Keraunea Cheek & Simao-Bianchini , Nord. J. Bot. 31: 454. 2013.

Moonlight, Peter W. & Cardoso, Domingos Benicio Oliveira Silva, 2023, A taxonomic revision of Keraunea, including three new species and its phylogenetic realignment with Ehretiaceae (Boraginales), PhytoKeys 219, pp. 145-170 : 145

Keraunea Cheek & Simao-Bianchini, Nord. J. Bot. 31: 454. 2013.

Type species.

Keraunea brasiliensis Cheek & Simão-Bianchini.

Description.

Scandent shrubs or lianas. Stems woody, cylindrical, hollow, lacking lenticels. Stipules lacking. Leaves on the main stems alternate, simple, petiolate; margins entire; venation pinnate, camptodromous or brochododromous. Side shoots with 2-4 aborted leaves, then 2-6 progressively larger leaves along the shoot. Inflorescences terminal on side shoots, determinate, corymbose, with 3-6 flowers; bracteoles one per flower or rarely lacking, leaf-like, inserted halfway along the pedicel. Flowers 5-merous, cosexual. Calyx campanulate, fused at the base, alternating with the petals; aestivation imbricate. Corolla with the tube campanulate, fused at the base; aestivation imbricate. Stamens epipetalous, inserted at the base of the corolla tube, alternating with the petals; filaments free; anthers basifixed, introrse, dehiscing via lateral slits; connectives extended. Nectary disk present, at base of the ovary. Ovary superior, subglobose, 2-locular, the locules biovulate, each with one functional and one aborted ovule. Style single, with two apical stigmas. Fruit a dry, indehiscent drupe, usually inserted in the centre of the persistent and accrescent bracteole; calyx persistent; corolla caducous; style persistent.

Distribution.

Keraunea is endemic to Brazil and thus far known from the states of Bahia (3 spp.), Espírito Santo (1 sp.), Minas Gerais (1 sp.) and Rio de Janeiro (1 sp.). Each of the species is restricted to a single state except for K. capixaba , which is found in both Bahia and Espírito Santo (Fig. 2 ).

Habitat.

Two species are known from seasonally dry forest within the Caatinga domain ( K. brasiliensis and K. confusa ); two from humid forests within the Mata Atlântica domain ( K. capixaba and K. velutina ); and a fifth from transitional, semi-deciduous forests between the Caatinga and Mata Atlântica domains ( K. bullata ). The genus has a marked preference for rock outcrops or forest on rocky soils. Both K. brasiliensis and K. confusa are found mostly on karstic outcrops, while K. capixaba and K. velutina have both been collected at the base of granitic inselbergs.

Etymology.

The epithet derives from the Greek, keraunos, or lightning bolt. This was intended to signify the unexpected but now disproven appearance of a neuropeltoid genus of the Convolvulaceae in the Americas.

Notes.

Cheek and Simão-Bianchini (2013) treated the flower and fruit of Keraunea as being inserted at the centre of a large, leaf-like bract. This ‘bract’ is inserted halfway up and adnate to the pedicel, so we instead follow Lombardi (2014) and treat it as a bracteole rather than a bract.

Identification notes.

Keraunea species are distinctive in being semi-scandent shrubs or lianas with simple, alternate, exstipulate leaves and inflorescences terminal on foliose side shoots. The flowers and fruits are highly unusual in being inserted at and appearing to arise from the centre of an accrescent bracteole.

Several specimens of Keraunea were erroneously identified as Bougainvillea Comm. ex Juss. ( Nyctaginaceae ), which is understandable, as both genera have exstipulate leaves, a semi-lianescent habit, and flowers and fruits associated with showy bracts or bracteoles. Keraunea spp. are however never spinescent, and the flowers and fruits are inserted directly onto the bract, whereas in Bougainvillea several flowers or fruits are clustered on a pedunculate inflorescence surrounded by two or more bracts.

Figures

Figure 2. Distribution of species of the genus Keraunea. Shading denotes elevation; two letter codes represent the standardised two letter codes for the states of Brazil. Species are coloured as follows: blue, K. brasiliensis Cheek & Simao-Bianchini; black, K. bullata Moonlight & D. B. O. S. Cardoso; yellow, K. capixaba Lombardi; red, K. confusa Moonlight & D. B. O. S. Cardoso; green, K. velutina Moonlight & D. B. O. S. Cardoso.