Floristic composition, structure and species-area relationships on a neotropical inselberg in southeastern Brazil

Abstract

The inselberg vegetation, in general, occurs in patches that vary in size, shape, number of plant species and are surrounded by a bare rock. The present study evaluated the species composition, structural analysis, and species-area relationships of vegetation patches on a neotropical inselberg in Rio de Janeiro state, southeastern Brazil. A total of 69 vascular plant species, from 31 families, were sampled in 84 vegetation patches varying in area from 0.02 to 500 m², totaling 0.33 ha. Fabaceae and Cactaceae were the most representative families. Vellozia plicata and Selaginella sellowii presented the highest relative frequencies, relative dominances and importance values and were the most successful in the colonization of the studied rocky outcrop. A linear regression showed a positive correlation between patch size and species richness. Phanerophytes were the predominant life-form, with small patches being less rich in species and dominated by Selaginella mats. Our results suggest that the vegetation patches on the “Morro do Itaoca” inselberg currently represent a refuge against fire and other anthropogenic disturbances for many typical species of the surrounding matrix. In addition, the locality is home to endemic and endangered species, which reinforces its importance for conservation actions.

Key words
Atlantic Forest; conservation; endangered species; life forms; rock outcrops

Resumo

A vegetação de inselbergs, em geral, ocorre em manchas que variam em tamanho, forma e número de espécies e são cercadas por uma matriz de rocha nua. O presente estudo avaliou a composição de espécies, estrutura e a relação espécie-área em um inselberg neotropical no Estado do Rio de Janeiro, sudeste do Brasil. Foram amostradas 69 espécies de plantas vasculares, de 31 famílias, em 84 manchas de vegetação com área variando de 0,02 a 500 m², totalizando 0,33 ha. Fabaceae e Bromeliaceae foram as famílias mais representativas. Vellozia plicata e Selaginella sellowii apresentaram as maiores frequências relativas, dominâncias relativas e valores de importância e foram as mais bem sucedidas na colonização do afloramento rochoso estudado. A regressão linear mostrou uma correlação positiva entre o tamanho da mancha e a riqueza de espécies, e fanerófito foi a forma de vida predominante, com pequenas manchas apresentando menor riqueza de espécies e dominadas pelos tapetes de Selaginella. Nossos resultados sugerem que os trechos de vegetação no inselberg Morro do Itaoca representam atualmente um refúgio contra incêndios e outros distúrbios antropogênicos para muitas espécies típicas da matriz circundante. Além disso, a localidade abriga espécies endêmicas e ameaçadas de extinção, o que reforça sua importância para as ações de conservação.

Palavras-chave
Mata Atlântica; conservação; espécies em perigo; formas de vida; afloramentos rochosos

Introduction

Precambrian rocky outcrops are hotspots of plant diversity around the world supporting plant communities that are distinctive, both structurally and floristically, from the surrounding vegetation (Safford & Martinelli 2000; Porembski 2007; Hopper 2009; Sarthou et al. 2017; de Paula et al. 2017). In Brazil, rupicolous vegetation grows on a range of underlying substrates, including quartzite-sandstone (Conceição & Pirani 2005; Alves et al. 2014;), ironstone (Jacobi et al. 2007; Lima et al. 2019), carbonate or karstic outcrops (Bystriakova et al. 2019) and granite and/or gneiss outcrops (Porembski et al. 1998; Meirelles et al. 1999; Couto et al. 2016, 2017; de Paula et al. 2017; Pereira et al. 2018). In the Atlantic Forest Domain in southeastern Brazil, rocky outcrops of granite and/ or gneiss predominate, with different degrees of insulation, sizes, and elevations, ecologically known as inselbergs (Safford & Martinelli 2000; de Paula et al. 2020). Inselbergs represent isolated terrestrial islands that rise above from their surrounding natural ecosystems, mainly tropical forests (Barthlott & Porembski 2000; Sarthou et al. 2017).

Inselbergs are ecosystems characterized by strong ecological isolation due to severe environmental filters, including high exposure to radiation, high evaporation, total or partial absence of soil, low water and nutrient availability and exposure to constant wind (Porembski & Barthlott 2000a). This environmental filters are responsible for the high richness and endemism in these environments (Safford & Martinelli 2000; Porembski 2007; de Paula et al. 2017), that present a floristic composition clearly distinguished from their surrounding matrices (Porembski 2007; de Paula et al. 2015). However, despite the ecological importance of this ecosystem (Hopper 2009; Porembski et al. 2016) inselbergs are threatened, mainly by mining activities (Hopper 2009).

In Brazil, the number of studies on inselberg vegetation has been increasing, especially in the last decades (Araújo et al. 2008; Gomes & Alves 2009, 2010; Couto et al. 2017; de Paula et al. 2017; Pena & Alves-Araújo 2017; Francisco et al. 2018; Paulino et al. 2018; Pereira et al. 2018). However, ecological and phytosociological studies of plants communities are still scarce (Porembski et al. 1998; Safford & Martinelli 2000; Meirelles et al. 1999; Medina et al. 2006; Caiafa & Silva 2007). The difficulty in establishing replicable samples in different topographies and habitat heterogeneity on rocky outcrops helps to explain this scarcity of studies (Caiafa & Silva 2007).

Rupicolous vegetation on inselbergs is generally distributed in isolated patches of different sizes, shapes and limited on all sides by the rocky surface (Meirelles et al. 1999; Ribeiro et al. 2007; Conceição et al. 2007a, 2007b; de Paula et al. 2015, 2019) and these patches contain aggregates of a few to many species. The increase in species richness in the patches over time can be attributed to an increase in area as emphasized the Island Biogeography Theory (MacArthur & Wilson 1967). Large patches may have greater resource availability, mainly due to deeper soils (Houle 1990; Meirelles et al. 1999; Michelangelli 2000; Gram et al. 2004; de Paula et al. 2015, 2019; Villa et al. 2018).

In the northern region of Rio de Janeiro state, southeastern Brazil, inselbergs are distributed in an anthropized matrix, and are very isolated in the landscape. The biodiversity of these environments is directly threatened by the mining and extractivism of plants (Pessanha et al. 2014). Furthermore, inselbergs in this region have been neglected in scientific studies, with few publications on their biodiversity (Aguiar & Gaglianone 2011; Pessanha et al. 2014; Mauad et al. 2014; Marques et al. 2018), and this prevents conservation actions for inselbergs in this area.

In this context, we studied the structure of vascular plant communities in vegetation patches, of different sizes, on an inselberg in the northern region of Rio de Janeiro state, due to the importance of the inselberg vegetation for the floristic diversity of Rio de Janeiro (Werneck et al. 2011) and the pressure from the mining industry in the region. Our expectations were that the flora of Morro do Itaoca inselberg harbors a number of endemic plant species and rupicolous species richness increases with patch size. Thus, we hope to contribute positively to the knowledge of rupicolous flora in southeastern Brazil, and our data will serve as a basis for conservation and restoration actions of these unique rock outcrop systems.

Material and Methods

Study site

The study was conducted on an inselberg in the Atlantic Forest Domain (21°48’S, 41°26’W), known as Morro do Itaoca, located in the municipality of Campos dos Goytacazes, in the northern region of Rio de Janeiro state (Fig. 1). The climate in the region has been classified as AW (sensu Köppen 1948), characterized by tropical hot and humid with a dry winter (April to September) and wet summer (October to March). The Morro do Itaoca stands amidst the surrounding flat landscape and flooded areas that can be characterized by a vegetation mosaic, represented mostly by Seasonal Semidecidual Forest (sensu Vellozo et al. 1991). Aside from the natural communities, the inselberg is in an anthropogenic matrix of livestock and sugarcane plantations and rock mining activity (Pessanha et al. 2014; Marques et al. 2018).

Figure 1
Location of the Morro do Itaoca inselberg, with emphasis on the north/northwest Fluminense region, highlighted (in gray), Rio de Janeiro state, southeastern Brazil.

The area sampled is located on the west face of Morro do Itaoca and covers approximately 20 ha. It is situated along an elevation gradient ranging from 8 to 266 m a.s.l., extending 900 m from the base to the top of the inselberg. This area was selected because of its accessibility without the need for rock climbing equipment (Fig. 2).

Figure 2
a. General view of the Morro do Itaoca inselberg, Campos dos Goytacazes, Rio de Janeiro state, and its surrounding matrix. b. monospecific community of the poikilohydric fern Selaginella sellowii in small patches. c. typical landscapes of the north Fluminense region, with flat and flooded areas, livestock activities and Desengano State Park mountains in the back. d. view of a large vegetation patch, with occurrence of Vellozia plicata, Coleocephalocereus fluminensis, Anthurium minarum and Selaginella sellowii, restricted to the edge of a large patch. e. rock mining in Morro do Itaoca, the greatest threat to its flora. Photos by D.R. Couto.

Data collection

Vegetation patches were sampled between October and November 2007, along three parallel linear transects of 900 m in length distributed systematically in intervals of 40 m. This arrangement allowed us to maximize environmental variation in the sampling. All vegetation patches (from now on, patches) intercepted along the transections were examined and the composition and abundance of vascular plants in each patch was recorded and quantified. The surface area of each patch was estimated through the maximum width and length of each patch, measured with a tape measure, and subsequently applying the equation for calculating an ellipse, according to de Paula et al. (2019). The cover of each species in each patch was estimated using the mean value of a six-point scale (modified from Daubenmire 1959): 2.5 (0–5%), 7.5 (5–10%), 17.5 (10–25%), 37.5 (25–50%), 62.5 (50–75%) and 87.5 (75–100%).

Taxonomic identification was done using specialized taxonomic literature, herbarium data and by sending specimens to specialists. An exception was for the Poaceae family, because in addition to the difficulties in taxonomic identification, it was not easy to recognize individuals in the field, which in many cases formed dense clusters that made it difficult to assess unless we pulled and separated the material. Thus, to ensure better data quality, we lumped all morphospecies of Poaceae (ca. three) into one group denominated Grass.

Species names and authors followed the Flora do Brasil 2020 on-line (<http://floradobrasil.jbrj.gov.br/>) and endangered species were cited according to the official list of endangered species of Centro Nacional de Conservação da Flora (CNC Flora 2019 - <http://floradobrasil.jbrj.gov.br/>). The classification of angiosperm families follows the recommendations of APG IV (2016) for magnoliids, monocotyledons (monocots), and eudicotyledons (eudicots), and PPG I (2016) for lycophytes and monilophytes (grouped together as ferns). Species life forms were classified according to Raunkiaer (1934), with adaptations: Ch = chamaephyte, Cr = cryptophyte (including geophytes), Hc = hemicryptophyte, Ph = phanerophyte, Th = therophyte and Epi = epiphyte. Voucher specimens were deposited in the herbaria HUENF and RB (herbaria acronyms follow Thiers, continuously updated).

Data analysis

The phytosociological parameters calculated for the species were: absolute and relative frequency (AF; RF), absolute and relative dominance (ADo; RDo) based on species cover value, and importance value index (IV) (Müller-Dombois & Ellenberg 1974). We calculated the importance value index (VI) by the sum of the relative values of frequency (RF) and dominance (RDo) (Müller-Dombois & Ellenberg 1974 modified by Caifa & Silva 2007) and expressed it as a percentage (%VI = RF+RDo/2).

We used linear regression to test the relationship between species richness and patch size, species richness was used as the dependent variable and patch size as the independent variable. Both variables were log-transformed before analysis. The transformed data followed the assumptions of normality and homoscedasticity of the residuals.

Differences in species richness by patch size class were evaluated using the non-parametric Kruskal-Wallis test (Zar 2010), since Shapiro-Wilk and Levene’s tests showed non-normality and non-homoscedasticity of the data. A posteriori comparisons were conducted using Dunn’s post hoc test. Differences were considered significant at p < 0.05. All analyses were performed using the R software (R Development Core Team 2019).

Results

We sampled 84 vegetation patches with a total area of 3,344 m² (0.33 ha). The patches varied in size from 0.02 to 500 m² and were distributed in 31 small (≤ 5 m²), 24 medium (5–25 m²), and 29 large (> 25 m²), with an average match size (m²) of 1.09 ± 1.18 (small), 12.56 ± 5.50 (medium) and 103.74 ± 114.09 (larger).

A total of 69 species (considering grass group as a species), 59 genera and 31 families, were sampled in the 84 patches (Tab. S1, available on supplementary material <https://doi.org/10.6084/m9.figshare.16864600.v1>). The most representative families were Fabaceae (8 spp.), Cactaceae (7 spp.), Asteraceae (6 spp.), Orchidaceae and Bromeliaceae (5 spp. each), Malvaceae and Cyperaceae (4 spp. each). These families accounted for 57% of the total species richness recorded in the patches. The contribution of the most representative families according to the size classes of the patches showed that only Cactaceae and Malvaceae had representation in the small patches (Fig. 3). The species with the highest relative frequency in the sample were represented by two poikilohydric species, Selaginella sellowii Hieron. (13.42%) and Vellozia plicata Mart. (9.27%), followed by the cacti Coleocephalocereus fluminensis (Miq.) Backeb. (9.27%) (Tab. S1, available on supplementary material <https://doi.org/10.6084/m9.figshare.16864600.v1>).

Figure 3
Contribution of the main families of vascular plants recorded in the 84 vegetation patches sampled on the Morro do Itaoca inselberg, Campos dos Goytacazes, Rio de Janeiro state, southeastern Brazil. Vegetation patch classes: small (≤ 5 m²; n = 31), medium-sized (5–25 m²; n = 24), and large (> 25 m²; n = 29).

When we compared the relative frequency of the main species between the different patch size classes (Tab. S2, available on supplementary material <https://doi.org/10.6084/m9.figshare.16864600.v1>), the results were similar to the pattern found for the general sampling, with these three species occurring as the most representative in all patch size classes. Selaginella sellowii was by far the most frequent species in all the patch size classes, forming mats in 100% of the patches.

According to the RDo, species with the highest values in the sample were V. plicata (50.96%), S. sellowii (18.89%), Grass group (5.49%), and C. fluminensis (2.34%) which altogether amounted to 77.68% of the RDo (Tab. S1, available on supplementary material <https://doi.org/10.6084/m9.figshare.16864600.v1>). The RDo values in the different sizes patches, showed S. sellowii (small = 44.5%; medium = 52.5% and larger = 11.7%) and V. plicata (small = 39%; medium = 24.9% and larger = 53.6%) as the most dominant species (Tab. S2, available on supplementary material <https://doi.org/10.6084/m9.figshare.16864600.v1>).

Vellozia plicata had the highest importance value (30.11%), followed by S. sellowii (16.15%) and C. fluminensis (5.8%), which together represent 52% of the importance value. Ten species were responsible for 70.2% of the total importance value (Tab. S1, available on supplementary material <https://doi.org/10.6084/m9.figshare.16864600.v1>). This pattern was observed in all three patch size classes, with S. sellowii and V. plicata having the highest importance value indices (Tab. S2, available on supplementary material <https://doi.org/10.6084/m9.figshare.16864600.v1>). In general, the 20 most abundant species in the patch size classes represented around 80% or more of the importance values (Tab. S2, available on supplementary material <https://doi.org/10.6084/m9.figshare.16864600.v1>).

The total number of species per patch size class was nine (small), 38 (medium) and 64 (large). The median values of species richness per patch size class were significantly different (Kruskal-Wallis test, x² = 58.44, df = 2, p < 0.0001), with small patches having lower richness. There was a strong and significant positive relationship between the area of the vegetation patch and the number of vascular rupicolous species (r² = 0.699, p < 0.001; Fig. 4).

Figure 4
Linear regression between species richness and vegetation patch size (r² = 0.699, p < 0.001) on Morro do Itaoca inselberg, Campos dos Goytacazes, Rio de Janeiro state, southeastern Brazil.

The predominant life-form in the patches were phanerophytes with 19 species (28%), followed by therophytes with 16 species (23.53%), hemicryptophytes with 12 species (17.65%) and chamaephytes with 11 species (16.18%). Epiphytes and cryptophytes did not occur in the small patches. However, all other life forms had an increase of representativeness in the largest patches, mainly therophytes and phanerophytes (Fig. 5).

Figure 5
Life-forms recorded in different patch size classes on the Morro do Itaoca inselberg, Campos dos Goytacazes, Rio de Janeiro state, southeastern Brazil. Cr = cryptophyte; Ep = epiphyte; Ch = chamaephyte; Ph = phanerophyte; Th = therophyte; and Hc = hemicryptophyte. Vegetation patch classes: small (≤ 5 m²; n = 31), medium (5–25 m²; n = 24), and large (> 25 m²; n = 29).

Of the 69 species recorded on the patches, three are threatened species (sensu CNCFlora 2019): Hippeastrum striatum (Lam.) Moore, Wunderlichia azulensis and Coleocephalocereus fluminensis, all classified as Endangered (EN).

Discussion

The most dominant species on the Morro do Itaoca inselberg (Vellozia plicata, Coleocephalocereus fluminensis, Selaginella sellowii, Trilepis lhotzkiana Nees ex Arn., Cyrtopodium glutiniferum Raddi) were also recorded in other studies on inselbergs in southeastern Brazil (Porembski et al. 1998; Meirelles et al. 1999; Couto et al. 2017; de Paula et al. 2017). They were also mixed with species typical of the lowland semi-deciduous seasonal forest that surrounds the inselberg (e.g., Astronium graveolens Jacq., Casearia decandra Jacq., Passiflora alata Curtis). However, species considered the most important (according to IVI) on the rocky outcrop were V. plicata, S. sellowii and C. fluminensis. Vellozia plicata is a rocky outcrop-specialist (it does not occur in the surrounding matrix), tolerant to desiccation, which forms mats on inselbergs in southeastern and northeastern Brazil (Porembski et al. 1998; Lucena et al. 2015). This species has been recognized as one of the most frequent species on coastal inselbergs in Rio de Janeiro state, along with S. sellowii and C. fluminensis (Meirelles et al. 1999).

Species richness recorded in vegetation patches on the Morro do Itaoca inselberg was higher than values found for four quartizite-sandstone rocky outcrop areas in Bahia (Conceição et al. 2007b), on an inselberg in the Amazon domain in Venezuela (Villa et al. 2018) and close to the richness recorded on eight other coastal inselbergs in Rio de Janeiro (Meirelles et al. 1999). The main factor that contributed to the floristic richness of the Morro do Itaoca inselberg, in addition to the rocky outcrop specialist species, was the presence of species of broad ecological value, capable of colonizing different types of habitats. Of all the species sampled, those belonging to the families Fabaceae, Salicaceae, Passifloraceae, Phyllantaceae, Clusiaceae, Euphorbiaceae and Calophyllaceae, are typical of the surrounding vegetation. Other families, like Asteraceae, Bromeliaceae, Malvaceae and Orchidaceae have species with wide distribution in different Brazilian ecosystems, and in the study area, and are represented by a few inselberg specialists (see Tab. S1, available on supplementary material <https://doi.org/10.6084/m9.figshare.16864600.v1>). Typical species of the surrounding vegetation on the rock outcrop vegetation were also registered on other tropical inselbergs (Burke 2002; Gram et al. 2004; Ribeiro et al. 2007; Couto et al. 2016, 2017), and questions about the inselbergs’ relationship with the surrounding flora need more detailed studies (Scarano 2002). However, the number of species per sampled area was lower than values found in other studies of vegetation patches on rocky outcrops in Brazil and Venezuela (Meirelles et al. 1999; Ribeiro & Medina 2007; Conceição et al. 2007a, 2007b; Villa et al. 2018) (Tab. S3, available on supplementary material <https://doi.org/10.6084/m9.figshare.16864600.v1>).

The poikilohydric species S. sellowii together with V. plicata, are the most frequent species on the Morro do Itaoca, forming mats. Species of the genera Selaginella and Vellozia occur as typical constituents of mat communities on Neotropical inselbergs (Porembski et al. 1998) and together with C. fluminensis, the third most frequent species in the sampled patches, they stand out in coastal inselbergs of the Rio de Janeiro State (Meirelles et al. 1999).

Three species, V. plicata, S. sellowii and C. fluminensis, with high frequency and dominance, form the group of greatest importance in the rupicolous community of the Morro do Itaoca inselberg, with 52% of the total. This oligarchic structure with a small number of dominant species and many rare species has also been recorded on other granite rock outcrops in southeastern Brazil (Meirelles 1996; Caiafa & Silva 2007), as well as on quartzite-sandstone outcrops (Conceição 2003) and it seems to follow a pattern for vegetation on rocky outcrops.

We found that S. sellowii has greater dominance (coverage) and importance value in small and medium size classes, however, it loses space to V. plicata in the larger patches (see Tab. S2, available on supplementary material <https://doi.org/10.6084/m9.figshare.16864600.v1>). According to some authors (see Ibish et al. 1995; Porembski et al. 2000), Selaginella species, mainly S. sellowii, represent a pioneer stage in the colonization of rocky outcrops, which are replaced by other groups in succession (mainly woody, monocots and eudicots), getting restricted to the peripheral areas of the patches (see Fig. 2e). Selaginella sellowii has a wide distribution in rocky environments, occurring from the Neotropics to Mexico (Heringer et al. 2016), is tolerant to desiccation and, in many cases, forms monospecific mats (Ibish et al. 1995; Porembski et al. 2000) as observed in the study area (see Fig. 2b). The mats formed by S. sellowii and V. plicata on the Morro do Itaoca possibly serve as a substrate, acting as nurse plants (Scarano 2002; Medina et al. 2006) for other plant groups, including species of the surrounding matrix, which are unable to establish directly on bare rocks.

In this study, the number of species increased significantly with increasing patch size, as predicted by the Island Biogeography Theory (MacArthur & Wilson 1967), corroborating one of the most consistent patterns in ecology (Begon 2006; Dodds 2009). This pattern is largely shown by other studies on inselberg-isolated patches (Porembski et al. 1996; Meirelles et al. 1999; Michelangeli 2000; Gram et al. 2004; Villa et al. 2018; de Paula et al. 2019; Henneron et al. 2019). Patch size includes a number of aspects that affect vascular plants richness, including mainly age (the time available for establishment of plants), surface area and microhabitats available for colonization. Also, large patches may have greater amount and depth of soil, which may promote more diverse plant communities (Houle 1990; Michelangeli 2000; Gram et al. 2004; Henneron et al. 2019). According to Houle (1990), soil availability appears to follow a gradient of depth, from the edge to center of the patches, providing different habitats for colonization of species with different ecological requirements. Thus, with the exception of epilithic species (which grow directly on the exposed rock), it can be speculated that colonization by rupicolous vegetation is more restricted where the soil is less developed (smaller patches or edges of larger patches) and constitutes a abiotic barrier for many species (Houle & Phillips 1989; Gram et al. 2004).

Phanerophytes were the most prevalent life form, similar to other rocky outcrops in Brazil (Meirelles et al. 1999; Ribeiro & Medina 2002; Conceição & Pirani 2005; França et al. 2005; Conceição et al. 2007; Gomes & Alves 2010; de Paula et al. 2017; Pena & Alves-Araujo 2017). In the study area, the phanerophytes (vines, cacti, subshrubs, shrubs and trees), occurred mainly in medium and increased their larger patches. In general, all life forms expanded their contribution in larger patches, probably due to soil development in these size classes, as suggested by other authors (Michelangeli 2000; Gram et al. 2004; de Paula et al. 2017).

Therophytes, the second most represented group in this study, have low representivity on Atlantic Forest inselbergs (Safford & Martinelli 2000; Caiafa & Silva 2005; Ribeiro et al. 2007), compared to inselbergs of the Caatinga Domain (Araújo et al. 2008; Gomes & Alves 2010) and Africa (Porembski et al. 1996, Porembski & Barthlott 1997). Its representativeness is due to the presence of a high number of ruderal species, typical of pastures that occur in the surrounding area present at the base of the inselberg.

An absence of epiphytes in small patches can be explained by the low (or lack of) availability of substrates (trunk and branches of woody plants - phorophytes) for colonization. The richness of epiphytic species in rocky outcrops is related mainly to woody-plant species (Alves et al. 2008; Couto et al. 2016, 2017; Francisco et al. 2018; Henneron et al. 2019) or number of stems of Vellozia genus (Werneck & Espírito-Santo 2002; Porembski 2003), associated with a positive effect of rainfall and altitude (Henneron et al. 2019). Epiphytes represent a key group in tropical ecosystems because they provide fundamental resources for fauna such as nectar, fruit, shelter, nesting material and sites, making neotropical ecosystems the most complex in the world (Benzing 1999).

The rupicolous vegetation patches sampled on the Morro do Itaoca included 15 endemic species from rocky outcrops in southeastern Brazil. The southeastern Brazil is recognized as a worldwide center of richness and endemism of inselberg plants (de Paula et al. 2020), along with Madagascar and eastern Australia (Porembski 2007). In addition, the Morro do Itaoca is home to rare species, such as Cryptanthus delicatus Leme, a small bromeliad described in the 90’s (Leme 1995) endemic to this location. Other rupicolous taxa such as Begonia ibitiocensis E.L. Jacques & Mamede (Begoniaceae - Jacques & Mamede 2004), Sinningia bragae Chautems, M. Peixoto & Rossini (Gesneriaceae - Chautems et al. 2015) and Pleroma ceciliana P.J.F.Guim.& Oliveira da Silva (Melastomataceae - Guimarães & Silva 2015) were described from samples collected in this location. These data, together with the presence of endangered species, increasing mining activities, removal of ornamental plants and fire occurrence (Pessanha et al. 2014) reinforce the need for conservation actions for Morro do Itaoca.

It is important to note that inselbergs provide relevant ecosystem services (Porembski et al. 2016). The runoff from the rocky slopes can increase the supply of drinking water surrounding human populations and provide nutrients for surrounding agricultural areas (Schut et al. 2014). The inselbergs also may serve as refugia for biodiversity (Burke 2002; Couto et al. 2016) as well as promoting regional development through ecotourism, adventure sports and cultural activities (Porembski & Barthlott 2000b; Larson et al. 2000), generating financial resources and life quality for families living around these ecosystems.

However, habitat destruction generated by mining activity is surely the biggest global threat to inselberg vegetation in worldwide (Porembski et al. 2016), and negatively affects the people who live around them. In addition, the licensing of mining activity usually does not include the inventory of the biota associated with this environment, including its flora, probably due to its non-forest vegetation, completely disregarding the unique biota of these ecosystems (Couto et al. 2019).

In this study, we present information on the most abundant species (especially the nurse species, Vellozia plicata and Selaginella sellowii) that can be very useful for restoration purposes, which is highly desirable on the study area that faces serious threats because of the mining sector. Restorationists, based on our data, can select species based on their functional role (e.g., nurse species) and on their abundance. However, it is necessary for public authorities to pay more attention to these environments, promoting laws that guarantee the protection of the biodiversity of these ecosystems.

The presence of threatened species and endemism is recognized as a priority indicator for the creation of protected areas worldwide (Brooks et al. 2006; Mittermeier & Scarano 2013). Thus, we hope that our results reinforce the urgent need to protect the Morro do Itaoca, with its rich biodiversity and its natural resources serving as guide for conservation actions in this important location in the northern region of Rio de Janeiro.

Acknowledgements

This study was financed in part by the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brazil (CAPES) - Finance Code 001. To the Programa de Pós-doutorado da Universidade Estadual do Norte Fluminense Darcy Ribeiro, for the research scholarship (PROPPG 02/2018) awarded to DRC; the FAPERJ Mata Atlântica program, for the grant of the Master’s scholarship to MLD. MTN has been supported by the National Council for Scientific and Technological Development of Brazil (CNPq; 305617/2018-4) and Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ E-26/202.855/2018). To Fernando P. Uribbe, for help making the location map; and Dr. John DuVall Hay, for English revision and helpful comments. Finally, we want to thank the two anonymous reviewers and the associate editor Dr. Bruno Rosado, for their comments which greatly improved the manuscript.

References

• Aguiar WM & Gaglianone MC (2011) Euglossine bees (Hymenoptera Apidae Euglossina) on an inselberg in the Atlantic Forest domain of southeastern Brazil. Tropical Zoology 24: 107-125.
• Alves RJV, Kolbek J & Becker J (2008) Vascular epiphyte vegetation in rocky savannas of southeastern Brazil. Nordic Journal of Botany 26: 101-117.
• Alves RJV, Silva NG, Oliveira JA & Medeiros D (2014) Circumscribing campo rupestre - megadiverse Brazilian rocky montane savanas. Brazilian Journal of Biology 74: 355-362. <http://dx.doi.org/10.1590/1519-6984.23212>
• APG IV - Angiosperm Phylogeny Group (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. <https://doi.org/10.1111/boj.12385>
• Araújo FS, Oliveira RF & Lima-Verde LW (2008) Composição, espectro biológico e síndromes de dispersão da vegetação de um inselbergue no domínio da caatinga, Ceará. Rodriguésia 59: 659-671.
• Barthlott W & Porembski S (2000) Vascular plants on inselbergs: systematic overview. In: Porembski S & Barthlott W (eds.) Inselbergs - biotic diversity of isolated rock outcrops in tropical and temperate regions. Ed. Springer-Verlag, Berlin. Pp. 103-116.
• Begon M, Townsend CR & Harper JL (2006) Ecology: from individuals to ecosystems. Blackwell Publishing, Oxford. 759p.
• Burke A (2002) Patch-matrix relationships in Nama Karoo inselberg landscapes. Part 1: do inselbergs provide a refuge for matrix species? Plant Ecology 160: 70-90.
• Bystriakova N, Melo PH, Moat J, Lughadha EN & Monro AK (2019) A preliminary evaluation of the Karst flora of Brazil using collections data. Scientific Reports 9: 1-13. <https://doi.org/10.1038/s41598-019-53104-6>
• Chautems A, Peixoto M & Rossini J (2015) A new species of Sinningia Nees (Gesneriaceae) from Espírito Santo and Rio de Janeiro states, Brazil. Candollea 70: 231-235. DOI: 10.15553/c2015v702a8
  » https://doi.org/10.15553/c2015v702a8
• Conceição AA & Pirani JR (2005) Delimitação de habitats em campos rupestres na Chapada Diamantina, Bahia: substratos, composição florística e aspectos estruturais. Boletim de Botânica da Universidade de São Paulo 23: 85-111.
• Conceição AA, Pirani JR & Meirelles ST (2007a) Floristics, structure and soil of insular vegetation in four quartzite-sandstone outcrops of “Chapada Diamantina”, Northeast Brazil. Revista Brasileira de Botânica 30: 641-656.
• Conceição AA, Giulietti AM & Meirelles ST (2007b) Ilhas de vegetação em afloramentos de quartzito-arenito no Morro do Pai Inácio, Chapada Diamantina, Bahia, Brasil. Acta Botanica Brasilica 21: 335-347.
• Couto DR, Dias HM, Pereira MCA, Fraga CN & Pezzopane JEM (2016) Vascular epiphytes on Pseudobombax (Malvaceae) in rocky outcrops (inselbergs) in Brazilian Atlantic Rainforest: basis for conservation of a threatened ecosystem. Rodriguésia 67: 583-601. <https://doi.org/10.1590/2175-7860201667304>
• Couto DR, Francisco TM, Manhães VC, Dias HM & Pereira MCA (2017) Floristic composition of a Neotropical inselberg from Espírito Santo state, Brazil: an important area for conservation. Check List 13: 2043. <https://doi.org/10.15560/13.1.2043>
• Couto DR, Fontana AP, Rocha Neto AC, Gomes JML, Calazans LSB, Silva HL, Valadares RT, Saka MN, Siqueira GS, Lopes AS, Novelli FZ, Bergher IS & Fraga CN (2019) Angiospermas monocotiledôneas ameaçadas de extinção no estado do Espírito Santo. In: Fraga CN, Formigoni MH & Chaves FG (eds.) Fauna e flora ameaçadas de extinção no estado do Espírito Santo. Instituto Nacional da Mata Atlântica, Santa Teresa. Pp. 164-191.
• Daubenmire R (1959) A canopy-coverage method of vegetational analysis. Northwest Science 33: 43-64.
• de Paula LFA, Mota NFO, Viana PL & Stehmann JR (2017) Floristic and ecological characterization of habitat types on an inselberg in Minas Gerais, southeastern Brazil. Acta Botanica Brasilica 32: 199-211. <https://doi.org/10.1590/0102-33062016abb0409>
• de Paula LFA, Colmenares-Trejos SL, Negreiros D, Rosado BHP, Mattos EA, Bello F, Porembski S & Silveira FAO (2019) High plant taxonomic beta diversity and functional and phylogenetic convergence between two Neotropical inselbergs. Plant Ecology & Diversity 13: 61-73. <https://doi.org/10.1080/17550874.2019.1673846>
• de Paula LFA, Azevedo LO, Mauad LP, Cardoso LJT, Braga JMA, Kollmann LJC, Fraga CN, Menini Neto L, Labiak PH, Mello-Silva R, Porembski S & Forzza RC (2020) Sugarloaf Land in south-eastern Brazil: a tropical hotspot of lowland inselberg plant diversity. Biodiversity Data Journal 8: e53135. <https://doi.org/10.3897/BDJ.8.e53135>
• Dodds WK (2009) Laws, theories and patterns in ecology. University of California Press, Berkeley. 256p.
• Francisco TM, Couto DR, Evans DM, Garbin ML & Miranda CRR (2018) Structure and robustness of an epiphyte-phorophyte commensalistic network in a neotropical inselberg. Austral Ecology 43: 903-914. <https://doi.org/10.1111/aec.12640>
• França F, Melo E, Santos AKA, Melo JGAN, Marques M, Silva Filho MFB, Moraes L & Machado C (2005) Estudo ecológico e florístico em ilhas de vegetação de um inselberg no semi-árido da Bahia, Brasil. Hoehnea 32: 93-101.
• Gomes P & Alves M (2009) Floristic and vegetational aspects of an inselberg in the semi-arid region of Northeast Brazil. Edinburgh Journal of Botany 66: 1-18.
• Gomes P & Alves M (2010) Floristic diversity of two crystalline rocky outcrops in the Brazilian northeast semi-arid region. Brazilian Journal of Botany 33: 661-676. <http://dx.doi.org/10.1590/S0100-84042010000400014>
• Gram WK, Borer ET, Cottingham KL, Seabloom EW, Boucher VL, Goldwasser L, Micheli F, Kendal BE & Burton RS (2004) Distribution of plants in a California serpentine grassland: are rocky hummocks spatial refuges for native species? Plant Ecology 172: 159-171.
• Guimarães PJF & Silva MFO (2015) A new species of Pleroma (Melastomataceae, Melastomeae) from southeastern Brazil. Phytotaxa 205: 51-58. <http://dx.doi.org/10.11646/phytotaxa.205.1.4>
• Henneron L, Sarthou C, Massary JC & Ponge JF (2019) Habitat diversity associated to island size and environmental filtering control the species richness of rock-savanna plants in neotropical inselbergs. Ecography 42: 1536-1547. <http://dx.doi.org/10.1111/ecog.04482>
• Heringer G, Valdespino IA & Salino A (2016) Selaginella P.Beauv. from Minas Gerais, Brazil. Acta Botanica Brasilica 30: 60-77. <http://dx.doi.org/10.1590/0102-33062015abb0247>
• Houle G (1990) Species-area relationship during primary succession in granite outcrop plant communities. American Journal of Botany 77: 1433-1439.
• Houle G & Phillips DL (1989) Seed availability and biotic interactions in granite outcrop plant communities. Ecology 70: 1307-1316.
• Hopper SD (2009) OCBIL theory: towards an integrated understanding of the evolution, ecology and conservation of biodiversity on old, climatically buffered, infertile landscapes. Plant Soil 322: 49-86.
• Jacobi CM, Carmo FF, Vincent RC & Stehmann JR (2007) Plant communities on ironstone outcrops: a diverse and endangered Brazilian ecosystem. Biodiversity and Conservation 16: 2185-2200.
• Jacques EL & Mamede MCH (2004) Novelties in Begonia (Begoniaceae) from the coastal forests of Brazil. Brittonia 56: 75-81.
• Köppen W (1948) Climatologia: con un estudio de los climas de la tierra. Fondo de Cultura Econômica, Ciudad de México. 479p.
• Larson DW, Matthes U & Kelly PE (2000) Cliff Ecology: pattern and process in cliff ecosystems. Cambridge University Press, Cambridge. 340p.
• Lima MS, Takahasi A, Damasceno Junior GA & Araujo AC (2019) Checklist of the flora in ironstone outcrops at the Urucum Plateau, Corumbá, Mato Grosso do Sul. Biota Neotropica 19: e20180708. <http://dx.doi.org/10.1590/1676-0611-bn-2018-0708>
• Leme EMC (1995) Miscellaneous new species of Brazilian Bromeliaceae. Selbyana 6: 110-122.
• MacArthur RH & Wilson EO (1967) The theory of island biogeography. Princeton University Press, Princeton. 201p.
• Marques MF, Deprá MS & Gaglianone MC (2018) Seasonal variation in bee-plant interactions in an inselberg in the Atlantic Forest in Southeastern Brazil. Sociobiology 65: 612-620.
• Mauad LP, Buturi FOS, Souza TP, Nascimento MT & Braga JMA (2014) New distribution record and implications for conservation of the endangered Wunderlichia azulensis Maguire & G.M. Barroso (Asteraceae: Wunderlichieae). Check List 10: 706-708.
• Medina BMO, Ribeiro KT & Scarano FR (2006) Plant-plant and plant-topography interactions on a rock outcrop at high altitude in southeastern Brazil. Biotropica 38: 1-7.
• Meirelles ST, Pivello VR & Joly CA (1999) The vegetation of granite rock outcrops in Rio de Janeiro, Brazil, and the need for its protection. Environmental Conservation 26: 10-20.
• Michelangeli FA (2000) Species composition and species-area relationships in vegetation isolates on the summit of a sandstone mountain in southern Venezuela. Journal of Tropical Ecology 16: 69-82.
• Müller-Dombois D & Ellenberg H (1974) Aims and methods of vegetation ecology. John Wiley & Sons, New York. 547p.
• Paulino RC, Gomes VS & Silveira AP (2018) Flora de Inselbergues do Monumento Natural Monólitos de Quixadá, no sertão central do Ceará. Iheringia, Série Botânica 73: 182-190. <http://dx.doi.org/10.21826/2446-8231201873110>
• Pena NTL & Alves-Araújo A (2017) Angiosperms from rocky outcrops of Pedra do Elefante, Nova Venécia, Espírito Santo, Brazil. Rodriguésia 68: 1895-1905. <http://dx.doi.org/10.1590/2175-7860201768522>
• Pereira MMD, Braga PET, Guiomar N, Santos FDS & Ribeiro S (2018) A flora e a vegetação dos afloramentos rochosos em três municípios na região Norte do Ceará, Brasil: caracterização fitossociológica. Rodriguésia 69: 281-299. <http://dx.doi.org/10.1590/2175-7860201869202>
• Pessanha AS, Menini Neto L, Forzza RC & Nascimento MT (2014) Composition and conservation of Orchidaceae on an inselberg in the Brazilian Atlantic Forest and floristic relationships with areas of Eastern Brazil. Revista de Biología Tropical 62: 829-841.
• Porembski S, Szarzynski J, Mund JP & Barthlott W (1996) Biodiversity and vegetation of small-sized inselbergs in a West African rain forest (Tai, Ivory Coast). Journal of Biogeograph 23: 47-55.
• Porembski S, Martinelli G, Ohlemüller R & Barthlott W (1998) Diversity and ecology of saxicolous vegetation mats on inselbergs in the Brazilian Atlantic rainforest. Diversity and Distributions 4: 107-119.
• Porembski S, Becker U & Seine R (2000) Patches on Patches: habitats on inselbergs. In: Porembski S & Barthlott W (eds.) Inselbergs: biotic diversity of isolated rock outcrops in tropical and temperate regions. Ecological Studies 146. Springer-Verlag, Berlin. Pp. 49-67.
• Porembski S & Barthlott W (2000a) Granitic and gneissic outcrops (inselbergs) as centers of diversity for desiccation-tolerant vascular plants. Plant Ecology 151: 19-28.
• Porembski S & Barthlott W (2000b) Inselbergs: biotic diversity of isolated rock outcrops in tropical and temperate regions. Ecological Studies 146. Springer-Verlag, Berlin. 522p.
• Porembski S (2003) Epiphytic orchids on arborescent Velloziaceae and Cyperaceae: extremes of phorophyte specialisation. Nordic Journal of Botany 23: 505-512.
• Porembski S (2007) Tropical inselbergs: habitat types, adaptive strategies and diversity patterns. Revista Brasileira de Botânica 30: 579-586. <http://dx.doi.org/10.1590/S0100-84042007000400004>
• Porembski S, Silveira FAO, Fiedler PL, Watve A, Rabarimanarivo M, Kouame F & Hopper SD (2016) Worldwide destruction of inselbergs and related rock outcrops threatens a unique ecosystem. Biodiversity and Conservation 25: 2827-2830. <http://dx.doi.org/10.1007/s10531-016-1171-1>
• PPG - The Pteridophyte Phylogeny Group (2016) A community-derived classification for extant lycophytes and ferns. PPG I. Journal of Systematics and Evolution 54: 563-603. <https://doi.org/10.1111/jse.12229>
• R Core Team (2016) R: a language and environment for statistical computing. Vienna, Austria. Available at <https://www.r-project.org/>. Access on 15 November 2016.
  » https://www.r-project.org/
• Ribeiro KT, Medina BMO & Scarano FR (2007) Species composition and biogeographic relations of the rock outcrop flora on the high plateau of Itatiaia, SE-Brazil. Revista Brasileira de Botânica 30: 623-639.
• Safford HD & Martinelli G (2000) Southeast Brazil. In: Porembski S & Barthlott W (eds.) Inselbergs: biotic diversity of isolated rock outcrops in tropical and temperate regions. Springer, Berlin. Pp. 339-389.
• Sarthou C, Pavoine S, Gasc JP, Massary JC & Ponge JF (2017) From inselberg to inselberg: floristic patterns across scales in French Guiana (South America). Flora 229: 147-158. <https://doi.org/10.1016/j.flora.2017.02.025>
• Scarano FR (2002) Structure, function and floristic relationships of plant communities in stressful habitats marginal to the Brazilian Atlantic forest. Annals of Botany 90: 517-524.
• Schut AGT, Wardell-Johnson GW, Yates CJ, Keppel G, Baran I, Franklin SE, Hopper SD, Van Niel KP, Mucina L & Byrne M (2014) Rapid Characterisation of Vegetation Structure to Predict Refugia and Climate Change Impacts across a Global Biodiversity Hotspot. PLoS ONE 9: e82778. doi: 10.1371/journal.pone.0082778
• Veloso HP, Rangel Filho ALR & Lima JCA (1991) Classificação da vegetação brasileira adaptada a um sistema universal. Instituto Brasileiro de Geografia e Estatística, Rio de Janeiro. 123p.
• Villa PM, Cardinelli LS, Magnago LF, Heringer G, Martins SV, Campos PV, Rodrigues AC, Neri AV & Meira-Neto JAA (2018) Relación especie-área y distribución de la abundancia de especies en una comunidad vegetal de un inselberg tropical: efecto del tamaño de los parches. Revista de Biología Tropical 66: 937-951. <https://doi.org/10.15517/RBT.V66I2.33424>
• Werneck MS & Espirito-Santo MM (2002) Species diversity and abundance of vascular epiphytes on Vellozia piresiana in Brasil. Biotropica 34: 51-57.
• Werneck MS, Sobral MEG, Rocha CTV, Landau EC & Stehmann JR (2011) Distribution and endemism of Angiosperms in the Atlantic Forest. Natureza & Conservação 9: 188-193.
• Zar JH (2010) Biostatistical Analysis. Prentice-Hall, New Jersey. 944p.

Supplementary Material

See supplementary material at <https://doi.org/10.6084/m9.figshare.16864600.v1 >

Edited by

Area Editor: Dr. Bruno Rosado

Publication Dates

• Publication in this collection
  03 Dec 2021
• Date of issue
  2021

History

• Received
  05 June 2020
• Accepted
  13 Nov 2020