Checklist of aquatic and marshy Monocotyledons from the Araguaia River basin, Brazilian Cerrado

Abstract Background The Araguaia River basin runs through the states of Goiás, Mato Grosso, Tocantins, and Pará, covering 373,000 Km2, mostly within the Brazilian Cerrado. The region has a wide variety of wetlands. The climate is characterized by high temperatures and strongly seasonal precipitation. There are two well defined seasons: the dry season (winter-spring) and the rainy season (summer- fall). The Araguaia River basin is dominated by plinthosoils that are found in low flat areas, poorly drained and prone to flooding, yielding wetland habitats of high plant diversity. Since the 1970s, human activities have led to reduction in both the diversity and area of wetlands. The construction of the Belém-Brasília highway and hydroelectric dams, as well as the expansion of agricultural and mining activities, have had major impacts on the region. New information The flora diversity data of the Araguaia River basin was developed through field work, herbarium research, and use of a database (Species Link). The resulting checklist of 162 aquatic and marshy monocotyledons from the Araguaia River basin represents 20 families and 50 genera. Cyperaceae (51 spp.), Poaceae (39 spp.), and Eriocaulaceae (16 spp.) are the most representative families. Life form analysis indicates that helophytes predominate (98 spp.; 60.5%). One hundred one species are native to tropical and/or subtropical America and twenty one are endemic to Brazil. Ninety-three species are new occurrences for the Araguaia River basin. Among them, three species are reported in the Brazilian Cerrado for the first time. This work contributes to the understanding of aquatic plant diversity in the Cerrado and other savanna-like vegetation physiognomies; environments and habitats poorly understood taxonomically and undercollected generally.


Introduction
The Brazilian Cerrado is one of the most threatened ecosystems in Brazil and was ranked among the 34 most important biodiversity hotspots of the world (Mittermeier et al. 2004). In the first survey of the Cerrado flora, Mendonça et al. (1998) listed ca. 6,000 angiosperm species. After that, efforts to raise the knowledge on biodiversity for this area nearly doubled the number of species, with the monocotyledons (Lilianae) accounting for roughly 25% of the increase (Sano et al. 2008). The Araguaia River basin runs through the states of Goiás, Mato Grosso, Tocantins, and Pará; covering 373,000 Km , mostly within the Cerrado. The region is rich in wetlands like rivers, streams, temporary or permanent swamps and pools. The climate is characterized by high temperatures that reach 100.4 °F in September and October and strongly seasonal precipitation of 1750 to 2000 mm per year. There are two well-defined seasons: the dry season (July-November) and the rainy season (December-June) (IBGE 1989). This basin is dominated by plinthosoils, which are poorly drained and usually found in low flat areas prone to flooding (Resende et al. 1995), forming temporary or permanent swamps. The importance of wetland habitats ecologically and in terms of plant biodiversity globally has been emphasized by many authors (e.g. Gopal and Junk 2000, Thomaz and Cunha 2010, Paz and Bove 2011, Mendonça et al. 2012, Moura-Júnior et al. 2013). On the other hand their taxonomic diversity is rarely the focus of wetland studies (e.g. Pedralli et al. 997, Bove et al. 2003, Moreira et al. 2011, Contaifer et al. 2013, Sabino et al. 2015.
The first study to include aquatic plants in Brazil was carried out by Hoehne (1915) in the Cerrado and in the Amazon Forest. The same author published "Plantas Aquáticas" (Hoehne 1948), a pioneer study of aquatic flora from Brazil. Also, species from Pantanal have been studied Pott 1997, Pott andPott 2000). A checklist from the states of Mato Grosso and Mato Grosso do Sul (Dubs 1998) and the vascular flora of the Emas National Park, located in the Araguaia River basin (Batalha and Martins 2002) incidentally included some aquatic plants, though they did not survey aquatic ecosystems. In spite of the vast area encompassed by the Araguaia River basin and the broad diversity of wetland habitats, the aquatic and marshy flora of this region is little known. This work contributes to 2 a better understanding of the aquatic environments in the Cerrado and other savanna-like vegetation physiognomies. Notably, herbarium collections are depauperate with respect to aquatic plants, reflecting both the difficulty of collecting in wetlands, as well as the scarcity of specialists in the taxonomic groups included. Generally, these plants are incidentally collected by terrestrial plant specialists and the quality of incidental collections may challenge correct identification. Thus, the real diversity of the aquatic flora from the Brazilian Cerrado will be better known through studies carried out by specialists focusing on aquatic habitats on the region. Our efforts to improve the knowledge of the aquatic flora from the Araguaia River basin have resulted in the discovery of new species Bove 2001, Oliveira et al. 2011) and on the better understanding of taxonomic groups such as the Alismatales (Koehler and Bove 2004) and Cyperaceae (Gil et al. 2007, Oliveira et al. 2011. As a result of an intensive search of collections and field work, we provide here an annotated list of aquatic and marshy monocots found in the Araguaia River basin. The results increase our knowledge of biodiversity in this basin and in the Cerrado. Species not previously reported to this area are highlighted. We also include images of the specific habitats and species from the Araguaia River basin.

Materials and methods
Material for this study is from collections made between 5-20°S and 45-55°W, located approximately between the city of Alto Araguaia at the southern limit and the city of Formoso do Araguaia at the northern limit (Fig. 1). Collections were made randomly, primarily along state roads (MT-100,  and federal roads (BR-070, BR-158, BR-242 and BR-251); in both, rainy and dry seasons (1997, 1999, 2004, 2006, and 2007). Part of this material has been used in previous studies (Gil et al. 2007, Koehler and Bove 2001, Koehler and Bove 2004, Oliveira and Bove 2011, which overlap some portion of the study area for the present study. Surveyed habitats included rivers, streams, seasonally and permanently flooded areas (Fig. 2). The specimens were dried following standard techniques (Fidalgo and Bononi 1989). Voucher materials were deposited in the herbarium of the Museu Nacional from the Federal University of Rio de Janeiro (R). Material from the following herbaria: R, RB, UB and UFG (http://sweetgum.nybg.org/science/ih/) were also analyzed. The search in the consulted herbaria was done analyzing all monocotyledonous material from the Araguaia River basin. The database SpeciesLink (2002) was consulted using the searching word "Araguaia". Only those vouchers identified by experts in each family were added to the checklist. The data were compared to the previous bibliography on the Cerrado above mentioned and to the Lista de espécies da flora do Brasil (2010). The taxa were displayed in alphabetic order by family. The circumscription of families followed APG III (2009), the binomials and the geographic distribution is according the World Checklist of selected plant families (2013). The definition of aquatic plants adopted herein is sensu Cook 1996: "…whose photosynthetically active parts are permanently or, at least, for several months each year submerged in water or floating on the surface of water". It includes the life form helophytes from the marshy areas as well the strictly aquatic species with their related life forms (submerged-fixed or submerged-free, floating-fixed or floatingfree, and emergent). Araguaia River basin map (Gil et al. 2007, Oliveira et al. 2011). Checklist of aquatic and marshy Monocotyledons from the Araguaia River ...

Discussion
We report 162 species of aquatic and marshy monocotyledons, distributed in 20 families and 50 genera (Table 1). Cyperaceae (51 spp.) (Fig. 2b)   In terms of floristics, 101 species are native to tropical and/or subtropical America, 40 are widely distributed and twenty are endemic to Brazil. Ninety-three species are new occurrences to the Araguaia River basin (Table 1). Floristic analysis generally emphasizes arboreal and shrub species. Among the studies that includes the herbaceous species; the aquatic taxa are rarely included or, at least, underestimated. This is reflected in the scarcity of aquatic vouchers in collections (Paz and Bove 2007). 2004), only 13 out of 1273 vascular species are common with the list we produce herein. Clearly there is a need for more field work specifically focused on aquatic environments. Also, the detailed search through the database SpeciesLink (2002) added three families (Arecaceae, Cannaceae and Orchidaceae) and 62 species to the previous list based on field efforts (Table 1), showing the importance of a database as a tool in analyzing floristic diversity. The Araguaia River basin is far richer in aquatic and marshy species than previously realized. In addition to the new species described for this region mentioned above, the description of another new species of Eriocaulon is in progress.
Three species are not cited to the Brazilian Cerrado in any publication: Panicum latissimum J.G.Mikan ex Trin., Philodendron imbe Schott, and Rhynchospora aff. unisetosa T. Koyama. Panicum latissimum and Philodendron imbe are endemic from Brazil and Rhynchospora unisetosa is not reported to occur in Brazil (Alves et al. 2010) but it is found in Colombia and Venezuela; neighboring countries of Brazil (World Checklist of selected plant families 2013). The specimen identified as affinis R. unisetosa could also be another new species to the Araguaia region that needs attention from taxonomists. These species were, probably, overlooked and undercollected, highlighting the importance of field work by specialists, and points to the problem of relying on existing collections to determine real aquatic plant diversity. Incongruent data on geographic distribution and/or taxonomic identity were observed in some species; although Syagrus petraea (Mart.) Becc. and Xyris caroliniana Walter are recognized for the Cerrado and reported for the Araguaia basin using herbarium collections, these species are not mentioned in database of the Brazilian species list (Coelho et al. 2010, Wanderley et al. 2010. These apparent inconsistencies need the notice of the specialists to be resolved. We opted to keep these taxa in our survey in order to call attention to this matter and, moreover, we prefer to superestimate rather than subestimate the diversity. We consider that the consequences regarding conservation actions are worse given subestimates. Since the 1970s, many projects have led to reduction in both diversity and area of wetlands. The construction of the Belém-Brasília highway and hydroelectric dams, as well as the expansion of agricultural and mining activities (Moss and Moss 2005), caused major impacts to wetlands in those areas. Notably, no species in this study is mentioned in the official list of Brazilian endangered species (Martinelli and Moraes 2013) probably as a result of insufficient data. Burmannia flava Mart. and Paspalum cinerascens (Döll) A.G.Burm. & M.Bastos are in redlists compiled by SpeciesLink (2002); Eriocaulon araguaiense and E. cylindratum are considered endangered by Oliveira and Bove (2015), both belonging to the ENB2 category (IUCN 2001).
help in identification of species and Paula Philbrick for the English language revision on the manuscript. This work was supported by grants of CAPES to A.L.R.O. and CNPq to C.P.B.