Duguetia leucotricha (Annonaceae), a new species from the Atlantic Coastal Forest of Brazil

Abstract A new species of Annonaceae, Duguetia leucotricha M.L.Bazante & Maas, from lowland to submontane forests of southern Bahia, Brazil, is described. It differs from other species of the genus mainly by the dense greyish white stellate hairs on vegetative and reproductive structures, rather widely-spaced flowers, the large bract in the upper part of the well-developed pedicel, sepals and petals almost equal in length, and the few-carpellate fruits with rounded apex of the areoles. Commentaries concerning its morphological aspects and relationships of affinity, geographic distribution, conservation status and photos are provided, as well as a key to all Atlantic Coastal Forest species of Duguetia.


Introduction
The genus Duguetia A. St.-Hil. (1825: 35) is an important ecological component in lowland tropical forests of the Neotropics (Maas et al. 2003).Several species have economic value because of their wood, bark fibers, fruits, and medicinal properties (Maas et al. 2003;Saldanha et al. 2021).Duguetia comprises ca.94 species of trees or shrubs, the majority of which distributed in the Neotropics, from Nicaragua to Brazil, and only four species in Africa (Maas et al. 2003;Maas & Westra 2010;Bazante & Alves 2017).Duguetia belongs to the subfamily Annonoideae, tribe Duguetieae, which also includes four other genera: the African Letestudoxa Pellegr.
Phylogenetic studies support the monophyly of Duguetia and indicate Duckeanthus and Fusaea as its sister genera (Pirie et al. 2005;Guo et al. 2017;Xue et al. 2020).These three genera share the aggregate fruit formed by lateral fusion of carpel walls, or by free, strongly coherent and sessile carpels, with their basal parts immersed in the fruiting receptacle.Another similarity among them is the common presence of a ring-shaped structure at the fruit base, called collar.However, the collar in Duguetia is derived from few, sterile and connate carpels, while in the two other genera it represents the floral receptacle that remains visible.
More than half of the Neotropical species of Duguetia occur in Brazil (67 species), of which ca. 30 are endemic and about 20 classified as threatened (Lobão & Bazante 2020;MMA 2022).Although the majority of the species inhabit the Amazon basin, ca.50 species, the Atlantic Coastal Forest is also an important center of diversity of the genus, with 14 of its 18 species being endemic to this domain (Lobão & Bazante 2020;Bazante & Alves 2021).
The Atlantic Coastal Forest in southern Bahia stands out for its high floristic biodiversity and local endemism, with eight species of Duguetia, four of them locally restricted (Martini et al. 2007;Lobão & Bazante 2020).However, Bahia is nowadays the second Brazilian State in the deforestation ranking, with an increase of 54% between 2020 and 2021 (SOS Mata Atlântica & INPE 2022), adding pressure on its forest remnants.As part of an effort to recognize the taxonomic diversity in the Atlantic Coastal Forest of northeastern Brazil, highlighting this region as a priority for conservation and biological research, a new species of Duguetia, found in southern Bahia, is being described here.

Materials and methods
Specimens of the new species were collected, in addition to others found in CEPEC, JPB, NY and U (herbarium acronyms following Thiers 2020, continually updated).Those in CEPEC and JPB were analyzed in loco.Those in NY and U were studied by their images online in web-based resources such as Reflora -Virtual Herbarium (https:// floradobrasil.jbrj.gov.br/reflora) and SpeciesLink system (https://specieslink.net/).Specimens analyzed are indicated here with an exclamation mark (!).The barcode numbers of the examined specimens are cited within square brackets [bc].Comparative analyzes with known species of Duguetia and the identification key were based on types and other herbarium specimens, protologues, relevant literature (Maas 1996;1999;Maas et al. 1993;1994;2003) and recent fieldwork.
The morphological and indument descriptions were analyzed with a stereomicroscope Leica M125.The terminology adopted was based on Maas et al. (2003).The types of cauliflory followed Mildbraed (1922), where ramiflory refers to flowers borne on the leafless portions of branches and trunciflory to those that borne along the main trunk.In the fruits, the exposed apical part of the carpels is referred to as areoles, and the basal ring-shaped structure composed of sterile connate carpels as the collar (Maas et al. 2003).
Information on habitat, phenology, and color of vegetative and reproductive structures were taken from herbarium labels and field observations.The distribution map was generated in the Quantum GIS 3.16.10software (QGIS 2022) using layers available at IBGE (2022).The preliminary conservation status follows the IUCN Red List Categories and Criteria (2019).The GeoCAT tool (Bachman et al. 2011) was used to estimate the extent of occurrence (EOO) and the area of occupancy (AOO).Duguetia sp.nov.2, Maas et al., Flora Neotropica Monograph 88: 226. 2003 Duguetia leucotricha is distinct from congeneric species by the combination of the greyish white indument of stellate hairs on flowers, fruits, and the lower side of the leaves, the elongated sympodial rachis with rather widely-spaced flowers, the large bract in the upper part of a well-developed pedicel, the flower buds acute and distinctly keeled, the sepals (sub)equaling the petals, and the paucicarpellate fruits of which the apex of the areoles is rounded and apiculate.
Distribution and habitat: Duguetia leucotricha is endemic to southern Bahia, Brazil, where it is known from a few specimens and four populations, which are present in three Conservation Units (UCs): Lagoa Encantada e Rio Almada Environmental Protection Area, Serra do Conduru State Park, and Una Biological Reserve (Fig. 3).According to Jardim (2003)  Conservation status: Duguetia leucotricha individuals are found within UCs, with its few collections resulting in an extension of occurrence (EOO) estimated to be 894.1 km² and in an area of occupancy (AOO) estimated to be 16 km².These data indicate a species with a very restricted distribution and small population sizes.Moreover, the implementation of the UCs in which it is located has been deficient and only achieves partial results of environmental protection.Among the reasons is the lack of infrastructure, human and financial resources to inspect, monitor and recover these areas (Orlando & Cunha 2012).
The APA (environmental protection area) Lagoa Encantada e Rio Almada, one of the UCs with occurrence of the species, had its area expanded and currently presents 157.745 ha (Brasil 2003a).Since then, few studies have been carried out to minimize the environmental impacts on the APA which has been suffering from deforestation, mineral extraction and pollution, for example (Brasil 2015).In the Serra do Conduru State Park, which covers 9.725 ha (Brasil 2003b), the main environmental conflicts involve sporadic inspection, disorderly visits, and cutting and removal of native vegetation.In the Una Biological Reserve, in turn, with an area of 18.500 ha (Brasil 2007), the greatest environmental pressures are hunting, deforestation, real estate speculation and illegal sand extraction (Orlando & Cunha 2012).For these reasons, D. leucotricha is assigned a preliminary status of endangered (EN), considering the criteria of EOO less than 5,000 km², AOO less than 500 km², with distribution in no more than five locations, and continuing decline in habitat area and quality (B1ab(i,ii,iii) + B2ab(i,ii,iii)).
Etymology: The specific epithet derives from the Greek "leucos" for 'white', and "trichos" for 'hairs'.It refers to the white colour of the hairs present on several structures of the plant.
Phenology: Collected with flowers from June to December, and with fruits from December to June.
Taxonomic notes: Maas et al. (2002) mentioned two specimens as a possible new species, both with immature flowers (Santos & Alves 209, CEPEC!, U!).These same specimens were the only ones used by Maas et al. (2003) for the description of Duguetia sp.nov. 2 in the monograph of the genus.These specimens also represent the first collected material of Duguetia leucotricha, dated from 1987, in the municipality of Una.Only after 17 years another specimen was recorded.The former description could be completed with the analysis of additional specimens collected during a botanical trip to the Serra do Conduru State Park in September 2022, in addition to others found deposited in CEPEC, JPB, NY and U.
The inflorescence in Duguetia leucotricha can be either supra-axillary, pseudo-axillary, leaf-opposed to ramiflorous with one rhipidium and inflorescence branch up to 22 mm long, or trunciflorous with two or more rhipidia and inflorescence branches up to ca. 60 mm long.These two types of flower presentation, among leaves and cauliflory, have been found in the same individual (e.g.Bazante et al. 1513).Cauliflory is known in a few species of Duguetia, many of them restricted to the Amazon basin (Maas et al. 2003).In the Atlantic Coastal Forest, four species of the genus can also present flowers along the trunk: Duguetia bahiensis Maas (1993: 83), D. sessilis (Vell.)Maas (1994: 38), D. sooretamae Maas (1999: 486) (Maas et al. 2003;Lopes &Mello-Silva 2014), andD. moricandiana Mart. (1841: 22) (M.L. Bazante, personal observation).D. leucotricha is easily distinguished from these species by its young twigs and lower leaf side with greyish white indument of stellate hairs (vs.yellowish or pale brown indument of entire and/or stellate scales), sepals free (vs.connate for 10-35% of their length) and fruit with areoles depressed ovoid, green when young (vs.areoles pyramidal to broadly obovoid or, if depressed ovoid, pinkish-white to vinaceous when young).
When using the key of the Monograph of Duguetia for Flora Neotropica (Maas et al. 2003), Duguetia leucotricha comes closest to D. granvilleana Maas (1999: 476), due to its indument of stellate hairs on young twigs, leaf shape, free sepals persistent in fruit, and low number of fruiting carpels.On the other hand, D. granvilleana shows great resemblance with D. arenicola Maas (1999: 466) and D. pauciflora Rusby (1920: 18), which already have been considered a single species (Maas 1999;Mass et al. 2003).D. leucotricha differs from these three species, however, by its peduncle 6 mm long or more (vs.0.5-4 mm long), upper bract 6-15 mm long (vs.1-4.5 mm long), distinctly 3-ridged flower buds (vs.not ridged) and ellipsoid fruit (vs.globose to subglobose).Still according to Maas et al.' key, the new species is also related to D. rionegrensis Zuilen & Maas (1994: 233) based on the same previous similarities, but it is distinct mainly by the glabrous upper leaf side (vs.covered with simple and stellate hairs densely concentrated on the primary and secondary veins) and upper bract at 3/4 of the base of the pedicel (vs. at 1/3).Furthermore, D. pauciflora is restricted to Guyana and Venezuela, while D. arenicola, D. granvilleana and D. rionegrensis occur only in the Amazon basin of Brazil, Colombia, French Guiana, and Venezuela (Maas et al. 2003).
Duguetia leucotricha also resembles D. pycnastera Sandwith (1930: 471) by the rhipidum with elongate sympodial rachis, rather widely-spaced flowers, indument of stellate hairs, sepals (sub)equaling the petals, and rounded apex of fruiting areoles.According to Maas et al. (2003), D. pycnastera is morphologically related to D. neglecta Sandwith (1930: 470), D. tenuis R.E.Fr.(1957: 327) and D. tobagensis (Urb.)R. E.Fr. (1934: 93) because of leaf and floral features.D. leucotricha can be distinguished from these four species by the glabrous upper leaf side (vs.an upper leaf side of which the primary vein is densely covered with stellate hairs), equal-sided leaf base (vs.unequal to slightly so) and persistent upper bract and sepals (vs.soon falling).Furthermore, D. tobagensis is endemic to Trinidad and Tobago, D. neglecta is restricted to Guyana and Suriname, and D. pycnastera and D. tenuis are distributed only in the Amazon basin of Brazil, the Guianas and Venezuela (Maas et al. 2003).

Figure 3 .
Figure 3. Duguetia leucotricha, geographic distribution and habitat.A. Distribution map of the species in protected areas in the state of Bahia, Brazil.APA: Área de Proteção Ambiental (Environmental Protection Area); PES: Parque Estadual (State Park); REBIO: Reserva Biológica (Biological Reserve).B. Habitat of the species in the Serra do Conduru State Park, Bahia, Brazil (arrow indicates the collection site).Photograph by Márcio L. Bazante.