Checklist and a new species of Lippia (Verbenaceae) from the Diamantina Plateau, Minas Gerais, Brazil

The Diamantina Plateau is located in the central region of the Espinhaço Range, in the State of Minas Gerais, which is dominated by campo rupestre formations. We describe a new species of Lippia L., endemic to the Diamantina Plateau, and provide an annotated checklist and identifi cation key for the 17 species of the genus occurring in the area. Lippia raoniana P.H.Cardoso & Salimena sp. nov. is mainly distinguished by its ovate leaves with adaxial and abaxial surfaces densely covered by sessile glandular trichomes, and drupaceous fruits with two pyrenes. It is known only from two populations, and thus can be provisionally considered as Critically Endangered. Details on the species’ ecology, as well as a comparison with morphologically similar species, a distribution map, and fi eld photographs, are provided. In this work, we also present pictures of the 17 species in their habitats, and we hope that these illustrations will help in the identifi cation and conservation of these taxa.


Introduction
The flowering plant genus Lippia L. is a member of the tribe Lantaneae Endl. in the vervain family (Verbenaceae J.St.-Hil.). It contains approximately 120 species of perennial herbs, shrubs and subshrubs, often aromatic, native to tropical regions of the Americas and Africa (Atkins 2004;Marx et al. 2010). The genus is difficult to distinguish from Lantana L., given that the two genera are segregated by the fruit morphology only. Chamisso (1832) characterized Lippia by the presence of schizocarpic fruits bearing two cluses or drupaceous fruits with two pyrenes. Schauer (1847) assigned species with drupes to Lantana and species with schizocarps to Lippia. Finally, Silva & Salimena (2002) redelimited Lantana and reestablished the circumscription proposed by Chamisso (1832) to include only species with monopyrenous drupes.
The relationship between Lippia and Lantana is subject to a continuous taxonomic discussion and several delimitations have previously been proposed (Chamisso 1832;Schauer 1847;Troncoso 1974;Silva 1999;Sanders 2001;Silva & Salimena 2002;Atkins 2004). Phylogenetic analyses indicate that neither genus is monophyletic and both must be recircumscribed (Lu-Irving & Olmstead 2013), but an updated classification is yet to be published.
The highest species richness in Lippia is concentrated in Brazil, with ca 90 species Cardoso et al. 2019bCardoso et al. , 2019cCardoso et al. , 2020b. The majority of these occur in the Espinhaço Range ), which extends for over 1000 km, north to south, from the State of Bahia to the State of Minas Gerais. The region is characterized primarily by its quartzite rocky outcrops (i.e., campos rupestres), with elevations reaching 2000 m (Almeida-Abreu 1995; Giulietti et al. 1997;Gontijo 2008).
The Diamantina Plateau, located in the mid-southern region of the Espinhaço Range, Minas Gerais State, is bounded north from the Serra do Cipó and south from Grão Mogol (Gonçalves et al. 2017). It represents the highest plane surface (King 1956), and the watershed between the São Francisco and Jequitinhonha River basins along the N / S axis. The Diamantina Plateau is considered one of the most important centres of plant diversity and endemism in the Espinhaço Range (Giulietti et al. 1997;Echternacht et al. 2011). It is included in the Espinhaço Range Biosphere Reserve (UNESCO 2005), situated between the Cerrado and the Atlantic Forest domains, two global hotspots of biodiversity and conservation priorities (Myers et al. 2000).
Ongoing taxonomic studies on Verbenaceae for the "Flora do Brasil 2020" project (http://floradobrasil.jbrj.gov.br/), with extensive analyses of herbarium specimens and fieldwork, allowed the recognition of a new species of Lippia. This new species appears endemic to the Diamantina Plateau in the Espinhaço Range, State of Minas Gerais, and is described and illustrated in the present study. Furthermore, we provide an annotated checklist, identification key, and pictures of the species of Lippia in the Diamantina Plateau, with the aim of increasing our knowledge of the local flora, which is essential for conservation purposes.

Material and methods
Collections of the new species deposited in the herbaria CESJ, ICN, RB and SPF (acronyms of herbaria follow Index Herbariorum (Thiers, continuously updated)) were examined and field expeditions were conducted to observe individuals in their natural habitat. Morphological terminology follows Radford et al. (1974), Harris & Harris (2003), and Gonçalves & Lorenzi (2007). Conservation status is in accordance with the IUCN (2019) criteria; the area of occupancy (AOO) is based on 2 × 2 km grids. The geographical distribution map was prepared using QGIS ver. 3.8 (QGIS Development Team 2018). An identification key to the species of Lippia from the Diamantina Plateau was elaborated by consulting the type specimen images available at Global Plants on JSTOR (https://plants.jstor.org/)and collections available from BR, CESJ, F, G, HAL, K, M, MBML, P, R, RB, SP, SPF, VIC and W as well as several herbaria at Herbário Virtual Reflora (reflora.jbrj.gov.br/). Species' distribution records were obtained from the herbaria consulted and followed the delimitation of the Diamantina Plateau proposed by Gonçalves et al. (2017). This delimitation differs from the one proposed by Rapini et al. (2002) since it excludes the Serra do Cabral. This location is separated from the remaining Espinhaço Range by the geological depression, which is drained by the Jequitaí and Curimataí Rivers (Saadi 1995).

Distribution, habitat and phenology
Lippia raoniana P.H.Cardoso & Salimena sp. nov. is known only from two localities in the Diamantina Plateau (Felício dos Santos and Serro), on the Espinhaço Range, Minas Gerais, Brazil, where it seems to be endemic (Fig. 2). The populations are quite small and grow on quartzitic rock outcrops (campos rupestres), at an elevation of 1200-1400 m. Plants were collected with flowers and fruits in January, June, and November.

Prelimiminary conservation status
Lippia raoniana P.H.Cardoso & Salimena sp. nov. is only known from two localities, presenting an estimated Area of Occupation (AOO) smaller than 10 km². The first known population is small and located in the municipality of Serro, along an unpaved road, near to a residential area under urban pressure. The other population is recorded from the municipality of Felício dos Santos, inside a conservation unit. The Diamantina Plateau is now witnessing increasing, uncontrolled tourism, exposing the vulnerability of its soils and vegetation (Schaefer et al. 2002). Thus, L. raoniana sp. nov. may be considered Critically Endangered (CR) based on criteria and sub-criteria B2ab(ii, iii, iv) of IUCN (2019), due to its restricted AOO, number of known locations, and the continuous decline in the quality of its habitat.

Notes
Lippia raoniana P.H.Cardoso & Salimena sp. nov. most closely resembles L. spiraeastrum, which is also endemic to the Espinhaço Range, occurring in Grão Mogol, Minas Gerais State , due to the shrubby habit, conspicuous nodes, leaves concentrated in the upper portion of the stem, adaxial surface glandular, axillary inflorescences, capituliform, hemispherical, corolla lilac, and fruit with dry mesocarp, 2-pyrenate. However, several characters of the leaves, peduncles and bracts can be used to distinguish them. The new species is mainly characterized by the combination of ovate leaves with adaxial and abaxial surfaces densely covered by sessile glandular trichomes, peduncles 0.8-1.3 cm long, and ovate bracts with adaxial and abaxial surfaces densely covered by sessile glandular trichomes.

Discussion
Our floristic knowledge of Lippia in the State of Minas Gerais has gradually increased in recent years thanks to studies focusing on the Verbenaceae of small areas in the state (e.g., Salimena-Pires & Giulietti 1998;Cruz & Salimena 2017;Cardoso et al. 2018Cardoso et al. , 2019aCardoso et al. , 2019dCardoso et al. , 2020aSantiago et al. 2020). These studies have revealed new distribution records (Cardoso et al. 2019a), and in some cases, new species (Cardoso et al. 2019c(Cardoso et al. , 2020b. It is not surprising that the Diamantina Plateau harbors some yet undescribed species of Lippia, since the region is ultimately considered one of the main diversity and endemism centres in the Espinhaço Range (Giulietti et al. 1997;Echternacht et al. 2011). Thus, we present an annotated checklist of the species of Lippia from the area (Table 1). It is important to emphasize that all are found in campos rupestres. In addition, we also provide photographs and an identification key for the 17 species currently recognized in the region (Figs 3-4). This study improves our understanding of species diversity and distributions, and will aid the proposal of new conservation measures for the Espinhaço Range.