Hydrochorea uaupensis M.P. Morim, Iganci & E.J.M. Koenen, 2022

Vinicius Batista Soares, Marcos, Mathieu Koenen, Erik Jozef, Ricardo Vieira Iganci, Joao & Morim, Marli Pires, 2022, A new generic circumscription of Hydrochorea (Leguminosae, Caesalpinioideae, mimosoid clade) with an amphi-Atlantic distribution, PhytoKeys 205, pp. 401-437 : 401

10. Hydrochorea uaupensis M.P. Morim, Iganci & E.J.M. Koenen sp. nov.

Figs 2A, E-G , 3J, K , 8

Diagnosis.

Hydrochorea uaupensis is morphologically similar in appearance to H. leucocalyx (Britton & Rose) Iganci, M.V.B. Soares & M.P. Morim by its leaflets and inflorescence, however it differs by having a red or green calyx, pink corolla, 1-2 pairs of pinnae, and crypto-lomentiform fruits (vs. white calyx and corolla, 3-5(-6) pairs of pinnae and indehiscent fruits in H. leucocalyx ).

Type material.

Brazil, Amazonas, São Gabriel da Cachoeira. Igarapé Tibuari, afluente do Vaupés 0°05'5"N, 67°23'16"W, 23 July 2012, fl. and fr., M.P. Morim, J.R.V. Iganci, F. Bonadeu, E. Koenen 577 (holotype: RB [RB00728413]!; isotypes: HUEFS!, INPA!, K!, MBM!, MG!, MO!, NY!, PEL!, S!, US!, Z!).

Description.

Trees 2-6 m tall, trunk not observed, partially underwater during seasonal inundation. Branches, leaf axes and peduncles sparsely pubescent to glabrescent. Stipules linear, to 1.2 cm long, densely pubescent on outer surface. Leaves with 1-2 pairs of pinnae; petiole including pulvinus 1.5-4.5 cm, cylindrical; rachis 0 or 3-4(-9) cm, glabrous, canaliculate; extrafloral nectaries borne between first or both pairs of pinnae, sessile, patelliform and smaller nectaries usually present between the leaflet pairs; pinnae 3-5 jugate; leaflets subsessile on pulvinules, chartaceous, c. 2-4(-6) × 1.5-2(-3) cm, rhomboid or ovate, apex emarginate or obtuse, sometimes with a minute mucro, base asymmetrically oblique to acute; adaxial and abaxial surfaces glabrous, discolorous, adaxial surface sometimes lustrous; venation pinnate with c. 11-17 secondary veins, tertiary venation reticulate and prominent on both surfaces when leaflets dry. Inflorescences dimorphic, umbelliform with 7-10 peripheral flowers and an enlarged sessile terminal flower, peduncle 4-6(-8) cm. Bracts and bracteoles not seen. Flowers with a reddish or green calyx, pink corolla and white filaments, the flower buds oblong, ca. 8 mm long, with the corolla concealed by the calyx prior to anthesis, peripheral flowers on pedicels 0.7-1.5 cm, calyx campanulate, c. 9 mm long, 5-angulate due to prominently raised veins, sparsely puberulent or ciliate at the apex of the lobes, corolla tubular, with a prominulous midvein on the lobes, c. 1.5 cm long, sparsely puberulent on the upper half of the lobes, stamens c. 50-60, the filaments white, c. 3 cm long, exserted from the corolla ca. 2 cm; ovary glabrous, 3-4 mm, sub-truncate to truncate at the apex, style 3.5-4 cm, stigma funnel-shaped; terminal flower similar to peripheral flowers but more robust and c. 5 mm wide at base, calyx c. 1.2 cm long, corolla 1.6 cm long, stamens ca. 75, ca. 3.5 cm long. Pods typically 1-3 per infructescence, crypto-lomentiform, up to 15-seeded, oblong, slightly curved, lignescent, c. 9.5 × 2.5 cm excluding a ca. 5 mm long mucro, dehiscence follicular, the smooth exocarp and transversely fibrous mesocarp continuous, the endocarp septate, enveloping the seeds which are released in monospermous articles. Seeds not seen in mature state, oblong, c. 1.6 × 0.4-0.7 cm, pleurogram extending from apex to base, c. 1.3 × 0.3-0.4 cm, closed.

Distribution and habitat.

Brazil. Known only from the Upper Rio Negro region in the Brazilian Amazon (Amazonas state), in seasonally inundated “campinarana” vegetation.

Phenology.

Flowering and fruiting in July.

Etymology.

The specific epithet refers to the type locality, near the River Uaupés, in the state of Amazonas, Brazil. The indigenous people living in this area (e.g., the Tucanos) were known as Uaupés, and later the river took the same name.

Notes.

Hydrochorea uaupensis is only known from Amazonas state, Brazil, where it was collected at “Igarapé Tibuari", in the municipality of São Gabriel da Cachoeira, during fieldwork in July 2012. The species grows in open vegetation on white sand, known in Brazil as campinarana in the Amazon Domain. During times of flood, only the treetops are exposed above the water line. A second herbarium collection from close to the type locality (Rio Tourí, afl. do Rio Negro, igapó; R.L. Fróes 28691, IAN [IAN78279]), of which we have only seen an image, is here tentatively included under H. uaupensis because the fruit and leaves match the type material and the flowers are described as pink on the specimen label. Since these two occurrence records are close to the borders with Colombia and Venezuela, the species is to be expected in those two countries.

The phylogenetic position of H. uaupensis , as the sister lineage of the clade composed of Hydrochorea sensu Barneby and Grimes (1996) and the African Hydrochorea spp., provides ample support for this as a distinct taxon and a species new to science, as it does not form a sister pair with any other known species. Furthermore, this phylogenetic position is in line with the fruit morphology of the species being intermediate between Balizia and Hydrochorea , adding further support, along with the paraphyly of Balizia , for not maintaining these as distinct genera.

Conservation status.

Data deficient. The species is known only from two adjacent localities in the Upper Rio Negro region of Amazonas state, Brazil. More collections are needed to assess the species’ conservation status.

Figures

Figure 2. The genus Hydrochorea Barneby & J. W. Grimes A The amphi-atlantic geographic distribution of Hydrochorea B Hydrochorea pedicellaris (DC.) M. V. B. Soares, Iganci & M. P. Morim foliage and fruits C Hydrochorea corymbosa (Rich.) Barneby & J. W. Grimes foliage and fruits D Hydrochorea panurensis (Spruce ex Benth.) M. V. B. Soares, M. P. Morim & Iganci foliage and fruits E Hydrochorea uaupensis M. P. Morim, Iganci & E. J. M. Koenen in habitat, with foliage and fruits F Flowers of H. uaupensis after rain G mature fruits of H. uaupensis. B, C from M. V. B Soares D from D. Cardoso E-G from J. R. V. Iganci.

Figure 3. The genus Hydrochorea Barneby & J. W. Grimes (continued). Species from the Americas A flowering branch of Hydrochorea corymbosa (Rich.) Barneby & J. W. Grimes B close-up of inflorescence of H. corymbosa C discolorous leaves of H. corymbosa D close-up of inflorescence of Hydrochorea panurensis (Spruce ex Benth.) M. V. B. Soares, M. P. Morim & Iganci E unripe lomentiform pod of H. panurensis F close-up of inflorescence of Hydrochorea pedicellaris (DC.) M. V. B. Soares, Iganci & M. P. Morim, with a few peripheral flowers removed to expose sessile terminal flowers G unripe pods of H. pedicellaris H dehisced follicular pods of H. pedicellaris showing papery septate endocarp I detail of primary rachis of H. pedicellaris showing interpinnal extra-floral nectaries J inflorescence of Hydrochorea uaupensis M. P. Morim, Iganci & E. J. M. Koenen showing large sessile central flower and pedicellate peripheral flowers K unripe crypto-lomentiform pod and seed enveloped by septate endocarp of H. uaupensis; African species L inflorescence of Hydrochorea obliquifoliolata (De Wild.) E. J. M. Koenen M pinnae of Hydrochorea rhombifolia (Benth.) E. J. M. Koenen showing rhombic leaflets. A-E, J, K Erik Koenen F-I Colin Hughes L Jan Wieringa M William Hawthorne. Vouchers A-C J. R. V. Iganci 862 D, E M. P. Morim 563 F-I L. P. Queiroz 15529 J, K M. P. Morim 577 L J. J. Wieringa 6519 M unvouchered.

Figure 8. Hydrochorea uaupensis M. P. Morim, Iganci & E. J. M. Koenen A branch with inflorescences B branch with fruits C ovary D terminal flower E peripheral flower F dehisced fruit G detail of fruit endocarp forming 1 - seeded articles H, I monospermous articles. A-I from M. P. Morim et al. 577. Illustration by Joao Augusto Castor Silva.