Bryophytes of the Serra dos Órgãos National Park: endemism and conservation in the Atlantic Forest.

1. Introduction

Serra dos Órgãos National Park (PARNASO), established on November 30th, 1939, holds the distinction of being the third national park created in Brazil. This protected area is situated within the Atlantic Forest domain, specifically in the Serra do Mar massifs and called Órgãos because its peaks resemble and are named as “organs”. The Serra do Mar is an extensive mountain ranging approximately 1,500 kilometers along the Brazilian coast, from the northern Santa Catarina State to Rio de Janeiro State [1,2].

PARNASO currently represents one of the most important remaining biodiversity hotspots in Rio de Janeiro State, since its environment formations are one of the largest centers of flower plant endemism in the Atlantic Forest. It also plays a vital role in preserving essential water sources that feed two main watersheds — Paraíba do Sul and several streams of the Baía de Guanabara [3,4,5,6,7,8].

The Atlantic Forest domain is one of the most species-rich forests in the tropics [9,4,10] , with. It is also recognized for having high levels of biodiversity and endemism, expressed via its complex structural environments [11,12].

Tropical forests hold the highest diversity of bryophyte species in the world due to their structural complexity and microhabitat diversity [13,14]. This diversity varies in altitudinal, both in structure and floristic composition [14,15,16,17,18,19,20,21,22].

The Atlantic Forest within PARNASO comprises well-preserved forests characterized by four distinct vegetation formations based on altitude, climate, and soil conditions, among other factors [23,24,25,6,26]. In the lower parts around Sede Guapimirim, Sub-montane Forest prevails, while near Sede at Teresópolis, the forest transitions from Montane Forest to Upper-montane Forest, culminating above 2,000 m.a.s.l. and High-altitude Fields along the trail from Teresópolis to Petrópolis [27].

Latitude, climatic variation and substrate disponibility due strong influence on species diversity with the altitude of these belts in different regions [15,18], while low species occurrence follows lower altitudinal ranges [28].

The species list of the vascular plants in Flora Organensis [23] is strongly based on the work of 18th century botanists and on collections made especially by A.C. Brade (1881-1971) and C.T. Rizzini (1921-1992), between the 1930s and 1950s of the 20th century. These collectors also recorded bryophytes and the specimens are studied by Bartram (1954), who found 146 species. Most bryophyte specimens from Serra dos Órgãos are deposited in the Herbarium of Jardim Botânico do Rio de Janeiro (RB).

Bryophytes from PARNASO were low explored, even though several researchers collected and published new taxa, the information was dispersed as examined material in taxonomical revisionary work. Faria et al. (2021) do collections trying to re-collect species founded by Glaziou in Serra dos Órgaos and the taxonomic reclassification of an Atlantic Forest endemic [30].

There is no other information of bryophytes in PARNASO, thus, no detailed data on the floristic structure and composition of bryophytes. A list of the species will fill an important area of the Rio de Janeiro state and help the threatened evaluation of bryophytes species. As well as provide revised herbarium specimens and new collections to stimulate new research on ecology and biogeography in this important National Park.

This work aimed to provide an inventory of the bryophyte species in PARNASO and discuss the following topics: (i) Species richness and floristic composition; (ii) Substrate colonization; and (iii) Endemism and conservation status.

2. Results

2.1. Species Richness and Floristic Composition

The present study documented 507 species, in 206 genera and 77 families (Table 1). The Serra dos Orgaos National Park preserves 57% of the known bryophyte flora of Rio de Janeiro State and 31% of Brazil. Seventeen new species occurrences for Rio de Janeiro State are founded, indicated by # in Table 1. We analyse ca 3,000 specimens for 428 species, while 79 species (indicated by * in Table 1) remains known only in the literature.

Three species are locally endemic, being known only from the type specimens collected over 100 years ago: Southbya organensis (Lützelburg 6003 p.p. [holotype JE]), Plagiochila pseudoradicans (Lützelburg 6029b [holotype JE]) and Dicranodontium pulchroalare ssp. brasiliense (Lützelburg 1519 [holotype JE]). Efforts are needed to obtain new records for these species.

The most species-rich families of liverworts are Lejeuneaceae (65 spp.) and Lepidoziaceae (16 spp.), while for moss they are Leucobryaceae (30 spp.) and Sphagnaceae (25 spp.). Eight species of hornworts were found, distributed among the families Dendrocerotaceae (4 spp.), Anthocerotaceae (2 spp.) and Nothotyladaceae (2 spp.). The most species-rich genera were: Campylopus (Leucobryaceae, 23 spp.); Plagiochila (Plagiochilaceae, 21 spp.); Fissidens (Fissidentaceae, 20 spp.); Lejeunea (Lejeuneaceae, 16 spp.) and Metzgeria (Metzgeriaceae, 14 spp.). Considering the samples analyzed, the species comonest species and more recorded were: Campylopus arctocarpus (7 specimens); Lejeunea acanthogona (7); Lejeunea flava (7); Radula nudicaulis (7); Bryum capillare (6); Fissidens wallisii (6); Lejeunea serpillifolioides (6); Rigodium toxarion (6); Trichocolea brevifissa (6) and Zelometeorium ambiguum (6).

2.2. Substrate Colonization

The bryophyte species predominantly colonized rocks (210 spp.), followed by tree trunks (209 spp.), soil (205 spp.), logs (50 spp.), and leaves (29 spp.).

Phorophyte availability within the forests of PARNASO clearly influences the bryophyte species occurrence. Mosses predominantly colonize tree trunks, with only four species being found on leaves: Paraleucobryum longifolium (Dicranaceae); Philophyllum tenuifolium (Hookeriaceae); Toloxis imponderosa (Meteoriaceae) and Schlotheimia tecta (Orthotrichaceae).

The colonization of rocks by bryophytes is mainly related to the rare species such as Campylopus uleanus. The high-altitude rocky outcrops of igneous and metamorphic origin (Figure 1) are characteristic of altitudes above 1800 m.a.s.l.

The lowest bryophyte colonization was for leaves (epiphyllous). Most of the species that colonized this substrate in High-altitude Fields were mosses (60%), followed by liverworts (40%).

The leaf-colonizing species most frequent were the leafy liverworts of the family Lejeuneaceae (21 spp.), followed by Radulaceae (2 spp.) and the thallose liverwort family Metzgeriaceae (2 spp.). According to Gradstein et al. (2001) and Ilkiu-Borges & Lisboa (2004) species of Lejeuneaceae can colonize different types of substrates, but their occurrence on leaves is indicative of preserved native areas.

2.3. Endemism and Conservation Status

The Serra dos Orgaos Park protects three species locally endemic, 8 from Rio de Janeiro state and 69 Brazilian (Table 2). The species endemic to Rio de Janeiro state recorded in the park was in High-altitude Fields (Table 2) Endemism and species richness are high with increase of altitudes, as was also found in Itatiaia National Park located in Serra da Mantiqueira [22].

Of the 28 species of Brazilian endemic bryophytes exclusive to High-altitude Fields, 12 belong to the family Sphagnaceae (42%), representing almost half of the Brazilian endemic species found in this vegetation formation. The species Sphagnum luetzelburgii and S. sehnemii are endemic to Brazil, occurring in the states of Paraná, Santa Catarina, Rio Grande do Sul and Rio de Janeiro. However, in Rio de Janeiro State, these species are restricted to mountains of the Atlantic Forest and have only been reported for PARNASO by Costa (2021), and not by the present work.

The lower number of endemic species recorded in Sub-montane Forest, probably reflecting the effects of ecological and biogeographic processes, as well as human interference [22]. Among the 19 endemic species exclusively found in Montane Forest, 13 are liverworts and six are mosses. The predominant liverwort family is Lejeuneaceae, with nine species, followed by Metzgeriaceae with three and Jamesoniellaceae with two.

We have re-collected some species considered rare like: Bryum limbatum, Ochi (1980) cite a collection from (43 years ago; Metzgeria furcata, Bartram (1954) cite a collection from 69 years ago; Sphagnum cuspidatum, collected by Luetzelburg in 1923 (100 years ago) and Andreaea acutifolia, collected by Mueller in 1845 (178 years ago). Andreaea acutifolia is always mistakenly identified as A. rupestris, the two differing mainly by perichaetial leaves [30]. The species S. cuspidatum is widespread in Brazil [33], but has been collected only once in PARNASO.

The Serra dos Orgaos Park also protects eleven of the species indicated as threatened by CNCFlora and Flora e Funga do Brasil (Figure 2 and Table 2) to the Rio de Janeiro state: seven as Endangered (EN), two as Critically Endangered (CR) and two as Vulnerable (VU). Among these threatened species, three are known only from the type material, and were not found in the field trips. Southbya organensis was described by Herzog (1948-1949) and is classified as Critically Endangered (CR) by CNCFlora (2012) due to its distribution being restricted to Serra dos Órgãos, specifically Morro do Açu peak that has an excessive tourism and recurrent criminal fires. Plagiochila pseudoradicans, and Dicranodontium pulchroalare ssp. brasiliense was described by Herzog (1925) and both were not assessed by CNCFlora (2012) because they were considered as Data Deficient (DD) at that time.

3. Discussion

The Serra dos Órgãos National Park (PARNASO) exhibits remarkable bryophyte diversity. This richness highlights the park as a key conservation area for bryophytes in the Atlantic Forest. The discovery of 17 species newly recorded for the state of Rio de Janeiro emphasizes the urgent need for continued floristic inventories, particularly in underexplored regions. These findings suggest that even in areas already considered well-studied, significant knowledge gaps remain, highlighting the dynamic nature of bryophyte diversity and distribution

One important factor contributing to this diversity is the presence of forested areas with abundant tree trunks, which serve as critical substrates for epiphytic bryophytes. The architectural, morphological, phenological, and chemical traits of different tree species create varied microhabitats that support a wide range of bryophyte taxa [36,37]. Shade-loving epiphytes, in particular, are commonly found in these forest environments, but are highly sensitive to environmental disturbances. As such, they are often among the first species to disappear following canopy opening or habitat degradation [38] making them reliable indicators of forest health.

In contrast, mosses exhibit a broader ecological amplitude due to their desiccation tolerance and structurally complex adaptations, such as costa development, hyaline leaf apices, papillae, and specialized conducting tissues like hydroids and leptoids [39, 40, 41]. These features enable many mosses to colonize exposed and drier substrates, including rocky outcrops. Similar patterns of moss dominance on rock surfaces have been observed in other highland regions of Brazil, such as Chapada Diamantina [42,43], Serra do Caraça [44], and Serra da Canastra [45].

The high-altitude ecosystems of PARNASO further enhance bryophyte diversity by creating isolated and unique habitats. Mountain summits, often compared to ecological islands due to their environmental isolation, support specialized flora adapted to harsh conditions such as strong winds, low temperatures, and nutrient-poor soils [46,47,48]. These rupestrian fields form natural refugia, acting as barriers to typical forest species and favoring the emergence of narrow endemics and rare taxa [49,50,51].

Overall, the findings of this study underscore the ecological importance and conservation value of Serra dos Órgãos National Park. Alongside Itatiaia National Park, PARNASO remains one of the most critical remnants of Atlantic Forest in Rio de Janeiro and Brazil, particularly in terms of bryophyte conservation. The park’s diverse topography, wide range of microhabitats, and climatic heterogeneity—marked by high altitudes, low temperatures, and high light availability—create optimal conditions for bryophyte diversity. Furthermore, the presence of endemic and threatened species reinforces the park’s role as a conservation priority. Such studies are valuable as they reveal the significance of endemism and species richness, crucial factors in determining conservation priorities [52], and emphasize the importance of preserving Serra dos Órgãos National Park.

4. Materials and Methods

Serra dos Órgãos National Park (PARNASO) is located in the highlands region of Rio de Janeiro State, Brazil, raging the municipalities of Teresópolis, Petrópolis, Guapimirim and Magé (22°23’36,96’’–22°34’57,72’’ S, 43°10’57,72’’– 42°58’43,68’’ W). It is a protected area with 20,024 hectares of Atlantic Forest in a central position in the Serra do Mar Ecological Corridor. Ranging in altitude from 80 to 2,275 m.a.s.l. (Figure 3), it is the highest portion of the entire Serra do Mar [2]. The climate is tropical super humid (80 – 90% relative humidity), with the annual average temperature ranging 13° – 23°C, although minimums can reach -5°C during winter above 800 m.a.s.l. [53,54,6,8]. The average annual rainfall ranges from 1,500 mm to 3,000 mm, with higher concentrations of rain during summer (December to March) and a dry season during winter (June to August), while heat is well distributed throughout the year [53,54,6,8].

The species list developed here is based on a bibliographic survey, herbarium specimens, and new collections (Figure 4). Herbarium specimens were located by on line sources like (GBIF, jabot, JStorTypes and SpeciesLink). All specimens are re-determined and carefully examined for small species associations. The collection, preservation and herborization methodologies follow Frahm (2003), and employed free walks [56] for covering all available substrates like: tree trunks, logs, soil, rocks and leaves.

Field trips in the Park intended to check if species collected in the past are yet present, taxa not recorded and fill the elevation information. Collected samples were deposited in the herbarium of the University of Brasília (UB), with duplicates sent to the herbarium of Instituto de Pesquisas Ambientais (SP). The classification system used here follows Crandall-Stotler et al. (2009) for Marchantiophyta, Buck & Goffinet (2009) for Bryophyta and Renzaglia et al. (2009) for Anthocerotophyta. Data referring to endemic species of Brazil and of Rio de Janeiro State came from Flora e Funga do Brasil (floradobrasil.jbrj.gov.br), while conservation status followed CNCFlora (cncflora.jbrj.gov.br).

The vegetation classification adopted follows Veloso et al. (1991) and Safford (1999): Sub-montane Forest below 600 m.a.s.l., Montane Forest (600 – 1.500), Upper-montane Forest (above 1.500), and High-altitude Fields (above 1800 – 2000) (Figure 4).

5. Conclusions

The Serra dos Órgãos National Park stands out as a key refuge for bryophyte diversity in the Atlantic Forest, hosting numerous endemic and threatened species. The discovery of several new records for Rio de Janeiro highlights the importance of continued floristic surveys. The park’s altitudinal variation, diverse microhabitats, and unique environmental conditions favor high species richness and endemism. These findings reinforce the ecological value of PARNASO and underscore the urgency of conserving this unique mountainous ecosystem.