Checklist of the flora of the restingas of Piauí state , Northeast Brazil

Sandy coastal plain vegetation (Restinga) is composed of communities of plants that grow on Quaternary Neosols along the entire extension of the Brazilian coast. The state of Piauí has a coastal extension of 66 km and is entirely located in the semi-arid zone of Northeastern Brazil. This study catalogued the phanerogam species found along the coast of the state of Piauí, the data of which was compiled from surveys in online databases and literature, and herbarium collections. A total of 363 species distributed among 235 genera, and 74 families were identified. The families with the greatest number of species included Fabaceae (108 species), Euphorbiaceae (19), Amaranthaceae (13), Apocynaceae (12), Cyperaceae (12), Rubiaceae (12), Bignoniaceae (11), Malvaceae (11) and Poaceae (11) and represent over 57.6% of the species collected. Approximately 87% of the species were common to other restinga areas in Northeastern Brazil, and ca. 13% were restricted to the coast of the state of Piauí.


INTRODUCTION
The restinga is an ecosystem associated with the Atlantic Forest (Scarano 2002) that shows extreme fragility because of its long occupation and human interference or increasing predation, in which degradation has been intensified by predatory human activity (Rocha et al. 2004;Santos-Filho et al. 2013).
In addition to being highly degraded, this ecosystem is recognized for presenting itself as an environment that is in the process of ecological succession because of its recent establishment during the Quaternary period (Zaluar and Scarano 2000;Santos-Filho et al. 2013).It is believed that species that colonized the restingas originated in the Atlantic forest or other adjacent ecosystems (Rizzini 1997;Araujo 2000;Scarano 2002) but adjusted to the new environmental conditions in the restingas.
Because soil and climatic conditions are the most influential factors for successfully establishing plant communities (Mather and Yoshioka 1968;Araújo et al. 2004), knowing which species are present and how these species are distributed along the Brazilian coast become important for better understanding the dynamics of restingas because such environments typically have poor soil with high salinity (Hay et al. 1981).
Among the Northeastern states, more floristic and structural studies of restinga ecosystems have been undertaken in Pernambuco, Piauí, Bahia, Paraíba and Rio Grande do Norte.In Pernambuco (Zickel et al. 2007) and Ceará (Santos-Filho et al. 2011), studies have provided catalogued the flora in their restingas through the compilation of species records for those that occur in this ecosystem.
Studies aimed at recognizing the species composition of coastal forests have proven to be essential in face of the constant threat of the eradication of these environments due to the rapid degradation and loss of habitat (Rocha et al. 2007), which could trigger the loss of biodiversity and the loss of endemic species in more severe cases (Silva and Tabarelli 2000).
Therefore, the compilation of records of punctual species from floristic inventories and herbarium collections makes it possible to understand the history of species that existed and were no longer collected either by lower collecting efforts or species extinction (Almeida Jr. et al. Santos-Filho et al. | Flora of the restingas of Piauí state, Brazil questionable identification were excluded. The herbarium survey covered plants collected in the territory of the four cities of Piauí state's coast (Ilha Grande, Parnaíba, Luiz Correia and Cajueiro da Praia), which are all located in coastal plains with neosols predominantly quaternary or Barriers Formation (Santos-Filho 2009).
The catalog lists the botanical families and species in alphabetical order.The classification system used was based on APG III (2009).Current species names were confirmed by consulting the MOBOT database (2012), "Flora do Brasil" list (2014) and specialized literature for certain groups.The biological forms of species were identified based on the classification system of Whittaker (1975), and information on the life forms was obtained from herbarium labels.

RESULTS
The final list of phanerogam species reported for restinga areas in the state of Piauí totaled 363 species distributed among 235 genera and 74 families (Table 1).
The state of Piauí has 66 km of coastline that is predominantly composed of sea cliffs of the Barreiras Formation and quaternary quartz sand deposits.Restinga vegetation occupying dunes and inter-dune regions can be found along the entire coast of that state and can have different physiognomies that vary from grassy fields to shrublands or forests and grassy fields with "carnaubais" (Copernicia prunifera) (Santos-Filho et al. 2010).
Even with a small coastline, few studies have been conducted on the coast of Piauí including only two scientific (Santos-Filho et al. 2013;Santos-Filho and Zickel 2013) and one technical study (Fernandes et al. 1996) that has been published with data referring to the restinga vegetation in Piauí.In an effort to fill this lacuna, this study provides a catalog of the phanerogams registered in the restinga areas of Piauí state, Brazil.

MATERIALS AND METHODS
The state of Piauí has a total territorial area of 251.529 km 2 , making it the third largest state in Northeastern Brazil (Figure 1).In addition to the Restinga, the vegetation cover of this area also includes a vegetation mosaic ecotone consisting of Cerrado, Caatinga and Cerrado-Caatinga transitions (Farias and Castro 2004).According to the classification proposed by Velloso et al. (2002), Caatinga occurs in the state in the "Depressão Sertaneja Setentrional" region and the "Campo Maior" and "Ibiapaba-Araripe" complexes.
The species listed in this study were compiled from data available at HAF, IPA, PEUFR and TEPB (acronyms according to Thiers 2014) and from floristic surveys performed in the Delta do Parnaíba Environmental Protection Area (Fernandes et al. 1996;Santos-Filho et al. 2013).All herbarium specimens were considered, including invasive species that grow in lacustrine environments and species typical of areas in contact with mangrove swamps and exotic species.Plants with incomplete or     In a recent floristic survey performed in Piauí state that included part of the upper Northeastern coast (Santos-Filho et al. 2013), the Fabaceae, Poaceae, Cyperaceae, and Euphorbiaceae were found to have the highest number of species.These same families together with the Orchidaceae, Bromeliaceae, and Sapotaceae (Araújo and Henriques 1984;Assis et al. 2004;Martins et al. 2008) are well represented in restinga areas in Southeastern Brazil.
In general, the composition of species observed along the coast of Northeast Brazil resembles the one at the Cerrado and Caatinga.The influence of these biomes on figures in the list of endangered species (IUCN 2012).
Among the species listed, 37% were the first records in the state of Piauí, including Anemopaegma brevipes, Cereus jamacaru, Maytenus distichophylla, Commelina erecta, Andira nitida, Cuphea flava, Byrsonima verbascifolia, and Chiococca alba.This percentage is due primarily to the low record samples (Almeida Jr. et al. 2012) and scarcity of studies in the Northern coastal restinga (Santos-Filho and Zickel 2013), which indicates the importance of not only further floristic but also taxonomic and ecological studies.
The species composition observed were reflections of not only the peculiarities of the restinga ecosystem (with high salinity and low levels of soil nutrients among others) but also environmental degradation (Santos-Filho et al. 2011).Blutaparon portulacoides, Chamaecrista flexuosa, Ipomoea asarifolia, Ipomoea pes-caprae, Mollugo verticillata, Remirea maritima, Richardia grandiflora and Sesuvium portulacastrum (in addition to many members of the Fabaceae, Poaceae and Cyperaceae families) are among the most common plants in dune areas and restingas in Ceará (Matias and Nunes 2001;Santos-Filho et al. 2011), Rio Grande do Norte (Almeida Jr. et al. 2006;Almeida Jr. and Zickel 2009), and Pernambuco states (Zickel et al. 2007;Silva et al. 2008, Almeida Jr. et al. 2009;Cantarelli et al. 2012).
As the biological forms, the results reflects the significant presence of pioneer species that rapidly colonize this environment, mainly dune areas typical of the coast of the state of Piauí, which is similar to that found for the state of Ceará (Santos-Filho et al. 2011) with low open physiognomies of erect herbaceous species and vine-psammophytes.the species composition of restingas in the Northeast was also confirmed for the coast of Piauí, in which 48 species (13% of species surveyed in this study) were previously cited in other floristic studies carried in Cerrado and Caatinga areas of this state (Lemos and Rodal 2002;Lemos 2004;Chaves et al. 2007;Castro et al. 2007;Mesquita and Castro 2007;Castro et al. 2009;Mendes and Castro 2010;Oliveira et al. 2011;Pessoa and Santos-Filho 2011).Among the woody species, Allamanda blanchetii, Cordia rufescens, Croton blanchetianus, Jatropha molissima, Copaifera luetzelburgii, Copaifera martii, Piptadenia moniliformis were notable, and Borreria spinosa, Marsypianthes chamaedrys, Pectis oligocephala, and Zornia sericea were prominent among herbaceous species.
In addition, nine species belonging to the Amazon Domain were recorded and are specific to the conditions of the ecotonal state of Piauí.These species represent 2.5% of the species in this survey and include Byttneria divaricata, Crenea maritima, Helicteres pentandra, Machaerium inundatum, Machaerium lunatum, Manihot tristis, Manilkara cavalcantei, Pachira aquatica, and Pilocarpus microphyllus (Table 1).Among the species cited, it is noteworthy that Manilkara cavalcantei was first recorded on the coast of Piauí state by Almeida Jr. et al. (2011).This fact demonstrates the importance of conserving the remaining restingas, since Manilkara cavalcantei The data presented here indicate the importance of herbaceous species in the physiognomic composition of beach areas.However, as occurs in other coastal areas of Northeastern Brazil (Silva et al. 2008;Almeida Jr. et al. 2009;Santos-Filho et al. 2011;Cantarelli et al. 2012), it is quite possible that due to their immediate proximity to the ocean, the restinga areas of Piauí state have been widely altered due to human activity, namely leisure and tourism.Therefore, conservation efforts focusing on these coastal vegetation communities must include quantitative studies and attempt to decelerate anthropogenic impact.

Figure 2 .
Figure 2. Distribution of the number of species in relation to the biological form of the species listed in the coastal areas of Piauí state, Brazil.

Table 1 .
List of phanerogamic species of restinga areas in Piauí state.Filho et al. | Flora of the restingas of Piauí state, Brazil ContinuedSantos-
Continued Santos-Filho et al. | Flora of the restingas of Piauí state, Brazil