navari-Izzo (1995, 2000) described an unusual composition of thylakoid membranes and analysed the changes in lipids and proteins upon dehydration and rehydration. See also Dorcoceras.

Selected references: Burtt, Notes Roy. Bot. Gard. Edinburgh 41: 401-452 (1984), emend. & rev.; Zhou & Guo, Acta Phytotax. Sin. 29: 477-478 (1991); Navari-Izzo et. al., Physiol. Plant. 94(1): 135-142 (1995); Navari-Izzo et al., Plant Physiol. 124: 1427-1436 (2000), physiol., resurrection; Wang et al. in Wu & Raven (eds.), Fl. China 18: 367-368 (1998) (Chinese spp.); Burtt, Thai Forest Bull. (Botany) 29: 81-109 (2001), annot. checklist (Thailand); Kiew, Weber & Burtt, Beitr. Biol. Pflanzen 70(2-3): 383-403 (1998, "1997"), establ. Emarhendia, Senyumia, Spelaeanthus; Burtt, Nordic J. Bot. 21(2): 115-119 (2001), Kaisupeea; Puglisi et al., Taxon 60(6): 1693-1702 (2011), mol. syst. Paraboea, Trisepalum, Phylloboea; Puglisi et al., Taxon 65(2): 277-292 (2016), mol. phyl. Leptoboeinae; Puglisi & Middleton, Edinburgh J. Bot. 75 (1), 19-49 (2017a), rev. Boea; Puglisi & Middleton, Thai Forest Bull. (Bot.) 45(1): 10-17 (2017b), reg. rev. Dorcoceras, Thailand.

Tax. details, cytology, and bibliography: Gesneriaceae Resource Centre (GRC). Royal Botanic Garden Edinburgh.

Page content and update responsibility/contact: David J. Middleton.
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