Introduction

The legume genus Weberbauerella Ulbr. comprises three species (Saldivia & Faúndez 2014; Whaley et al. 2019) which occur in the coastal lomas vegetation of Peru and the arid Andes of northern Chile in the Atacama Desert. In these hyperarid regions, fog is the main source of moisture. The genus is a member of the Dalbergia clade in the Leguminosae, subfamily Papilionoideae, in which it occupies an isolated position (Klitgaard & Lavin 2005), there are limited molecular sequences available for Weberbauerella, but none, to date, suggests a relationship to any other genus in the clade (LPWG 2017).

Ulbrich (1906) published the genus Weberbauerella to accommodate a new species, W. brongniartioides Ulbr., specimens of which he had collected from the Lomas of Mollendo, in the Arequipa region of Peru. He named the new genus in honour of the German naturalist Augusto Weberbauer (1871 – 1948), who conducted botanical explorations in Peru with particular focus on the coast. In 1951, the Peruvian botanist Ramon Ferreyra found and described a second species, W. raimondiana Ferreyra, from the Lomas de Chala (Ferreyra 1951), a more northerly coastal location than that of the W. brongniartioides type specimen. León et al. (2006) considered the genus to be endemic to Peru, however, in 2014 a third, apparently disjunct species, W. chilensis Faúndez & Saldivia, was described from specimens collected in northern Chile, near Salar de Huasco in the Tarapaca region (Saldivia & Faúndez 2014).

Here we present a taxonomic revision and ecological assessment of the genus Weberbauerella which includes a species identification key, species descriptions, illustrations, distribution maps and conservation assessments. Due to the often remote desert locations and ephemeral nature, characterised by short growth and flowering periods, of these species, there are only 62 known collections available in herbaria worldwide, 16 of which were collected by the authors of this study.

Materials and Methods

The revision presented here is based on studies of herbarium material, flower dissections and field observations. The following herbaria were searched and specimens seen and studied where found, CONC, E, K, MOL, SGO and USM; likewise the digital collections and images of specimens in B, CUZ, F, GB, GH, HUSA, HUT, L, MO, P, US and WAG (herbarium abbreviations according to Thiers 2022, continuously updated); and likewise online images of type collections available at JSTOR (JSTOR Global Plants, http://plants.jstor.org/). Sixty-two herbarium collections were studied, including all available type specimens. A list of specimen collections is provided for each species, including specimens seen ("!") and the herbarium locations of duplicates; and a complete list of specimens, ordered alphabetically by collector name, is included in the List of Exsiccatae (Appendix 1). Key bibliographies and publications involving the lomas flora or specifically on Weberbauerella were reviewed: Macbride (1943), Ferreyra (1953), Brako & Zarucchi (1993), León et al. (1997), Lavin et al. (2001), Cano et al. (2005), Jiménez et al. (2008), Dillon et al. (2012), Whaley et al. (2019) and Montesinos-Tubée & Mondragón (2020).

Field studies in Peru were undertaken between 2012 and 2021 and specimens resulting from them deposited at K and USM. Dissections of rehydrated flowers were made from all our collections, as well as from additional collections held at K. Ovaries and fruits were observed in the field, when available, using a hand lens (Hilkinson Ruper, 10× magnification, 20 mm), and on previously collected herbarium specimens held at K, using a Leica WILD M3Z binocular stereoscopic microscope and a TOUPTEK TZM0756TD digital microscope linked to a ToupCam digital camera XCAMLITE1080P at Huarango Nature, Peru. Measurements of foliage refer to mature, fully developed leaves and leaflets.

Study of the indumentum and gland morphology of leaflets and flowers was carried out using a Hitachi cold field emission S-4700-II scanning electron microscope (SEM) in the Jodrell Laboratory, Royal Botanic Gardens, Kew. Leaflets for SEM study were extracted from the following specimens at K: Ferreyra 6458 for Weberbauerella brongniartioides, Rosas s.n. for W. chilensis, Hutchison 1326 and Aparcana et al. 01 for W. raimondiana. The pustular glands on the calyces of all three species were also micrographed and fruit samples were analysed for the presence or absence of hairs.

Full assessments of the IUCN Red List conservation status (IUCN 2001) of the three species were made, using known threats and the specimen collection locations to estimate Extent of Occurrence (EOO) and Area of Occupancy (AOO), following IUCN (2019) guidelines. The R (R Core Team 2020) package rCAT (Moat & Bachman 2017) was used to evaluate the IUCN 'B' and 'D' criteria. All herbarium specimen locations were geo-referenced and included on the species distribution maps (Map 1).

Map 1.
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Distribution map of Weberbauerella species, with protected areas and major centres of population. prepared by j. moat.

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Taxonomic Treatment

Key to the species of Weberbauerella in Peru and Chile

  • 1a. Ovary covered with hairs or at least margin hairy, glands not prominent; leaves with 6 – 18 leaflet pairs ………………………………………………………………………………………………….2

  • 1b. Ovary glabrous, slightly rugose, glands prominent; leaves obovate-elliptic, with (11 –) 14 – 34 leaflet pairs; endemic to Ica and Arequipa regions, south-west Peru …………………………………………………………… …………………………………….3. W. raimondiana

  • 2a. Ovary margin ciliate, lateral surfaces with a few glands; leaves linear-elliptic, with 6 – 12 leaflet pairs; endemic to Tarapaca region, northern Chile..…………………………………………………………… …………………………………….2. W. chilensis

  • 2b. Ovary pubescent to villous, rugose, slightly glandular; leaves elliptic-obcordate, with 8 – 18 leaflet pairs; endemic to Arequipa region, southern Peru…………………………………………………………… …………………………………….1. W. brongniartioides

1. Weberbauerella brongniartioides Ulbr. (Ulbrich 1906: 551). Type: Peru, Arequipa, Oct. 1902, Weberbauer 1513 (holotype B!; isotype F!).

Erect ephemeral herb or suffrutex, 5 – 90 cm tall. Root deep and tuberous. Stem sulcate, sparsely glandular, internodes 9 – 32 mm long on mature branches. Leaves imparipinnate; stipules 3 – 8 × 1 – 2 mm; leaflets in 8 – 18 pairs per leaf, elliptic-obcordate, 4 – 13 × 5 – 10 mm, upper surface pilose to glabrescent and densely covered with glands, lower surface pilose to slightly villous, base obtuse to cuneate, apex rounded or retuse to emarginate, margin entire. Inflorescence a 3 – 11-flowered raceme; rachis 3 – 9.2 cm long. Flowers pedicellate; calyx glandular and pubescent with whitish trichomes; standard petal 16 × 14 mm; wing petals 15 × 8 mm; keel petals 17 × 8 mm. Stamens 10; filaments united, the staminal sheath 19 mm long. Ovary pubescent to villous, rugose, sparsely glandular. Fruit a 6 – 8-articulate lomentum; mature fruit not known. Figs 1, 2, 3 and 4.

Fig. 1.
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Leaflets of Weberbauerella species. 1 W. raimondiana (Ferreyra 2505 at K); 2 W. chilensis (Rosas s.n. at K); 3. W. brongniartioides (Ferreyra 6458 at K). A adaxial surface; B abaxial surface. drawn by a. orellana-garcia.

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Fig. 2.
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Standard petal (inner surface) of Weberbauerella species. 1 W. raimondiana (Ferreyra 2505 at K); 2 W. brongniartioides (Holt 146 at K). drawn by a. orellana-garcia.

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Fig. 3.
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SEM images of Weberbauerella species. W. raimondiana A leaflet, abaxial surface pubescent with prominent pustular glands (red arrows) [Hutchison 1326 at K]; B part of ovary, glabrous, portion over the ovule with prominent pustular glands (red arrow) [Ferreyra 2505 at K)]. W. chilensis C leaflet, abaxial surface pubescent with pustular glands [Rosas s.n. at K]; D part of ovary, with one pilose margin, portion over ovule weakly glandular [Rosas s.n. at K]. W. brongniartioides E leaflet, abaxial surface pilose with sparse pustular glands (red arrow) [Ferreyra 6458 at K]; F part of ovary, pubescent to villous over the entire surface, portion over the ovule obscurely glandular [Ferreyra 6458 at K].

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Fig. 4.
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Weberbauerella brongniartioides on dunes towards Bahía Catarindo, Islay, Arequipa, Peru. photo: © a. orellana-garcia.

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distribution. A Peruvian endemic, in lomas vegetation between Atico, Ocoña, Camaná, Quilca, Yuta, Matarani, Catarindo, Mollendo and Mejía; occurring to the centre and south-west of the coastal strip of the fog oases (Moat et al. 2021) of the Arequipa region, at elevations between 50 – 900 m. Map 1.

specimens examined and duplicates. peru. Arequipa, Camaná Prov.: Lomas entre Ocoña y Camaná, 14 Nov. 1957, fl., Angulo 2577 (HUT); Lomas de Cerrillos, 14 Feb. 1998, fl., Cáceres 16 (HUSA); Lomas entre Ocoña y Camaná, 13 Nov. 1949, fl., Ferreyra 6458 (K!, MOL [×2], USM); entre Camaná y Ocoña a más o menos 40 km al N, 13 Nov. 1952, fl., Ferreyra 8869 (USM); Lomas de Camaná, 28 Nov. 1955, fl., Ferreyra 11557 (USM); 30 km antes de Ocoña, 5 Dec. 1997, fl., FLSP 464 (HUSA, USM); Ocoña, without collection date, Raimondi 11780 (F). Islay Prov.: alrededores de la Urb. Alto Catarindo, 2 Dec. 2004, fl., Arce et al. 37 (HUSA); Catarindo, Mollendo, 1 Oct. 1972, fl., Bornáz et al. 39 (USM); Lomas of Mejia, c. 8 km N of Mejia, 25 Oct. 1983, fl., Dillon & Dillon 3742 (F, HUT, K!); Lomas of Mollendo c. 3 km N of Mollendo on road to Islay, 20 Nov. 1983, fl., Dillon & Dillon 3909 (F, HUT); Lomas de Mejía, 17 Nov. 1986, fl., Dillon et al. 4818 (F); Mollendo, 18 Nov. 2005, fl., Dillon et al. 8976 (HUSA); arriba de Mejía, al sur de Mollendo, 12 Nov. 1949, fl., Ferreyra 6410 (MOL [2 sheets], USM [2 sheets]); Lomas de Mollendo, 7 Oct. 1957, fl., Ferreyra 12595 (USM); Mollendo, 24 Oct. 1976 (st.), Ferreyra 18656 (USM); Quebrada de Catarindo. Lomas, 3 Feb. 1998, fl., FLSP 907 (HUSA, P); Lomas de Mejía, 8 Oct. 2002, fl., Huertas 48 (USM); Asociación San Agustín, Bahía Catarindo, 28 Nov. 2022, fl., Orellana et al. 1316 (K!, USM!); Vía a Catarindo, Bahía Catarindo, 28 Nov. 2022, fl., Orellana et al. 1318 (K!, USM!); Asociación San Agustín, Bahía Catarindo, 28 Nov. 2022, fl., Orellana et al. 1319 (K!, USM!); alrededores de la nueva carretera Catarindo, 9 Oct. 2004, fl., Ortiz et al. 144 (HUSA); alrededores de INDEHI-UNAS, Catarindo, Mollendo, 5 Dec. 2002, fl., Quipuscoa & Dillon 2844 (HUSA, HUT); Lomas de Mollendo, 9 Aug. 1949, fl., Vargas 8430 (CUZ); Mollendo, Loma, 4 Oct. 1902, fl., Weberbauer 1513 (B!, F!); N Mollendo, road to Playa Catarindo, 2 Oct. 2007 (st.), Weigend et al. 8730 (USM); Mollendo, 16 Oct. 1975, fl., Holt 146 (K!); Mollendo, Aug. – Sept. 1932, fl., Stafford K.21 (K!).

habitat. Weberbauerella brongniartioides occurs on sand dunes and lomas at elevations between 50 – 900 m. It grows in association with Argylia radiata (L.) D.Don (Bignoniaceae), Atriplex rotundifolia Dombey ex Moq. (Amaranthaceae), Cenchrus echinatus L. (Poaceae) and Nolana pallida I.M.Johnst. (Solanaceae).

conservation status. Endangered [EN B1ab(i,ii,iii)+2ab(i,ii,iii)]. Weberbauerella brongniartioides is provisionally assessed as Endangered, sensu IUCN (2001), based on an AOO estimated at >68 – <500 km2, EOO estimated at >1333 – <5000 km2, 4 – 6 known locations (the threshold is ≤5) and continuing decline observed and inferred from ground observations in its AOO, EOO and habitat. A precautionary approach is appropriate, as the habitat and wider ecosystem where this species occurs is highly fragile with multiple threats and, notably, this species does not occur within any protected areas. Threats include new roads, gas pipelines, windfarms, mining and 4×4 off-roading. In addition, pollution and climate change, particularly as they affect El Niño-Southern Oscillation (ENSO) cycles, are likely to have an impact, but this has yet to be quantified for this species. More research is needed to understand the natural population size, distribution and trends, as it is unclear whether this species is severely fragmented and, because of the habitat it occupies, subject to extreme population fluctuations. Our assessment agrees with Baldeón et al. (2006) who considered it as EN B1ab(iii) and the species is listed as Critically Endangered [CR] at the country level in the Peruvian Red List (MINAG 2006).

phenology. The species flowering period runs from June to November, with a peak from October to November. Fruit begin to mature in December, but fruiting duration is unknown.

etymology. The specific epithet “brongniartioides” refers to the apparent morphological similarity with the legume genus Brongniartia Kunth (Ulbrich 1906) and presumably to the only species of that genus in South America: Brongniartia ulbrichiana Harms. The two genera are not closely related taxonomically.

illustrations. Ulbrich (1906: 552, fig. 1). The same illustration was reproduced by Weberbauer (1945: 236, fig. 9) and by Klitgaard & Lavin (2005: 335, fig. s.n.).

notes. Both Weberbauerella brongniartioides and W. raimondiana have been recorded as supposedly growing in the outlying Lima region, in the protected area of Zona Reservada Lomas Ancon (Vazquez 2011), although in the absence of any herbarium specimens. In Cano et al.’s (2001) study, only two legumes are recorded from Ancon: Acacia macracantha Willd. [= Vachellia macracantha (Willd.) Seigler & Ebinger] and Hoffmannseggia prostrata Lag. ex DC. Based on images seen on the internet, it is likely that records by Vazquez (2011) are misidentifications for the species Hoffmannseggia prostrata.

2. Weberbauerella chilensis Faúndez & Saldivia (in Saldivia & Faúndez 2014: 42, figs 1, 2). Type: Chile, Tarapaca, 31 March 2008, Faúndez & Larraín s.n. (holotype SGO!; isotypes CONC!, SGO!).

Ephemeral prostrate herb, 10 – 15 cm tall. Root rotund, tuberous, 20 cm below the soil surface. Stem cylindrical with prominent glands, internodes 12 – 24 mm long on mature branches. Leaves imparipinnate; stipules 4 – 5 × 0.7 – 1 mm; leaflets in 6 – 12 pairs per leaf, linear-elliptic, 8 – 17 × 3 – 7 mm, upper surface villous and eglandular, lower surface villous to tomentose and covered with prominent glands, base obtuse, apex rounded, with visible pustular glands, margin entire. Inflorescence a 2 – 5-flowered raceme; rachis 20 – 30 mm long. Flowers pedicellate; calyx glandular and pubescent with whitish trichomes; standard petal 16 × 14 mm; wing petals 16 × 7 mm; keel petals 16 × 7 mm. Stamens 10; filaments united, the staminal sheath 16 – 17 mm long. Ovary lateral surface glabrous, with sparse glands in the areas above the ovules, margins ciliate. Fruit a 4 – 6-articulate lomentum; mature fruit not known. Figs 1, 3, 5.

Fig. 5.
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Weberbauerella chilensis in Pica, Pampa Tamarugal, Tarapaca region, Chile. photo: © bárbara larraín.

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distribution. Weberbauerella chilensis is a Chilean endemic restricted to high elevations of the Atacama Desert in the Tarapaca region. The species grows in sandy soils at elevations of between 2,400 – 3,700 m, east of Tamarugal on the way to Salar de Huasco. Plants only appear above ground after precipitation, which is infrequent and irregular. Map 1.

specimens examined and duplicates. chile. Tarapaca region: Tamarugal Prov.: Camino Pintados, Quebrada Blanca, Tarapacá, 18 May 2012, Rosas R7988 (INIA Seed Bank); Comuna Pica, Camino a Salar del Huasco, 31 March 2008, fl., Faúndez & Larraín s.n. (CONC! SGO! [2 sheets]); Comuna de Pica, Quebrada Choja, 8 Sept. 2012, fl., Faúndez et al. s.n. (CONC, SGO).

habitat. Weberbauerella chilensis grows in open habitats together with other annuals and ephemeral, geophytic, herbaceous species, including Metharme lanata Phil. ex Engl. (Zygophyllaceae), Nolana tarapacana (Phil.) I.M.Johnst. (Solanaceae), and Tiquilia grandiflora (Phil.) A.T.Richardson (Boraginaceae).

conservation status. Endangered [EN B1ab(i,ii,iii)+2ab(i,ii,iii)]. Weberbauerella chilensis is provisionally assessed as Endangered, sensu IUCN (2001), based on an AOO estimated at >12 – <500 km2, EOO estimated at >91 – <5000 km2, c. 3 known locations, and continuing decline observed and inferred in its AOO, EOO and habitat from ground observations. Continuing decline was observed and inferred from ground observations within the W. chilensis AOO, a hyperarid, fragile ecosystem with multiple threats. Notably, this species does not occur within any protected areas. Threats include extension of existing mining activities and associated road and infrastructure building. Pollution and climate change, particularly as they affect ENSO cycles, are likely to have an impact, but this has yet to be quantified for this species. More research is needed to understand the natural population size, distribution and trends, as it is unclear whether this species is severely fragmented and, because of the habitat it occupies, subject to extreme population fluctuations.

phenology. Flowering from September to March. Fruiting period not known.

illustrations. Saldivia & Faúndez (2014: 43, fig. 1).

3. Weberbauerella raimondiana Ferreyra (1951: 3: 2, fig.). Type: Peru, Arequipa, Nov. 1949, Ferreyra 6498 (holotype US 1998730!; isotypes F!, MOL!, US 1998729!, USM 32526!).

Perennial woody herb, stems 10 – 35 cm tall, creeping to ascending, angled, slightly zig-zag. Root at maturity rounded, tuberous, 15 – 40 cm below the soil surface. Stem terete, with scattered prominent glands, internodes 5 – 21 mm long on mature branches. Leaves imparipinnate; stipules glandular, 2 – 6 × 0.4 – 1.2 mm; leaflets in (11 –) 18 – 34 pairs per leaf, obovate-elliptic, 3 – 10 × 1.5 – 5 mm, upper surface pubescent to glabrescent and covered with scattered glands, lower surface pubescent and covered with pustular dark red glands, base obtuse, apex rounded to retuse, margin entire. Inflorescence a 4 – 7-flowered raceme, rachis 2.2 – 11.2 cm long. Flowers pedicellate; calyx glandular, with whitish pubescence; standard petal 18 × 14 mm; wing petals 14 × 9 mm; keel petals 15 × 8 mm. Stamens 10; filaments united, the staminal sheath 14 mm long. Ovary glabrous, rugose, with prominent glands, 4 – 6 ovules. Fruit a 4 – 6-articulate lomentum, glabrous, portion over the seeds conspicuously rugose with prominent glands. Figs 1, 2, 3 and 6.

Fig. 6.
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Weberbauerella raimondiana in Lomas vegetation in the San Fernando National Reserve, Ica, Peru. photo: © a. orellana-garcia.

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distribution. Endemic to Peru; restricted to lomas ecosystems (fog oases) outcrops, and especially to the lomas dunes of north-western Arequipa and south-western and -eastern Ica regions, at elevations between 50 – 1800 m. Map 1.

specimens examined and duplicates. peru. Arequipa: Caravelí Prov., Lomas de Jaguay, between Nazca and Chala, 15 Sept. 1957, fl., Hutchison 1326 (F, K!, MO, USM); Lomas de Jaguay, 18 Nov. 1957, fl., Hutchison 1896 (E!, F, GB, GH, K!, L, P, USM, WAG); Jaguay, 20 Oct. 1946, fl., Ferreyra 1521 (F, USM [2 sheets]); Lomas de Jaguay, 7 Nov. 1947, fl., Ferreyra 2505 (B, K! [2 sheets], USM [2 sheets]); Lomas de Jaguay, entre Nazca and Chala, 9 Nov. 1949, fl., Ferreyra 6346 (USM); Jaguay, 14 Nov. 1949, fl., Ferreyra 6498 (F!, MOL!, US! 1998729, 1998730, USM!); Lomas de Jaguay, between Nazca and Chala, 9 Nov. 1952, fl., Ferreyra 8796 (USM). Ica Prov.: Lomas de Amara, 14 Aug. 2017, fl., Orellana et al. 571 (K!, USM!); Lomas de Amara, 22 Nov. 2018, fl., Whaley et al. 1820 (K!, USM!); Nasca Prov.: Lomas de Marcona, Marcona, Nasca, 5 Nov. 2016, fl., Aparcana et al. 01 (K!, USM); Cerro Blanco, 4 June 1994, fl., Cano & Roque 6014 (HUSA, USM); Cerro Blanco, km. 9, Carretera Nazca-Puquio, 20 Nov. 1994, fl., Cano et al. 6171 (USM); Lomas de Marcona, 6 March 2020, fl., Capcha et al. 169 (K!, USM!); Quebrada La Cueva, Clavelina, 10 Nov. 2021, fl., Capcha et al. 201 (K!, USM!); Lomas San Fernando, Marcona, 27 Nov. 2012, fl., Cárdenas & Orellana KPP 76 (K!, USM!); Lomas de San Nicolás, 22 Sept. 1958, fl., Ferreyra 13384 (USM); Lomas San Fernando, Marcona, 30 Oct. 2012, fl., Klitgaard et al. KPP 005 (K!, USM!); Lomas San Fernando, Marcona, 1 Nov. 2012, fl., Klitgaard et al. KPP 50 (K!, USM!); Lomas de San Fernando, 24 Nov. 2018, fl., Lewis et al. 3869 (K!, USM!); Lomas de San Fernando, 24 Nov. 2018, fl., Lewis et al. 3870a (K!, USM!); Lomas de San Fernando, 24 Nov. 2018, fl., Lewis et al. 3870b (K!, USM!); Lomas de San Fernando, 24 Nov. 2018, fl., Lewis et al. 3874 (K!, USM!); Lomas de Marcona, 25 Nov. 2018, fl., Lewis et al. 3877 (K!, USM!); Lomas de Marcona, 27 Dec. 2018, fl., Orellana et al. 744 (K!, USM!); Lomas de Marcona, 27 Dec. 2018, fl., Orellana et al. 745 (K!, USM!); Lomas de Marcona, 27 Dec. 2018, fl., Orellana et al. 746 (K!, USM!); Lomas de Marcona, 27 Dec. 2018, fl., Orellana et al. 747 (K, USM); Quebrada La Cueva, 26 Nov. 2021, fl., Orellana et al. 1307 (K!, USM!); Quebrada La Cueva, 26 Nov. 2021, fl., Orellana et al. 1314 (K!, USM!); Lomas de Marcona, Marcona, Nasca, 28 Nov. 2016, fl. & fr., Padilla et al. 02 (K!, USM!); Lomas de Marcona, Marcona, 19 Nov. 2013, fl., Whaley et al. 1698 (K!, USM!).

habitat. Lomas dunes and occasionally near rock refugia (see Whaley et al. 2019), and sporadically in flushes in aeolian sand over desert pavements amongst mobile crescent dunes; at elevations of between 90 – 1380 (– 1829) m. Weberbauerella raimondiana occurs occasionally in almost monospecific flushes but, more often, when established, in association with Argylia radiata (L.) D.Don (Bignoniaceae), Nolana pallida I.M.Johnst. (Solanaceae) and Tiquilia ferreyrae (I.M.Johnst.) A.T.Richardson (Boraginaceae).

conservation status. Vulnerable [B1ab(i,ii,iii)+2ab(i,ii,iii)]. Weberbauerella raimondiana is provisionally assessed as Vulnerable, sensu IUCN (2001), with an AOO estimated at >40 – <500 km2, EOO estimated at c. 6773 km2 and 7 known locations. Continuing decline in EOO, AOO and habitat is inferred from ground observations, as the habitat and wider desert ecosystem of Weberbauerella raimondiana is highly fragile with multiple threats. These threats include development of roads, gas pipelines, windfarms, afforestation, mining and 4×4 off-roading. Pollution and climate change, particularly as they affect ENSO cycles, are likely to have an impact, but this has yet to be quantified for this species. We have observed that this species may experience extreme population fluctuations, exacerbated by the low frequency of lomas development in Lomas San Fernando: we estimate that c. 15% of its total population is protected in San Fernando National Reserve. More research is needed to understand the natural population size, distribution and trends, as it is unclear whether this species is severely fragmented and, because of the habitat it occupies, subject to extreme population fluctuations. Baldeón et al. (2006) assessed this species as EN B1ab(iii), but, when this work was published, the species was assumed to have only two to four disjunct populations. W. raimondiana is listed as Critically Endangered [CR] at the country level in the Peruvian Red List (MINAG 2006). More research is needed to understand the natural population (Baldeón et al. 2006) and its distribution and trends.

phenology. Flowering from June to November; mature fruits have been seen in November and December.

etymology. The specific epithet “raimondiana” honours the Italian botanist, naturalist and geologist Antonio Raimondi (1826 – 1890) who lived in Peru for 40 years from 1850 and devoted himself to the study of Peruvian biodiversity.

illustrations. Ferreyra (1951: 5, fig. s.n).

notes. The collection of Weberbauerella raimondiana, Ferreyra 2505, with duplicates deposited in B, K, USM and available on JSTOR, was collected, according to the label, in "Peru: Dept. Arequipa; Prov. Caraveli; Lomas de Jahuay, entre Nazca y Chala, 7.11.1947". Although there is a topotype label on the herbarium sheets, this collection is not here considered a type, as its collection locality and year are different to those given in the original description of the species.

There are three herbarium specimens of Weberbauerella raimondiana (Klitgaard et al. KPP 005, KPP 50 and Cárdenas & Orellana KPP 076) that exhibit some leaves with less than 18 pairs of leaflets. This reduced leaflet number is uncommon and all other collections of W. raimondiana seen for this revision have 18 – 34 pairs of leaflets. The three collections with fewer leaflet pairs are from frontal ridge dunes of Lomas San Fernando and Marcona, and most likely to be local adaptations to soil type and available moisture. Further understanding of these populations might be gained from molecular analysis.

The collection Whaley et al. 1820 (K, USM), collected in December 2018 from Lomas Amara, extends the northern limit for Weberbauerella, but also shows interesting morphological variation worthy of comment. The population, spread over an area of less than 1 hectare, is found among sheltered, north facing rocks and cliffs, where individual plants <20 cm in height grow in rocky clefts. Notably, this locality shows archaeological vestiges of rudimentary shelters, similar to those found previously in some lomas areas. A number of pre-Columbian diagnostic pot shards, indicative of hunter-gatherer shelters, have been found at the site. Although this collection resembles W. raimondiana due to its glabrous ovary, it has a suite of distinct characters not seen in any other Weberbauerella specimens. These include large, oblong-lanceolate to orbicular leaflets measuring 4 – 18 × 2 – 10 mm, which have farinaceous lower and upper surfaces, ciliate margins and densely pilose midribs. Additional field work needs to be carried out, and further material collected, to fully determine this population's taxonomic status. We speculate that it may be an ancient introduction displaying ecotypic variation.

Weberbauerella species all grow in hyperarid desert enclaves where fog is the primary source of moisture. They occupy topographic niches on stabilised sand dunes favouring frontal ridges. Very little is known about Weberbauerella ecology or historical use. However, it is notable that W. raimondiana, is an established perennial (as are the other species in the genus) that develops long, woody rhizomes bearing deeply buried, spheroid tubers (see Fig. 7). These storage structures may have evolved at some depth in the ground partly to avoid excavation by foraging guanacos (Lama guanicoe), these animals are long associated with seasonal migration between lomas and Andean quebrada habitats. Guanacos have been observed, by local fisherman in Lomas San Fernando, excavating tubers by pawing at the sand. Guanacos can also be observed excavating or scraping to forage buried parts of other lomas species. We also note that the rhizomes of W. raimondiana host abundant nodules of rhizobium bacteria: this is apparent from their diagnostic presence when underground parts are excavated carefully (see Fig. 7). That Weberbauerella apparently so freely accommodates this association may be an adaptation allowing the species to thrive in poor, sandy soil conditions. The state of nodulation, through the long dry season, raises research questions about the duration of subsoil moisture that is derived seasonally from fog.

Fig. 7.
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Weberbauerella raimondiana. A species in habitat; B development of long woody rhizomes and tubers; C – D spheroid tubers and roots with nodules containing Rhizobium nitrogen fixing bacteria (black circles). photos a, c © g. p. lewis; b © a. orellana-garcia; d © o. q. whaley.

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Little is known about pollination of Weberbauerella raimondiana, however, Melissodes aff. ecuadorius and Centris aff. mixta (Hymenoptera, Apidae) have been observed visiting flowers of W. raimondiana (pers. obs. by A. Orellana-Garcia and J. Capcha-Ramos). These bee species have an elongated proboscis allowing them to access flower nectaries and, thanks to their hairiness, collect pollen, and are clearly true pollinators (see Fig. 8).

Fig. 8.
figure 9

Floral visitors and pollinators of Weberbauerella raimondiana A Melissodes aff. ecuadorius; B Centris aff. mixta. photos: a © j. capcha-ramos; b - c © a. orellana-garcia.

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