Abstract:

"Cangas" are ironstone outcrops occurring at the foot of the Urucum Plateau, on the western edge of Pantanal, Corumbá-MS. In Brazil, the knowledge about flora and ecology of the plant communities associated with these formations is still incipient. These habitats are among the most threatened and less studied in Brazil because of their association with high quality iron ore deposits. We present a cheklist of the flora from these formations, resulting from different authors' collecting efforts in 10 areas of the Plateau. A total of 302 species have been recorded; they were distributed in 53 botanical families and 175 genera. Poaceae (43 species), Fabaceae (41), Euphorbiaceae (22), Cyperaceae (19), Malvaceae (19), Convolvulaceae (15), Malpighiaceae (13) and Apocynaceae (11) accounted for 60.6% of the species richness. Our data add 59 new occurrences of species of angiosperms to the ironstone outcrops flora in the Urucum Plateau. Among these, 27 species had no occurrence record for Mato Grosso do Sul and three species had not yet been recorded for Brazil. The high diversity and presence of endemic, rare, endangered and/or not yet cataloged species for the Urucum Plateau region, reinforces the need for local conservation units that can guarantee the preservation of these species, since the existing environmental protection areas are insufficient to guarantee the maintenance of typical species from this habitat in the region.

Keywords:
biodiversity; ferruginous geosystem; Pantanal

Resumo:

As cangas são afloramentos ferruginosos que ocorrem ao sopé do Maciço do Urucum, na Borda Oeste do Pantanal, Corumbá-MS. No Brasil, o conhecimento sobre a florística e ecologia das comunidades vegetais associadas a essas formações ainda é incipiente. Esses habitats estão entre os mais ameaçados e menos estudados do Brasil, devido à sua associação a depósitos de minério de ferro de alta qualidade. Nós apresentamos um cheklist da flora desses ambientes, resultante de diversos esforços de coleta de diferentes autores em 10 áreas do Maciço. Foram registradas 302 espécies distribuídas em 53 famílias botânicas e 175 gêneros. Poaceae (43 espécies), Fabaceae (41), Euphorbiaceae (22), Cyperaceae (19), Malvaceae (19), Convolvulaceae (15), Malpighiaceae (13) e Apocynaceae (11) representaram 60,6% da riqueza específica. Nossos dados adicionam 59 novas ocorrências de espécies de angiospermas para a flora de cangas do Maciço do Urucum. Das espécies apresentadas, 27 ainda não possuíam registro de ocorrência para o Mato Grosso do Sul e três espécies não haviam sido ainda registradas para o Brasil. A alta diversidade e a presença de espécies endêmicas, raras, ameaçadas e/ou ainda não catalogadas para a região do Maciço do Urucum reforça a necessidade de unidades de conservação locais que possam garantir a preservação dessas espécies, uma vez que as áreas de proteção ambiental existentes na região são insuficientes para garantir a manutenção de populações típicas desse habitat.

Palavras-chave:
biodiversidade; geossistema ferruginoso; Pantanal

Introduction

Ferruginous geosystems are landscapes of great value due to the uniqueness of their flora and fauna, presence of endemic species and/or provided ecosystem services (Tibbett 2015TIBBETT, M. 2015. Mining in ecologically sensitive landscapes: concepts and challenges. In Mining in ecologically sensitive landscapes (M.Tibbett, ed.). Csiro Publishing. Leiden, p.3-6.). Due to the soil porosity and permeability in these formations, they have high water recharge capacity and storage, forming large aquifers that supply springs and cities (Carmo et al. 2012CARMO, F.F., CARMO, F.F., CAMPOS, I.C. & JACOBI, C.M. 2012. Cangas: ilhas de ferro estratégicas para a conservação. Ciênc. Hoje 295:48-53.). However, because they are located in regions with large mineral deposits of economic interest, they are among the most endangered landscapes in the world (Jacobi & Carmo 2008aJACOBI, C.M. & CARMO, F.F. 2008a. The contribution of ironstone outcrops to plant diversity in the Iron Quadrangle, a threatened Brazilian landscape. Ambio 37:324-326. , Tibbett 2015TIBBETT, M. 2015. Mining in ecologically sensitive landscapes: concepts and challenges. In Mining in ecologically sensitive landscapes (M.Tibbett, ed.). Csiro Publishing. Leiden, p.3-6.).

These environments, originated in the Archean and Paleoproterozoic period, are usually located in mountain tops, but can also be found in foothills (Souza & Carmo 2015SOUZA, C. R. & CARMO, F. F. 2015. Geossistemas ferruginosos no Brasil. In Geossistemas Ferruginosos do Brasil (F.F. do Carmo & L.H.Y. Kamino, eds.), 3i Editora, Belo Horizonte, p.47-76.). In addition to presenting high biological value, these environments harbor sites of inestimable archaeological value and important water resource deposits (Jacobi et al. 2015JACOBI, C.M., CARMO, F.F., CARMO, F.F. & CAMPOS, I.C. 2015. Iron geosystems: priority areas for conservation in Brazil. In Mining in ecologically sensitive landscapes (M.Tibbett, ed.). Csiro Publishing. Leiden, p. 55-77., Souza & Carmo 2015SOUZA, C. R. & CARMO, F. F. 2015. Geossistemas ferruginosos no Brasil. In Geossistemas Ferruginosos do Brasil (F.F. do Carmo & L.H.Y. Kamino, eds.), 3i Editora, Belo Horizonte, p.47-76.). In Brazil, ferruginous geosystems occur in the states of Bahia, Minas Gerais, Mato Grosso do Sul and Pará, and they are important mineral exploration areas (Carmo et al. 2012CARMO, F.F., CARMO, F.F., CAMPOS, I.C. & JACOBI, C.M. 2012. Cangas: ilhas de ferro estratégicas para a conservação. Ciênc. Hoje 295:48-53.). These geosystems, known in Brazil as "cangas", usually occur in higher relief areas, with tabular tops (Souza & Carmo 2015SOUZA, C. R. & CARMO, F. F. 2015. Geossistemas ferruginosos no Brasil. In Geossistemas Ferruginosos do Brasil (F.F. do Carmo & L.H.Y. Kamino, eds.), 3i Editora, Belo Horizonte, p.47-76.). However, in the Urucum Plateau region, located in the municipalities of Corumbá and Ladário, state of Mato Grosso do Sul, they not only occur on tops but also in low altimetric levels and slopes (Del'arco et al. 1982DEL'ARCO, J.O., SILVA, R.H., TARAPANOFF, I., FREIRE, F.A., PEREIRA, L.G.M., SOUZA, S.L., LUZ, D.S., PALMEIRA, R.C.B. & TASSINARI, C.C.G. 1982. Geologia. In Projeto RADAMBRASIL Folha SE.21 - Corumbá e parte da Folha SE.20 (Levantamento de Recursos Naturais, 27). Ministério de Minas e Energia, Rio de Janeiro, p.25-160., Takahasi 2015TAKAHASI, A. 2015. Flora das cangas de Corumbá, MS: Diversidade e conservação. In Geossistemas Ferruginosos do Brasil (F.F. do Carmo & L.H.Y. Kamino, eds.), 3i Editora, Belo Horizonte, p.317-334.). These low altimetric ironstone outcrops are called "bancadas lateríticas" (Takahasi & Meirelles 2014TAKAHASI, A. & MEIRELLES, S.T. 2014 Ecologia da vegetação herbácea de bancadas lateríticas (cangas) em Corumbá, MS, Brasil. Hoehnea 41(4):515-528.).

The Urucum Plateau represents the lithostratigraphic unit of most economic interest in Mato Grosso do Sul, due to the presence of important deposits of iron and manganese (Del'arco et al. 1982DEL'ARCO, J.O., SILVA, R.H., TARAPANOFF, I., FREIRE, F.A., PEREIRA, L.G.M., SOUZA, S.L., LUZ, D.S., PALMEIRA, R.C.B. & TASSINARI, C.C.G. 1982. Geologia. In Projeto RADAMBRASIL Folha SE.21 - Corumbá e parte da Folha SE.20 (Levantamento de Recursos Naturais, 27). Ministério de Minas e Energia, Rio de Janeiro, p.25-160.). Ironstone outcrops of Urucum plateau are Quaternary deposit formations produced under climatic conditions different from those of the current era. They probably occurred at the time of the Paraguay River Depression and the plio-plestocene plediplain origin, period in which a semi-arid weather subjected to torrential rains and erosive processes prevailed (Del'arco et al. 1982DEL'ARCO, J.O., SILVA, R.H., TARAPANOFF, I., FREIRE, F.A., PEREIRA, L.G.M., SOUZA, S.L., LUZ, D.S., PALMEIRA, R.C.B. & TASSINARI, C.C.G. 1982. Geologia. In Projeto RADAMBRASIL Folha SE.21 - Corumbá e parte da Folha SE.20 (Levantamento de Recursos Naturais, 27). Ministério de Minas e Energia, Rio de Janeiro, p.25-160.).

In Brazil, the knowledge about floristic and ecology of plant communities associated with ferruginous geosystems is still incipient (Jacobi & Carmo 2011JACOBI C.M. & CARMO, F.F. 2011. Life-forms, pollination and seed dispersal syndromes in plant communities on ironstone outcrops, SE Brazil. Acta Bot. Bras. 25:395-412., Jacobi et al. 2015JACOBI, C.M., CARMO, F.F., CARMO, F.F. & CAMPOS, I.C. 2015. Iron geosystems: priority areas for conservation in Brazil. In Mining in ecologically sensitive landscapes (M.Tibbett, ed.). Csiro Publishing. Leiden, p. 55-77.). These habitats are among the most threatened and least studied in Brazil respectively due to their association with iron ore deposits with high quality and the difficulty of access (Jacobi & Carmo 2008aJACOBI, C.M. & CARMO, F.F. 2008a. The contribution of ironstone outcrops to plant diversity in the Iron Quadrangle, a threatened Brazilian landscape. Ambio 37:324-326. ). Studies on ironstone outcrops flora are recent and concentrated largely on the Iron Quadrangle, in the state of Minas Gerais (Mourão & Stehmann 2007MOURÃO, A. & STEHMANN, J.R. 2007. Levantamento da flora do campo rupestre sobre canga hematítica couraçada remanescente na Mina do Brucutu, Barão de Cocais, Minas Gerais, Brasil. Rodriguésia 58:775-786., Viana & Lombardi 2007VIANA, P.L. & LOMBARDI, J.A. 2007. Florística e caracterização dos campos rupestres sobre canga na Serra da Calçada, Minas Gerais, Brasil. Rodriguésia 58(1): 159-177., Pifano et al. 2010PIFANO, D.S., VALENTE, A.S.M., ALMEIDA, H.S., MELO, P.H.A., CASTRO, R.M. & VAN DEN BERG, E. 2010. Caracterização florística e fitofisionômica da Serra do Condado, Minas Gerais, Brasil. Biota Neotropica, 10(1): http://www.biotaneotropica.org.br/v10n1/pt/fullpaper?bn01010012010+pt. Last acess: Aug 5th, 2018.
http://www.biotaneotropica.org.br/v10n1/... , Ataíde et al. 2011ATAÍDE, E.S., CASTRO, P.T.A. & FERNANDES, G.W. 2011. Florística e caracterização de uma área de campo ferruginoso no Complexo Minerário Alegria, Serra de Antônio Pereira, Ouro Preto, Minas Gerais, Brasil. Rev. Árvore, 35(6):1265-1275., Carmo & Jacobi 2013CARMO, F.F. & JACOBI, C.M. 2013. A vegetação de canga no Quadrilátero Ferrífero, Minas Gerais: caracterização e contexto fitogeográfico. Rodriguésia, 64(3):527-541.). The results obtained by those studies indicate that ironstone outcrops harbor a large number of plant species, contributing to the increase of the alpha diversity of the regions where they occur (Jacobi & Carmo 2008aJACOBI, C.M. & CARMO, F.F. 2008a. The contribution of ironstone outcrops to plant diversity in the Iron Quadrangle, a threatened Brazilian landscape. Ambio 37:324-326. ).

In the region of Corumbá, some ironstone outcrops in the Urucum plateau have been studied for their ecological aspects (Takahasi 2010TAKAHASI, A. 2010. Ecologia da vegetação em bancadas lateríticas em Corumbá, MS. Tese de doutorado, Universidade de São Paulo, São Paulo., Takahasi & Meirelles 2014TAKAHASI, A. & MEIRELLES, S.T. 2014 Ecologia da vegetação herbácea de bancadas lateríticas (cangas) em Corumbá, MS, Brasil. Hoehnea 41(4):515-528., Oliveira 2016OLIVEIRA, P.P. 2016. A influência do tamanho insular sobre a fenologia de plantas em bancadas lateríticas (cangas) de Corumbá, Mato Grosso do Sul. Dissertação de Mestrado, Universidade Federal de Mato Grosso do Sul, Campo Grande.) and flora (Takahasi 2010TAKAHASI, A. 2010. Ecologia da vegetação em bancadas lateríticas em Corumbá, MS. Tese de doutorado, Universidade de São Paulo, São Paulo., Takahasi 2015TAKAHASI, A. 2015. Flora das cangas de Corumbá, MS: Diversidade e conservação. In Geossistemas Ferruginosos do Brasil (F.F. do Carmo & L.H.Y. Kamino, eds.), 3i Editora, Belo Horizonte, p.317-334.); but there is no listing that includes all species already collected in the region. In this study we present a checklist of species of Angiosperms from the ironstone outcrops in Urucum Plateau, based on several collecting efforts carried out in region from the 1990s to the present time, in order to fill the information gaps about the flora of these environments and evaluate the similarity between the ferruginous outcrops from Mato Grosso do Sul and those ferruginous outcrops from other regions.

Material and Methods

The studied ironstone outcrops are located at the foot of the Urucum Plateau Residual, a non-floodable region around the municipalities of Corumbá and Ladário (Figure 1), the western border of Pantanal, Mato Grosso do Sul, Midwest region of Brazil. The plateau, also known as Urucum Massif, is a complex of hills called locally as Ururum, Santa Cruz, Grande, Rabichão, São Domingos and Tromba dos Macacos, whose altitudes vary between 80 to 1.065 m, being the highest hill recognized as the highest point of the State (Borges et al. 1997BORGES, C.A., WERLE, H.J.S., ROSA, D.B., PAIVA, D.J., MORAES, E.P. & SILVA, L.B.S.M. 1997. Geomorfologia. In BRASIL. Ministério do Meio Ambiente, dos Recursos Hidrícos e da Amazônia Legal. Plano de Conservação da Bacia do Alto Paraguai (Pantanal) - PCBAP. Diagnóstico dos meios físico e biótico.MMA/SEMAM/PNMA, Brasília, v.2, t.3, p.73-119., Damasceno-Junior 2005DAMASCENO-JUNIOR, G.A. 2005. Estudo florístico e fitossociológico de um gradiente altitudinal no Maciço do Urucum, Mato Grosso do Sul, Brasil. Tese de Doutorado, Instituto de Biologia, UNICAMP, Campinas.). The area covers approximately 1.211 km² and is bordered on north by the Paraguay River, on west by the Bolivian border, on south and east by the Pantanal floodplain (Silva et al. 2000SILVA, J.S.V., POTT, A., CARDOSO, E. L., MORAES, A. S., SALIS, S. M., POTT, V. J., MAURO, R. de A. & GALDINO, S. G. 2000. Avaliação integrada do Maciço do Urucum e adjacências - procedimentos e diretrizes. In Zoneamento ambiental da borda oeste do Pantanal: Maciço do Urucum e adjacências (J.S.V.SILVA, ed.). Embrapa Informação e Tecnologia, Brasília, p.9-22.). Ironstone outcrops from this region occur along the drainage lines at the foot of the plateau hills (about 100 to 150 m altitude), and due to the predominantly flat terrain, small pools of water may accumulate during the rainy season.

Ten ironstone outcrops were included in this inventory: Pantanal Park Road, Band'alta farm, Monjolinho farm, Figueira farm, São João farm, São Sebastião do Carandá farm, two sites in the Municipal Natural Park Piraputangas, Uruba farm and Rabicho farm (Table 1).

In the Urucum Plateau region, the average annual temperature is 25.1 ºC and the average rainfall is 1.070 mm annually (Soriano 1997SORIANO, B.M. 1997. Caracterização Climática de Corumbá-MS. Boletim de Pesquisa, 11, Embrapa, Corumbá.). There are two well-defined seasons, a dry season that runs from May to September and a rainy season from October to March, with 45% of rainfall occurring from December to February (Loureiro et al. 1982LOUREIRO, R.L., LIMA, J.P.S. & FONZAR, B.C. 1982. Vegetação. In Projeto RADAMBRASIL Folha SE.21 - Corumbá e parte da Folha SE.20 (Levantamento de Recursos Naturais, 27). Ministério de Minas e Energia, Rio de Janeiro, p.329-372.).

The vegetation surrounding these ironstone outcrops is a Submontane Seasonal Decidual Forest (Damasceno-Junior 2005). We can characterize three habitats in ironstone outcrops at Urucum Plateau: the first one is hardened ferruginous substrate where plants established directly on them or in places with a thin layer of sediment. The second one consists of soil islands, specially mats of monocotyledons, with a deeper layer of soil that allows establishment of phanerophytes. Finally, the third one is constituted by ephemeral flush communities that occurs on runoff-habitats like the slopes of ironstone outcrops allowing the establishment of typical flooded plant species.

The checklist of the ironstone outcrops flora in the Urucum Plateau was elaborated through data collected in Fazenda Band'alta, from January 2017 to July 2018; in researches made by the authors over several years in the outcrops from the region and Herbaria queries at Universidade Federal de Mato Grosso do Sul, Campus Corumbá (COR) and Campo Grande (CGMS); Herbarium of Embrapa Pantanal (CPAP); Herbarium Friburguense of Pontifícia Universidade Católica do Rio de Janeiro (FCAB); Herbarium of Universidade Estadual de Campinas (UEC); Herbarium of Instituto de Biociências at Universidade do Rio Grande do Sul (ICN); Herbarium Maria Eneyda P. K. Fidalgo, at Instituto de Botânica de São Paulo (SP) and Herbarium of Universidade de Brasília (UB). The obtained dataset covers a large part of the ironstone outcrops flora in the region, and was later supplemented with herbaria data available on internet (CRIA 2018CRIA. Centro de Referência e Informação Ambiental. 2018. SpeciesLink. Available in: http://www.splink.org.br/index. Access in: Jul 26th, 2018.
http://www.splink.org.br/index... , Flora do Brasil 2020FLORA DO BRASIL 2020 em construção. 2018. Jardim Botânico do Rio de Janeiro. Available in: <http://floradobrasil.jbrj.gov.br/>. Access in: Sep 4th, 2018.
http://floradobrasil.jbrj.gov.br/... , Jabot 2018JABOT. 2018. Banco de Dados da Flora Brasileira. JBRJ - Instituto de Pesquisas Jardim Botânico do Rio de Janeiro. Available in: <http://cor.jbrj.gov.br/v2/consulta.php >. Access in: Sep 5th, 2018.
http://cor.jbrj.gov.br/v2/consulta.php... ). We considered only specimens identified at the taxonomic level of species and excluded those with dubious identification or at the genera-level. The taxa classification followed the APG IV system (2016)APG. 2016. An update of the Angiosperm Phylogeny Group classification for the orders and families of flowering plants: APG IV. Botanical Journal of the Linnean Society 181:1-20., and the nomenclature and synonymizations were updated according to Flora do Brasil 2020 (2018)FLORA DO BRASIL 2020 em construção. 2018. Jardim Botânico do Rio de Janeiro. Available in: <http://floradobrasil.jbrj.gov.br/>. Access in: Sep 4th, 2018.
http://floradobrasil.jbrj.gov.br/... . The similarity in species composition among the 10 analyzed ironstone outcrops was calculated using the Sorensen Similarity Index.

Results

A total of 302 species distributed in 53 botanical families and 175 genera were cataloged (Table 2). The richest species families were Poaceae (43 species), Fabaceae (41), Euphorbiaceae (22), Malvaceae (19), Cyperaceae (19), Convolvulaceae (15), Malpighiaceae (13) and Apocynaceae (11) that represented 60.6% of the specific richness found in the ironstone outcropsof the region (Figure 2). Poaceae, Fabaceae, Euphorbiaceae and Malvaceae are also the families with the highest number of genera, being Cyperus (9), Croton (8), Mimosa (7), Portulaca (7) and Evolvulus (6) the most common genera.

In the soil islands, there are deciduous forest species as Aspidosperma quirandy Hassl., Pseudobombax marginatum (A.St.-Hil.) A.Robyns and Myracrodruon urundeuva Allemão, whereas in areas where there is a thin layer of soil only herbaceous species can be established, in many cases annuals for example, Gomphrena centrota E. Holzh. and Borreria verticillata (L.) G.Mey. In the seasonally wet areas we can find species such as Ludwigia lagunae (Morong) H. Hara, Crotalaria pallida Aiton, Sporobolus indicus (L.) R.Br. and Eleocharis contracta Maury ex Micheli.

Based on the species list of Flora do Brasil 2020FLORA DO BRASIL 2020 em construção. 2018. Jardim Botânico do Rio de Janeiro. Available in: <http://floradobrasil.jbrj.gov.br/>. Access in: Sep 4th, 2018.
http://floradobrasil.jbrj.gov.br/... , among the total number of recorded species, 177 (58.61%) are of wide distribution, occurring in almost all regions in Brazil, such as Acrocomia aculeata (Jacq.) Lodd. ex Mart., Anadenanthera colubrina (Vell.) Brenan, Bromelia balansae Mez, Conyza bonariensis (L.) Cronquist, Handroanthus impetiginosus (Mart. ex DC.) Mattos, Myracrodruon urundeuva Allemão, Ludwigia leptocarpa (Nutt.) H. Hara and Urochloa brizantha (Hochst. ex A. Rich.) R.D.Webster. Other species are recorded as common in other biomes, such as Myrcia pyrifolia (Desv.) Nied. (Amazon Rainforest), Sida coradinii Krapov. and Zephyranthes cearensis (Herb.) Baker (Caatinga), Aspidosperma quirandy Hassl. (Atlantic Forest), Frailea cataphracta (Dams) Britton & Rose, Digitaria sanguinalis (L.) Scop. and Staelia thymoides Cham. & Schltdl. (Pampas).

Twenty species are listed in the International Union Conservation of Nature and Natural Resources (IUCN 2018IUCN. 2018. The IUCN Red List of Threatened Species, Version 2018-1, IUCN Red List Unit, Cambridge. Available in: <http://www.iucnredlist.org>. Access in: Sep 4th, 2018.
http://www.iucnredlist.org... ) as endangered species, and nine species in the Red Book of Brazilian flora (Martinelli & Moraes 2013MARTINELLI, G. & MORAES, M.A. (orgs.) 2013. Livro Vermelho da Flora do Brasil. Centro Nacional de Conservacao da Flora (CNCFLORA), Rio de Janeiro.), (Table 2). The species Muellera variabilis (RR.Silva & AMG.Azevedo) MJ.Silva & AMG.Azevedo, Gomphrena centrota E. Holzh., Bonamia balansae Hallier f. and Bauhinia leptantha Malme are considered as rare species because of their restricted distribution or the scarcity of information on the size of their populations (Giulietti et al. 2009GIULIETTI, A.M., RAPINI, A., ANDRADE, M.J.G., QUEIROZ, L.P. & SILVA, J.M.C. 2009. Plantas Raras do Brasil. Conservation International, Belo Horizonte.). Two species are considered endemic to the ironstone outcrops at the Urucum Plateau: G. centrota (Tomás et al. 2010TOMÁS, W.M., ISHII, I.H., STRUSSMANN, C., NUNES, A.P., SALIS, S.M., CAMPOS, Z., FERREIRA, V.L., BORDIGNON, M.O., BARROS, A.T.M. & PADILHA, D.R.C. 2010. Borda oeste do Pantanal e Maciço do Urucum em Corumbá, MS: área prioritária para conservação da biodiversidade. In Anais do V Simpósio sobre Recursos Naturais e Socioeconômicos do Pantanal (W.M.Tomás, coord), Embrapa Pantanal, Corumbá, p.1-6.) and Discocactus ferricola Buining & Brederoo, being the latter also present in Morro do Mutum, Bolivia (Tomás et al. 2010TOMÁS, W.M., ISHII, I.H., STRUSSMANN, C., NUNES, A.P., SALIS, S.M., CAMPOS, Z., FERREIRA, V.L., BORDIGNON, M.O., BARROS, A.T.M. & PADILHA, D.R.C. 2010. Borda oeste do Pantanal e Maciço do Urucum em Corumbá, MS: área prioritária para conservação da biodiversidade. In Anais do V Simpósio sobre Recursos Naturais e Socioeconômicos do Pantanal (W.M.Tomás, coord), Embrapa Pantanal, Corumbá, p.1-6., Takahasi & Meirelles 2014TAKAHASI, A. & MEIRELLES, S.T. 2014 Ecologia da vegetação herbácea de bancadas lateríticas (cangas) em Corumbá, MS, Brasil. Hoehnea 41(4):515-528.).

The herbaceous habit was the predominant growth form on ironstone outcrops in the Urucum Plateau (47.02%), probably due to the high species richness in the families Poaceae and Cyperaceae, and the high frequency of herbaceous species in Malvaceae, Fabaceae and Passifloraceae (Figure 3). Shrub (21.85%) and arboreal species (10.26%) were also common in these areas, with great contribution of Fabaceae, Euphorbiaceae, Malvaceae, Myrtaceae and Apocynaceae.

Lianas (13,91%) were represented by the families Convolvulaceae, Malpighiaceae and Apocynaceae mainly (Figure 3). Although succulent species represent only 6.29% of the richness of the local flora, they are quite conspicuous in the landscape, forming dense mats of vegetation composed of Bromelia balansae Mez, Deuterochnonia meziana Kuntze ex Mez, Opuntia retrorsa Speg. and rupicolous vegetation of Portulaca sp.

Considering the floristic associations present on the rocky outcrops at the Urucum plateau, we can distinguish ecological relationships between vegetation and edaphic variables, such as Gomphrena centrota E. Holzh., Discocactus ferricola Buining & Brederoo and Polycarpaea corymbosa (L.) Lam., that lodge directly on the hardened substrate, on slopes or in small cavities and fissures, covering rocky substrates; and soil islands, generally formed by mats of Bromelia balansae Mez and Deuterocohnia meziana Kuntze ex Mez, containing in their interior trees or shrubs of Acrocomia aculeata (Jacq.) Lodd. ex Mart., Bauhinia pentandra (Bong.) Vogel ex Steud., Commiphora leptophloeos (Mart.) J.B. Gillett, Myracrodruon urundeuva Allemão and Tocoyena formosa (Cham. & Schltdl.) K.Schum., among others (Takahasi 2010TAKAHASI, A. 2010. Ecologia da vegetação em bancadas lateríticas em Corumbá, MS. Tese de doutorado, Universidade de São Paulo, São Paulo., Takahasi & Meirelles 2014TAKAHASI, A. & MEIRELLES, S.T. 2014 Ecologia da vegetação herbácea de bancadas lateríticas (cangas) em Corumbá, MS, Brasil. Hoehnea 41(4):515-528., Takahasi 2015TAKAHASI, A. 2015. Flora das cangas de Corumbá, MS: Diversidade e conservação. In Geossistemas Ferruginosos do Brasil (F.F. do Carmo & L.H.Y. Kamino, eds.), 3i Editora, Belo Horizonte, p.317-334.; Figure 4 F). At the edges of soil islands, there are also many herbaceous and annual species, such as Borreria capitata (Ruiz & Pav.) DC., Calea rupicola Chodat, Mimosa bimucronata (DC.) Kuntze, M. xantocentra Mart. and Waltheria operculata Rose, which desiccate completely during the dry season. Other species such as Portulaca mucronata Link, Cipura formosa Ravenna and Zephyranthes cearensis (Herb.) Baker occur in seasonally flooded sites at topographically lower areas (Takahasi & Meirelles 2014TAKAHASI, A. & MEIRELLES, S.T. 2014 Ecologia da vegetação herbácea de bancadas lateríticas (cangas) em Corumbá, MS, Brasil. Hoehnea 41(4):515-528., Takahasi 2015TAKAHASI, A. 2015. Flora das cangas de Corumbá, MS: Diversidade e conservação. In Geossistemas Ferruginosos do Brasil (F.F. do Carmo & L.H.Y. Kamino, eds.), 3i Editora, Belo Horizonte, p.317-334., Figure 4 C).

About 58.28% of the species were found in only one of the ironstone outcrops at the Urucum Plateau, and none of the species was recorded in all 10 analyzed areas. The similarity índex (Table 3) in the composition of the angiosperm flora between the ironstone outcrops was low and ranged from 0 (Rabicho farm, P8 and the Municipal Natural Park Piraputangas, P10) to 41% (Pantanal Park Road, P1 and Band'alta farm, P2).

By crossing data contained in SpeciesLink (CRIA 2018CRIA. Centro de Referência e Informação Ambiental. 2018. SpeciesLink. Available in: http://www.splink.org.br/index. Access in: Jul 26th, 2018.
http://www.splink.org.br/index... ), Flora do Brasil 2020 (2018)FLORA DO BRASIL 2020 em construção. 2018. Jardim Botânico do Rio de Janeiro. Available in: <http://floradobrasil.jbrj.gov.br/>. Access in: Sep 4th, 2018.
http://floradobrasil.jbrj.gov.br/... , Jabot (2018)JABOT. 2018. Banco de Dados da Flora Brasileira. JBRJ - Instituto de Pesquisas Jardim Botânico do Rio de Janeiro. Available in: <http://cor.jbrj.gov.br/v2/consulta.php >. Access in: Sep 5th, 2018.
http://cor.jbrj.gov.br/v2/consulta.php... and checklists of Flora from Mato Grosso do Sul state (Pott & Pott 1996POTT, A. & POTT, V.J. 1996. Flora do Pantanal - listagem atual de fanerógamas. In Anais do Simpósio sobre Recursos Naturais e Sócio-Econômicos do Pantanal, Manejo e Conservação, 2, Embrapa Pantanal, Corumbá, p.297-325., Schutz 2014SCHÜTZ, N. 2014. Deuterocohnia meziana (Bromeliaceae): Subspecies classification and the description of the new subspecies D. meziana subsp. vogtii from northern Paraguay. Phytotaxa 162(1):18-30., Profice et al. 2015PROFICE, S.R., KAMEYAMA, C., CÔRTES, A.L.A., BRAZ, D.M., INDRIUNAS, A., VILAR, T., PESSOA, C., EZCURRA, C. & WASSHAUSEN, D. 2015. Acanthaceae. In Lista de Espécies da Flora do Brasil. Jardim Botânico do Rio de Janeiro. Available in: <http://floradobrasil.jbrj.gov.br/jabot/floradobrasil/FB104453>. Access in: Jul 26th, 2018.
http://floradobrasil.jbrj.gov.br/jabot/f... , Machate et al. 2016MACHATE, D.J., ALVES, F.M. & FARINACCIO, M.A. 2016. Aspidosperma (Apocynaceae) no estado de Mato Grosso do Sul, Brasil. Rodriguésia 67(4):1011-1024., Araújo & Trevisan 2018ARAÚJO, A.C. & TREVISAN, R. 2018. Cyperaceae da flora Sul-matogrossense: composição florística. Iheringia, Sér. Bot., 73(supl.):190-200., Barbosa 2018BARBOSA, M.R.V. 2018. Check-list das Rubiaceae do Estado de Mato Grosso do Sul, Brasil. Iheringia, Sér. Bot., 73(supl.):335-341., Bortolotto et al. 2018BORTOLOTTO, I.M., DAMASCENO-JUNIOR, G.A. & POTT, A. 2018. Lista preliminar das plantas alimentícias nativas de Mato Grosso do Sul, Brasil. Iheringia, Sér. Bot., 73(supl.):101-116., Damasceno-Junior et al. 2018DAMASCENO-JUNIOR, G.A., POTT, A., NEVES, D.R.M., SCIAMARELLI, A. & FINA, B.G. 2018. Flora lenhosa de Florestas estacionais do estado de Mato Grosso do Sul: estado da arte. Iheringia, Sér. Bot., 73(supl.):65-79., Farinaccio & Simões 2018FARINACCIO, M.A. & SIMÕES, A.O. 2018. Check-list das Apocynaceae do estado de Mato Grosso do Sul, Brasil. Iheringia, Sér. Bot., 73(supl.):131-146., Fiaschi 2018FIASCHI, P. 2018. Check-list da família Oxalidaceae no estado de Mato Grosso do Sul. Iheringia, Sér. Bot., 73(supl.):297-300., Francener et al. 2018FRANCENER, A., ALMEIDA, R.F. & SEBASTIANI, R. 2018. Check-list de Malpighiaceae do estado de Mato Grosso do Sul. Iheringia, Sér. Bot., 73(supl.):264-272., Groppo et al. 2018GROPPO, M., MARGALHO, L.F., FERREIRA, P.L. & ERBERT, C. 2018. Check-list de Sapindaceae (Angiospermae) do estado de Mato Grosso do Sul, Brasil. Iheringia, Sér. Bot., 73(supl.):342-347., Guglieri-Caporal et al. 2018GUGLIERI-CAPORAL, A., POTT, A., FELISMINO, M.F., CAPORAL, F.J.M. & VALLS, J.F.M. 2018. Check-list das Poaceae do estado de Mato Grosso do Sul, Brasil. Iheringia, Sér. Bot., 73(supl.):313-328., Lobão et al. 2018LOBÃO, A.Q., LOPES, J.C. & MELLO-SILVA, R. 2018. Check-list das Annonaceae do estado de Mato Grosso do Sul, Brasil. Iheringia, Sér. Bot., 73(supl.):123-126., Loiola & Cordeiro 2018LOIOLA, M.I.B. & CORDEIRO, L.S. 2018. Check-list das Erythroxylaceae no estado de Mato Grosso do Sul, Brasil. Iheringia, Sér. Bot., 73(supl.):201-206., Panfiglio et al. 2018PANFIGLIO, T., CORNEJO, X. & FARINACCIO, M.A. 2018. Check-list de Capparaceae do estado de Mato Grosso do Sul, Brasil. Iheringia, Sér. Bot., 73(supl.):174-177., Proença et al. 2018PROENÇA, C.E.B., SOARES-SILVA, L.H., VILLARROEL, D., GOMES-BEZERRA, K.M., ROSA, P.O., FARIA, J.E.Q. & SOBRAL, M. 2018. Flora do Mato Grosso do Sul: Myrtaceae. Iheringia, Sér. Bot., 73(supl.):277-282., Roque et al. 2018ROQUE, N., TELES, A.M., MOURA, L., PACHECO, R.A., SILVA, G.H.L., ALVES, M. & NAKAJIMA, J.N. 2018. Check-list de Asteraceae no estado de Mato Grosso do Sul, Brasil. Iheringia, Sér. Bot., 73(supl.):147-156., Sartori et al. 2018SARTORI, A.L.B., LIMA, L.C.P., POTT, V.J., VALLS, J.F.M., CRISTALDO, A.C.M., POLIDO, C.A., COSTA, L.C., POTT, A., FORTUNA-PEREZ, A.P., SILVA, G.M., VAZ, A.M.S.F., BORTOLUZZI, R..L.C., PESTANA, L.T.C., SILVA, R.R., SOUZA-LIMA, E.S., MANSANO, V.F. & SCIAMARELLI, A. Check-list das Leguminosae do estado de Mato Grosso do Sul. Iheringia, Sér. Bot., 73(supl.):239-254., Secco et al. 2018SECCO, R.S., BIGIO, N.C., CORDEIRO, I. PSCHEIDT, A.C. MARQUES O. & CARUZO, M.B.R. 2018. Check-list de Euphorbiaceae s. str., Phyllanthaceae e Peraceae de Mato Grosso do Sul, Brasil. Iheringia, Sér. Bot., 73(supl.):207-215., Versieux et al. 2018VERSIEUX, L.M., COFFANI-NUNES, J.V., PAGGI, G.M. & COSTA, A.F. 2018. Check-list of Bromeliaceae from Mato Grosso do Sul, Brazil. Iheringia, Sér. Bot., 73(supl.):163-168., Zappi et al. 2018ZAPPI, D.C., TAYLOR, N.P., DAMASCENO-JUNIOR, G.A., POTT, V.J. & MACHADO, M.C. 2018. Check-list das Cactaceae do estado do Mato Grosso do Sul, Brasil. Iheringia, Sér. Bot., 73(supl.):169-173.), it was verified that from the species presented here, 27 were not previously recorded for Mato Grosso do Sul and three species have no information of occurrence in Brazil (Table 4).

Discussion

Previous works on floristics, phytosociology and/or phenology indicated the occurrence of 243 species distributed in 66 botanical families, including pteridophytes (Takahasi 2010TAKAHASI, A. 2010. Ecologia da vegetação em bancadas lateríticas em Corumbá, MS. Tese de doutorado, Universidade de São Paulo, São Paulo., Takahasi & Meirelles 2014TAKAHASI, A. & MEIRELLES, S.T. 2014 Ecologia da vegetação herbácea de bancadas lateríticas (cangas) em Corumbá, MS, Brasil. Hoehnea 41(4):515-528., Takahasi 2015TAKAHASI, A. 2015. Flora das cangas de Corumbá, MS: Diversidade e conservação. In Geossistemas Ferruginosos do Brasil (F.F. do Carmo & L.H.Y. Kamino, eds.), 3i Editora, Belo Horizonte, p.317-334., Oliveira 2016OLIVEIRA, P.P. 2016. A influência do tamanho insular sobre a fenologia de plantas em bancadas lateríticas (cangas) de Corumbá, Mato Grosso do Sul. Dissertação de Mestrado, Universidade Federal de Mato Grosso do Sul, Campo Grande.), not included in this study. Thus, this study added 59 new occurrences of species of angiosperms to the ironstone outcrops flora in the Urucum Plateau. The high richness of species found, similar to other ferruginous outcrops areas (Jacobi et al. 2007JACOBI, C.M., CARMO, F.F., VINCENT, R.C. & STEHMANN, J.R. 2007. Plant communities on the ironstone outcrops - a diverse and endangered Brazilian ecosystem. Biodivers. Conserv. 16:2185-2200. , Mourão & Stehmann 2007MOURÃO, A. & STEHMANN, J.R. 2007. Levantamento da flora do campo rupestre sobre canga hematítica couraçada remanescente na Mina do Brucutu, Barão de Cocais, Minas Gerais, Brasil. Rodriguésia 58:775-786., Viana & Lombardi 2007VIANA, P.L. & LOMBARDI, J.A. 2007. Florística e caracterização dos campos rupestres sobre canga na Serra da Calçada, Minas Gerais, Brasil. Rodriguésia 58(1): 159-177., Pifano et al. 2010PIFANO, D.S., VALENTE, A.S.M., ALMEIDA, H.S., MELO, P.H.A., CASTRO, R.M. & VAN DEN BERG, E. 2010. Caracterização florística e fitofisionômica da Serra do Condado, Minas Gerais, Brasil. Biota Neotropica, 10(1): http://www.biotaneotropica.org.br/v10n1/pt/fullpaper?bn01010012010+pt. Last acess: Aug 5th, 2018.
http://www.biotaneotropica.org.br/v10n1/... , Jacobi & Carmo 2008bJACOBI, C.M. & CARMO, F.F. 2008b. Diversidade dos campos rupestres ferruginosos no Quadrilátero Ferrífero, MG. Megadiversidade 4:24-32., Jacobi & Carmo 2011JACOBI C.M. & CARMO, F.F. 2011. Life-forms, pollination and seed dispersal syndromes in plant communities on ironstone outcrops, SE Brazil. Acta Bot. Bras. 25:395-412., Carmo & Jacobi 2013CARMO, F.F. & JACOBI, C.M. 2013. A vegetação de canga no Quadrilátero Ferrífero, Minas Gerais: caracterização e contexto fitogeográfico. Rodriguésia, 64(3):527-541., Skirycz et al. 2014SKIRYCZ A., CASTILHO A., CHAPARRO C., CARVALHO N., TZOTZOS G. & SIQUEIRA J.O. 2014. Canga biodiversity, a matter of mining. Front. Plant Sci. 5:653.), may be related to the proximity of seasonal forest patches bordering these formations, and related to the existence of cavities that allow the accumulation of soil and water pools, resulting in microhabitats that enable a variety of plant associations (Jacobi & Carmo 2008aJACOBI, C.M. & CARMO, F.F. 2008a. The contribution of ironstone outcrops to plant diversity in the Iron Quadrangle, a threatened Brazilian landscape. Ambio 37:324-326. , Takahasi & Meirelles 2014TAKAHASI, A. & MEIRELLES, S.T. 2014 Ecologia da vegetação herbácea de bancadas lateríticas (cangas) em Corumbá, MS, Brasil. Hoehnea 41(4):515-528.).

The high turnover of species between the areas of ironstone outcrops sampled, together with the seasonality, where some species are only perceived during the rainy season, help to explain the high richness found in these environments. Another factor that contributes to species richness is the presence of subspontaneous and ruderal species from adjacent pastures, such as Megathyrsus maximus (Jacq.) B.K.Simon & S.W.L.Jacobs and Melinis minutiflora P.Beauv.

Overall, species are established according to the topographic characteristics in the environment and the substrate granulometry, so that the structure and spatial-temporal distribution of the species are not homogeneous on ironstone outcrops (Takahasi & Meirelles 2014TAKAHASI, A. & MEIRELLES, S.T. 2014 Ecologia da vegetação herbácea de bancadas lateríticas (cangas) em Corumbá, MS, Brasil. Hoehnea 41(4):515-528.). The topographic development of these formations resulted in unique habitats such as fissures, cavities, small temporary ponds, depressions and exposed rocks, which differ from adjacent landscapes, constituting refuges for species adapted to xeric and mesic conditions (Jacobi et al. 2007JACOBI, C.M., CARMO, F.F., VINCENT, R.C. & STEHMANN, J.R. 2007. Plant communities on the ironstone outcrops - a diverse and endangered Brazilian ecosystem. Biodivers. Conserv. 16:2185-2200. , Jacobi & Carmo 2008bJACOBI, C.M. & CARMO, F.F. 2008b. Diversidade dos campos rupestres ferruginosos no Quadrilátero Ferrífero, MG. Megadiversidade 4:24-32.).

During the driest season of the year, most of the ironstone outcrops species present intense deciduousity, assuming a similar xeric aspect to that found in other ferruginous geosystems in Brazil (Mota et al. 2015MOTA, N.F.O., SILVA, L.V.C., MARTINS, F.D. & VIANA, P.L. 2015. Vegetação sobre sistemas ferruginosos da Serra dos Carajás. In Geossistemas Ferruginosos do Brasil: áreas prioritárias para conservação da diversidade geológica e biológica, patrimônio cultural e serviços ambientais (F.F. do Carmo & L.H.Y. Kamino, eds.), 3i Editora, Belo Horizonte, p. 289-315.). The difficulty for soil drainage, associated with climatic conditions in the region, gave rise to a prickly vegetation, physiognomically similar to the Caatinga, adapted to extreme conditions of evapotranspiration, thermal amplitude, underdeveloped soil, presence of heavy metals and drought periods in the region (Loureiro et al. 1982LOUREIRO, R.L., LIMA, J.P.S. & FONZAR, B.C. 1982. Vegetação. In Projeto RADAMBRASIL Folha SE.21 - Corumbá e parte da Folha SE.20 (Levantamento de Recursos Naturais, 27). Ministério de Minas e Energia, Rio de Janeiro, p.329-372., Jacobi & Carmo 2008aJACOBI, C.M. & CARMO, F.F. 2008a. The contribution of ironstone outcrops to plant diversity in the Iron Quadrangle, a threatened Brazilian landscape. Ambio 37:324-326. , Jacobi et al. 2015JACOBI, C.M., CARMO, F.F., CARMO, F.F. & CAMPOS, I.C. 2015. Iron geosystems: priority areas for conservation in Brazil. In Mining in ecologically sensitive landscapes (M.Tibbett, ed.). Csiro Publishing. Leiden, p. 55-77.). These adaptations may involve partial or total loss of aerial structures in the dry season, succulence, pseudo-bulbs in orchids, clonal reproduction, imbricate leaves, slow growth and CAM photosynthesis in order to resist desiccation cycles and subsequent rehydration (Jacobi et al. 2007JACOBI, C.M., CARMO, F.F., VINCENT, R.C. & STEHMANN, J.R. 2007. Plant communities on the ironstone outcrops - a diverse and endangered Brazilian ecosystem. Biodivers. Conserv. 16:2185-2200. , Jacobi & Carmo 2008bJACOBI, C.M. & CARMO, F.F. 2008b. Diversidade dos campos rupestres ferruginosos no Quadrilátero Ferrífero, MG. Megadiversidade 4:24-32., Skirycz et al. 2014SKIRYCZ A., CASTILHO A., CHAPARRO C., CARVALHO N., TZOTZOS G. & SIQUEIRA J.O. 2014. Canga biodiversity, a matter of mining. Front. Plant Sci. 5:653., Jacobi et al. 2015JACOBI, C.M., CARMO, F.F., CARMO, F.F. & CAMPOS, I.C. 2015. Iron geosystems: priority areas for conservation in Brazil. In Mining in ecologically sensitive landscapes (M.Tibbett, ed.). Csiro Publishing. Leiden, p. 55-77.).

The predominance of species of wide distribution differs from that expected for ironstone outcrops in other regions of Brazil, where there are occurrences of exclusive species and different species from neighboring ecosystems (Skirycz et al. 2014SKIRYCZ A., CASTILHO A., CHAPARRO C., CARVALHO N., TZOTZOS G. & SIQUEIRA J.O. 2014. Canga biodiversity, a matter of mining. Front. Plant Sci. 5:653.). The deciduous forests in the Urucum Plateau that border the ironstone outcrops are characterized by the confluence of species from different biomes that surround it, keeping floristic relationships with the Bosque Seco Chiquitano in Bolivia (Jardim et al. 2003JARDIM, A., KILLEEN, T.J. & FUENTES, A. 2003. Guia de los árboles y arbustos del Bosque Seco Chiquitano, Bolivia. Editorial Fundación Amigos de La Naturaleza, Santa Cruz.), and representatives from Chaco, Cerrado, Amazon Rainforest, Atlantic Forest and Southern Forests in the south and east (Rizzini 1997RIZZINI, C.T. 1997. Tratado de fitogeografia do Brasil: aspectos ecológicos, sociológicos e florísticos. 2 ed. Âmbito Cultural Edições, Rio de Janeiro., Pott & Pott 2003POTT, A. & POTT, V.J. 2003. Espécies de fragmentos florestais em Mato Grosso do Sul. In Fragmentação florestal e alternativas de desenvolvimento rural na região Centro-Oeste (R.B. Costa, ed.). UCDB, Campo Grande, p.26-52., Tomás et al. 2010TOMÁS, W.M., ISHII, I.H., STRUSSMANN, C., NUNES, A.P., SALIS, S.M., CAMPOS, Z., FERREIRA, V.L., BORDIGNON, M.O., BARROS, A.T.M. & PADILHA, D.R.C. 2010. Borda oeste do Pantanal e Maciço do Urucum em Corumbá, MS: área prioritária para conservação da biodiversidade. In Anais do V Simpósio sobre Recursos Naturais e Socioeconômicos do Pantanal (W.M.Tomás, coord), Embrapa Pantanal, Corumbá, p.1-6.). In addition, it presents common species to the Caatinga, a vestige of a vegetative distribution pattern of the Pleistocene period. The period was characterized by a dry climate which resulted in the expansion of the seasonal forests and the retreat of the humid forests, allowing the connection of the previously disjunct vegetation of Northeast and Midwest regions of Brazil and Argentina (Prado & Gibbs 1993PRADO, D.E. & GIBBS, P. 1993. Patterns of species distributions in the dry seasonal forests of South America. Ann. Missouri Bot. Gard. 80(4):902-927., Linares-Palomino et al. 2003LINARES-PALOMINO, R., PENNINGTON, R.T. & BRIDGEWATER, S. 2003. The phytogeography of the seasonally dry tropical forests in Equatorial Pacific South America. Candollea 58:473-499.).

The high proportion of herbaceous and arboreal-shrub species is explained by the representativeness of the families Fabaceae and Poaceae, similar to the results found for other plant communities in ferruginous outcrops in Brazil (Mourão & Stehmann 2007MOURÃO, A. & STEHMANN, J.R. 2007. Levantamento da flora do campo rupestre sobre canga hematítica couraçada remanescente na Mina do Brucutu, Barão de Cocais, Minas Gerais, Brasil. Rodriguésia 58:775-786., Viana & Lombardi 2007VIANA, P.L. & LOMBARDI, J.A. 2007. Florística e caracterização dos campos rupestres sobre canga na Serra da Calçada, Minas Gerais, Brasil. Rodriguésia 58(1): 159-177., Pifano et al. 2010PIFANO, D.S., VALENTE, A.S.M., ALMEIDA, H.S., MELO, P.H.A., CASTRO, R.M. & VAN DEN BERG, E. 2010. Caracterização florística e fitofisionômica da Serra do Condado, Minas Gerais, Brasil. Biota Neotropica, 10(1): http://www.biotaneotropica.org.br/v10n1/pt/fullpaper?bn01010012010+pt. Last acess: Aug 5th, 2018.
http://www.biotaneotropica.org.br/v10n1/... , Jacobi & Carmo 2011JACOBI C.M. & CARMO, F.F. 2011. Life-forms, pollination and seed dispersal syndromes in plant communities on ironstone outcrops, SE Brazil. Acta Bot. Bras. 25:395-412., Carmo & Jacobi 2013CARMO, F.F. & JACOBI, C.M. 2013. A vegetação de canga no Quadrilátero Ferrífero, Minas Gerais: caracterização e contexto fitogeográfico. Rodriguésia, 64(3):527-541., Skirycz et al. 2014SKIRYCZ A., CASTILHO A., CHAPARRO C., CARVALHO N., TZOTZOS G. & SIQUEIRA J.O. 2014. Canga biodiversity, a matter of mining. Front. Plant Sci. 5:653.). On the other hand, the family Asteraceae, that is well represented in ironstone outcrops of other regions of the country (Mourão & Stehmann 2007MOURÃO, A. & STEHMANN, J.R. 2007. Levantamento da flora do campo rupestre sobre canga hematítica couraçada remanescente na Mina do Brucutu, Barão de Cocais, Minas Gerais, Brasil. Rodriguésia 58:775-786., Viana & Lombardi 2007VIANA, P.L. & LOMBARDI, J.A. 2007. Florística e caracterização dos campos rupestres sobre canga na Serra da Calçada, Minas Gerais, Brasil. Rodriguésia 58(1): 159-177., Pifano et al. 2010PIFANO, D.S., VALENTE, A.S.M., ALMEIDA, H.S., MELO, P.H.A., CASTRO, R.M. & VAN DEN BERG, E. 2010. Caracterização florística e fitofisionômica da Serra do Condado, Minas Gerais, Brasil. Biota Neotropica, 10(1): http://www.biotaneotropica.org.br/v10n1/pt/fullpaper?bn01010012010+pt. Last acess: Aug 5th, 2018.
http://www.biotaneotropica.org.br/v10n1/... , Ataíde et al. 2011ATAÍDE, E.S., CASTRO, P.T.A. & FERNANDES, G.W. 2011. Florística e caracterização de uma área de campo ferruginoso no Complexo Minerário Alegria, Serra de Antônio Pereira, Ouro Preto, Minas Gerais, Brasil. Rev. Árvore, 35(6):1265-1275.), presented low species richness in the studied region. According to Rizzini (1997)RIZZINI, C.T. 1997. Tratado de fitogeografia do Brasil: aspectos ecológicos, sociológicos e florísticos. 2 ed. Âmbito Cultural Edições, Rio de Janeiro., the cangas are hardened ferrous formations and therefore have discontinuous vegetation and are typically covered by very specialized herbaceous vegetation, while on its edge woody species remain. The families Poaceae and Fabaceae are not abundant only on ironstone outcrops of the Urucum Plateau, but also among the herbaceous and woody groups, and in general between Angiosperms in Brazil (Forzza et al. 2010FORZZA, R.C., BAUMGRATZ, J.F.A., BICUDO, C.E.M., CARVALHO-JR., A.A., COSTA, A., COSTA, D.P., HOPKINS, M.G., LEITMAN, P.M., LOHMANN, L.G., MAIA, L.C., MARTINELLI, G., MENEZES, M., MORIM, M.P., COELHO, M.A.N., PEIXOTO, A.L., PIRANI, J.R., PRADO, J., QUEIROZ, L.P., SOUZA, V.C., STEHMANN, J.R., SYLVESTRE, L.S., WALTER, B.M.T. & ZAPPI, D. (ORG.). 2010. Catálogo de plantas e fungos do Brasil. Volumes 1 e 2. Andrea Jakobsson Estúdio, Instituto de Pesquisas Jardim Botânico do Rio de Janeiro, Rio de Janeiro. 1700p., BFG 2015BRAZIL FLORA GROUP BFG. 2015. Growing knowledge: an overview of Seed Plant diversity in Brazil. Rodriguésia 66(4): 1085-1113.).

Sørensen's similarity estimates found between the areas were low, with values below 0.5, which corroborates other studies indicating high beta diversity for these phytophysiognomies (Mourão & Stehmann 2007MOURÃO, A. & STEHMANN, J.R. 2007. Levantamento da flora do campo rupestre sobre canga hematítica couraçada remanescente na Mina do Brucutu, Barão de Cocais, Minas Gerais, Brasil. Rodriguésia 58:775-786., Jacobi & Carmo 2008bJACOBI, C.M. & CARMO, F.F. 2008b. Diversidade dos campos rupestres ferruginosos no Quadrilátero Ferrífero, MG. Megadiversidade 4:24-32., Pifano et al. 2010PIFANO, D.S., VALENTE, A.S.M., ALMEIDA, H.S., MELO, P.H.A., CASTRO, R.M. & VAN DEN BERG, E. 2010. Caracterização florística e fitofisionômica da Serra do Condado, Minas Gerais, Brasil. Biota Neotropica, 10(1): http://www.biotaneotropica.org.br/v10n1/pt/fullpaper?bn01010012010+pt. Last acess: Aug 5th, 2018.
http://www.biotaneotropica.org.br/v10n1/... , Messias et al. 2012MESSIAS, M.C.T.B., LEITE, M.G.P., MEIRA-NETO, J.A.A. & KOZOVITS, A.R. 2012. Fitossociologia de campos rupestres quartzíticos e ferruginosos no Quadrilátero Ferrífero, Minas Gerais. Acta Bot. Bras. 26(1): 230-242.). The areas of Pantanal Park Road and Band'alta farm are the closest to each other, which justifies the highest similarity found. However, it should be noted that due to the species surveying method used in this study, sampling effort among the ironstone outcrops was not uniform. Thus, some common and abundant species may not have been listed for some of the ironstone outcrops because they represent species already cataloged for the environment, this way reducing similarity between some areas. In rupestrian grassland on ferruginous outcrops in Iron Quadrangle (Jacobi & Carmo 2008bJACOBI, C.M. & CARMO, F.F. 2008b. Diversidade dos campos rupestres ferruginosos no Quadrilátero Ferrífero, MG. Megadiversidade 4:24-32.) low proportion (5%) of common species was found among the analyzed areas, suggesting high beta diversity, probably resulting from the topographic and microclimatic variations in the habitat between areas.

Recent studies have updated the occurrence of some of the species recorded here for Mato Grosso do Sul such as Tradescantia boliviana (Hassk.) J.R.Grant (Pellegrini et al. 2017PELLEGRINI, M.O.O., FORZZA, R.C. & SAKURAGUI, C.M. 2017. Novelties in Brazilian Tradescantia L.(Commelinaceae). PhytoKeys 80: 1-31.), Deuterohconia meziana Kuntze ex Mez (Schutz 2014SCHÜTZ, N. 2014. Deuterocohnia meziana (Bromeliaceae): Subspecies classification and the description of the new subspecies D. meziana subsp. vogtii from northern Paraguay. Phytotaxa 162(1):18-30.), Dyckia excelsa Leme (Paggi et al. 2015PAGGI, G.M., LOUZADA, R.B., ISHII, I.H., TAKAHASI, A., ARRUDA, R.C.O. & LORENZ-LEMKE, A.P. 2015. Rediscovering Dyckia excelsa (Bromeliaceae) in Mato Grosso do Sul, Brazil: taxonomy, geographic distribution and notes on leaf anatomy. Systematic Botany 40(1):129-135.) and Tarenaya eosina (J.F.Macbr.) Soares Neto & Roalson, a species considered endemic to Paraguay (Costa-e-Silva 2000COSTA-E-SILVA, M.M. 2000. Cleome eosina J. F. Macbr. (Capparaceae Juss.), a new record for Brazil. Ernstia, 10(2):43-46., Soares-Neto et al. 2018SOARES-NETO, R.L., THOMAS, W.W., BARBOSA, M.R.V. & ROALSON, E.H. 2018. New combinations and taxonomic notes for Tarenaya (Cleomaceae). Acta Bot. Bras. Epub March 19. Available in: <https://dx.doi.org/10.1590/0102-33062017abb0417>.
https://dx.doi.org/10.1590/0102-33062017... ). Portulaca hoehnei D. Legrand is not a species of occurrence for Brazil, although its holotype is from the region of Corumbá (Hoehne R 3565). New occurrences of species in the ironstone outcrops of the Urucum Plateau demonstrate the need for continuous research to update the knowledge about the size and distribution of the species that occur in these formations, and the level of conservation in which they are found.

Although the ironstone outcrops in the Urucum Plateau do not directly undergo mineral extractive activity, due to their location at the foothill and relative distance of the mines of iron and manganese extraction, these environments are under intense anthropic action. Extraction of ornamental species such as orchids, bromeliads and cacti for sale at local fairs, grazing by cattle, fire action and removal of local vegetation by owners are pressures undergone by the flora from these areas (Takahasi & Meirelles 2014TAKAHASI, A. & MEIRELLES, S.T. 2014 Ecologia da vegetação herbácea de bancadas lateríticas (cangas) em Corumbá, MS, Brasil. Hoehnea 41(4):515-528., Figure 4 G).

Even in a situation of maximum vulnerability, less than 1% of canga areas in Brazil are included in Full Protected Conservation Units, such as National and State Parks (Carmo et al. 2012CARMO, F.F., CARMO, F.F., CAMPOS, I.C. & JACOBI, C.M. 2012. Cangas: ilhas de ferro estratégicas para a conservação. Ciênc. Hoje 295:48-53.). The high diversity and presence of endemic, rare, endangered and/or not yet cataloged species for the Urucum Plateau region, reinforces the need for local conservation units that can guarantee the preservation of these species, since the environmental protection areas in the region are insufficient to guarantee the maintenance of typical populations from this habitat (Tomás et al. 2010TOMÁS, W.M., ISHII, I.H., STRUSSMANN, C., NUNES, A.P., SALIS, S.M., CAMPOS, Z., FERREIRA, V.L., BORDIGNON, M.O., BARROS, A.T.M. & PADILHA, D.R.C. 2010. Borda oeste do Pantanal e Maciço do Urucum em Corumbá, MS: área prioritária para conservação da biodiversidade. In Anais do V Simpósio sobre Recursos Naturais e Socioeconômicos do Pantanal (W.M.Tomás, coord), Embrapa Pantanal, Corumbá, p.1-6.). In addition, our data can significantly contribute for changing the conservation status of some species, since only 13% of the rare species present in ferruginous geosystems from Brazil are cited in the List of Endangered Species, in large part due to insufficient data for this type of environment (Giulietti et al. 2009GIULIETTI, A.M., RAPINI, A., ANDRADE, M.J.G., QUEIROZ, L.P. & SILVA, J.M.C. 2009. Plantas Raras do Brasil. Conservation International, Belo Horizonte., Jacobi et al. 2015JACOBI, C.M., CARMO, F.F., CARMO, F.F. & CAMPOS, I.C. 2015. Iron geosystems: priority areas for conservation in Brazil. In Mining in ecologically sensitive landscapes (M.Tibbett, ed.). Csiro Publishing. Leiden, p. 55-77.).

Acknowledgments

We thank CAPES for the financial assistance and the PhD scholarship granted to the first author, to CNPq for the grants to Geraldo Alves Damasceno Junior and to Andréa C. Araujo (310999/2018-9), the Instituto Federal de Mato Grosso do Sul for supporting this research, the Missão Salesiana for permitting the access to Band'alta ranch, and the owners of the other farms for allowing our access to the study sites, to the herbaria where the collectings are deposited.

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