Diversity of Bignoniaceae in coastal Piauí, Northeast Brazil

Abstract The present study is a taxonomic treatment of Bignoniaceae from the four municipalities of the coastal region of Piauí state (Cajueiro da Praia, Ilha Grande, Luís Correia, Parnaíba) in Northeast Brazil, based on morphological study of newly collected and existing herbarium material. The study recorded 26 species in 12 genera: Adenocalymma, Anemopaegma, Bignonia, Cuspidaria, Dolichandra, Fridericia, Handroanthus, Lundia, Neojobertia, Pleonotoma, Stizophyllum and Tanaecium. Apart from Handroanthus impetiginosus, which belongs to tribe Tecomeae, all other species belong to tribe Bignonieae. Five species (Adenocalymma apparicianum, A. pedunculatum, Anemopaegma heringeri, A. prostratum, Dolichandra hispida) are new records for the state of Piauí, 15 species are endemic to Brazil, and one has “Vulnerable” conservation status. The results emphasize the importance of taxonomic studies for knowledge of biodiversity and threats to native species, and reinforce the importance of conserving the region’s flora. Species descriptions, illustrations, identification keys and information on geographic distribution and habitat are provided.


Introduction
The family Bignoniaceae Juss. consists of approximately 840 species and 80 genera distributed in tropical and subtropical regions of the world and is especially diverse in South America (Judd et al. 2002;Gentry 1980;Olmstead et al. 2009;Lohmann & Ulloa 2014). It is one of the most important families in the composition of Neotropical forests, where approximately 80% of the species occur, mainly as lianas (Gentry 1972). There are five major regions of distribution: Central America and western South America, the Guyana region, the lowlands of Amazonia, the Cerrados and Caatingas of Brazil and the Brazilian coastal region, including the Atlantic Forest. Brazil is the most important distribution center of the family (Gentry 1979; Barroso et al. 1991), comprising 416 species and 33 genera in three tribes (Bignonieae, Crescentieae and Tecomeae), which differ in habit and fruit morphology (Bureau & Schumann 1897;Gentry 1980;BGF 2018).
The family occurs in different environments ranging from open savannahs to humid evergreen forests (Gentry 1980;Lohmann & Ulloa 2007). The plants are characterized by their woody habit, mostly lianas, trees or semi-shrubs, with cylindrical or angular branches, with usually opposite compound leaves, rarely alternate and simple. In the lianas, the leaves are bi-or tri-foliolate with the terminal leaflet modified into tendrils (Lohmann & Taylor 2014). The leaf indumentum may vary widely within the same species and can include a mixture of glandular and non-glandular trichomes. The inflorescence may be racemose or thyrsoid and the calyx may be campanulate, cupular, or spathaceous. The fruit is dehiscent with winged seeds (Fisher et al. 2004;Cipriani 2006;Pereira & Mansano 2008).
Piauí is located in an ecotonal zone that lies between the Amazonian humid evergreen forest to the west, the seasonal Cerrados to the southwest and south and the semiarid deciduous Caatinga vegetation to the east. As a result, the plant communities of the state are rich in species and have variable phytophysiognomies that are influenced especially by climatic differences arising from their location (SEMA 2005). Although the coast of Piauí is the least extensive in the northeast region, it includes habitats that have been little investigated by taxonomists and ecologists, and is a priority area for research due to the increasing impact of human development. The objective of this study was to carry out a taxonomic survey of the species of Bignoniaceae occurring in this region, providing descriptions, an identification key, geographic distribution, and illustrations showing diagnostic characteristics.

Material and Methods
Access to genetic patrimony for this project has been officially registered by the Universidade Federal do Piauí on the data base of the Sistema Nacional de Gestão do Patrimônio Genético e do Conhecimento Tradicional Associado (Ministério do Meio Ambiente, Conselho de Gestão do Patrimônio Genético) under the registration code A8B44BB.
Field expeditions were conducted from August 2014 to August 2018 in the four coastal municipalities of Piauí (Cajueiro da Praia, Ilha Grande, Luis Correia, and Parnaíba). The climate of this region is megathermic according to the classification of Köppen-Geiger (Alvares et al. 2014), with summer rains and warm winters, minimum annual average temperatures of 20 ºC and maxima of 32 ºC (Aguiar 2004) and an annual average precipitation of 1,223 mm (Radam 1973;Cepro 2010). The topography mainly comprises re-worked tabular surfaces (low plateaux), the flat relief including gently undulating areas with elevations ranging from 150 to 250 m (Jacomine et al. 1986). The soils of the region are hydromorphic, gleyed, dystrophic, with marine and alluvial quartz sands (Radam 1973;Cepro 2010). The landscape Rodriguésia 72: e02312019. 2021 is formed by quaternary sediments and three geomorphological units are recognized: beach zone and dunes, fluvial-marine plain, and river plain (Chaves et al. 2007). The vegetation is composed of shrubs and low trees characteristics of restinga, dune, and Caatinga vegetation (Cepro 2010), and herbaceous species especially on dunes adjacent to mangrove areas and in seasonally flooded or non-flooded campos (natural grassland-herbaceous vegetation) (Santos-Filho et al. 2010).
The descriptions of the taxa were worked up using material collected in the study area and examined in the HDELTA herbarium with the use of a LEICA EZ4D stereomicroscope. Information on flowering and fruiting seasons and habitats of the species were based on field observations. The phytogeographic distribution data are in accordance with the Brazilian Flora Species List (Bignoniaceae in BGF 2018). Lists of threatened species were consulted using the National Flora Conservation Center (CNC-Flora 2013), the Fundação Biodiversitas (2017), and the Brazilian Ministry of the Environment (MMA 2007).
This species is endemic to Brazil and occurs in Southeast region (Minas Gerais) and in the Cerrado phytogeographic domain (BGF 2018). In the study area it was collected in flower in January in an ecotone between Caatinga and Cerrado, in sandy soil near the river Igaraçu.   Anemopaegma laeve is characterized by the presence of orbicular foliate prophylls and can be distinguished from A. citrinum Mart. ex DC by its chartaceous leaflets with revolute, corolla with yellow tube and whitish lobes, and flattened orbicular fruit capsule.
This species is a Neotropical liana widely distributed in the tropics (Gentry 1974). It is not endemic to Brazil where it occurs in the North (Acre, Amazonas, Pará, Rondônia, Tocantins), Northeast (Alagoas, Bahia, Ceará, Maranhão, Pernambuco, Piauí, Sergipe), Central-West (Goiás, Mato Grosso do Sul, Mato Grosso), and Southeast (Espírito Santo, Minas Gerais, Rio de Janeiro, São Paulo) regions and in the Amazon, Cerrado, and Atlantic Forest phytogeographic domains (BGF 2018). In the study area, it is popularly known as "liana" and was collected on sand banks associated with river banks and stream sides, characterized as an amphibious or semi-aquatic macrophyte. In coastal Piauí it was observed in flower and fruit during all months of the year.

Dolichandra hispida
This species is not endemic to Brazil, where it occurs in the Central-West (Mato Grosso do Sul, Mato Grosso), Southeast (Minas Gerais, São Paulo), and South (Paraná, Rio Grande do Sul, Santa Catarina) regions and in Atlantic Forest vegetation (Fonseca & Lohmann 2019), near wetlands. In the study area the species was collected in flower in January in Caatinga. This is a new record for the state of Piauí.

22.
Pleonotoma castelnaei is endemic to Brazil, occurring in Northeast (Bahia, Maranhão, Piauí) and Southeast (Minas Gerais) regions and in the Caatinga and Cerrado phytogeographic domains (Gomes 2019). In the study area it was collected in Caatinga with flowering was observed from September to December and fruiting between November and December.