Manihot takape sp. nov. (Euphorbiaceae), a new tuberous subshrub from the Paraguayan Chaco

Abstract Manihot takape De Egea & Peña-Chocarro, sp. nov. is described and illustrated as a new species from the Paraguayan Chaco. It was collected while carrying out fieldwork related to the study of the most important Wild Crop Relatives of the country’s flora. Morphological characteristics that differentiate this species from closely related taxa, as well as its habitat, geographical distribution and conservation status are provided.


Introduction
Manihot Mill. (Euphorbiaceae) is a Neotropical genus, most likely of Mesoamerican origin, which diversified secondarily throughout South America, colonising all available types of lowland and seasonally dry environments (Deputié and Salick 2011), with the greatest centre of diversity in Brazil (Silva and Sodré 2014). The taxonomy of Manihot was first studied by Pohl (1827) and Pax (1910), but it was not until Rogers and Appan (1973) that the most complete taxonomic study of the genus was carried out. They recognised 98 species organised into 19 sections and distributed from Texas to Argentina. Several new species, however, have been described in recent years, mainly from Brazil and Bolivia, increasing this number to more than 120 species (Mendoza 2014, Mendoza 2016, Silva 2014, Silva 2015, Inocencio and Silva 2016, Silva et al. 2017, Lopes Martins et al. 2018. In Paraguay, the genus is represented by 15 taxa, of which 6 are endemic to the country (Rogers and Appan 1973, Peña-Chocarro and De Egea in press). The majority of them are found in the Oriental region of the country, while only four occur in the Chaco region.
During botanical expeditions to the Chaco region, while carrying out research on the most important genera of Wild Crop Relatives of the Paraguayan flora, a collection of Manihot was made that could not be assigned to any known species. Later, herbarium specimens with similar diagnostic characters were found and these had been misidentified as another species of Manihot. In this paper, we assign these specimens to a new taxon, which we describe under the name Manihot takape De Egea & Peña-Chocarro. The species is illustrated and its geographical distribution, ecology, phenology and conservation status are included. The new species is compared with M. anomala Pohl subsp. glabrata Chodat & Hassl. and M. populifolia Pax, which, in morphological terms, are the most similar taxa amongst the species found within Paraguay.

Materials and methods
The description of this new species is based on field observations of wild populations and the examination of herbarium specimens deposited in BM, CTES, F and FCQ. Specimens of Manihot from Paraguay deposited in K and MA were also reviewed, but this species was not found. The holotype collection was deposited in FCQ and duplicates can be found in BM, CTES and G. The terminology used for general morphology is in compliance with Rogers and Appan (1973).
Distribution and ecology. This species has been collected in dry areas of the Paraguayan Chaco, more specifically within the Departments of Boquerón and Presidente   Etymology. The specific epithet stems from the vernacular name takape (Guarani language). This word is used for a particular habitat characterised by a wooded savannah or open woodland (Bertoni 1940). The word is also applied to small woody plants (i.e. subshrubs). This is based on the word takã (twig or branch) and the suffix 'pe' (short or dwarf ). Both meanings fit the newly described species of Manihot.
Conservation status. A preliminary conservation assessment with the GeoCat Tool indicates that M. takape can be initially considered as Endangered, with an extent of occurrence of 1,887 km 2 and an area of occupancy of 28 km 2 (based on an UICN default cell width of 2 km). Furthermore, with only 5 locations known to this date and considering the high deforestation and land use changes in the Paraguayan Chaco (Arévalos et al. 2018, Cardozo et al. 2013, Huang et al. 2009, Mereles and Rodas 2014, Yanosky 2013, the preliminary UICN category proposed for this species is Endangered B1ab(iii)+2ab(iii). It is worth mentioning that the type locality, known as Parque Valle Natural in Neuland, Boquerón, is a private reserve of approximately 0.5 km 2 that harbours a small population of the new species. The current conservation status of the remaining four locations is unknown. Further field observations and collections are strongly recommended to achieve a more conclusive conservation assessment.

Discussion
Manihot takape, as far as known, is restricted to a particular area of the Paraguayan dry Chaco and its diagnostic characteristics and ecological associations are consistent amongst all 10 specimens examined. It stands out from other Manihot species of the region (taking into consideration the entire Paraguayan territory and border areas) by its predominantly unlobed leaves, the particularly long, glabrous inflorescences and its subshrubby, decumbent or "clambering" habit; the latter term, following Rogers and Appan (1973), refers to plants with stems that start erect, but may later drop over.
Due to the presence of both lobed and unlobed leaves and the basal (or nearly so) petiole attachment, the new species is morphologically most similar to Manihot anomala Pohl subsp. glabrata (Chodat & Hassl.) D.J.Rogers & Appan, from which it differs by the characters shown in Table 1. M. anomala subsp. glabrata is an erect and taller plant, frequently with a shrubby or tree-like habit up to 3 m, with mostly lobed leaves except for the ones close to the inflorescence, and inflorescences normally to 15 cm long with flowers densely pubescent to velutinous. In terms of habitat, M. anomala can be found in a wide range of vegetation types: subhumid and xerophytic Due to its subshrubby habit and predominance of unlobed leaves, Manihot takape can also be mistaken for M. populifolia Pax, from which can be easily differentiated by the petiole insertion, which is basal or essentially so in the former and peltate in the latter. In addition, the species also have different habitat preferences, with M. populifolia being a species known from cerrados of the Amambay and Concepción departments in the Oriental region, where it also seems to have a restricted distribution range (Zuloaga and Belgrano 2018). There is one record of M. populifolia from Chuquisaca, Bolivia (Jørgensen et al. 2015 onwards), but the specimen (Pensiero & Marino 4380, MO) could not be examined to confirm its determination. However, based on examination of the digitised image of this specimen available from TROPICOS, we believe it might be misplaced within M. populifolia and that it could actually be a collection of M. takape.
Similarities between Manihot takape and the two aforementioned species indicate that the new species could belong to one of their sections, Sinuatae or Peltatae, respectively, according to Rogers and Appan (1973). However, recent molecular evidence (Deputié and Salick 2011) highlights the need for a major reclassification of the genus Manihot. According to their results, cerrado shrubs are placed in a well supported clade that includes M. anomala. Undoubtedly, molecular data are needed for a complete assessment on the infrageneric placement of the newly described species.