Dalechampia seccoi (Euphorbiaceae), a threatened new species from Southeastern Brazil

Abstract Dalechampia seccoi is a new endemic species of Euphorbiaceae from the Atlantic Forest domain, southeastern Brazil. Here we describe and illustrate the new species. Collections of botanical material, and standard herbarium practices were applied. The new species is vegetatively similar to D. alata, D. erythrostyla, D. pentaphylla, D. violacea, and D. purpurata, however it is distinguished by exclusive characters such as involucral bracts 4‒5-lobed, pinkish, staminate sepals vinaceous, resin darkish and stigma yellow lobed to crateriform. The new species is restricted to Seasonal Semideciduous Forest with altitudes of ca. 700 m from Caparaó, south of the state of Espírito Santo. In addition, we provide field photographs, preliminary conservation status assessments using IUCN Red List guidelines, as well as a checklist and key for morphological correlated species.


Introduction
Dalechampia L. is a consistent morphologically genus, characterized by its peculiar pseudanthial inflorescence, which stands out due the involucral bracts, usually colorful.Its pistillate cymule present three flowers and the staminate pleiochasium has few to numerous flowers (Webster & Armbruster 1991).Dalechampia is one species-rich genera of the subfamily Acalyphoideae (Euphorbiaceae), it includes ca.130 species, being the neotropical region the center of greatest diversity with 90 species, representing 69% of global taxa (Pereira-Silva et al. unpubl. res.).
In Brazil, about 73 species are recorded and distributed in all phytogeographic domains, of which 35 are reported for the Southeastern region (Pereira-Silva et al. 2019).The Atlantic Forest is one of the richest domains in number of Dalechampia species (29 spp.), three less than in the Cerrado (Pereira-Silva et al. 2022).Recent studies in Dalechampia recorded 15 species for the state of Espírito Santo, in addition to the confirmation of a new taxon for science (Mendes et al. 2022).

Taxonomic treatment
Distribution -Dalechampia seccoi is recorded until this moment to the municipality of Alegre, Espírito Santo, Southeast Brazil, specifically in the Parque Estadual da Cachoeira da Fumaça (PECF), see Figure 4.
Habitat and ecology -The species occurs in Semideciduous Seasonal Forest vegetation, growing in edge areas in hillside forests with altitudes ranging from 663 to 700 m (Fig. 4).According to Borges and Azevedo (2017) the PECF is compose by several phytophysiognomies, such as rocky vegetation, herbaceous swamp, fragments in the initial, medium and advanced stage of regeneration, exotic vegetation and agriculture areas.In addition, the presence of several exotic species, with high invasive potential, present threats to the conservation of native species of the PECF vegetation that has environments in regeneration.
Due to the vegetational similarity, we believe that the species also occur in other isolated forest areas along the Caparaó region.New expeditions should be conducted to better explore the region in search of new records, mainly in the Reserva Particular do Patrimônio Natural da Cachoeira da Fumaça in the municipality of Ibitirama, located close to the area where the species occurs.
Phenology -Dalechampia seccoi was collected with flowers in August and November and with fruits in August.
Etymology -The specific epithet honors Dr. Ricardo de S. Secco, renowned botanist at the Museu Paraense Emílio Goeldi, who contributes significantly to knowledge of the Amazonian flora, as well as of the whole of Brazil, specifically the Euphorbiaceae family, and who greatly assists in the formation of stimulating human resources Euphorbiologists.
IUCN preliminary conservation assessment -Dalechampia seccoi is known for only two records in the same locality, with an area of occupancy (AOO) of 4 km² in which habitat fragmentation is the main threat observed.The fragmentation indicates a decline in habitat quality and a decline in extent of occurrence and area of occupation.The unique known populations are protected by the PECF, which is a conservation unit, but not fully protected because tourist activities are allowed.Based on the geographic criteria B1ab (i,ii,iii) and knowing the threats, we propose that if a formal assessment were performed D. seccoi would probably be evaluated as Critically Endangered (CR).

Taxonomic notes for D. seccoi and related species: a morphological inference
Currently, the section Dioscoreifoliae comprises 26 species (Webster & Armbruster 1991;Athiê-Souza et al. 2019), which present morphological variation in the leaves being simple (unlobed and palmately lobed) and compound.However, the three types rarely coexist in the same species, as occurs in Dalechampia sect.Dalechampia and Dalechampia sect.Tiliifoliae G.L. Webster & Armbr.(Webster & Armbruster, 1991).In addition, the section Dioscoreifoliae presents involucral bracts diverse in color, but the most are pinkish, magenta or purplish, as D. aristolochiifolia Kunth, D. colorata (Pereira-Silva et al.The section Dioscoreifoliae is subdivided into five informal groups, named 1 to 5 that are differentiated by the shape of leaves and number of pistillate sepals (6−12, entire, bifid, laciniate or pinnatifid), as well as the shape of stylar column apex, including the texture of seeds (Webster & Armbruster 1991).We analyzed the five informal groups, and based in morphological data, here D. seccoi is included in the group 4, mainly due the number and shape of pistillate sepals (12, pinnatifid) and stylar column apically dilated.
Dalechampia violacea differs of the new species by presenting involucral bracts deeply 3-lobed, pistillate sepals fimbriate, stylar column and stigma reddish.The pistillate sepals of D. violacea have an irregularly dentate apex and never lobed, which we treat here as fimbriate.Even so, worth mentioning that stigmatic surface of Dalechampia can be useful to differentiate some species according to Webster & Armbruster (1991), in some representatives, the style column is notable for having longitudinal bands of stigmatic surfaces running halfway or more towards the base.In the case of D. erythrostyla (Pereira-Silva et al. 2016) and D. violacea (Mendes et al. 2020) these stigmatic surfaces run up to the middle of the stylar column and become reddish.While in other species of the section, as in D. seccoi, the longitudinal bands of the stigmatic surfaces can be shorter and yellow in color.
Another important aspect among the species correlated to D. seccoi is the geographic distribution, where D. pentaphylla has a wide distribution in Brazil (Central-West, Northeast, Southeastern and South), reaching Paraguay and D. alata occurs in Northeast and Southeastern of Brazil (Webster & Armbruster 1991;Mendes et al. 2022).Dalechampia seccoi, D. erythrostyla, D. purpurata and D. violacea present a restrict geographical distribution in the country, being D. seccoi in the Southeastern region, while D. erythrostyla and D. purpurata are listed to the Northeast, and D. violacea to the Central-West.
A. Pereira-Silva & A.L. Melo, D. pentaphylla Lam., D. violacea Pax & K.Hoffm.and D. purpurata Cordeiro, however it is distinguished by unique reproductive characters.Here we describe, illustrate and present images of D. seccoi, including a distribution map, preliminary assessments of the conservation status, identification key and table with main diagnostic characters of the most similar species of Dioscoreifoliae section.

Table 1 .
Comparison of morphological characters for Dalechampia seccoi and related species.