Euploca riochiquensis J.R.I. Wood & P. Muñoz, 2022

Wood, John R. I. & Muñoz-Rodríguez, Pablo, 2022, A new species of Euploca (Boraginales: Heliotropiaceae) from the Inter-Andean dry valleys of Bolivia, Phytotaxa 543 (4), pp. 219-232 : 221-225

Euploca riochiquensis J.R.I. Wood & P. Muñoz sp. nov. Fig. 3 .

Type:— BOLIVIA, Dept. Chuquisaca, Prov. Oropeza, Río Chico Valley between Bellavista and Zurima, scattered plants in steep gullies on sandstone hills covered in sparse xerophytic scrub 18°44.772’S, 65°08.521’W, 1693 m a.s.l., 17 March 2016, J.R.I. Wood 28121 (holotype: USZ!, isotypes: FHO!, HSB!, K!, LPB!) .

Diagnosis:— Euploca riochiquensis is related to three other Bolivian species placed in Euploca , E. campestris , E. lagoensis and E. procumbens , but the four species are not very similar in facies and are very unlikely to be confused. Euploca riochiquensis is conspicuously woody forming a much-branched subshrub 0.4–1 m in height with linear leaves 5–15 × 2–4 mm and solitary flowers unlike E. campestris and E. procumbens which have several stems from a woody base reaching a maximum of 50 cm in height, oblong-elliptic to obovate leaves, 7–30 × 6–12 mm and flowers aggregated into scorpioid cymes. Although in E. lagoense the flowers are solitary and axillary, this is a slender, usually prostrate, annual herb of drying mud, the stems <10 cm long and the leaves small, oblong-elliptic <10 mm long, very different from the erect or ascending woody stems of the subshrub E. riochiquensis , which reaches 1 m in height and grows on dry rocky hillsides. Phylogenetic studies ( Figure 1 ) suggest E. riochiquensis is most closely related to the Mexican species, E. mexicana and E. karwinskyi . The three species are somewhat similar in their leaf shape but the two Mexican species differ clearly in their scorpioid inflorescences.

Subshrub, mostly 0.4–1 m high. Stems several from a woody rootstock, ascending, woody, much branched upwards; when old, brown with flaky bark, glabrous; when immature, brown, strigose; when young densely strigose and appearing whitish. Leaves subsessile, alternate but often clustered, especially below, 5–15 × 2–4 mm, diminishing in size towards the branch tips, narrowly oblong-elliptic, less commonly lanceolate, base narrowly cuneate, apex acute, margin entire, involute, adaxially grey-green, bullate, strigose, abaxially paler, more densely strigose, pustulate, venation of a single vein prominent abaxially; petioles 0–2 mm long, densely white-strigose. Inflorescence of solitary, very shortly pedunculate flowers borne in the leaf axils, mostly towards the apex of juvenile branches, many apparently aborting leaving small dried calyces; peduncles 0–1.5 mm long; pedicels absent; bracteoles linear-subulate, 2–3 mm long; calyx unequally 5-lobed to base, longest lobe 5 mm long, shortest lobe 3.5 mm, lobes linear-lanceolate, strigose on exterior; corolla 5 mm long, white, tubular with spreading lobes; tube 3.5–4 mm long, strigose externally, lobes ca. 1.5 mm long, oblong-ovate, obtuse at apex; stamens inserted near base of tube, anthers subsessile, oblong, ca. 1 mm long, glabrous; ovary yellowish, conical, pubescent, stigma sessile, ca. 3 mm long. Schizocarp rarely formed, subglobose, pubescent, ca. 1.3 mm in diam., tardily splitting into four rounded nutlets.

Distribution:— Endemic to the Rio Chico Valley between Chuquichuqui and Imillahuanusca, especially near Zurima, Prov. Oropeza, Dept. Chuquisaca, Bolivia. Fig. 4

Habitat:— Very locally frequent in sparse xerophytic scrub with abundant Senegalia gilliesii (Steud.) Seigler & Ebinger (2006) on steep rocky slopes in the Rio Chico Valley, some 10–15 km above its confluence with the Rio Grande, principally, perhaps exclusively, on sandstone, between about 1600 and 1900 m. The area is not particularly diverse in terms of species numbers but is very interesting in terms of endemism. As well as the new species, Puya ugentiana L.B.Sm. ( Smith 1966) , Puya valida L.B.Sm. ( Smith 1964) , Salvia graciliramulosa Epling & Játiva (1966) , Tillandsia helmutii L.Hrom. ( Hromadnik 1990) , Tillandsia oropezana L.Hrom. ( Hromadnik 1989) are other pinpoint endemics growing on the same formation in the same area. Other Bolivian endemic species occurring in the same dry valley include Brongniartia ulbrichiana Harms (1908) , Hippeastrum mollevillquense (Cárdenas) Van Scheepen (1997: 18) , Justicia consanguinea (Lindau) Wassh. & C.Ezcurra (1997) , Funastrum rupicola Goyder (2008) , Salvia orbignaei Benth. (1848) , S. sucrensis J.R.I. Wood (2007) , Tecoma beckii A.Gentry ex J.R.I. Wood (2008) , Tillandsia lotteae H.Hrom. ( Rauh 1978) and Varronia lantanifolia J.S.Miller & J.R.I.Wood , but all of these occur in other locations in the inter-Andean dry valley system of central Andean Bolivia. The Río Grande Valley and its tributaries the Río Chico and Río Grande are remarkable for the presence of scattered, narrowly restricted endemics from many plant families. An earlier publication ( Wood 2013) has drawn attention to the endemics found in Puente Santa Rosa area, while this paper highlights one of the side valleys, the Río Chico valley in Chuquisaca as an important centre of endemism.

Phenology:— Found in flower towards the end of the summer rainy reason, all collections of flowering material having been made in March.

Etymology:— The epithet riochiquensis is derived from the Río Chico, to whose valley the species is endemic.

Preliminary conservation status:— As far as it is known, this species is restricted to a limited area of the Rio Chico Valley in Chuquisaca. All collections have been made close to the Sucre-Cochabamba highway and no search has been made at any distance from this road. As the steep scrub-covered slopes on various geological formations including sandstone extend over huge botanically unexplored areas, there is no reason to believe this species is as rare as the few records might suggest. Equally, there are no obvious threats to this habitat from mining, deforestation or human settlement and even goats do not seem to find this species particularly palatable. Until systematic search has been made in suitable areas in the same general region, this species can only be realistically assessed as Data Deficient (DD) according to IUCN (2019) guidelines.

Additional specimens examined (Paratypes):— BOLIVIA. Dept. Chuquisaca, Prov. Oropeza, Río Chico Valley ca. 15 km below Chuquichuqui, scattered plants on open, almost bare sandstone hill slopes in hot, dry valley ca. 1900 m, 26 March 1995, J.R.I. Wood 9612 (K, LPB, USZ); ibid., 1 km north of Zurima , hot valley lined with steep-sided red sandstone hills covered in sparse spiny bushland. Locally frequent in rock crevices on steep open sandstone hills, 1800 m, 15 March 2002, J.R.I Wood 17828 (HSB, K, LPB) .

Morphological charactersation. Euploca riochiquensis is unlikely to be confused with any other species once it is recognised as belonging to Heliotropiaceae . The combination of shrubby habit with small solitary white flowers appears to be unique.

Figures

FIGURE 1. Maximum Likelihood ITS phylogeny of Heliotropiaceae showing the position of Euploca riochiquensis. Numbers above branches indicate rapid bootstrap support values; branches without values received 100% bootstrap support.

FIGURE 3. Euploca riochiquensis. A habit and separate branch; B adaxial leaf surface; C abaxial leaf surface; D flower; E calyx; F corolla opened out to show stamens; G fruiting calyx; H nutlets.A–F drawn by Eliana Calzadilla from J.R.I. Wood 28121; G–H drawn by Rosemary Wise from J.R.I. Wood 9612.

FIGURE 4. Map showing location of Euploca riochiquensis in Chuquisaca in the Rio Grande catchment area of Bolivia’s central Andean valleys.