Nomenclatural Type Identification of Names in North African Tamarix (Tamaricaceae)

1. Introduction

Tamarix L. (Tamaricaceae Link) is a genus native to Eurasia, occurring from the Atlantic European coasts to the Pacific Asian ones, which is also present in both the northern areas and the southernmost territories of Africa. Due to human activities, some species spread into other parts of the globe, and became invasive in America and Oceania [1,2]. Although some authors estimate between 60 and 90 species in the genus [3,4,5,6,7], more recently Villar et al. [2] considered between 70 and 75 species as more reliable numbers. Taxa of Tamarix are usually halophytic tall-shrubs inhabiting arid, desertic or subdesertic areas under Mediterranean, Temperate or Subtropical climates [7]; there, they can constitute the potential shrubby vegetation of saline soils [8].

Most of the authors who dealt with Tamarix considered the taxonomy of the genus to be complex [3,4,7,9,10], since many species were described based on morphological characters that later revealed unstable or highly variable, even in a single individual [11]. In consequence, scarce consensus exists on the delimitation of Tamarix species in different taxonomic treatments over time. Further, hybridisation can occur between taxa morphologically quite distinct [12,13] and those processes must have played a key role in the evolution of the genus [2]. The taxonomic and nomenclatural contributions by Baum [3,4] much improved the knowledge of Tamarix in its distribution area, stressing the importance of some characters such as the staminal disk morphology or papillosity of the inflorescence rachis, among others. However, recent integrative research combining morphological, molecular and biogeographical data has shown that even those characters, often accepted as diagnostic, exhibit indeed a wider plasticity. This points out to a broader circumscription of species and different synonymic relationships among them, not fitting entirely with Baum’s traditional arrangement [14].

In this scenario, the study of the type material is necessary to fix the use of names described in Tamarix, so that botanists can produce consistent decisions on taxonomy of the genus [15]. Some authors have made effective typification of Tamarix names in the past [16], especially Baum [3,4] who compiled almost every name published to that time and referred to the types of each one. However, as stressed in recent works [15,17,18,19], some of these type indications required some technical corrections according to the nomenclatural rules of the Shenzhen Code, hereafter abbreviated as ICN [20].

In the southwestern part of the Mediterranean basin (i.e., the Iberian Peninsula and the Maghreb), Tamarix is currently accepted to be represented by 10 species [14,21]: T. africana Poir., T. amplexicaulis Ehrenb., T. aphylla (L.) Karst, T. boveana Bunge, T. gallica L. (T. canariensis auct.), T. macrocarpa (Ehrenb.) Bunge and T. passerinoides Desv. (native species), plus T. chinensis Lour., T. parviflora DC., and T. ramosissima Ledeb. (aliens). None is exclusive of that territory, and they all spread into other parts of the Mediterranean basin. Several additional taxa were described from that area in the first half of the 20th century, mainly by Jules Battandier, René Maire, Carlos Pau, Frère Sennen, and their collaborators. Most of them were synonymised previously to any of the above-mentioned species accepted here, and their types partly discussed elsewhere [3,4,15,17,18,19].

Continuing with our taxonomic studies on Tamarix, in the present contribution we discuss taxonomy and nomenclature of nine names published for plants occurring in the southwestern territories of the Mediterranean basin, mainly in North Africa. Seven intended holotypes are corrected here to lectotypes, one epitype is designated for T. africana to warrant current use of that name, and one isotype, 27 isolectotypes and 11 syntypes are identified for some of the concerned names. The taxonomic identity is commented for all names, and their synonymic placement is confirmed or discussed accordingly.

2. Materials and Methods

Herbarium material and digital images of specimens from ABH, BC, FI, G, H, K, LY MPU, P, VAL, and W (acronyms according to [22] were studied. Other data were also retrieved from diverse internet sources, such as GBIF, JACQ, JSTOR, NHM, PARLATORE, or ReColNat [23,24,25,26,27,28]. Authorities of plant names follow IPNI [29], though other nomenclatural databases such as POWO and APD [30,31] were checked for verification. Barcode numbers are placed after the corresponding herbarium acronym when available. The names analysed are numbered consecutively and listed alphabetically. For nomenclatural purposes, labels of types are transcribed literally as in the herbarium sheets and between inverted commas, leaving our own notes or comments aside. Typewritten words on labels have maintained the standard form, whereas handwritten text has been converted to italics. Names previously treated in synonymy of T. canariensis Willd. are now included in T. gallica following Villar [21], since the circumscription of the former name is regarded here in a narrower sense that applies only to plants from the Canary Islands [2]. Nomenclatural issues conform to the articles of the ICN [20].

3. Results and Discussion

3.1. Tamarix africana Poir., Voy. Barbarie 3: 139. 1789.

Type: [Algeria]. “Cotê de barbarie. Poiret” (indicated as “holotype” by Baum [3], and corrected to lectotype by Villar et al. [11]: P-LA00287249! from Herbier de Lamarck; isolectotype: P00166702! [Label 1: “Tamarix africana. Floribus pentandris confertissimis, spicis crassis, brevibus.”; Label 2: “Tamarix africana (n.) ex Numidia”; Label 3: Herb. Poiret in Herb. Moquin-Tandon]; epitype designated here: P05113423! [Algérie. Dèp. Alger: Bas-fonds humides, au pied des collines du Sahel, au Sud de Koléa, 23 mars 1960, A. Dubuis & L. Faurel 3815]. Figure 1a.

Tamarix africana is one of the most common species within the genus along its Western Mediterranean distribution [11] (Figure 1b). The taxonomic identity and phylogenetic relations of the species are clear overall, with some discussion about the recognition of T. africana var. fluminensis (Maire) B.R.Baum (T. brachystylis var. fluminensis Maire) as a rightful taxon [2,4,11,32]. The name was proposed by Poiret [33] and the description was based on materials collected in his trip through the northwestern African coast (ancient Numidia or Barbary, partly including the current territory of Morocco, Algeria, Tunisia and western Libya) in 1785 and 1786. Although no precise location was cited in the protologue, Poiret [34] later noted in Lamarck’s Encyclopédie Méthodique: “J'ai découvert cet arbrisseau dans la Barbarie, aux environs d'Hippone, proche les bords de la mer. M. Desfontaines l'a également recueillie aux environs d'Alger.” [I have found this shrub in Barbary, in the surroundings of Hippone –currently Annaba, Algeria–, near the seashore. Mr Desfontaines has also gathered it around Algiers]. Therefore, any North African material collected in that area and belonging to Poiret’s herbarium, or being collected by him, might be considered as original material.

Baum [3,4] stated that the “holotype” was a specimen by Poiret kept at Lamarck’s herbarium in the MNHN, Paris (P00287249). Moreover, Baum also mentioned two isotypes from Cosson’s herbarium and Moquin-Tandon's herbarium, both conserved at P. The authors visited the Paris herbarium several times since 2013 and were unable to locate Cosson’s voucher. The specimen kept at Moquin-Tandon collection (P00166702) is part of the former Poiret’s herbarium and bears a fragment morphologically and phenologically resembling those in the lectotype specimen kept at Lamarck’s herbarium, and probably they all are part of a sole gathering. Therefore, Baum’s mention of holotype is to be corrected to effective lectotype designation (Art. 9.10 of the ICN) as suggested by Villar et al. [11], and the specimen at Moquin-Tandon Herbarium can be considered an isolectotype (a true duplicate of the lectotype). Moreover, due to their age, the state of conservation of both existing specimens is not good enough to serve as proper references for the name, since they lack the minimum features necessary for identification and to warrant a precise application of the name. The specimen from Lamarck’s herbarium is represented by a single branch that bears only a few leafed twigs and a couple of broken racemes with no complete flowers on them. The specimen at Moquin-Tandon’s is in a similar state, but for a small envelope with a few racemes. Moreover, the syntype is affixed on the right side of the herbarium sheet, the left corresponding to a different specimen. Under these circumstances we consider that the designation here of an epitype (Art. 9.9 of the ICN) on the specimen P05113423 (Figure 1a), an Algerian collection from near Algiers that matches the current concept of the species, will provide stability to further use of the name Tamarix africana.

3.2. Tamarix bounopoea J.Gay ex Batt. in Batt. & Trab., Fl. Algérie, Dicot.: 321. 1889.

Type: [Algeria]. “B. BALANSA, PL. D’ALGERIE, 1852. 671. TAMARIX DESERTI (Boiss. Diagn. Pl. or. X, p. 9) Var. (J. Gay) Bords du Chott-el-Chergui, près de Khrider, cercle de Saïda. 30 mai.” (indicated as “holotype” by Baum [3], and corrected here to lectotype) K000242686 [digital image!]; isolectotypes: G00015657!, G00015658!, MPU008075!, MPU008077!, W1889-66955!). Syntypes: “B. BALANSA, PL. D’ALGÉRIE, 1853. 989. TAMARIX BOUNOPOEA, Gay in Coss. Rapp. Alg. 1852. T. deserti var. Gay in Balansa alg. exicc., 1852, nº 671. (J. Gay.) Environs de Biskra. Commencement d’avril.” (MPU008076!, MPU008078!, LY0130366 [digital image!], P05171516!).

Battandier [35] rescued and validated this unpublished name by John Gay, which was taken into consideration by later authors such as Munby [36,37]. We have not been able to check Gay’s original manuscript, which is kept at Kew Main Library. Battandier and Trabut’s description mentions three sites with not much detail on dates or collection numbers, but mentioning three localities: Le Kreider, Biskra, and Tunisia. Baum [3] who did have access to Gay’s manuscript, stated that the holotype was a specimen at K, belonging to the Balansa 671 gathering, and mentioning other copies present at E, G, O and W. The only specimen found at K (K000242686; Figure 2a) is here corrected to lectotype (Art. 9.10 of the ICN), and all other specimens belonging to Balansa 671 are therefore isolectotypes. Given that the valid publication was accomplished by Battandier [35], materials collected around Biskra in 1853 and belonging to Balansa 989 can be considered as syntypes. There is an issue with the right spelling of T. bounopoea. In some taxonomical databases [29,30,31], it appears as “Tamarix bounopaea”. Others [23,28] admit double entries, either with “a” or “o”, which difficult the location of the specimens. Both the original publication by Battandier [35] and labels on original materials use the spelling “Tamarix bounopoea”. Therefore, we consider this latter variant to be the original and correct spelling to be used onwards. The name T. bounopoea is currently accepted as a synonym of T. boveana Bunge [38].

3.3. Tamarix malenconiana Maire in Bull. Soc. Hist. Nat. Afrique N. 35: 194. 1935.

Type: [Morocco]. “DR. MAIRE – Iter maroccanum XXIV. Socio D^re E Wilczek 1934. Tamarix Malenconiana Maire. Ad ripas fluminis Drâa prope Zagora. Leg. G. Malençon. die 23 februarii” (indicated as “holotype” by Baum [3], and corrected here to lectotype): P00166729!; isolectotype: MPU003361!).

Tamarix malenconiana was described by Maire [39] on materials collected by G. Malençon near Zagora (Morocco). Baum [3] stated that the “holotype” of the name was kept at P, and included that specimen under the studied material of T. africana. There is indeed a specimen (P00166729; Figure 2b) that matches Maire’s protologue. However, the presence of a duplicate specimen at MPU (MPU003361) means that Baum’s indication is to be considered a lectotype designation, and it is accordingly corrected here (Art. 9.10 of the ICN). After examining the available original material, we have some doubts about the taxonomic placement of T. malenconiana. The floral parts fall into an intermediate range between T. africana and T. gallica. Moreover, the collection date and phenology does not match with the afore mentioned species. There are still several features we have not been able to observe in the field on specimens that south of Morocco. There is scarce information regarding if those specimens are evergreen or deciduous, and the extant phylogenetic information [2] did not include specimens collected around that area. Therefore, we prefer not to provide a taxonomical adscription to this name, until new observations on living material or more complete collections are available.

3.4. Tamarix muluyana Sennen, Diagn. Nouv.: 189. 1936

Type: [Morocco]. “1933.- PLANTES D’ESPAGNE.- F. SENNEN. Nº 8784. Tamarix muluyana Sennen. Maroc: Ulad-Settut, bords du Muluya. 12-X. Leg. Hno. Mauricio” (indicated as “holotype” by Baum [3], and corrected here to lectotype): MA79042!; isolectotypes: BC137946 [digital image!], G00015652!, H1380512 [digital image!], MPU009320!, P00166732!, RAB008049 [not seen], VAL157910!, W1934-7864!).

The name Tamarix muluyana was first published without a description or diagnosis [40] and therefore it was a nomen nudum (Art. 38 of the ICN). However, three years later Sennen [41] validated the name by providing a proper diagnosis. Baum [3] stated that the “holotype” was housed in Madrid (MA), and cited isotypes at BM, G, P and W. Nevertheless, the protologue [41] did not refer to a single voucher, but to an entire gathering distributed in the exsiccata “Plantes d’Espagne - F. Sennen - 1933”, numbered 8784: “Hab.–Maroc: Ulad-Settut, rives du Muluya. Leg. Hno. Mauricio”. Given that vouchers of the same collection are scattered in different herbaria, the only specimen found in MA (MA79042) should be considered not a holotype but a lectotype designated by Baum [3], which is accordingly corrected here (Art. 9.10 of the ICN). We consider T. muluyana as a perfect example of an autumnal bloom of T. gallica, which is congruent with Sennen’s comment in the protologue: “gr. gallica?”

3.5. Tamarix tenuifolia Maire & Trab. in Bull. Soc. Hist. Nat. Afrique N. 25: 296. 1934.

Type: [Algeria]. “D^r R. MAIRE – Itinera Algerica 1933. Tamarix tenuifolia Maire et Trabut. In Saharae septentr. ditione Oued Rhir, prope El_Arfiane in salsuginosis. 19-3.” (indicated as “holotype” by Baum [3], and corrected here to lectotype): P00166709!; isolectotypes: BC137954 [digital image!], RAB013568 [ReColNat data (not seen)], P00166711! [“D^r R. MAIRE – Itinera algerica. HERBIER DE L’AFRIQUE DU NORD Tamarix tenuifolia Maire et Trabut. In ditione Oued Rhir, prope el Arfiane in salsuginosis corolla alba 19-3-1933.”]). Syntypes: “UNIVERSITÉ D’ALGER. HERBIER DE L’AFRIQUE DU NORD. Tamarix tenuifolia Maire et Trabut (Typus). Sahara: Oued Rhir, dunes salées a El Arfiane. Leg D^r L. Trabut nº 2394. 20.3.1918. Dr R Maire.” (MPU003236!, P00166710!); “(Tamarix tenuifolia Trabut) El Arfiane 20 mars 1928 [sic]. 2394” (MPU003237!, MPU003238!).

In the protologue of Tamarix tenuifolia, Maire [42] wrote about the species: “Hab. in salsuginosis dittionis Oued Rhir Saharae algeriensis, prope El-Arfiane ! (TRABUT)”. Maire also explained he was able to study living specimens himself at that locality in 1933, which convinced him T. tenuifolia was a rightful species. There are specimens at several herbaria from at least two gatherings that can be considered as original material: (i) the collection Trabut 2394 made in March-1918 that matches Maire’s habitat indication, though it was not explicitly cited; and (ii) the gatherings made by Maire at the type locality in 1933 that surely correspond to those living specimens referred to in the protologue. Baum [3] stated that the “holotype” was one of the Maire’s specimens collected in 1933 of which he transcribed the label information, and isotypes were cited to be present at FI and RAB. Although two specimens kept at P belong to Maire’s 1933 gathering, P00166709 can be traced as the one mentioned by Baum [3] by literal transcription of its label, which shows slight differences regarding the one on P00166711. Given that there are several syntypes and no clear indication of a precise specimen by Maire, Baum’s holotype mention is here corrected to lectotype designation (Art. 9.10 of the ICN). Other copies of that gathering must be considered isolectotypes, and specimens belonging to Trabut 2394 are to be regarded as syntypes. It is worth mentioning that two of those syntypes at Montpellier (MPU003237, MPU003238) bear a smaller label showing a different collection year, March-1928, which is considered here a transcription mistake for March-1918. Tamarix tenuifolia can be found at some taxonomic treatments as a synonym of T. passerinoides [3,4,21]. However, it belongs to a group of taxa with amplexicaul leaves and 10-stamened flowers that is in need of deeper taxonomic revision to clarify the real number of different species involved.

3.6. Tamarix tingitana Pau in Mem. Soc. Esp. Hist. Nat. 12: 293. 1924.

Type: [Morocco]. “VIAJE BOTÁNICO POR LA MAURITANIA por C. PAU.- Abril y Mayo 1921. Comisión de la Real Sociedad Española de História Natural. Tamarix tingitana Pau. De Tanger a Fondak. 2 mayo” (holotype: MA78992!; isotype: MPU008862! “UNIVERSITÉ D’ALGER HERBIER DE L’AFRIQUE DU NORD Tamarix tingitana Pau fragmentum typi M. Tanger Leg C. Pau”; Label 2: “Tanger a Begazen 2 mayo 1921 C. Pau”).

Tamarix tingitana was described by Pau [43] from material collected in northern Morocco. The protologue only includes a location reference indicating “De Tánger al Fondak” [from Tangier to El Fondak]. Only one specimen with that information on the label has been found (MA78992; Figure 4a). Given that no other materials are available, it is acceptable that this is the specimen upon which Pau based his description and, therefore, it should be considered as the holotype of T. tingitana as Baum [3] already pointed out. However, there is a specimen in the Montpellier herbarium (MPU008862) that is supposed to contain a fragment of the type. The collection date and the collector information match with those in the holotype, however, the locality differs slightly and does not mention El Fondak, but “Begazen”. At that time, El Fondak was a spot on the route between Tangier and Tétouan, but we have not been able to locate Begazen. If we assume that the fragment at MPU008862 was taken from the holotype (“fragmentum typi”, as shown on the accompanying label), we have to consider that voucher an isotype. Tamarix tingitana is currently regarded as a synonym of T. africana [3,21].

3.7. Tamarix trabutii Maire in Bull. Soc. Hist. Nat. Afrique N. 22: 35. 1931.

Type: [Algeria]. “D^r R Maire – Iter Saharicum. HERBIER DE L’AFRIQUE DU NORD. Tamarix trabutii Maire. In montibus Emmidir (Mouydir) Haci-el-Kheneg, in alveo amnis. 310 m. 28-2-1928. nº 253” (indicated as “holotype” by Baum [3], and corrected here to lectotype): P00166707!; isolectotypes: FI000642 [digital image!], MPU002363!, MPU002364!, RAB008000 [not seen]).

Maire [44] described T. trabutii explicitly citing a precise gathering (Maire 253). Baum [3] stated that the “holotype” was kept at P, with isotypes at FI, RAB and US. We have traced two additional vouchers belonging to Maire 253 at MPU. Given that no specific voucher among the original material was designated by Maire [44], Baum`s indication of “holotype” is here corrected to valid lectotype designation (Art. 9.10 of the ICN) on the voucher P00166707 (Figure 4b). Regarding the taxonomic identity of T. trabutii, it is usually considered a synonym of Tamarix amplexicaulis [4,21]. However, we would keep our reservations since deeper taxonomical and phylogenetic studies will deal with the 10-stamened and amplexicaul-leaved group already commented in the above entry of T. tenuifolia.

3.8. Tamarix valdesquamigera Sennen, Diagn. Nouv.: 125. 1936.

Type: [Morocco]. “1931 - PLANTES D’ESPAGNE.- F.SENNEN. Nº 7846. Tamarix valdesquamigera Sennen. grex gallica. Maroc: Lit et marges du Nékor, Route d’Alhucemas. 7-VII. Leg. Sennen et Mauricio.” (indicated as “holotype” by Baum [3], and corrected here to lectotype): MA78835!; isolectotypes: BC137955 [digital image!], G00015654!, MPU008382!, MPU008383!, VAL157907!, W1933-5245!).

First published as a nomen nudum (Sennen and Mauricio [40], Tamarix valdesquamigera was validated by Sennen [41] with a description, the indication of a collection number (nº 7846), and a location described as “Marges du Nekor et de l’Amekran, dans leur cours inférieur”. On that basis, Baum [3] cited a specimen kept at MA (MA78835; Figure 5a) as the “holotype”, alongside isotypes kept at G and BM. All specimens mentioned by Baum, together with some others found by the authors during the last years, are in fact syntypes. Therefore, Baum’s mention of holotype is corrected here to effective lectotype designation (Art. 9.10 of the ICN). The remaining materials should be considered isolectotypes. Tamarix valdesquamigera is currently considered a synonym of T. gallica [21].

3.9. Tamarix weyleri Pau in Mem. Soc. Españ. Hist. Nat. 22: 293. 1924, “weylerii”.

Type: [Algeria]. “VIAJE BOTÁNICO POR LA MAURITANIA por C. PAU.- abril y mayo 1921. Comisión de la Real Sociedad Española de Historia Natural. Tamarix Weylerii Pau, p. 31. Tetuan; Río Martín, cerca del paso de la barca, margen derecha del río. Mayo” (indicated as “holotype” by Baum [3], and corrected here to lectotype: MA78856!). Syntypes: “VIAJE BOTÁNICO POR LA MAURITANIA por C. PAU.- abril y mayo 1921. Comisión de la Real Sociedad Española de Historia Natural. Tamarix Weylerii Pau, Pl de Yébala, 31. T. gallica Weyler, catálogo. Tetuan ad ripas fluminis, 8 Mayo” (MA78854!); “VIAJE BOTÁNICO POR LA MAURITANIA por C. PAU.- abril y mayo 1921. Comisión de la Real Sociedad Española de Historia Natural. Tamarix Weylerii Pau. Tetuan 15 Mayo” (MA78855!); “UNIVERSITÈ D’ALGER. HERBIER DE L’AFRIQUE DU NORD. Tamarix weyleri Pau. Fragmentum typi. M. Tétouan. Leg. C. Pau. Dr R. Maire” (MPU008866!).

Tamarix weyleri was described [43] including the type locality: “Margen derecha del río Martín, antes de llegar a la barra [sic; most probably a typographic error for “barca”, which is indeed annotated on the label of the type material in Pau’s hand], en el camino de Beni Hozmar a Tetuán” [Right bank of Martín river, before the bar (sic; surely a mistake for ”boat”), on the way from Beni Hozmar to Tétouan]. Baum [3] regarded the specimen MA78856 (Figure 5b) as the t“holotype” of the name. That specimen was collected by Pau and shows a label with an almost perfect match with the location described in the protologue. However, there are some other specimens at MA that were collected by Pau around the same date (May-1921) in Tétouan and the Martín river and labelled by himself as T. weyleri. Moreover, a small fragment of the type material is preserved at MPU. All those specimens are to be considered syntypes, since it is almost sure that Pau used all of them for the description associated to T. weyleri. Therefore, Baum`s mention of holotype is here corrected to lectotype, and hence considered a valid lectotypification (Art. 9.10 of the ICN). Tamarix weyleri is currently considered a synonym of T. gallica [21].