Check-list of vascular plant communities on ironstone ranges of south-eastern Brazil: dataset for conservation

Abstract Background Ironstone ranges are considered hotspots for higher plants α and β diversity. The lack of studies and the intense degradation of the ironstone ranges, due to mining, motivated us to compile, for the first time, a list of vascular plants collected on iron-rich derived substrates from ancient landscape of south-eastern Brazil. All existing records in the Brazilian Virtual Herbarium of Flora and Fungi for each of the 43 municipalities containing ironstone ranges were downloaded, resulting in 17,954 vouchers identified to the species level. We found 2,933 species belonging to 160 families and 818 genera. New information For the first time, we identified 148 species mentioned in endangered flora official lists and 48 narrow endemic species. Collecting efforts must still be supported to properly sample the vegetation since, for 143 sites, less than 10 records/site were found. This dataset will assist with the indication of dozens of plant species whose threat criteria must be urgently assessed to subsidise public policies on the use and conservation of the Brazilian flora.


Introduction
Ironstone ranges occur mainly in Brazil, Australia, South Africa and India and are predominantly comprised of rock blocks of banded iron formations -BIF -from the Archean and Paleoproterozoic ages Carmo 2015, Hagemann et al. 2016). Flora knowledge of these ancient ecosystems is still incipient. Yet, some sites such as Quadrilátero Ferrífero and the Carajás Range (Brazil) and the Pilbara and Yilgarn Cratons (Australia) are considered hotspots (sensu Gibson et al. 2010) for higher plants α and β diversity.
In Brazil, covering the highest parts of iron mountains and, therefore, with even more restricted insular distribution, there are duricrusts known as cangas. These duricrusts originated from the intense weathering of BIF rock blocks and other lithotypes with high metal content. Some canga outcrops can be about 20-30 m thick, with records of origin that started at ca. 50 Ma, thus representing one of the oldest landscapes in Brazil (Dorr 1969, Monteiro et al. 2014, Salgado and Carmo 2015. Plants in ironstone ranges are frequently subjected to abiotic stressors such as acid substrates, daily temperature variation, very shallow soils with reduced water availabilityand anomalous metal contents. In sites characterised by substrates (rock and soil) with natural anomalous metal contents, outstanding plant communities can be found, called metallophytes, which are able to tolerate metal toxicity (Baker et al. 2010). Due to these characteristics and their disjunct distribution, ironstone ranges are sources of taxonomic novelties and various endemic species , Gibson et al. 2015a).
In some Brazilian ironstone ranges, the mineralogical constitution of the rock outcrops can reach 90% of iron oxides -haematite Fe O -and hydroxides -limonite FeO(OH).nH O, in addition to high manganese and aluminium contents , Schaefer et al. 2015. Soils developed in these systems are practically deprived of exchangeable nutrients, the result of both intense lixiviation and the oxidic nature of the rocks, characterising an environment with extreme oligotrophy. When associated with forest formations, the soils 2 3 2 have higher organic matter values, but the prevailing carbon is recalcitrant and, therefore, very resistant to microbial cycling (Schaefer et al. 2015). These conditions represent a restrictive environmental filter, determining the establishment of specialised plant communities (Gibson et al. 2015a, Silveira et al. 2015.  researched reference databases (Scientific Electronic Library Online and Portal de Periódicos da Capes) with keywords associated with ironstone ranges and found that, out of 189 articles produced in 31 countries, published between 1962 and 2015, only 10% of the content were related to Botany works. On the other hand, 77% of the articles addressed Geology issues. The authors pointed out that this imbalance between contents could generate inadequate public policies regarding use of natural resources and biodiversity conservation programmes.
Intense loss and degradation of areas in ironstone ranges are associated with the exploitation of natural resources, since they are home to the largest global reserves of iron ore, in addition to manganese and bauxite (aluminium). This geo-economical peculiarity favours a concentration of megastructures for ore extraction, generating an enormous environmental liability (Butcher et al. 2008, Sonter et al. 2014). The consequences for plant populations, in addition to the massive habitat losses, have yet to be properly assessed.
In view of the lack of studies and rapid degradation of these unique ecosystems, the purpose of this study was to assemble, for the first time, a list of vascular plants collected on Fe-rich derived substrates from ancient ironstone ranges in south-eastern Brazil, updating their taxonomic nomenclature, indicating life forms and highlighting endemic taxa and threat categories. Additionally, we identified the main vegetation types and highlighted locations where inventory efforts must be encouraged.

Geographical context
In south-eastern Brazil, ironstone ranges spread non-continuously over a 500 km-long north-south axis, in 43 municipalities distributed over three mineral provinces: Quadrilátero Ferrífero (QF) in the south; Serra da Serpentina-Morro do Pilar region (SS-MP) at the centre; and the Peixe Bravo River Valley region (VPB) in the north (Fig. 1).
In the QF and SS-MP ironstone ranges, there is a prevalence of the subtropical highland climate (Cwb) according to Köppen's classification, characterised by dry winters and rainy summers (Davis et al. 2005, Souza and. The vegetation matrix is comprised mainly of Brazilian Atlantic Rainforest, one of the most megadiverse and endangered rainforests in the world (Stehmann et al. 2009). In the VPB, dry weather with rainy summers (BSw) prevail. In these semi-arid conditions, the matrix is comprised predominantly by Cerrado, the Brazilian savanna, although there are still some spots of Brazilian Atlantic Forest. VPB is also in close contact with Caatinga, the largest seasonally dry tropical area of South America . Comparisons between some of the physical and geographical variables can be seen in Table 1. A peculiar feature of these ironstone ranges is the high physical heterogeneity, represented by regolithic materials and various types of outcrops (Fig. 2). The pronounced topographic heterogeneity in cangas may influence the proportion of functional plant groups, depending on the variation of substrate roughness .

Vascular plants dataset
All existing records in the Virtual Herbarium of Flora and Fungi (INCT 2017) for each of the 43 municipalities containing ironstone ranges were downloaded. We selected only the records of specimens collected in canga areas, banded iron formations and soils developed from ferruginous rocks. For the vouchers without information on substrate type, the collection localities were used to determine if the specimen occurred in ironstones. For this validation, the geological database (1:25,000 from 1:100,000) available at the webgis Atlas Digital Geossistemas Ferruginosos (Instituto Prístino 2018) was used, see Fig. 3.
The checklist of vascular plants in the ironstone ranges was composed by both native and naturalised plants and included only records identified to the species level. The current accepted nomenclature followed the List of Species of the Brazilian Flora (Flora do Brasil 2020 em construção 2017). Families and genera were listed in alphabetical order following Judd et al. (2008), APG (2016) and PPG I (Pteridophyte Phylogeny Group) I (2016). The herbaria were identified according to Thiers (2014), to the chronology of sampling and the main collectors.

Vegetation types and life forms
We analysed the life form spectra based on five categories: trees, shrubs, subshrubs, lianas/vines and herbs, according to Carmo and Jacobi (2013) and the List of Species of the Brazilian Flora (Flora do Brasil 2020 em construção 2017).
Using voucher information, taxa were organised under three phytophysiognomies (sensu Pirani et al. 2003): forest, comprising semi-deciduous Seasonal Forest under the names Gallery Forest and Capão; savanna, including Cerrado and Carrasco; and grassland, covering Campo Limpo, Campo Sujo, vegetation associated with canga and BIF outcrops, seasonal water pools, ponds and bogs.

Endemisms and species threatened with extinction
Complementary records and refined information on the sites of occurrence of the taxa, including cases of restricted endemicity, follow the list of studies presented in Suppl. material 1. Species with restricted geographic range and habitat specificity were deemed as narrow endemic species (sensu Rabinowitz 1981). For each taxon, we followed the threat category in the Official Lists of Endangered

Construction and validation of vascular plants dataset in ironstone ranges of south-eastern
Brazil.

Analysis Vascular plants dataset
We found 17,954 records (vouchers) identified to the species level, originating predominantly from specimens collected in the QF ironstone ranges (93%), followed by samples from SS-MP (4%) and VPB (3%), see Of the 43 municipalities that contain ironstone ranges, only seven had more than 1,000 records each, all located in the QF. On the other hand, 11 municipalities had less than 10 records each and five of them had no vouchers. Of the 206 sites associated to Fe-enriched derived substrates, 10 alone concentrate 71% (12,515) of all vouchers (Table 2).  The 160 botanic families found account for 58% that occur in Brazil and 44 were represented by a single taxon. The 10 most representative families grouped 1,538 taxa (52% of the total): Asteraceae (387)

Life forms and vegetation types
The life forms (Fig. 5), with their respective numbers and taxa percentages, were: herbaceous (1,085 or 37.6%), of which 278 were graminoids; subshrubs (648 or 22.5%); shrubs (576 or 19.9%); trees (305 or 10.6 %); lianas/vines (278 or 9.4%). In the substrate composed of regolithic materials (shallow, gravelly soils or small fragments of BIF and canga), the physiognomy was predominantly represented by graminoid herbs (such as Cyperaceae and Poaceae) and sclerophytic shrubs. In a lesser proportion, we also found communities associated with bogs and ponds, dominated by graminoid herbs of Cyperaceae, Eriocaulaceae, Poaceae and Xyridaceae.
We found 735 taxa (25%) in forest physiognomies. These included "vegetation islands" known as capões, developing on the organic material deposited in large fractures, depressions or caves in iron formations. Forest formations also occur along the drainage of the colluvial ramps and on the margins of waterways, places where the soil becomes less shallow and wetter. Arboreal and shrub species of Fabaceae, Lauraceae, Melastomataceae, Myrtaceae, Rubiaceae and Solanaceae are frequent. In the understorey, many Monilophyta, Lycophyta, Bromeliaceae, Orchidaceae and Piperaceae are found, as well as lianas/vines of Apocynaceae, Bignoniaceae and Dioscoreaceae.
The recorded species number was low in savanna formations, as a result of fewer collections in these formations, particularly at VPB. In the Carrasco physiognomy, there is a prevalence of xeromorphic scrubs and deciduous trees of Euphorbiaceae, Fabaceae, Malvaceae and Salicaceae, in addition to columnar cacti (Cereus and Pilosocereus) that also occur in the Caatinga. The Cerrado occurs associated with ferruginous rock blocks/ boulders found on slopes and at the top of some plateaus, with the shrub layer comprised of Asteraceae, Bignoniaceae, Calophyllaceae, Fabaceae, Lythraceae, Rubiaceae and Vochysiaceae. The herbaceous layer is also very developed and Apocynaceae, Cyperaceae and Poaceae species prevail. In addition, 645 taxa (21%) were collected in more than one physiognomy. Examples of some phytophysiognomies can be observed in Fig. 6. Life forms found in plant communities in the ironstone ranges of south-eastern Brazil. Light grey bar represents graminoid herbs.

Endemisms and species threatened with extinction
The ironstone ranges hold exclusive records of 48 species (Table 2), mostly collected in the QF and all considered narrow endemic species. In addition to these, three species concentrate the records of ironstone substrates in the QF: Calibrachoa elegans, Senecio linearilobus and Stachytarpheta confertifolia, but each of these has only one disjunct record outside of ironstone ranges (Teles and Hattori 2012, Giacomin and Stehmann 2012, Salimena 2012. Taxa are contained in 20 families and 28 genera. The families with the largest number of endemic taxa were Bromeliaceae (13), Eriocaulaceae and Fabaceae (6 each) and Velloziaceae (5), totalling 61% of the endemic species. The most representative genera were Dyckia (10), Paepalanthus (6), Barbacenia (4) and Mimosa (3), comprising 47% of the exclusive taxa.
We found 148 species included in official lists of endangered flora (Suppl. material 3). Asteraceae (40), Lauraceae (11), Cactaceae (7), Fabaceae and Orchidaceae (6 each) were the families with the largest numbers of endangered species. Amongst genera, Lychnophora (8) and Mikania (6) stand out. The grassland physiognomies were home to 102 endangered species, most associated with canga and BIF outcrops; forest formations contained 27 species; the aquatic environments and savanna physiognomy registered only one species each. Seventeen endangered species occurred in more than one type of physiognomy/environment. Only 12 of the 48 narrow endemic species in ironstone ranges are mentioned in the official lists of endangered species. Probably seven species are extinct in the wild, caused by the loss of natural areas due to mining (Table 3).

Discussion
The ironstone ranges in south-eastern Brazil stand out as areas of great value for the conservation of plant diversity. In a very restricted total area -less than 0.02% of the Brazilian territory -2,933 species collected from Fe-rich substrates have been recorded so far. Although incomplete, this dataset already corresponds to 8% of all vascular plants occurring in the country, currently estimated at 34,475 (Flora do Brasil 2020 em construção 2017).
In the SS-MP and the VPB regions (see Fig. 1), collecting efforts must still be supported to properly sample the vegetation in these ironstone ranges since, for 143 sites (69% of the total), less than 10 records/site were found. Even for regions thoroughly sampled, notably the QF, intense efforts from plant taxonomists must be encouraged, since a relevant number of records still remains in herbaria without identification to the specific level (Jacobi and Carmo 2012). Amongst the material collected in some QF cangas (Carmo and Jacobi 2012), at least 10 taxa, deemed as new to science, were identified, but only one has been formally described (see Freitas Oliveira et al. 2014). As advocated by Mace (2004) and Callmander et al. (2005), promptly reducing collection gaps and increasing taxonomic efforts are needed to generate proper knowledge about the conservation status and levels of endemism of ironstone range species.
The phytogeographical context also favoured the high floristic diversity. The ironstone ranges in southeast Brazil receive influence from elements in the Atlantic Forest, Cerradoand Caatinga domains (see Fig. 1). Additionally, elements of Campos Rupestres (rupestrian grasslands) of the Espinhaço Range, one of the largest world centres of plant endemicity, have been found Jacobi 2013, Silveira et al. 2015).
A peculiar feature in iron-rich regions is the presence of plant communities characterised by species with remarkable ecological value due to their adaptation to metal substrates. In the ironstone ranges, some metalliferous ecotypes (sensu Whiting et al. 2004 Within a global context, the α-diversity (2,933 spp.) and number of narrow endemic species (48 spp.) found in the ironstones of south-eastern Brazil have more representative values than those known for plant diversity hotspots in other metallicolous floras. In Australia, 44 species are known whose distribution is restricted to, or centred on, ironstones (BIF) located in Yilgarn and 20 endemic species to Pilbara Ranges. Together, these sites contain about 1,300 inventoried species (Gibson et al. 2015a, Gibson et al. 2015b). In the ironstone ranges from Serra de Carajás, Brazilian Amazon, Viana et al. (2016) estimate that at least 600 species will be recorded for the cangas, of which at least 40 are presumably endemic.
Attributes such as rarity and endemicity were observed, with several taxa underrepresented in herbaria, some only by type-material collected over a century ago. With several species mentioned in the Catalog of Rare Brazilian Plants (Rapini et al. 2009, the ironstone ranges therefore represent sites of global interest, identified as Key Biodiversity Areas. Amongst the 48 narrow endemic species in the ironstone ranges, only 12 are mentioned in official endangered flora lists. This scenario does not reflect the current and intense extinction threat due to loss and degradation of natural areas caused by mining, resulting in probable extinction of several species. We stress the negligence of the State, both by failing to update the official lists -particularly the regional list (Minas Gerais 1997) -against that which is set forth by the Global Strategy for Plant Conservation (GSPC) programme and for reducing the already insufficient area of legally protected ironstone ranges (e.g. Minas Gerais 2017).
Therefore, the present database will assist with the indication of dozens of species whose threat criteria must be urgently assessed. These actions are essential because "Red Lists" are internationally recognised as a tool for defining the conservation status of species and populations. They are essential for subsidising environmental public policies and decisionmaking concerning the use, planning and conservation of natural resources (Gärdenfors et al. 2008, Callmander et al. 2005.