Untangling the taxonomy and geographic distribution of Quararibea floribunda (Malvaceae: Malvoideae)

Quararibea floribunda, a species endemic to Brazil, is poorly studied taxonomically, and little is known about its ecology and conservation status. Since its publication in 1842, only a few studies have reported on its morphological circumscription, thus remaining as a complex in the taxonomy of Quararibea. In addition, little is known about its geographic distribution, which, according to most authors, is restricted to the Cerrado Biome, a phytogeographic biome of dry forests. Therefore, we herein review and clarify the morphological circumscription and distribution of Q. floribunda in different vegetation types, designate a lectotype, and recognize its conservation status as Vulnerable (VU). The present study is based on analysis of protologues and further pertinent literature. Several herbaria were consulted, both in person and online. Fieldwork was done between 2017 and 2020 in different locations of midwestern and southeastern Brazil, mainly in dry forests of the Cerrado Biome. We confirm that Q. floribunda also occurs in the Atlantic Forest Biome and that it is not exclusive to the Cerrado Biome, as previously thought. All known populations in this biome inhabit humid habitats, and as such, they are closer to the vegetation of the Atlantic Forest Biome than the typical Cerrado dry forests. In addition to assessing the conservation status of Q. floribunda, we evaluate its nomenclatural history, leading to the designation of a lectotype, finally highlighting vegetative and floral diagnostic characters. A distribution map is provided, as well as a morphological comparative analysis between species with foliar domatia in extra-Amazonian Brazil.

Methods
The study involved a bibliographic search and examination of specimens placed at the following herbaria: ALCB, B*, BAK*, BHCB, BRNU*, C*, CEPEC, CVRD, ESA, F*, G*, GZU*, HAL*, HB, HST*, HUEFS, HVASF*, IPA, K*, LD*, LW*, LZ*, MAC, MBML, NY*, P*, PEUFR*, R, RB, RBR, RFFP, SI*, SP, SPF, U*, UEC, UFP*, UFRN*, US*, VIC, VIES, W*, and WU* (acronyms according to Thiers, continuously updated; * digital images). We also carried out field expeditions from 2019 to 2020 to update data on distribution, morphology, and habitat. The collected specimens were deposited in the herbarium RB. Morphological characters were described following Radford et al. (1974); the terminology for domatia was based on O'Dowd & Wilson (1989), and for trichomes, we referred to Payne (1978), Theobald et al. (1979) and Ferreira et al. (2018).

We used leaf samples taken from the specimen C.D.M. Ferreira et al. 533 (RB) to analyze the domatia microscopically, following the method of Ferreira et al. (2018) and Ferreira & Bovini (2020). Samples were fixed with carbon adhesive tape on stubs, coated with a thin gold layer of approximately 20 nm (Emitech K550X Sputter Coater), and observed under a scanning electron microscope (EVO 40, Zeiss) at a voltage of 15 kV.

The distribution map was prepared with the ArcGIS Desktop program (ESRI 2011) wherein locations were plotted based on the coordinates of herbaria specimens and obtained during fieldwork. The classification of biomes followed IBGE (2019), and for terminology of the vegetation types in which specimens occur, we adopted IBGE (2012). The conservation status of the species was determined following the categories and criteria defined by IUCN (2022), and the values of EAA and EOO were obtained through GeoCAT software (Bachman et al. 2011). Specimens collected in the 19th century were removed from the distribution map, as well as for the assessment of conservation status, owing to inaccurate or missing location.