Introduction

Vascular epiphytic plants (henceforth epiphytes) constitute a functional group that develops on woody species. Unlike parasitic plants, epiphytes obtain water and nutrients from the atmosphere, precipitation, and decomposing organic material, rather than relying physiologically on the host (^{Krömer & Gradstein, 2016}). Within epiphytes, 2 main categories are recognized: true epiphytes, which complete their entire life cycle on the host without producing roots that reach the soil, and hemiepiphytes, which in contrast, exhibit a mixed life cycle, since some germinate on the host and later develop roots that reach the ground (primary hemiepiphytes), whereas others begin their growth in the soil and, as they ascend, establish themselves on the host (secondary hemiepiphytes) (^{Granados-Sánchez et al., 2003}; ^{Zotz, 2016}). Epiphytes comprise about 10% of the known plant species worldwide (^{Zotz et al., 2021}). In the Neotropics, epiphytes significantly contribute to the overall diversity of the vegetation, as they can represent up to 50% of the vascular flora in some forests (^{Carmona-Higuita et al., 2025}; ^{Kelly et al., 2004}; ^{Taylor et al., 1986}). Tree species in the low and mountain forests have different structural characteristics (e.g., greater height, dense canopy, and great diversity of bark textures), which combined with particular environmental conditions (e.g., high humidity), allow the presence of a high number of epiphytic species (^{Ceja-Romero et al., 2008}; ^{Flores-Palacios & García-Franco, 2006}; ^{Hietz & Hietz, 1995}; ^{Krömer et al., 2007}, ²⁰¹⁴; ^{Martínez-Meléndez et al., 2011}; ^{Rzedowski, 1996}). In contrast, mangrove forests generally show a low richness of epiphytes (^{Benzing, 1990}; ^{Carmona-Díaz et al., 2014}; ^{Zotz & Reuter, 2009}; ^{Zimmerman & Olmsted, 1992}), which can be attributed to reduced tree diversity and consequently to low structural complexity of the habitat, but mainly due to environmental stress conditions such as the strong winds, waves, and high salinity present in coastal zones (^{Gómez & Winker, 1991}; ^{Jiménez-López et al., 2017}; ^{Zotz & Reuter, 2009}). However, epiphytes are frequent in mangrove ecosystems, as several species have been recorded in different studies even though the objectives and sampling efforts are directed toward tree species, which are the dominant physiognomic elements (^{Aksornkoae, 1993}; ^{Cach-Pérez et al., 2013}; ^{Carmona-Díaz et al., 2014}; ^{De Sousa & Colpo, 2017}; ^{García-Luna et al 2024}; ^{Jiménez-López et al., 2018}; ^{Kupec, 2018}; ^{Noguera-Savelli et al., 2021}; ^{Rahman et al., 2015}; ^{Rohani et al., 2020}).

Mangrove ecosystems are primarily distributed in tropical and subtropical regions, generally associated with the coast and brackish water bodies (^{Leal & Spalding, 2021}). However, mangrove ecosystems also have been recorded in freshwater wetlands, away from marine influence, known as inland mangroves. The inland mangroves have been reported in many countries worldwide, such as in Australia, Antigua and Barbuda, the Bahamas, Indonesia, and Pakistan, located 15 to 50 km from the coast, and between 6 and 37 m above sea level (^{Lugo, 1981}; ^{Patel, 2014}; ^{Patel & Agoramoorthy, 2012}; ^{Stoddart et al., 1973}; ^{Taylor, 1986}; ^{Tripathi et al., 2013}; ^{Woodroffe, 1988}).

Recently, in Mexico, individuals of Rhizophora mangle, along with another 112 coastal affinity species were reported along the banks of the San Pedro Mártir River and El Cacahuate Lagoon in Tabasco, the latter located almost on the border with Guatemala (^{Aburto-Oropeza et al., 2021}). The presence of this inland mangrove is attributed to the global climatic phenomenon that occurred about 120,000 years ago when an increase in global temperatures caused a rise in sea levels, displacing the coastline inland (^{Aburto-Oropeza et al., 2021}). As the planet cooled, the sea retreated to its current position, leaving mangrove trees dispersed along the riverbanks and creating an isolated mangrove ecosystem in the El Cacahuate Lagoon, 170 km from the Tabasco coast (^{Aburto-Oropeza et al., 2021}).

Currently, the El Cacahuate Lagoon is surrounded by a matrix composed of remnants of evergreen tropical forest belonging to the“Cañóndel Usumacinta” Flora and Fauna Protection Zone (^{Conanp, 2015}), fragments of several types of tropical forest, and large areas of land used for livestock and agriculture activities. However, despite this mixed landscape, the hydrophytic vegetation surrounding the water body restricts access to the mangrove, which has resulted in minimal human impact. El Cacahuate mangrove is considered a relict area from the Pleistocene and a refuge for biodiversity due to its high degree of conservation (^{Aburto-Oropeza et al., 2021}). This area together with the adjacent forest areas forms part of a core area of the recently designated Wanha’ Biosphere Reserve (^{Conanp, 2023a}; ^{Semarnat, 2023}).

Preliminary surveys indicate the presence of several species of epiphytes along the upper San Pedro River (^{Aburto-Oropeza et al., 2021}). However, in El Cacahuate mangrove the epiphyte species composition and its species similarities to the epiphytic communities of the surrounding vegetation or to the coastal mangroves of Gulf of Mexico are unknown. High epiphyte composition similarity with tropical forest would indicate processes of colonization after the sea retired, while high epiphyte composition with coastal mangroves communities should indicate that species arrived together with the mangrove during the interglacial period.

The aims of this study were to determine the richness and composition of the epiphyte community present in the inland mangrove of El Cacahuate Lagoon, and to assess the floristic similarity of the epiphytes of El Cacahuate with coastal mangroves and adjacent tropical forests. We expect that, given the inland Cacahuate mangrove’s location in a freshwater environment and its proximity to tropical forest areas, the similarity of the epiphyte community should be greater than that of the nearest terrestrial vegetation because the seeds of the epiphytes can likely reach the mangrove trees easily.

Materials and methods

The study was conducted in the El Cacahuate Lagoon, located in the “Sueños de Oro” rural community of the Tenosique Municipality, Tabasco State, Mexico (Fig. 1). It is a lentic water body associated with the sub-basin of the San Pedro Mártir River, situated 170 km in a straight line to the coast and over 300 km following the river’s course (17°17’58.949” N, 91°5’13.09” W, elevation 45 m asl). The region has a warm-humid climate with abundant rainfall in the summer (^{Aceves-Navarro & Rivera-Hernández, 2019}). The average temperature is 27 °C, and the average annual precipitation is 2,264 mm, with September being the rainiest month (391 mm) and March the driest (54 mm) (Conanp, 2023a). The lagoon area is approximately 13.7 ha and reaches a depth of up to 24 m. The soils surrounding the lagoon are clayey loam and gleysol (^{Conanp, 2023a}; ^{Palma-López et al., 2017}). In the mangrove, there is a surface layer of leaf litter 15 to 40 cm deep, followed by the mineralization of organic matter.

Figure 1 Location of the study area. A) Mexico, highlighting the state of Tabasco (orange) and the municipality of Tenosique (blue). B) El Cacahuate Lagoon (red outline) showing sampling transects (white lines) established in the mangrove vegetation. 

The vegetation present in the lagoon and around it consists of floodable grassland (60%), aquatic vegetation (15%), and mangrove (25%) (^{Conanp, 2023a}). The floodable grasslands are primarily composed of Hydrocotyle umbellata L. (Araliaceae), Eleocharis interstincta (Vahl) Roem. & Schult. (Cyperaceae), Cladium jamaicense Crantz (Cyperaceae), Acrostichum danaeifolium Langsd. & Fisch. (Pteridaceae), and Bletia purpurea (Lam.) DC (Orchidaceae). The aquatic vegetation includes rooted hydrophytes with floating leaves such as H. umbellata and Nymphaea ampla (Salisb.) DC. (Nymphaeaceae), free-floating hydrophytes like Salvinia auriculata Aubl. (Salvinaceae), and submerged free-floating hydrophytes like Cabomba palaeformis Fassett (Cabombaceae), Utricularia foliosa L., and U. purpurea Walter (Lentibulariaceae). The mangrove is in the southwest part of the lagoon, comprising 7 ha of continuous vegetation. In the mangrove vegetation, R. mangle is the most abundant tree species, with rare occurrences of Bucida buceras L. (Combretaceae), Chrysobalanus icaco L. (Chrysobalanaceae), Haematoxylum campechianum L. (Fabaceae), and Pachira aquatica Aubl. (Malvaceae). Additionally, other species are rarely present such as Vanilla insignis (Orchidaceae), Acoelorraphe wrightii (Griseb. & H.Wendl.) H.Wendl. ex Becc. (Arecaceae), Anthurium schlechtendalii Kunth subsp. schlechtendalii (Araceae), Monstera tuberculata Lundell, and Philodendron radiatum Schott. (Araceae).

Fieldwork was conducted from April 2022 to February 2023. The recording of epiphytes in mangrove vegetation was carried out in 10 rectangular plots of 75 m long by 20 m wide. Plots were oriented perpendicular from the edge of the lagoon to inland spaced 40 m from each other (1,500 m² per plot, 15,000 m² in total; Fig. 1). This design aimed to include as much as possible of the total epiphytic composition present in the mangrove. As R. mangle is the dominant tree species in this mangrove, the recording of epiphyte species focused exclusively on it. Within the sampling plots, we recorded all epiphyte species present on each individual R. mangle tree, excluding hemiepiphytes and parasitic plants. Voucher specimens were collected following standardized methods by ^{Lot and Chiang (1986)} and ^{Krömer and Gradstein (2016)}. For less abundant species, photographic records were obtained instead. All herbarium specimens were deposited in the UJAT herbarium (acronym following ^{Thiers, 2021}), and the photographs were stored in the photo archive of the Biological Sciences Division-UJAT.

The identification of the species was carried out with the support of taxonomic keys and specialized literature for the families Bromeliaceae, Cactaceae, and Orchidaceae (^{Alderete-Chávez & Capello-García, 1988}; ^{Ames & Correll, 1985}; ^{Beutelspacher, 2011}; ^{Campos-Díaz et al., 2020}; ^{Conap, 2010}; ^{Davidse et al., 1994}; ^{Espejo-Serna et al., 2004}; ^{Hágsater et al., 2005}; ^{Hietz & Seifert, 1994}; ^{Martínez-Meléndez et al., 2011}; ^{Mondragón-Chaparro et al., 2011}; ^{Noguera-Savelli & Cetzal-Ix, 2014}), as well as Aspleniaceae, Polypodiaceae, and Pteridaceae (^{Mickel & Smith, 2004}). For species identification, original descriptions were reviewed in the Biodiversity Heritage Library (^{BHL, 2022}). Additionally, to determine the conservation status of the recorded epiphyte species in the study area, we consulted the official Mexican environmental protection and species legislation NOM-059-Semarnat-2010 (^{Semarnat, 2010}) and the Red List of Threatened Species by the International Union for Conservation of Nature (^{IUCN, 2021}).

To determine similarities between the epiphyte species composition of the inland mangrove of El Cacahuate (IM-Cacahuate) and other epiphyte communities, available epiphyte floristic lists from various vegetation types were compiled within a 220 km radius starting from the study area, including sites in Mexico and Guatemala (Fig. 2). Radius length corresponds to the straight-lined distance between El Cacahuate Lagoon and the nearest coastal mangroves of Tabasco, Mexico. It is important to note that most of the studies reviewed were conducted with objectives and sampling efforts not specific to epiphytes, so only the epiphyte species reported were considered (excluding hemiepiphytes).

Figure 2 Location of El Cacahuate inland mangrove, the tropical forests, and coastal mangroves within a 220 km radius that include epiphytic floristic lists. The straight-line distance from each site to El Cacahuate is indicated in parentheses. Site acronyms are defined in the Materials and methods section. 

For the Mexican portion, the compiled lists correspond to coastal mangroves (CM-Paraíso: including localities of Cárdenas, Centla, Comalcalco, Paraíso, Tabasco; ^{Díaz-Jiménez, 2007}. CM-Centla: Centla, Tabasco; ^{Jiménez-López et al., 2017}, ²⁰¹⁸. CM-Nohan: UMA Nohan, Cd. del Carmen, Campeche; ^{Noguera-Savelli et al., 2021}); high evergreen tropical forest (HETF-Tenosique: Tenosique, Tabasco, ^{Hernández-Sastré et al., 2014}); medium evergreen tropical forest (METF-Macuspana: Macuspana, Tabasco; ^{López-Gómez, 2014}; METF-Tenosique: Tenosique, Tabasco; ^{Morales-Damián, 2012}); medium subevergreen tropical forest (MSTF-Catazaja: Catazajá, Chiapas; ^{Gutiérrez-Báez, 2004}); and tropical dry forest (TDF-Tenosique: Tenosique, Tabasco; ^{Morales-Damián, 2012}). Additionally, the riparian flora list of the San Pedro Mártir River was included, which comprises epiphyte records in high, medium, and low evergreen tropical forests with the presence of R. mangle individuals in the riparian vegetation (TF&IM-San Pedro Mártir, ^{Aburto-Oropeza et al., 2021}). There are floristic lists that report the presence of epiphyte species for the Calakmul Biosphere Reserve, Campeche, (^{Conanp, 2023b}; ^{Martínez et al., 2001}), which were not integrated into the database because this site belongs to the biotic province Yucatán Peninsula (^{Conanp, 2023b}; ^{García-Gil et al., 2002}), which reports greater floristic affinity with the districts within the Yucatán Peninsula, Guatemala, and Belize (^{Duno-de Stefano et al., 2012}) and the states of Chiapas, Oaxaca, and Veracruz (^{Ibarra-Manríquez et al., 2002}; ^{Morrone, 2019}).

In Guatemalan territory, only 2 floristic lists within the established distance for the analysis were obtained: one from a disturbed high evergreen tropical forest (TF-Tikal, ^{Hellmuth & D’Angelo-Jerez, 2022}), and the second from a high evergreen tropical forest combined with R. mangle from the El Petén area (TF&IM-Peten, ^{Conap, 2010}). Appendix presents the list of the recorded species in the present study and the species compiled from the reviewed studies. The classification of the types of vegetation is based on the proposal of ^{Conabio (2013}, ²⁰¹⁹⁾ for Chiapas and Tabasco, Mexico, and by ^{Melgar (2003)} and ^{Conap (2010)} for Tikal and El Petén, Guatemala.

A presence-absence data base was constructed, based on the epiphyte species recorded in our study area and the epiphyte species documented from the surrounding sites obtained of literature. The nomenclature was updated and standardized using the electronic database Tropicos (^{Tropicos, 2023}). Subsequently, the similarity between epiphyte communities of the different vegetation types and locations was explored using the data matrix in a hierarchical clustering analysis (UPGMA) based on the Jaccard similarity index (JSI). This index was selected as it uses species presence-absence data, which was the type of data obtained from the reviewed studies. The measure of similarity ranges from 0% (not similar) to 100% (the most similar). Finally, a beta diversity analysis was performed using Cody’s index (Ci) to assess species turnover between communities. If a high index is obtained, it means that the sites are very different, while a low index means that they share most of their species. Both analyses were conducted using the program Past 4.12b (^{Hammer et al., 2001}).

Results

A total of 6 families, 18 genera, and 27 species of epiphytes were recorded (Table 1) in El Cacahuate mangrove, with Orchidaceae and Bromeliaceae being the families with the highest number of species (11 and 10, respectively), followed by Cactaceae and Polypodiaceae (2 species each) and Aspleniaceae and Pteridaceae (1 species each; Fig. 3). The genera with the most species were Tillandsia (Bromeliaceae) with 8 species, and Epidendrum (Orchidaceae) with 3. Among the epiphyte species recorded in El Cacahuate, Asplenium serratum L. is listed as a threatened species under Mexican legislation (^{Semarnat, 2010}), while Tillandsia fasciculata Sw. and Selenicereus grandiflorus (L.) Briton & Rose are cited on the Red List of Threatened Species by ^{IUCN (2021)} as species of least concern.

Photographs by Jesús Rodríguez and Neil Morales.

Figure 3 Representative epiphyte species recorded in the inland mangrove of El Cacahuate Lagoon, Tenosique, Tabasco, Mexico. A) Microgramma nitida, B) Vittaria lineata, C) Asplenium serratum, D) Polypodium polypodioides, E) Deamia testudo, F) Selenicereus grandiflorus, G) Catopsis morreniana, H) Tillandsia balbisiana, I) T. bulbosa, J) T. streptophylla, K) T. dasyliriifolia, L) T. schiedeana, M) T. fasciculata, N) Epidendrum cardiophorum, O) E. nocturnum, P) E. diffusum, Q) Encyclia bractescens, R) Nidema boothi, S) Notylia barkerii, and T) Specklinia grobyi.  

Similarities between epiphyte communities. The present study and the review of published studies within the selected surrounding area allowed for the compilation of a total of 119 epiphyte species from sites with coastal mangrove, inland mangrove, tropical forests, and disturbed forests (Appendix). The sites with the highest number of epiphyte species were the high evergreen tropical forest of Tenosique (HETF-Teno, 53 species), the riparian vegetation of the San Pedro River (TF&IM-SPMR, 52 species), the medium evergreen tropical forest of Macuspana (METF-Macus, 45 species), the inland mangrove of El Cacahuate Lagoon (IM-Cac, 27 species), and the coastal mangrove of Centla (CM-Centla, 25 species). In the remaining sites, the number of epiphyte species ranged from 4 to 16, with 14 species recorded in the coastal mangroves of Nohan and Paraíso (CM-Nohan, CM-Paraíso; Appendix).

The clustering analysis (Fig. 4) clearly separated 4 groups (at a similarity level of 0.14). Two groups consisted of a single location: the first being the disturbed evergreen tropical forest of Tikal (TF-Tikal) and the second, the medium subevergreen tropical forest of Catazaja, Chiapas (MSTF-Catazaja). The other 2 groups contained several locations. The first group was made up of different forest types in Tabasco (HETF-Tenosique, METF-Macuspana, TDF-Tenosique, METF-Tenosique), while the second group included sites with coastal mangroves (CM-Nohan, CM-Paraíso, CM-Centla) and tropical forest and inland mangrove vegetation (TF&IM-San Pedro Mártir, TF&IM-Peten, IM-Cacahuate). In this latter group, the inland mangrove of El Cacahuate showed greater similarity in the epiphyte species with the coastal mangroves of Centla (JSI = 0.45, 16 shared species) and Paraíso (JSI = 0.38, 11 shared species), despite being 194 and 220 km away from El Cacahuate, respectively. The tropical forest and mangrove vegetation of the San Pedro River shared a greater number of species (19) with the El Cacahuate mangrove, but the similarity was slightly lower (JSI = 0.23), although the distance between these sites is lower, 59 km. The next ecosystem is the forest with inland mangrove of El Petén, sharing 8 species with El Cacahuate and showing a lower similarity than the previous groups (JSI = 0.18). At last, the coastal mangrove of Nohan, Campeche shared 7 species with El Cacahuate, with the lower similarity inner this group (JSI = 0.15).

Figure 4 Dendrogram showing the similarity of epiphyte communities among the El Cacahuate Lagoon mangrove, coastal mangroves, and adjacent forest vegetation sites. Site acronyms are defined in the Materials and Methods section. 

Among all groups, the lowest similarity of the epiphyte community of El Cacahuate was with the medium subevergreen tropical forest of Catazaja (JSI = 0.05) and the disturbed evergreen tropical forest of Tikal (JSI = 0.03), with 2 and 1 species in common, respectively; both located over 100 km from El Cacahuate Lagoon. Among sites with mangrove vegetation, beta diversity analysis (Table 2) shows that the inland mangrove of El Cacahuate presents low species turnover with the coastal mangroves (Centla and Paraíso; Ci = 10 and 9.5, respectively). In contrast, species turnover is higher with the riparian forest and mangrove vegetation of the San Pedro Mártir River (Ci = 19).

Discussion

As far as we know, our study is the first to be conducted on epiphytic species of inland mangroves in El Cacahuate Lagoon. The epiphyte community of El Cacahuate Lagoon, with 27 records species, is among the richest ever reported in a mangrove ecosystem. Previous studies have reported the presence of fewer species in coastal mangroves (^{De Sousa & Colpo, 2017}; ^{Díaz-Jiménez, 2007}; ^{Jiménez-López et al., 2017}, ²⁰¹⁸; ^{Menéndez-Liguori, 1976}; ^{Noguera-Savelli et al., 2021}; ^{Rohani et al., 2020}). However, it is true that many of these studies did not involve extensive sampling, or they were not specifically focused on epiphyte species. ^{Jiménez-López et al. (2017}, ²⁰¹⁸⁾, in the mangrove of El Cometa Lagoon, Centla, Tabasco, were specifically focused on epiphytes, recording 25 species. In contrast, the tropical forest sites of Tenosique and Macuspana (^{Hernández-Sastré et al., 2014}; ^{López-Gómez, 2014}; ^{Morales-Damián, 2012}), and the riparian forest and mangrove of San Pedro Mártir, Tabasco (^{Aburto-Oropeza et al., 2021}), have a higher reported number of epiphyte species than the mangrove of El Cacahuate. However, these differences in the number of species reported are because the forests of Tenosique, Macuspana, and the San Pedro Mártir River were collected in larger areas of vegetation, a greater number of phorophyte species were sampled, and different sampling methods were used. For example: A) in the forests of Tenosique (^{Morales-Damián, 2012}; ^{Hernández-Sastré et al., 2014}) sampled 25 × 25 m plots, recording the epiphytes associated with 9 species of phorophytes; B) in the Macuspana forest (^{López-Gómez, 2014}), a representative sampling method of 1 ha was used, sampling epiphytes in 8 plots of 20 × 20 m (400 m²), considering both trees and shrubs present; and finally C) on the San Pedro Mártir River (^{Aburto-Oropeza et al., 2021}), targeted sampling was carried out between 2014 and 2015 with sporadic collections until 2019, covering more than 25 linear km of river and sampling more than 30 species of phorophytes (Burelo-Ramos pers. com.). This shows that floristic lists targeting forests tend to have higher reports of epiphytes than mangrove ecosystems.

The low richness of epiphytes in coastal mangroves has been associated with the adverse environmental conditions present, such as high temperatures, low precipitation, and excess salinity (^{Benzing, 1990}; ^{Carmona-Díaz et al., 2014}; ^{García-Luna et al., 2024}; ^{Gómez & Winker, 1991};^{Zimmerman & Olmsted, 1992}; ^{Zotz & Reuter, 2009}). Mangrove trees eliminate excess salt through their leaves (^{Mikolaev et al., 2016}; ^{Zotz & Reuter, 2009}), so large amounts of salt could be accumulating in some epiphytes (e.g., orchids and bromeliads) due to leaf litter and rainwater falling from the canopy, which is captured in the roots and the rosette leaves of these plants. Salt decreases the osmotic potential of epiphyte cells, reducing their survival by promoting tissue necrosis and leaf loss, especially for species that do not have adaptations to survive under extreme water stress conditions, v.gr., xerophytic habits (^{Benzing, 2000}; ^{Du & Hesp, 2020}; ^{Zotz & Reuter, 2009}). However, ^{Gómez and Winkler (1991)} have pointed out a contrary position suggesting that the high precipitation in some coastal areas may dilute the high salinity that falls from the mangrove’s canopy, allowing for the existence of non-xerophytic epiphytes. Nevertheless, the low presence of epiphyte species in mangrove ecosystems suggests that the physiological limitations in many of these plants may be significant (Cach-Pérez et al., 2018). Considering the distribution of mangroves worldwide, more floristic studies are needed in this ecosystem to identify patterns in other epiphytes species numbers, physiological traits, and functional groups.

The mangrove of El Cacahuate Lagoon presents a less stressful environment compared to coastal mangroves, as it is in a freshwater body with high precipitation (annual average of 2,300 mm) and warm temperatures (annual average of 26 °C) (^{Aceves-Navarro & Rivera-Hernández, 2019}). In coastal mangroves, which are characterized as saline ecosystems (^{Feller et al., 2010}), R. mangle eliminates the excess of salt absorbed by its roots through lenticels on its leaves (^{Bento et al., 2024}). However, although El Cacahuate Lagoon is a freshwater aquatic system (0.4 psu) compared to nearby coastal sites (22 psu), calcium carbonate from mountain runoff has been reported in the area (^{Aburto-Oropeza et al., 2021}; ^{Conanp, 2023a}) and the sap salinity of the plants is like that of trees in coastal areas (J. López-Portillo pers. com.). This suggests that the R. mangle trees in El Cacahuate Lagoon still exude salt through the leaves. However, atmospheric humidity and high precipitation could dilute the concentration of salts reaching the epiphytes (J. López-Portillo pers. com.). These conditions seem to favor the presence of orchid, bromeliad, and fern species recorded at this site; it also suggests that the species shared between the inland mangrove and coastal mangroves have adapted to both environmental conditions. Specific ecophysiological studies of the shared and not shared epiphyte species between this inland mangrove and the coastal mangroves will provide a better understanding of the characteristics that limit and promote the distribution of epiphytes in these ecosystems.

Similarities between epiphyte communities. Given the proximity of the Tenosique mountain (ca. 2-32 km), we expected that the species composition of the study area showed greater similarity in epiphyte composition with the surrounding forests (HETF, METF, DTF). It has been recorded that the structure, anatomy, and seed dispersal mechanisms of many epiphytes permit frequent colonization and recolonization processes between nearby tropical sites (^{Chilpa-Galván et al., 2018}; ^{Toledo-Aceves et al., 2012}). Nevertheless, we found the highest similarity of El Cacahuate mangrove’s epiphyte species with the epiphyte communities of the coastal mangroves of Centla and Paraíso, located 194-200 km away. These facts suggest 2 possible hypotheses which can help to explain these similarities: the first suggests that when the sea encroached 120,000 years ago, not only R. mangle individuals and other terrestrial coastal species established along the banks of the San Pedro River and El Cacahuate Lagoon, but this process was accompanied by the coastal-affinity epiphytes recorded in the study area; the second one points to contemporary dispersal processes as the reason for the presence of these epiphytes with a coastal distribution. It has been documented that after ca. 30 years, 30% of the original epiphyte species recorded in mangrove trees in the natural part of a canal, colonized juvenile mangroves planted for reforestation in the artificial part of the canal (^{Kupec, 2018}). This suggests that the epiphyte species with coastal affinity may have arrived at the inland mangrove of El Cacahuate Lagoon by seed step-dispersal and colonization events throughout the mangrove established along the San Pedro River, or by long-distance dispersal events of minute seed from the coastal mangroves (^{Schurr et al., 2009}). The other epiphyte species with extensive tropical forest distribution surely have arrived by both dispersal ways.

These 2 processes do not exclude each other, and their success can be highly dependent on the number of viables seeds and habitat availability (^{Rodríguez-Romero et al., 2011}). However, successful establishment also depends on the morphological and anatomical characteristics of the seeds (^{Arditti & Ghani, 2000}; ^{Chilpa-Galván et al., 2018}). For instance, some ferns families (e.g., Aspleniaceae, Polypodiaceae, and Pteridaceae) produce many very small spores that are easily dispersed by wind over long distances (^{Martínez-Salas & Ramos, 2014}; ^{Perrie et al., 2010}; ^{Shepherd et al., 2009}). Similarly, orchid fruits (Orchidaceae) produce millions of tiny seeds, often just a few microns in size and weighing no more than 22 mcg (^{Arditti & Ghani, 2000}; ^{Menchaca-García & Moreno-Martínez, 2011}), which are also adapted for long-distance wind dispersal. Many bromeliad species (Bromeliaceae, subfamily Tillandsoideae) have plumose seed appendages that facilitate their movement through the air and their attachment to rough bark surfaces (^{Einzmann & Zotz, 2017}; ^{Mondragón-Chaparro et al., 2011}). Meanwhile, some species such as A. bracteata, which produce berry-like fruits, and cacti such as S. grandiflorus and D. testudo, which have pulpy fruits, are dispersed by birds. This suggests that short- or long-distance seed dispersal has contributed to structuring the epiphyte community in the inland mangrove of El Cacahuate Lagoon. Future genetic studies will reveal how closely related the populations of shared epiphyte species are between the inland mangroves of El Cacahuate Lagoon and the coastal mangroves of Tabasco, particularly for those species with a wide distribution range.

Our study clearly shows that the epiphyte community in the inland mangroves of El Cacahuate Lagoon is species-rich. The humid environmental conditions present apparently reduce the salinity concentration exuded by the mangrove trees, allowing the great epiphyte species richness recorded. Also, we have demonstrated that this epiphyte community has a high similarity in composition to the epiphyte communities of the coastal mangroves of Tabasco, suggesting a close genetic relationship between these populations. Future genetic studies will help elucidate the dispersal routes followed by the epiphytes to colonize this mangrove. These and other biological characteristics make this inland mangrove ecosystem one of great biodiversity and conservation value.