Nomenclatural review of Acalypha (Euphorbiaceae) of the Western Indian Ocean Region (Madagascar, the Comoros Archipelago, the Mascarene Islands and the Seychelles Archipelago)

Abstract This work presents a critical nomenclatural review of the Acalypha species of the Western Indian Ocean Region (Madagascar, the Comoros Archipelago, the Mascarene Islands and the Seychelles Archipelago). This is the first treatment of Acalypha of Madagascar since Leandri’s monograph in 1942. A total of 151 scientific names related to Acalypha from this region are treated. We recognise 35 species (28 native and seven introduced), treat 93 names as synonyms (28 of them for the first time) and identify three as doubtful or excluded names. We designate lectotypes for 41 names, make two new combinations and propose one new name.


Nomenclatural review of Acalypha (Euphorbiaceae) of the Western Indian Ocean Region (Madagascar, the Comoros Archipelago, the Mascarene Islands and the Seychelles Archipelago) Introduction
This work is part of the taxonomic and biogeographic revision of Acalypha (Euphorbiaceae) in the Western Indian Ocean Region (WIOR). According to the Taxonomic Databases Working Group standards (Brummit 2001), this region includes Madagascar, the Mascarene Islands (Mauritius and the French Department of Réunion), the Comoros Islands (Union of the Comoros and the French Department of Mayotte) and the Seychelles Archipelago. There are no species of Acalypha known from any of the smaller Scattered Islands of the Western Indian Ocean. The first two species of Madagascan Acalypha (A. filiformis and A. venosa) were described by Poiret (1804) in Lamarck's encyclopaedia. More than half a century later, Baillon (1861) published Euphorbiacées Africaines, Afrique Orientale (Bourbon, Maurice, Madagascar, Zanguebar etc.), where 21 species of Acalypha are cited, of which 19 are from the study area. Baker (1883Baker ( , 1884, 20 years later, described four new species. In 1891, Baillon, in his contribution to Grandidier`s Histoire Physique, Naturelle et Politique de Madagascar, provided 10 excellent plates of Acalypha species from Madagascar, five of which are cited for the first time . These plates are not accompanied by descriptions or any additional information. Soon thereafter, Baillon ( , 1895a published in several chapters his Liste des Plantes de Madagascar citing 32 Acalypha species, six of which were newly described. In the treatment of Acalypha for Engler´s Das Pfanzenreich,  included 31 species from WIOR. In this work, Acalypha was formally divided into three subgenera, "Euacalypha", Androcephala and Linostachys; the first two occur in WIOR. The most recent work treating Madagascan Acalypha ) is now almost 80 years old. Leandri's work included complete information about 22 species and 14 varieties of Acalypha, of which eight species and six varieties were described for the first time.
Only three floristic works included Acalypha species from the other islands of the Western Indian Ocean region. Baker (1877) cited five species from Mauritius and the Seychelles and de Cordemoy (1895) treated five species from Réunion. Most recently,  included five species, three subspecies and seven varieties from the Mascarene Islands.
While undertaking this nomenclatural review, we found 144 names related to Acalypha from the study area, many of which involved serious problems of taxonomic identity. All of these names have been evaluated in this work and our interpretation of their current taxonomic status and distribution is presented in Tables 1 and 2. Our aim is to lay the foundation for a complete taxonomic and biogeographical revision of Acalypha in the WIOR, a region of particular relevance to the origin and evolution of this genus. Preliminary results of Acalypha molecular phylogeny (Levin et al. 2005) suggest that the genus first appeared in Africa, where the highest morphological diversity within the genus is found. We share the same purpose as the recently published WIOR nomenclator of Croton (Berry et al. 2017), the second largest genus of the Euphorbiaceae, preceded by Euphorbia (Horn et al. 2012) and followed by Acalypha.

Materials and methods
We conducted a thorough bibliographical review and consulted the following herbaria for the Western Indian Ocean Acalypha types: B, BM, BREM, BRNU, C, CAS, G, GB, GDC, GH, JE, K, M, MA, MAU, MO, MPU, NY, P, S, US, TAN, TUB and W (acronyms according to Thiers 2018). Scanned images of types from these and other herbaria, available on JSTOR Global Plants (http://plants.jstor.org/), were also consulted.
The accepted species are cited in alphabetical order and all known synonyms are included, except for the introduced species. We include the notation "syn. nov." whenever we newly treat a taxon as a synonym. We provide details of the type collection(s) for each name. Lectotypes are designated after a careful review of the relevant original literature and examination of the nomenclatural types.
Five of the Acalypha treated names were illustrated first, without description, in Baillon`s Histoire Naturelle des Plantes . These are A. diminuta, A. humblotiana, A. leptomyura, A. madreporica and A. polynema. Except A. humblotiana, we consider each of the plates provided, which include extensive vegetative and reproductive morphological details, as the holotypes of the associated names, according to art. 38.8 of the ICN (McNeill et al. 2012).
When two or more syntypes were cited in the protologue, a lectotype is designated, using the best preserved specimen or the one most consistent with the protologue. The remaining syntypes are also cited.
The type locality information is taken mainly from the type specimen labels. We add additional information such as the province name of Madagascar or a modern or accepted spelling of a place name. If the locality is ambiguous or imprecise, we keep the literal citation (in quotation marks) as it appears in the protologue. Barcode numbers of type specimens are cited when available.
Under the "Distribution" section, we list the general distribution of each species in Africa (following Brummit 2001), if they occur there and in the WIOR region. We include the Madagascar provinces or island names within the studied archipelagos where they occur. This information should be taken as preliminary until a more complete study of the genus, in progress, is completed.
In the references section, we only include references which cite Acalypha in the WIOR region.
All information gathered as part of this work, including the complete listing of studied specimens, is available online at the regularly updated Acalypha Taxonomic Information System website, www.acalypha.es .

Results and discussion
In the present work, we record 151 published scientific names related to Acalypha of the WIOR (Table 1). Of these, 35 are accepted names, 93 are considered synonyms and three are doubtful or excluded (A. neptunica Müll.Arg., A. spiciflora Burm.f. and A. venosa Poir.). We also include 19 nomina nuda found in literature and one nomen invalidum. Type specimens are indicated for all valid names and we have designated 41 lectotypes.
In Madagascar, we accept 28 species, 23 native (of which 20 are endemic) and five introduced (Table 2).  recognised 22 species of Acalypha from Madagascar, of which we accept 19 (including A. gagnepainii under its correct name, A. medibracteata). We consider A. andringitrensis to be a synonym of A. radula. Our concept of what Leandri called A. reticulata is narrower than his; we consider A. reticulata s.s. (under its correct name, A. filiformis) to be endemic to the Mascarines and treat the Madagascan material Leandri assigned to this species as four distinct species (A. gracilipes, A. lamiana, A. paxii and A. urophylla). We exclude the name Acalypha spiciflora (accepted by Leandri), because it is not an Acalypha. We report two species, A. fimbriata and A. lanceolata, not previously cited for Madagascar. We also treat the name A. madagascariensis, previously excluded by Leandri, as a synonym of A. fasciculata. We anticipate the description of at least 2 more new species from Madagascar based on the material we now have on hand.
In the Comoros Archipelago, there are seven species of Acalypha, four native (one endemic) and three introduced, one of which, A. bailloniana, is first reported here. There are seven species on the Mascarene Islands, three native (all endemic) and four introduced. There are four species on the Seychelles, one endemic and three introduced.   Hutchinson (1913) and this treatment was followed in the subsequent floristic works. Radcliffe-Smith (1987 treated A. bailloniana as a synonym of A. indica. We consider that A. bailloniana is a distinct species which can be distinguished from A. indica by its dentante bracts with a prominent central tooth and with glandular hairs (vs. subentire bracts without prominent central tooth and without glandular hairs, in A. indica). A. bailloniana is distributed in the east coast of tropical Africa and cited for the WIOR region for the first time, where it is probably introduced. References. Baillon (1891: Pl. 192 as A. codonocalyx); Palacký (1907: 24); Voeltzkow (1917: 447); Pax and Hoffmann (1924: 165); Leandri (1942: 280); Govaerts et al. (2000: 55).  A. aldabrica;Fosberg (1974: 263); Renvoize (1975: 152); Robertson (1989: 199); Govaerts et al. (2000: 56).

Acalypha decaryana
Notes. Acalypha diminuta was first illustrated, without description, in Baillon`s Histoire Naturelle des Plantes ). The first description of this species, based only on Baillon`s illustration, appears in Engler`s Pflanzenreich . This is the only species included in Acalypha subgen. Androcephala Pax & K.Hoffm.  Palacký (1907: 25); Pax and Hoffmann (1924: 94) A. madreporica; Pax and Hoffmann (1924: 171); Leandri (1942: 283); Leandri (1948: 186 Notes. The correct number of the type specimen of A. madagascariensis is Humblot 447. In the protologue of this name, it is wrongly transcribed as "Humblot 449, which corresponds to a specimen of Psorospermum (Clusiaceae). Notes. Acalypha reticulata has been usually considered as the accepted name of this species.  noticed that A. filiformis and A. reticulata are conspecific, but he kept A. reticulata as the accepted name. Applying the rule of priority, the accepted name must be A. filiformis and A. reticulata should be placed as a synonym. Notes. This is the first time that this species is cited for the WIOR region, where it is almost certainly introduced.  Palacký (1907: 25); Pax and Hoffmann (1924: 106) as A. integrifolia var. gracilipes; Govaerts et al. (2000: 69, 100).

Acalypha gracilipes
Notes. Acalypha gracilipes has been usually treated as a variety of A. integrifolia Willd., which is endemic of Mascarene Islands, but A. gracilipes can be clearly distinguished by its elliptic-lanceolate leaves, denticulate female bracts and glabrous and glandular ovaries, vs. linear-lanceolate leaves, entire female bracts and hispidulous and echinate ovary in A. integrifolia.
A. gracilipes can be distinguished from both A. urophylla Boivin ex Baill. and A. paxii Aug.D.C. mainly by its glabrous leaves with crenate to subdentate margins and obtuse to subacute apices, glabrous female bracts and glabrous ovaries with minute sessile glands, vs. pubescent leaves with serrate margins and acuminate (A. urophylla) or usually caudate (A. paxii) apices, pubescent female bracts and hispidulous ovaries with long papillae. In addition, the female bracts of A. paxii have a prominent central tooth, which is absent in both A. gracilipes and A. urophylla. Leandri (1942) included the collection H. Perrier de la Bâthie 9746 as Acalypha reticulata var. cloiselana Leandri, however the specimen of this collection in P (P00513170) corresponds to A. urophylla. Burm.f., Fl. Ind. 303, pl. 61, f. 1 Palacký (1907: 25); Robertson (1989: 199).

Acalypha hispida
Notes. This shrub, native to Melanesia or Malesia, is frequent in gardens throughout the tropics and rarely appears naturalised. As all plants are pistillate, it can only reproduce clonally. We found collections from Madagascar and Seychelles where it is cultivated. It has been reported from Madagascar , Mauritius (Bojer 1837; Baillon 1861), Réunion (Baillon 1861: 274) and the Seychelles (Robertson 1989 A. urophylla). After studying the numerous type collections, it seems clear to us that A. lamiana must be considered as a distinct species. A. lamiana differs from A. urophylla mainly by the leaves that are rounded at the base and reddish at the margins and its subentire, eglandular female bracts vs. leaves that are usually acute at the base and not reddish at the margins and dentate female bracts with small sessile glands at margins, in A. urophylla.

Acalypha linearifolia
Acalypha humblotiana was first illustrated, without description, in Baillon`s (1891) Histoire Naturelle des Plantes, but this illustration is not consistent with Baillon`s (1895b) later description nor with the specimen on which the description presumably is based (L. Humblot 1461).

Acalypha perrieri
Notes. The specimens, indicated as isolectotypes, do not have Richard's original label. They instead have labels with Baillon's handwriting giving the location as "Madagascar". We believe that the correct location is the one indicated on the selected lectotype, "Ile Mohilla", whose current name is Mohéli, in the Comoros Archipelago. A search of specimens at P showed that Richard's collections numbered 284-286, 288, 290, 291 and 293 are also from Mohéli (289 has no locality and 292 is not listed). Richard 544 has an apparently original label showing the locality only as "Madagascar." Collections at P with nearby numbers are labelled as being from either "Nord de Madagascar" or "Ile Nos-bé" (now Nossi-bé), so this collection could be from northern Madagascar, although we have seen no other specimens from outside the Comoros Archipelago.