Abutilon albidum (Willd.) Sweet, Hort. Brit.: 54. 1826.

Verloove, Filip, Sennikov, Alexander N. & Reyes-Betancort, J. Alfredo, 2023, Taxonomy and nomenclature of Abutilon albidum (Malvaceae, Malvoideae), a cryptic Saharo-Canarian species recently rediscovered in Tenerife, PhytoKeys 221, pp. 41-60 : 41

Abutilon albidum (Willd.) Sweet, Hort. Brit.: 54. 1826.

Abutilon albidum ≡ Abutilon albidum (Willd.) Webb & Berthel., Hist. Nat. Iles Canaries (Phytogr. Canar.) Tome troisième, Deuxième partie, Sectio 1: 39. 1836, isonym.

Abutilon indicum albidum ≡ Abutilon indicum var. albidum (Willd.) Baker f., J. Bot. 31: 213. 1893.

Sida albida ≡ Sida albida Willd., Enum. Pl.: 722.1809, nom. cons. prop.

Abutilon albidum Non Abutilon albidum Hooker & Arn., Bot. Beechey’s Voy. 278. 1841, nom. illegit.

Type.

Spain. Teneriffa , Barranco Santo, Webb (FI barcode FI006084 ), typ. cons. prop. ( Verloove and Sennikov 2022) .

Description.

Erect, short-lived perennial herb or shrub up to 60(-100) cm tall. Branches densely covered by minute stellate hairs, mixed with numerous long, simple spreading hairs (especially, but not exclusively on new growth) and sparser multicellular hairs. Leaves (median cauline) up to 13 cm long and 7 cm wide, broadly ovate to almost rotund, deeply cordate at base, acute to acuminate at apex, irregularly crenate-toothed to double-toothed, very shortly stellate-pubescent on both sides; petiole up to 6 cm long, slightly shorter than blade, very densely stellate hairy mixed with rather numerous short, glandular, capitate hairs and scattered weak, simple, spreading hairs; longest stipules to 9 mm long (mostly shorter), filiform. Flowers axillary, mostly solitary, but sometimes merging to more or less distinct panicles, pedicel 2-4 cm long, elongating in fruit up to 1-8 cm, articulate and geniculate ca. 5 mm below the apex. Calyx 5-lobed for ca. ½ its length, sepals up to 8 mm long, densely long-pubescent on both sides, slightly accrescent, erect, ultimately reflexed; lobes lanceolate-acuminate. Corolla pale yellow to yellow, ca. 1.5 cm across; petals 7-10 mm long, 4-5 mm wide, obovate. Staminal column 2-3 mm long, stellate-pubescent. Fruit 8-10 mm long, ± 13 mm across; mericarps 10-15, black and rather star-like spreading at maturity, up to 9 mm long, 5 mm wide, the outer apical (dorsal) angle acute-triangular, without protuberances, stellate-pubescent towards the margin. Seeds 2(-3), brown, initially with scattered stellate hairs, pilose near margins, ca. 2 mm across.

Illustrations.

Webb and Berthelot (1836) presented the first superb line drawing of Abutilon albidum . Figs 1 - 4 show the species in nature in the Canary Islands (Tenerife) and Morocco (Tiglit), respectively.

Distribution.

Macaronesia (Spain: Canary Islands), north-western Africa (Algeria: Hoggar Mountains; Morocco: Anti-Atlas) (Fig. 6 ).

Webb and Berthelot (1836) reported Abutilon albidum from 'Barranco Santo’, near the Zurita Bridge, in Santa Cruz de Tenerife, in the south-eastern part of the Island. It had previously been collected from Tenerife in 1796 by A. de Jussieu (P!; see specimens examined). It was considered a Canarian endemic ( Masferrer y Arquimbau 1880). Nearly all collections that have been made since then originated from the Barranco de Santos Ravine (present-day name) in Santa Cruz (Fig. 7 ). Historical literature sources mostly also referred to that locality (e.g. Masferrer y Arquimbau (1880); Bornmüller (1904)). Some further historical literature sources reported it from additional localities in Tenerife. According to Lindinger (1926), it was also observed in La Orotava, ca. 35 km further SW. Pitard and Proust (1908) also mentioned it from another ravine in Santa Cruz, the Barranco del Bufadero. The species was said to be very rare in Tenerife. Burchard (1929) probably presented the most extensive (and most recent) update of its occurrence on the Island. It was mostly seen between San Andrés and Igueste [F.V.: i.e. Igueste de San Andrés], including below the Los Órganos cliffs [F.V.: i.e. north of the Las Teresitas Beach]. It was also said to have isolated occurrences in Santa Cruz, where it had probably become extinct. All documented occurrences, except for a single record from La Orotava, were from the extreme south-eastern part of the Island where it occupied an area of hardly more than 12 km2. In Tenerife, it was probably last collected in 1945 by E.R. Sventenius. According to some sources, it was formerly also collected in Gran Canaria (Barranco de la Angostura) ( Pitard and Proust 1908); unfortunately, no specimens are present in the LPA herbarium.

In December 2019, Abutilon albidum was rediscovered in Tenerife in Igueste de San Andrés, 74 years after Sventenius’ collection from 1945. In the same village, several small populations of identical plants were observed in December 2019. Some plants were seen along the side of the road Carretera de Igueste de San Andrés adjacent to the Barranco de Igueste (these plants are also visible on Google Streetview images from June 2012: https://www.google.com/maps/@28.5291262,-16.1568142,3a,75y,15.61h,60.37t/data=!3m6!1e1!3m4!1s6-0-oKg77q5kAJSCf1_wCQ!2e0!7i13312!8i6656). Further plants were seen as weeds in a plantation near the San Pedro Apóstol church. Finally, the species was also observed on both sides of the Paseo el Cementerio, a track that leads to the cemetery. In March 2022, a more detailed survey was carried out (Fig. 8 ): the species was found in several additional localities, but less than 100 individuals in total and in an area of at most 35,000 m2 (for details see: https://observation.org/soort/view/1029740). Interestingly, in the very same area, the Belgian amateur botanist Leon Delvosalle (1915-2012) collected this species in May 1962, but erroneously identified it as Sida rhombifolia , a subtropical Malvaceae weed that is also naturalised there. After the Meise Botanic Garden (BR) acquired his herbarium, this collection (consisting of four small fragments only) was re-identified by the first author as Abutilon cf. indicum in March 2013. All these localities fall within the distribution area as described by Burchard (1929). From this, it can be deduced that A. albidum has survived at least in Igueste de San Andrés in Tenerife. Meanwhile, Santa Cruz de Tenerife became the capital of the Island and has dramatically changed in the past century. Repeated botanical explorations over the years in the ravines where A. albidum formerly occurred, especially Barranco de Santos and Barranco del Bufadero, were fruitless. Additional fieldworks in May and June 2021 in potentially suitable areas in Barranco Tahodio, Barranco Valleseco, between Igueste de San Andrés and San Andrés, Playa de las Teresitas (Bajo Los Órganos) and in Playa de Las Gaviotas (Bajo Los Órganos) were also unsuccessful. The coastal area between Santa Cruz and San Andrés was mostly lost due to the expansion of the commercial port and the urbanisation of the capital. Moreover, the highly invasive grass species Cenchrus setaceus (Forssk.) Morrone has now colonised the entire area, including the habitats where A. albidum once occurred. In Los Órganos, the species probably grew near the old path between Las Teresitas and Las Gaviotas that goes through the base of the basaltic rocks of Los Órganos.

After its discovery in Tenerife, Abutilon albidum also was found in north-western Africa. Maire (1933) first reported it from Ideles and Imarera in the Hoggar Mountains, a highland region in the central Sahara in southern Algeria, along the Tropic of Cancer, where it was said to be rare ( Quézel and Santa 1963). Its presence there has not been confirmed lately and it is likely extinct (pers. comm., Prof. Said Amrani, January 2022). From Morocco, it was first reported from Assa in the southwest of the country ( Maire 1936; Emberger and Maire 1941). Later, it was also reported from Foum Zguid in south-eastern Morocco ( Fennane et al. 1999) and Maire collected it in 1937 in “Tiliouine” (Taliouine), slightly further north (UM-MPU-MPU084348!). There are apparently no recent herbarium collections or more recent reports of the species; however, it is still present at least in the surroundings of Tiglit in Morocco (https://www.teline.fr/en/photos/malvaceae/abutilon-albidum), where it had been confused with the introduced weed A. theophrasti . Abutilon albidum is probably rare throughout its entire distribution range and probably poorly known as well. It was assessed as endangered in a preliminary Red List of the Moroccon flora ( Fennane 2018).

Habitat and ecology.

In Algeria and Morocco, Abutilon albidum usually occurs on basaltic rocks in the desert or semi-desert, from subtropical to warm (Mediterranean) climate areas. It is most often found at higher elevations (up to 2,000 m above sea level), but may also grow at lower elevations. From herbarium labels, it can be deduced that the species also occurs in sandy, dried-out riverbeds. Habitats are usually natural and little disturbed although it was also collected (likely as a weed) in a palm grove ( Maire 1936). It is nowhere in the world known as a weed ( Randall 2017).

In Tenerife, Abutilon albidum is best known from its locus classicus, i.e. the dried-out riverbed of Barranco de Santos in Santa Cruz. It was said to grow in dry rock crevices and warm ruderal places ( Webb and Berthelot 1836; Bornmüller 1904; Pitard and Proust 1908). It formerly also was reported from basaltic rocks below the Los Órganos sea cliff ( Burchard 1929). However, the most recent observations are almost exclusively from more degraded, anthropogenic habitats: roadsides, plantations and ruderal places, where it is found along with, for example, Bituminaria bituminosa (L.) C.H. Stirt., Cynodon dactylon (L.) Pers., Fagonia cretica L., Forsskaolea angustifolia Retz., Patellifolia sp., Setaria adhaerens (Forssk.) Chiov. etc. In one locality, a few plants were also found on the basaltic rocks bordering the road; there, the species was accompanied by, amongst others, Aristida adscensionis L., Cenchrus ciliaris L. and Kleinia neriifolia Haw. In Tenerife, all populations, including the historical ones, are at elevations well below 100 m, often near to sea level.

Specimens examined.

Spain. Canary Islands, Tenerife: Teneriffa, Barranco Santo, Webb ( FI006084 , proposed conserved type); Canaries, s.d., herb. Webb (P06730933); Barranco Santo propè opp. Sta. Cruz, s.d., Webb (P06730936; BR); Ténérif, s.d., sine coll. (MNHN-P-P06731032); Barranco Sancto propè Sta. Cruz, s.d., sine coll. (BR 0000013462017); Teneriffe, 1796, A. de Jussieu (P06730938); Ténérife, Sa. Crux, 1816, C. Smith (G00219753, G00219752, G00219721); Teneriffa, in convalle aridiforme a Barranco Santo propè urbem Sanctam Cruceum, June 1834 (K000240407); Teneriffe, 1848, S. Berthelot (P06731022, K000240405, K000240406); Tenériffe, 1854, C. Bolle s.n. (COI00057130); Teneriffa, Barranco Santo près Santa Cruz, 12 April 1855, E. Bourgeau (P06730935, RAB078278); ibid. (P06641194); Barranco del Hierro, Sud-Est de Tenerife, 15 April 1855, H. de la Perraudière (P04694330); Reg. infer., Sud-Est de Tenerife , 15 April 1855, H. de la Perraudière (P06731031); Prope Sta. Crux, 15 April 1855, H. de la Perraudière (P06731023); ibid. (P06731030); ibid. (MPU748052); Barranco Santo, 1866, T. Husnot (Pl. Canarienses 632) (P04642214); ibid. (P04694328); ibid. (P06641193); ibid. (MPU748054); Teneriffa, Santa Cruz, Bco. Santo (loc. class.), 15 June 1901, J. Bornmüller 2132 (P06731034; BR; MPU748050); ibid. (P06731033); Inter Sanctum Andream et Igueste oppidula Teneriffae, in rup aridis, 3 May 1907, O. Burchard ( ORT 00001 ); San Andrés, Los Órganos, sitios rocosos y secos, +/- escasa, 3 April 1944, E.R. Sventenius ( ORT 12332 ); San Andrés, Roque de Los Organos , escasa, 11 January 1945, E.R. Sventenius ( ORT 12331 ); Igueste [de San Andrés], bord du chemin, 5 May 1962, L. Delvosalle 5235 (BR); Santa Cruz de Tenerife , Igueste de San Andres , Carretera de Igueste de San Andres N of the Barranco de Igueste , roadside, few plants, 23 December 2019, F. Verloove 13743 (BR); Santa Cruz de Tenerife , Igueste de San Andres , Paseo el Cementerio, alongside track, on both sides, ca. 15-20 individuals, 23 December 2019, F. Verloove 13744 (BR); Santa Cruz de Tenerife , Igueste de San Andres , Pasaje El Cascajo, roadside, scattered individuals, 26 March 2022, F. Verloove 14278 (BR) .

Figures

Figure 1. Abutilon albidum in Igueste de San Andres, Tenerife. General habit of plants growing below rocks along the side of the road. December 2019, F. Verloove.

Figure 4. Abutilon albidum near Tiglit, Morocco, December 2016, A. Garcin. In Morocco, this species is usually found in more natural habitats, often in crevices of basaltic rocks in (semi-) desert areas.

Figure 6. Worldwide distribution of Abutilon albidum (historical and current records).

Figure 7. Old (black cross) and recent (black bullet) distribution of Abutilon albidum in Tenerife, Canary Islands, Spain.

Figure 8. Distribution of recently discovered populations of Abutilon albidum in Igueste de San Andres in Tenerife, Canary Islands, Spain.