Three new species of Marsdenia ( Apocynaceae ) from Brazil

Th ree new species of Marsdenia (Apocynaceae) are described from Brazil: M. paganuccii, known from two disjunct populations, one in the Caatinga of Bahia and other in the Atlantic Forest of Espírito Santo; M. paraibana, restricted to the Restinga of Cabedelo National Forest in the Atlantic Forest of Paraíba; and M. trisegmentata, known from two populations in Caatinga, one in Bahia and other in Ceará. Illustrations, a geographic distribution map and comparisons with morphologically similar species are also presented for each species.


Introduction
Marsdenia (Apocynaceae: Asclepiadoideae) comprises approximately 200 species, mainly from tropical and subtropical regions (Liede & Albers 1994;Endress & Bruyns 2000;Stevens 2009), is one of the largest genus of Marsdenieae and the only genus of the tribe in the Neotropics.It comprises a great morphological variation and is easily distinguished from the other genera of asclepiads in the New World by the erect pollinia, attached to the caudicles at the base.In Brazil, Marsdenia is represented by 34 species (Flora do Brasil 2020) and is the fourth asclepiad genus in number of species (Rapini 2012), occurring in diff erent types of vegetation, from the Amazonian and Atlantic rain forests to the Caatinga seasonally dry forests.During the preparation of the treatment of Marsdenia from Brazil, we recognized three new species of the genus, which are described below as M. paganuccii, M. paraibana and M. trisegmentata.
Preliminary phylogenetic analyses using molecular data has shown that Marsdenia s. l., as traditionally circumscribed, is not monophyletic and the American species of the genus are not closely related to the Asian M. tinctoria R.Br., the type of Marsdenia (Livshutz et al. 2016;FS Espírito Santo unpubl. res.).To become monophyletic Marsdenia should comprise almost all other genera of the tribe or become reduced to only a few species closely related to M. tinctoria.A broader circumscription will require the synonymyzation of other genera, such as Gymnema R.Br., with 25 species, but probably also the more traditional Dischidia R.Br. and Hoya R.Br., with approximately 80 and 350 species, respectively, under Marsdenia.A narrower circumscription will require the segregation of the American species and the reinstatement of Ruehssia H.Karst. (see Rapini et al. 2001, for names available to this group under the synonymy of Marsdenia).Since Marsdenia is the only genus of Marsdeniae currently accepted in the New World, we are describing the three new species in it, predicting their transference to Ruhessia in a near future, as a recircumscription of Marsdenia is inevitable and then a reduced concept of the genus is more likely.Marsdenia paganuccii differs from all other Neotropical species of the genus by the combination of (sub)sessile, dense inflorescences, with few (up to 6) (sub)sessile, tiny flowers (< 2.5 mm long), corolla rotate, vinaceous, adaxially pubescent, and corona lobes subdeltate to ovate, puberulent at the base.
Conservation status: Despite exhaustive field work, only two specimens of Marsdenia paganuccii have been found at the location in Bahia, both on rocky outcrops surrounded by pasture, about 60 m distant from a busy vicinal road and 700 m from the BA-046 state highway.The specimen from Espírito Santo was collected more than 70 years ago and lacks information about population density and environmental conditions.The increase in anthropogenic disturbance in the Rio Doce basin, mainly caused by deforestation, disorderly occupation, mining and, more recently, the dam collapse in Mariana (Minas Gerais), and the lack of recent collections from Espírito Santo suggest that M. paganuccii is probably extinct in this state.Based on its small area of occupancy (AOO = c.4.5 km 2 , estimated from the polygon area in Google Earth Pro), restricted to one (or two) locations, and the small population observed in Bahia, with only two specimens occurring in a highly disturbed area, M. paganucci should be treated as Critically Endangered [CR B2ab(i,ii,iii,iv); D], according to the IUCN´s (2016) criteria.
Etymology: The epithet honors the Professor Dr. Luciano Paganucci de Queiroz, who has greatly contributed to the knowledge and conservation of the Brazilian flora, especially of the seasonally dry forests.
Phenology: The species was collected with flowers in November, December and March.
Distribution and habitat: The species is known only by the holotype, collected at the Restinga of Cabedelo National Forest, in a locality known as 'Mata da Amem'.This National Forest has 103.36 hectares and holds one of the last fragments of Atlantic Forest in the state of Paraíba (Brasil 2004).
Conservation status: The Restinga of Cabedelo National Forest is an environmental conservation unit established in 2004 at the João Pessoa metropolitan region.The region has the highest Gross Domestic Product of the state of Paraíba (IDEME 2016) and the conservation unit is the first in an urban area in Brazil (Brasil 2004).Although legally protected, Marsdenia paraibana is restricted to a small isolated fragment (AOO = c.0.5 km 2 , estimated from the polygon area in Google Earth Pro) of well-preserved vegetation, known as Mata da Amem (Associação Metropolitana para a Erradicação da Mendicância), which corresponds to approximately only one third of the National Forest area (c.1.6 km 2 ), and is under strong anthropogenic pressure and socioenvironmental conflicts (Andrade et al. 2014).The small area of occupancy and size of population, which is restricted to a single fragment of vegetation within the capital of Paraíba, are reasons to consider this species Critically Endangered, according to the IUCN´s ( 2016) criteria [CR B2ab(ii,iii); D].
Etymology: The epithet refers to the state of Paraíba, where M. paraibana occurs.
Phenology: The species was collected with flowers in January.
Notes: Marsdenia paraibana is characterized by the elliptic leaves, with acuminate apex and conspicuous tertiary veins in both faces, inflorescences with few flowers and a small peduncle, flowers shortly pedicellate, with elliptic to ovate sepals, urceolate brownish corolla, with elliptic to obovate long lobes, corona lobes in upside down V-shape (˄-shape), acute at the apex, the apical appendix of anthers cochleariform, surpassing the style-head, and caudicles distally plicate.It is morphologically similar to M. hilariana var.macieliana, but can be distinguished from it by the characters in the diagnosis.Marsdenia paraibana can also be related to M. amorimii Morillo and M. dorothyae Fontella & Morillo, both endemic to the Atlantic Forest, differing from them, among other characters, by the unique shape of the corona lobes, which are oblong-ovate in M. amorimii and ovate in M. dorothyae.Marsdenia trisegmentata is distinguished from all other Neotropical species of the genus by the combination of corolla widely campanulate, green to yellowish-green, with large lobes (≥ 6.3 × 3.6 mm), oblong to widely ovate, patent, and large corona lobes (6.7−7.6 mm long), trisegmented, with a lower portion suborbicular, concave or triangular invaginated, a middle portion rhomboid or triangular and an apical portion narrowly triangular, falcate.
Conservation status: In Bahia, M. trisegmentata is restricted to a fragment of vegetation under anthropogenic pressure, which is common in the whole region of the São Francisco valley.Due to agricultural activities and extensive breeding of goats and cattle, most vegetation in the Caatinga have been disturbed or changed.This population of M. trisegmentata is on the margin of a vicinal road, about 4 km distant from downtown, and therefore, also under the impact of urban expansion and car traffic.Although this population in Bahia is probably threatened, we have no data about the population of M. trisegmentata in Ceará.Therefore, we consider the Data Deficient (DD) to assess the conservation status of this species according to the IUCN´s (2016) criteria.
Etymology: The epithet emphasises the unique trisegmentate shape of corona lobes.
Phenology: The species was collected with flowers in November and December.
Notes: Like other species of the genus, Marsdenia trisegmentata is also toxic to livestock and is popularly known as "mata-calado" (silent killer; as "Marsdenia aff.zehntneri" in Pessoa et al. 2011).It is characterized by the fleshy leaves, inflorescences with few flowers, corolla widely campanulate, green to yellowish-green, with lobes patent, larger than the tube, and corona lobes long (> 6.5 mm long), trisegmentate, formed by a lower portion suborbicular and concave or triangular and invaginated, a middle portion rhomboid or triangular and an apical portion narrowly triangular, falcate, surpassing the style-head and the corolla fauce.This combination of features is found exclusively in M. trisegmentata, distinguishing it from any other Neotropical species of Marsdenia.

Figure 1 .
Figure 1.A-F.Marsdenia paganuccii. A. Branch with leaves and inflorescence; B. Branch with inflorescence; C. Flower, seen from above; D. Flower, perianth removed to show the corona in front of gynostegium; E. Corona lobe, frontal view; F. Pollinarium.G-L.M. paraibana.G. Branch with leaves and inflorescence; H. Inflorescence; I. Flower, lateral view; J. Flower, perianth removed to show the corona and anther wings in front of gynostegium; K. Corona lobes, frontal view; L. Pollinarium.M-S.M. trisegmentata: M. Branch with leaves and inflorescence; N. Flower, lateral view; O. Flower, seen from above; P. Flower, perianth removed to show the corona in front of gynostegium; Q-R.Corona lobe, frontal view; S. Pollinarium (Illustrated by Gustavo Surlo from the holotypes).