Mollinedia ruschii (Monimiaceae, Mollinedioideae), a new Critically Endangered species microendemic to the Atlantic rainforest, eastern Brazil

1Departamento de Botânica, Instituto de Biociências, Universidade de São Paulo. Rua do Matão 277, Edifício Sobre-as-ondas (Herbário) 05508-090, São Paulo, SP, Brazil 2Conservation Science Department, Royal Botanic Gardens, Kew, Richmond, TW9 3AE, UK 3Instituto de Pesquisas Jardim Botânico do Rio de Janeiro, Rua Pacheco Leão, 915, Jardim Botânico, 22460-030, Rio de Janeiro, RJ, Brazil *Corresponding author: lirioeltonj@gmail.com RESEARCH ARTICLE


INTRODUCTION
Mollinedia Ruiz & Pavón (1794) is the most species-rich neotropical genus of Monimiaceae, a pantropical family with ca 28 genera and 200 species (Renner et al. 2010;Flora do Brasil 2020). Mollinedia has ca 60 species, occurring from southern Mexico to Central and tropical South America (Lorence 2011;BFG 2015;Lírio & Peixoto 2017; Flora do Brasil 2020). The genus was described by Ruiz & Pavón (1794) based on three species from Peru. Later, Perkins (1898) included the genus in the tribe Mollinedieae (along with Macrotorus Perkins and Macropeplus Perkins), which is characterized by pistillate flowers with a circumscissile receptacle apex. This classification was accepted by later researchers (Philipson 1987(Philipson , 1993Peixoto & Pereira-Moura 2008;. Mollinedia is characterized by staminate flowers with buds almost round, perianth lobes with a ratio of ca 1:1 in relation to the length of the receptacle, and stamens ovate or rounded, the locules either with two longitudinal openings and an extended connective or confluent at the apex, making the anthers horseshoe-shaped (Perkins 1898(Perkins , 1900. Although Mollinedia is morphologically well circumscribed, molecular studies do not support the monophyly of this genus (Renner et al. 2010). However, phylogenetic studies with more data and more taxa are still needed. Thirty-six species of Mollinedia occur in Brazil, most of them in the Brazilian Atlantic rainforest, and most abundant in the states of Bahia, Espírito Santo, Rio de Janeiro, and São Paulo (BFG 2015;Lírio & Peixoto 2017).
In the state of Espírito Santo, three genera and 21 species of Monimiaceae are recorded. The municipality of Santa Teresa is the richest area of the state with 19 species (Lírio & Peixoto 2017). This area is also rich in species of several other plant groups and several new species have been described in recent years (e.g. Bünger et al. 2016;Goldenberg & Kollmann 2016;Oliveira et al. 2016;Alves-Araújo & Mônico 2017;Moraes & Vergne 2017;Sobral et al. 2017;Trad et al. 2018;Flores et al. 2019).
In the present work, we describe and illustrate Mollinedia ruschii, a new species endemic to Espírito Santo state, eastern Brazil. We also assess the conservation status of the new species according to the IUCN Red List of Threatened Species (hereafter referred to as IUCN Red List) and discuss the relationship to the morphologically similar species Mollinedia stenophylla Perkins (Perkins 1900) and Mollinedia boracensis Peixoto (Peixoto 1983).

MATERIAL AND METHODS
Morphological terms follow Harris & Harris (2001), except for hair terminology, which follows Payne (1978), and that of characters unique to Monimiaceae, which are described according to Perkins (1898Perkins ( , 1900. Descriptions and measurements are based on dry herbarium specimens. Herbaria acronyms follow Thiers (continuously updated), and nomenclature follows the latest ICBN (Turland et al. 2018). The diagnosis and table of characters for related species were based on herbaria material. The examined material for M. boracensis and M. stenophylla is available in supplementary file 1.
The ecological and conservation data were collected through field observations, collections deposited in herbaria and phytosociological studies (Thomaz & Monteiro 1997;Saiter et al. 2011;Saiter & Thomaz 2014;Eduardo F. Oza pers. comm. 2019). The extinction risk assessment follows the IUCN Red List of Threatened Species Categories and Criteria (IUCN 2012) and the Guidelines for Using the IUCN Red List Categories and Criteria (IUCN 2019). The area of occupancy (AOO) and extent of occurrence (EOO) were calculated with the Geospatial Conservation Assessment Tool -GeoCAT (Bachman et al. 2011). Lírio & Peixoto, sp isotypes: MBML, SPF, 3 duplicates to be distributed to P, NY, and K. Diagnosis -Mollinedia ruschii is morphologically similar to M. stenophylla, however, it is easily distinguished by its tree habit 3-15 m tall, corky bark, leaves and branchlets reddish when young, leaves opposite, entire or 1-2-teethed, odoriferous when fresh, staminate flowers with reddish pedicel, tepals 2/3 of the length of the flower, bracts and bracteoles ca 1 mm, ovate, drupelets 0.8-2.0 × ca 1.2 cm, glabrous, fruiting receptacle with prominent scars (vs shrub habit up to 1 m tall, bark not corky, young branchlets green, leaves ternate and opposite on the same branch, 3-12-teethed, without odour when fresh, staminate flowers with yellowish pedicel, tepals 1/2 of the length of the flower, bracts and bracteoles ca 1.5 mm long, lanceolate, drupelets ca 0.8 × 0.6 cm, strigose, fruiting receptacle without prominent scars in M. stenophylla). Mollinedia ruschii is also morphologically similar to M. boracensis, but it can be easily distinguished by its leaves with attenuate apex, 9-13 pairs of secondary veins, rachis in staminate flowers 0.2-1.1 cm long, tepals ca 2/3 of the flower length and 12-15 stamens (vs leaves with acute apex, 5-6 pairs of secondary veins, rachis in staminate flowers with 4-7 cm, tepals ca 1/2 of the flower length, and 22-24 stamens in M. boracensis). Description -Trees 3-15 m tall, dbh 10-21 cm, dioecious, rhytidome corky, longitudinally cracked, canopy sparse, twigs cylindrical, green or greyish when fresh, brownish or black when dried, striated, glabrous, nodes thickened, young branches glabrate and reddish. Leaves 6.5-13.5 × 1.2-3.8 cm, opposite, blade oblong to elliptical, base cuneate, rare acute, apex attenuate, frequently falcate, entire or with 1-2 teeth, when fresh dark green on adaxial face and light green on abaxial face, aromatic, when dry brown on adaxial face and paler on abaxial face, subleathery, glabrous, opaque, pellucid punctuated, secondary veins 9-13 pairs, immersed on adaxial face and prominent on abaxial face, petiole 0.6-1.8 cm long, canaliculate, glabrous. Staminate flowers yellow, in cymose thyrses with 1-6 cymes (3-florous), axillary or terminal, white-strigillose, rachis 0.2-1.1 cm long, peduncle 0.4-1.4 cm long, reddish, pedicel 0.2-1.3 cm long, reddish, bracts ovate, apex acute, 0.7-0.8 mm long, bracteoles ovate, apex acute, 1-1.5 mm long, receptacle campanulate, 5-6 × ca 5 mm, tepals 2/3 of the flower length, two external shorter, margin irregular, the two internal unequal, one with fimbriate appendix, the other with denticulate appendix, stamens 12-15, hippocrepiform, sessile, anthers dehiscent by longitudinal slits. Pistillate flowers not seen. Drupelets early exposed, 1-3(-14), ellipsoid or orbicular, 0.8-2 × ca 1.2 cm, not stipitate, base rounded or obtuse, apex obtuse, stigma persistent, glabrous, brown when dry, pericarp hard, rugose, fruiting receptacle 0.5-1 cm wide, reflexed, glabrous, brown when dry, fruit scars prominent, peduncle plus pedicel 0.9-2.5 cm long.   between 750 and 850 m elevation. The microendemism of M. ruschii is probably due to a climatic tolerance to a narrow set of environmental conditions, specific to the humid montane forests of the municipality of Santa Teresa, Espírito Santo state. Phenology -The species has been collected with flowers from May through September, and with fruits in January through March, May, and August. Etymology -The specific epithet honours the Brazilian naturalist Augusto Ruschi (1915Ruschi ( -1986 who created the Museu de Biologia Mello Leitão, a research institution dedicated to study the Atlantic forest (now referred to as Instituto Nacional da Mata Atlântica). The Estação Biológica de Santa Lúcia belongs to the Instituto Nacional da Mata Atlântica, the Universidade Federal do Rio de Janeiro, and the Associação de Amigos do Museu Nacional and is managed by the Instituto Nacional da Mata Atlântica. Augusto Ruschi contributed greatly to the conservation of Brazilian forests, especially in the Espírito Santo state. Due to his recognition as a naturalist and political influence, Ruschi participated in the process of conceptualization and demarcation of seven conservation units (UCs) in Espírito Santo, including the Reserva Biológica Nova Lombardia, nowadays renamed to Reserva Biológica Augusto Ruschi (Dean 2004;Gonçalves 2019). The two areas where Mollinedia ruschii occurs, the Estação Biológica de Santa Lúcia and the Reserva Biológica Augusto Ruschi, are preserved today in part due to the influence of Augusto Ruschi (Dean 2004;Gonçalves 2019). IUCN conservation assessment (provisional) -Mollinedia ruschii is endemic to Espírito Santo state, eastern Brazil, known only from two relatively small protected areas (Estação Biológica de Santa Lúcia and the Reserva Biológica Augusto Ruschi) with different levels of protection and management. The forest patches are embedded in a farming matrix, fragmented by agriculture, wood plantations (especially Eucalyptus spp.), and residential areas. Its extent of occurrence (EOO) is estimated at 8 km 2 , and considering that the convex hull formed by the points is smaller than the area of occupancy (AOO), estimated at 8 km 2 , it falls within the Critically Endangered category. The species is considered to have one location, since the mature individuals were recorded solely in two nearby sites, however, only one of those sites is a federal protected area with a management plan and surveillance (Biological Reserve Augusto Ruschi). A single event caused by fire, disease, or anthropic action at the second site (Estação Biológica de Santa Lúcia) could bring the species close to the extinction, considering potential lack of protection, resources, or delays in response caused by the need of concerted action by institutes from different sectors. The Estação Biológica de Santa Lúcia is owned by the Instituto Nacional da Mata Atlântica, linked to the Ministry of Science, Technology and Innovations, and by the Associação de Amigos do Museu Nacional, which is part of the nonprofit sector. The area is currently not surveyed, and the habitat of this species has suffered continuing decline and fragmentation, mainly due to urban expansion, agriculture, and livestock farming. The wood plantation of Eucalyptus expanded during the last decade in Santa Teresa (IBGE 2006(IBGE , 2017 and pastureland represent ca 12% of the municipality area (LAPIG 2020). The increased frequency of drought and fire (Fraga et al. 2019) are also important threats to this species, which cannot be properly managed without a management plan. Also, considering that the species is dioecious, the potential loss of pollinators represents an incident threat, because several species of invertebrates in the state of Espírito Santo have been assessed as threatened (Fraga et al. 2019).

Mollinedia ruschii
Mollinedia ruschii is known from no more than 12 collections in a well-collected region, and it currently comprises only three known male mature individuals, with no female individuals recently found. There is a growing concern about the mortality of adult individuals of this species within the Estação Biológica Santa Lúcia. For example, a floristic and phytosociological study conducted in the Estação Biológica Santa Lúcia in 1997 using plots (1.2 ha) found only four mature individuals of the species (Thomaz & Monteiro 1997). In later studies (Saiter et al. 2011;Saiter & Thomaz 2014; Eduardo F. Oza, pers. comm. 2019) on forest dynamics in the same area, three individuals of M. ruschii were found dead and no new individuals of this species were sampled. An intensive fieldwork was carried out between 2011 and 2018 by one of the authors (EJL), including targeted searches for individuals previously collected (e.g. Kollmann 2302, Demuner 599, andVervloet 1936) and potential habitats with the same altitudinal range and vegetational type. Those specimens were not found during the searches and they are likely to be dead. An individual from those sampled by Thomaz & Monteiro (1997) was also found dead. Pistillate individuals of this species were last seen in 2003 (Vervloet 1936). We also found only two young individuals in the localities where the species occurs (in Estação Biológica Santa Lúcia), which suggests that the species can reproduce but in very low numbers. We therefore estimate the total number of mature individuals to be less than 50 mature individuals.
The species present a restricted distribution in terms of extent of occurrence (EOO) and area of occupancy (AOO), however, based on the different levels of protection and management between the two protected areas where this species occurs, it is likely to have two different locations, falling into the Endangered category. Thus, based on the precautionary principle, this species is assessed as Critically Endangered (CR C2a(i); D), considering an inferred continuing decline (especially in terms of the number of locations and mature individuals), combined with a very small population size represented by a low number of mature individuals in each subpopulation.  (Renner et al. 2010). However, more robust data and sampling is necessary to resolve the relationships between these genera. Even if further studies confirm the polyphyly of Mollinedia, this genus has priority and the new species proposed here will remain unchanged.

Additional material examined (paratypes) -BRAZIL -
Mollinedia ruschii is morphologically similar to M. stenophylla in shape, colour, consistency and surface of the leaves, and the number and shape of the stamens. It is also similar to M. boracensis in the shape and consistency of leaves and the receptacle shape of the flower. The species differs from M. stenophylla and M. boracensis in the characters presented in the diagnosis and in table 1. This set of characters was considered important for the recognition of species in the genus Mollinedia by different authors (Peixoto 1979;Lorence 1999Lorence , 2011Molz & Silveira in press). Mollinedia ruschii also differs from M. boracensis and M. stenophylla in geographic distribution and habitat. While M. boracensis occurs in the state of São Paulo and Rio de Janeiro, M. stenophylla and M. ruschii have a very specific habitat (Lírio et al. 2018(Lírio et al. , 2020. Mollinedia stenophylla, recently rediscovered after 112 years without collections, occurs only on the banks of the Macaé River in the municipality of Nova Friburgo, in the state of Rio de Janeiro (Lírio et al. 2018). Mollinedia ruschii is also a microendemic species, restricted to the montane forests between 750 and 850 m elevation in Santa Teresa, Espírito Santo. Microendemic species are expected to be more sensitive to climate change and more susceptible to extinction due to the restricted range and habitat specificity (Bitencourt et al. 2016). There is a general concern in plant conservation regarding the best strategies to conserve microendemics. Potential strategies include research into artificial propagation, ecophysiology, pollination seed dispersal, phenology, genetic diversity, monitoring, modelling of potential distribution, threat mitigation, reintroduction, and ex situ conservation (Martins et al. 2014;Zhang et al. 2014;Kraaij et al. 2016).
We can affirm that Ruschi's efforts to create those protected areas in Espírito Santo were fundamental for conserving this rare tree species. Currently, the habitat protection has guaranteed the species presence (assessed as Critically Endangered, with less than 50 individuals), however, a single change in the legislation could drive the taxon to extinction in a very short time. We highlight the importance of retaining the site's protection, as well as the need for more ecological and population studies to support focused conservation actions for endemic species in these areas, including efforts to organise seed collection and propagation.