Nomenclatural novelties in Lessingianthus ( Asteraceae-Vernonieae ) : an extraordinary new species , a lectotypification , and a new combination from a resurrected synonym

Lessingianthus spinifolius is here described and illustrated as a new species of the tribe Vernonieae (Asteraceae) from Chapada dos Veadeiros, State of Goiás, Brazil. The new species is thus far known only from the type locality. The characteristics that most differentiate L. spinifolius from congeners are: (i) leaf blade strongly revolute; and (ii) leaf blade with spines on the margins. The new species is similar to L. onopordioides due to both having a similarly shaped involucre and the involucre being eximbricate with lanceolate phyllaries. Taxonomic and ecological comments, a distribution map, conservation status assessment, and illustrations of the new species are provided. Additionally, Vernonia araneosa is resurrected from the synonymy of L. durus, and a new combination, L. araneosus based on V. araneosa, is proposed, a lectotype designated, and its affinities with L. durus discussed.


Introduction
The family Asteraceae has approximately 1,600 genera and 25,037 species grouped in 44 tribes, distributed around the globe except for Antarctica (Funk et al. 2009;Panero et al. 2014;Panero & Crozier 2016).Asteraceae, with 6,316 species in South America, appears as the highest in species number in the continent (Panero & Crozier 2016).In the same way, it is one of the most species-rich in Brazil, where it can be found 2,065 species grouped in 304 genera, and 27 tribes widely distributed throughout the territory according to Flora do Brasil 2020 (2017).
The tribe Vernonieae was established by Cassini (1819), which in turn underwent taxonomic changes, and the main change was the reduction in size and distribution of the genus Vernonia Schreb., which for a long time included a large part of variation within the tribe (Keeley & Robinson 2009).At the moment, Vernonieae comprises approximately 1,500 species and 126 genera (Keeley & Robinson 2009), with pantropical distribution (Robinson 2007).
Lessingianthus belongs to the subtribe Lepidaploinae, and is one of the most representative in species number in the tribe.The genus was established to recognize the species originally described in Vernonia sect.Lepidaploa series Macrocephalae.Currently, the genus has more than 130 species distributed in South America, especially in Argentina and Brazil, in addition to one or two species in Colombia and Venezuela (Robinson 2007;Keeley & Robinson 2009).
In Brazil are reported 114 species of Lessingianthus, widely distributed throughout the Brazilian territory, of which 57 are cited to the State of Goiás, according to Flora do Brasil 2020 (2017).The genus Lessingianthus is distinctive from other genera of Vernonieae by having a combination of characters including capitula generally pedunculate, corolla lobes usually glandular, style with base usually cylindrical (without node), absence of glands in the cypsela wall, and type B pollen grains (Jones 1982;Robinson 1988;1999;Angulo & Dematteis 2010;2014).The basic chromosome number of the genus is x=16, divergent from the majority of the Vernonieae from the American continent, which have basic chromosome number x=17 (Dematteis & Angulo 2010).
A field trip to Chapada dos Veadeiros National Park during the Master degree of the first author resulted in collecting a new species of Lessingianthus.The new species is here described and illustrated, and its affinities are discussed.Additionally, Vernonia araneosa is resurrected from the synonymy of L. durus, and a new combination, L. araneosus based on V. araneosa, is proposed, a lectotype is designated, and its affinities with L. durus are discussed.

Materials and methods
The specimens of the new species were collected following the usual techniques in plant taxonomy (e.g., Mori et al. 2011).The holotype and paratypes were deposited in the UFG herbarium and the duplicates of holotype (isotypes) were sent to P, RB, and US herbaria (acronyms according to Thiers 2017).The species was morphologically described with the use of stereomicroscope.Dimensions of vegetative and reproductive structures presented in the description were measured from dried herbarium material (except for floral structures, which were collected and fixed in 70 % alcohol for measurements).The morphological terminologies are in agreement with Roque &Bautista (2008), andBeentje (2012).
The assessment of conservation status was performed using the GeoCAT tool (2017) as described by Bachman et al. (2011), with the IUCN (2012) default of Area of Occupancy (AOO) analysis with a grid size 2 km (a cell area of 4 km 2 ).
For the new combination proposed, the type-specimens were examined personally by the second author at K herbarium, and by digital photos available at JStor (2017) for the materials housed at GH, K, and NY herbaria.
Distribution and ecology: The new species is so far known only from Chapada dos Veadeiros National Park, in the municipality of Cavalcante, northern State of Goiás, a nuclear area of the Cerrado biome (Fig. 3).Although the Chapada dos Veadeiros exhibits all the phytophysiognomies of the Cerrado, the population of Lessingianthus spinifolius was found growing exclusively in an area of dry grassland known in Brazil as campo limpo ("clean field").The species grows among specimens of Microlicia vestita DC. camouflaging in the vegetation and fenced by rocks at 1421m a.s.l.
Etymology: The specific epithet is an allusion to the spines present on the margin of the leaf blade, an unusual feature for the species of the genus.very small and with a geographic range (extend of occurrence and area of occupancy) critically limited.Phenology: Flowering and fruiting specimens were collected in November, April, and May, period of the rainy season in the Cerrado biome.

Lessingianthus araneosus
Distribution and habitat: Species endemic to Brazil found in the State of Goiás and Distrito Federal.Lessingianthus araneosus is characteristically found in the Cerrado sensu stricto, more specifically in sparse vegetation locally known as "cerrado ralo", a subtype of phytophysiognomy of the Cerrado biome, according to Ribeiro & Walter (2008).Discussion: Baker (1873) described Vernonia araneosa based on a specimen collected by Pohl (Pohl 670).This species was placed under the synonymy of Lessingianthus durus (Mart.ex DC.) H.Rob. by Robinson (1999).However, V. araneosa (here treated as Lessingianthus araneosus) seems to be similar to L. durus only superficially, and this similarity is limited to vegetative organs, mainly the leaves.Nevertheless, the two species differ in some aspects, especially in the size of the involucre, number of series of phyllaries, and florets number as listed in Table 1.As a result, we are proposing to resurrect V. araneosa from the synonymy of L. durus, and its new combination in Lessingianthus.
Note: The exsiccate housed at GH herbarium (GH00013652) has a fragment and a drawing of Vernonia araneosa mounted on the left side of the sheet, and a nontype collection of Lessingianthus durus (Gardner 4291) on the right side of the sheet.