Sesuvium crithmoides Welw., Ann. Conselho Ultramar. ser. 1: 586 (1859)

Sukhorukov, Alexander P., Nilova, Maya V., Erst, Andrey S., Kushunina, Maria, Baider, Claudia, Verloove, Filip, Salas-Pascual, Marcos, Belyaeva, Irina V., Krinitsina, Anastasiya A., Bruyns, Peter V. & Klak, Cornelia, 2018, Diagnostics, taxonomy, nomenclature and distribution of perennial Sesuvium (Aizoaceae) in Africa, PhytoKeys 92, pp. 45-88 : 59-63

Sesuvium crithmoides Welw., Ann. Conselho Ultramar. ser. 1: 586 (1859) Figs 10 , 11

Lectotype

(designated here by Sukhorukov). ANGOLA, distr. Loanda [Luanda], in arenosis maritimis de Ilha de Loanda [on sandy seashores of Loanda Island], 12 Jun 1858, Welwitsch 2386 (BM000839897! specimen on the left; isolectotypes - BM001209752! BM001209753! K000076292! P04602195! COI00070549! [photo seen], LISU031837! [photo seen]).

Note.

Welwitsch collected this new species in 1854 and 1858 from several neighbouring locations in Luanda Province. All examined sheets were labelled with the same collector’s number (2386) and the location of the lectotype specimen is close to that mentioned in the protologue (Barra do Dande settlement, ca. 30 km N of Luanda). Surprisingly, none of the authentic specimens contained the name of Barra do Dande ( Welwitsch 1859) and the species itself was not mentioned in a subsequent treatment of the genus (Welwitsch in Oliver 1871).

- Sesuvium mesembryanthemoides Welw., Ann. Conselho Ultramar. ser. 1: 557 (1859), nomen nudum

Note. Welwitsch (1859) mentioned the name Sesuvium mesembryanthemoides (nomen nudum) for the first time, but did not describe the plant morphologically ("Uma nítida espécie de Sesuvium " [a distinct species of Sesuvium ]). He probably supposed that it was conspecific with S. crithmoides , which was described in the same article ( Welwitsch 1859). As mentioned above, all sheets of S. crithmoides and S. mesembryanthemoides (nomen), collected by Welwitsch, have the same collection number (2386).

= Sesuvium mesembryanthemoides Wawra in Wawra & Peyr., Sitzungsber. Acad. Wien, Math.-Nat. 38: 564 (1860).

Lectotype (designated here by Sukhorukov). [ANGOLA] Benguela, Dr Wawra 210 (LE!).

Note. Interestingly, Wawra collected the same species in Angola independently from Welwitsch and used the same epithet " Sesuvium mesembryanthemoides " for his new Sesuvium . Unfortunately, the original sheets of S. mesembryanthemoides Wawra cited in the protologue ("in littore maris prope Benguelam, Wawra 210 ": Wawra and Peyritsch 1860) were destroyed in B, W or WU ( Bohley et al. 2017; Johannes Walter, pers. comm.). Wawra and Peyritsch (1860) reported the presence of four to six bracteoles in the flowers of S. mesembryanthemoides and it therefore evidently differs from S. congense (with similar narrow leaves), which has flowers with two bracteoles only. Bohley et al. (2017) have designated the lectotype of S. mesembryanthemoides Wawra in the herbarium LISU (with isolectotypes in BM, BR, C, COI, K, LE) based on Welwitsch’s specimens ("Mossamedes [Namibe], seashore, 1 Jul 1859, Welwitsch 2389 "). However, the material collected by Welwitsch in Namibe province of Angola is not mentioned in the protologue of S. mesembryanthemoides Wawra and does not belong to the original material. Therefore, this lectotypification cannot be accepted. A lectotype using a Wawra’s specimen (syntype) seen in LE has been selected.

= Sesuvium crystallinum Welw. in Oliver, Fl. Trop. Afr. 2: 586 (1871).

Lectotype (designated here by Sukhorukov): [ANGOLA] Mossamedes [Namibe], hab.[itat] in arenosis maritimis pr.[ope] Mossamedes [on sandy seashores near Mossamedes], Jul 1859, Welwitsch 2389 (BM000839898! isolectotypes - C, COI, G! K! LE! LISU).

Two locations ( “Mossamedes” and “Benguela”) were indicated in the protologue. The lectotype of Sesuvium crystallinum is selected here from the specimens collected by Welwitsch with the number 2389 which were located in different herbaria including LISU ( “holotype” in Bohley et al. (2017); not correctable to “lectotype” under Art. 7.10).

Taxonomic and nomenclatural notes. The type material of S. crithmoides comprises the plant fragments with narrow (linear or lanceolate) leaves reaching 8 cm in length. The leaf length and shape is a single character used for its delimitation from the closely related S. crystallinum ( Gonçalves 1970) and S. mesembryanthemoides Wawra ( Bohley et al. 2017). Both species are considered to have shorter (up to 5 cm) and broader leaves. However, the authentic material and protologue of S. mesembryanthemoides clearly state that this plant was described as a remarkable species with subtriquetrous-terete (narrow) leaves (Wawra in Wawra and Peyritsch 1860). Therefore, the use of S. mesembryanthemoides as a priority name against S. crystallinum ( Hartmann 2002, Figueiredo and Smith 2008, Bohley et al. 2017) with broader and shorter leaves cannot be accepted. In all characters, including leaf length and shape, S. crithmoides and S. mesembryanthemoides are clearly conspecific.

The authors propose to merge the broad-leaved individuals ( S. crystallinum ) with S. crithmoides for the first time. Observations by the authors in Angola (C. Klak and P. Bruyns) did not confirm the separate existence of “short-leaved” or “long-leaved” plants. Other morphological and carpological characters are the same in both S. crithmoides and S. crystallinum . Only S. crithmoides (Winter 7786 (PRE) from Baba, Angola) was included in the molecular analysis ( Bohley et al. 2017).

Sesuvium crithmoides was considered as an endemic to Angola, although with possible records in coastal areas of the DR Congo ( Bohley et al. 2017). One collection of S. crithmoides from the DR Congo (see also Hauman 1951, sub S. mesembryanthemoides ) has been found and was also identified for the Republic of Congo for the first time (previously wrongly labelled as Sesuvium portulacastrum ). All specimens seen from the Republic of Congo or the DR Congo have long and narrow leaves.

Additional specimens examined.

ANGOLA: Benguela prov.: Benguela, [without date] H. Vanderyst 13141 (BR0000013827410); near Benguela, Lobito Bay , 1 Sep 1906, H. Bolus 12453 (BOL); S of Benguela, seashore at Cuio village , 25 Dec 2016, C. Klak 2558 (BOL) ; Cabinda prov: Landana, 9 Aug 1895, A. Dewevre 231 (BR0000013827380), Landana, 15 Aug 1913, Bequaert 616 (BR000000871151); Cabinda, Sumba village , 30 Nov 1957, Lebrun 11195 (BR0000013827441; K) ; Cuanza Sul prov.: Praia de Sousa , 11°36'S 13°47'E, 3 Feb 1975, J.D. Ward 82 (K, WIND) ; Luanda prov.: Luanda, Welwitsch 2380 (LE), the same place, 13 Sep 1955, J. Lebrun 10905 (BR0000013827403) ; Namibe prov.: Cabo Negro , Sep 1859, Welwitsch 2387 (BM); Cabo Negro, Aug 1937, H. Humbert 16391 (BM); the same place, 15 Apr 1973, P. Bamps et al. 4519 (BR0000013827465); Mossamedes [Namibe city], 1937, L.W. Carrisso and F. Sousa 218 (BM); Mossamedes, 21 Sep 1955, J. Lebrun 10926 (BR0000013827472); Baba, 23 Jan 2009, P.J.D. Winter 7786 (LUBA, PRE); seashore at mouth of Rio dos Flamingos, 17 Dec 2016, C. Klak 2551 (BOL) ; DEMOCRATIC REPUBLIC OF CONGO: Kongo Central prov.: Banana , [without date] Gillet S. n. (BR0000013827434); [Nature Reserve] Luki-Mayumbe, 1959, Flamigni 10773 (BR0000013827427) ; REPUBLIC OF CONGO (new records): Kouilou, 5 Sep 1962, L. Makany 63 (P04602222); Djeno Region [Pointe-Noire], 26 Jan 1966, C. Farron 4795 (P04602197 & P04602199); Pointe-Noire, Dec 1958, J. Koechlin 5528 (P04602193) .

General distribution

(Fig. 12 ). Angola, Democratic Republic of Congo, Republic of Congo. Sesuvium crithmoides has been introduced to USA (Georgia, Glynn county, Brunswick, on ballast, 15 Aug 1902, R.M. Harper 1524 (BM!); see also Small (1933)), probably as casual and not naturalised species ( Ferren 2003). The specimen seen also has long and narrow leaves.

Conservation status.

Sesuvium crithmoides has an estimated EOO of 177,271 km2 and AOO of 56 km2. It was found to be common in two localities in Angola (C. Klak 2551 & 2558), where it grows within 50 metres of the sea. Sources of disturbance include vehicles driven along the beach, which was observed near Namibe city. However, vehicles are even now rather few in Angola and much of the southern, very arid Angolan coastline is still relatively pristine. Due to its large EOO and low threat level, the authors therefore recommend this species to be classified as Least Concern (LC) according to the IUCN Red List Criteria ( IUCN 2017).

Figures

Figure 10. General view of Sesuvium crithmoides (incl. S. crystallinum) on the dunes of Rio dos Flamingos, Angola. Photographs by C. Klak and P. V. Bruyns (December 2016).

Figure 11. Parts of the plant of Sesuvium crithmoides: A reproductive shoots B close-up view of flowers. Photographs by C. Klak and P. V. Bruyns (at the mouth of Rio dos Flamingos, south of Namibe, Angola, December 2016).

Figure 12. Distribution map of Sesuvium crithmoides.