Introduction

Mexican orchids, because of their beauty, diversity and interest aroused have been the subject of growing and study for several years so far (Ávila-Díaz, 1998). They have a special attraction in tourism since the complexity, variety of guises and striking coloring; making it impossible not to see them, admire and contemplate (^{Hágsater et al., 2005}).

In some states of Mexico, they are known by common names refer either to the time when flowering, religious festivals or the shape resembling flower, for example torito, calaverita, flor de mayo, flor de Candelaria, flor de muerto, among others (^{Hágsater et al., 2005}).

The lack of information and knowledge of orchids in our rural areas (mangroves), together with the deterioration of natural resources due to lack of alternatives for development of the people and environmental culture and extensive agricultural activities, irrigation and put in danger existing populations of orchids (^{López-Hernández, 2006}).

^{Hágsater et al. (2005)} suggested that mangroves where suitable for the growth and development of orchids, such as Brassavola aff. nodosa, Encyclia alata, Epidendrum ciliare, Epidendrum nocturnum, Maxillaria dense, Maxillaria pulchra, Maxillaria tenuifolia, Maxillaria variabilis var. unipunctata, Nidema boothii, Onciduim sphacelatum, Polystachya cerea , and Trichocentrum ascendens (Veracruz) as well as, Brassavola cf. venous, B. aff. nodosa, Myrmecophylla brysiana, Myrmecophylla christinae, Myrmecophylla tibiscinis, and Prosthechea cochleata (Yucatán), Encyclia trachycarpa and Trichocentrum oestlundianum (Nayarit). Rather a tourist attraction because of their beauty.

Through this study we are looking to contribute to the conservation of orchids in mangroves of the Ejido Aquiles Serdan through integrated planning and management of their use to establish an environmental tourism culture that allows sustainable management.

Materials and methods

This research was conducted in the Ejido Aquiles Serdan Paraíso, Tabasco, Mexico, in the period August 2009 to January 2010, located at the geographical coordinates 18° 25' 13.00" north latitude and 93° 03'14.00" W, with an elevation of 10 meters, bordering the north by the González River, east to the lagoon La Tinaja, south of the lagoon Mecoacán and west of the Chiltepec barrier (Figure 1) (^{INEGI, 2005}).

Figure 1 Geographical location of the study area, Ejido Aquiles Serdan, Paraiso, Tabasco, Mexico. 

For the socio-economic analysis of the Ejido Aquiles Serdan, we took into account: the total population of men and women, health, education, religion, labour force, water bodies and vegetation (Statistical Yearbook, ^{INEGI 2005}; ^{CONAFOR, 2009}).

For locating the species of orchids in the study area we used the methodologies proposed by ^{Cox (1981)} for the establishment of monitoring units, and ^{Eberhardt (1978)} to determine transects. The sampled quadrants were drawn in less impacted mangrove area, with dimensions of 10 x 50 m (500 m ²), located at the geographical coordinates 18° 24' 599'' north latitude, west longitude 93° 03' 609'', 18° 24' 578'' North latitude, 93° 03 'west longitude 437'', 18° 24' 583'' North latitude, 93° 03' west 433'' latitude, 18° 24' 603'' North latitude, 93° 03' 605'' west longitude, in the month of January 2010 in which were observed and recorded in a field notebook orchids that were in each tree. The type of tree where orchids were identified, and their location in the tree or height (low, medium or high) and its position relative to the sun. The location of orchids: latitude, longitude, and elevation were recorded with a Garmin GPS model Rino 530 Radio (USA).

Four transects 600 m long were laid in the densest or best-preserved mangrove areas. Where five samples were taken every week during the month of August 2009, for searching and register orchids. At these transects registered plants, we applied the same process to the plants found in quadrants (photos, location, tree identification and position relative to the sun). In these transects all species of orchids found in trees, roots, vines and ground were counted. To measure or estimate the height of orchids on trees, a Haga gun was used.

In order to calculate the diversity of orchids in the study area the following indices were used: the ^{Shannon-Wiener (1949)}, which reflects the heterogeneity of a community based on two factors: the number of species present and their relative abundance and similarity index Sörensen (1948), which is used to analyze two or more communities or populations and expresses the percent similarity of species that live in the communities compared.

The assessment for tourism acceptance of recorded species was performed by analysing morphological variables such as the number of flowers, showy, life span of the flowers and inflorescence length. The tourism potential (attractive) species was carried through the aesthetic and perceptual evaluation of people towards the species found in the area, through photographs, following the methodology proposed by Muñoz- Pedreros (2004). Photographs taken of the flowers, leaves, bulbs and roots, were performed with a digital camera brand EVOLT E-410 SLR (Japan). The valuation and numerical expression of each evaluators (people-expert-knowledge) of the photographs showed the visual value (VV), which when added expressed the total visual value (TVV).

This TVV was divided by the total number of evaluators, thus obtaining the final visual value (FVV). The FVV compared to the hierarchical list of adjectives and their correlation with the universal scale of values (Pedreros-Muñoz et al., 1993) (Table 1), thus obtaining a category with its corresponding numerical value for each species evaluated. The species that won the category with the highest numerical value was the species with the highest tourism potential (attractive).

Results and discussion

The vegetation of the study area corresponds to various types generated because of alteration of primary ecosystems. The presence of mangrove species Rhyzophora mangle L., dominated by Thypha latifolia L. and hydrophytic vegetation. Near the study area, we found pasture (Brachiaria humidicola [Rendle] Schweickerdt) and areas of coconuts (Cocus nucifera L.) (^{Sol et al., 2011}).

According to the socio-economic analysis of the ejido, it has a population of 687 people, 51.09% are women (351) and 48.9% male (336). Of its total 681 people were born in the State. The 83.55% (574) of the population is not entitled to any health services. The average grade of incomplete primary schooling and 80% (556) of the population is catholic (^{INEGI, 2005}).

The economically active population is 30.56% (210) of the total population; 54.76% (115) is employed in the primary sector. The 11.9% (24) in the secondary sector and 29.04% (61) in the tertiary sector.

In the ejido, there are two bodies of brackish water, the lagoon La Tinaja located at the geographical coordinates 18° 24 'north latitude 218'', west longitude 93° 01' 879'' and lagoon El Eslabón, 18° 23' 590'' north latitude, 93° 02 'west longitude 095''. Both bodies of brackish water flooded mangroves into the ejido. ^{CONAFOR (2009)} notes that there are 790 ha of mangroves compact which are subject to conservation and development of the community through government programs in this ejido.

Mangroves have a natural beauty and is a major forest resource, and maintaining biodiversity among tropical coastal ecosystems. They are highly productive and generate many nutrients, which are exported by tidal marine waters of the coastal strip closest to the coast, where they are used by seagrasses and a variety of commercially important fish (^{CONAFOR, 2009}). Even when the conditions are unusual (high salinity) for the growth of other plant species, there is also a wide variety of associated plants such as epiphytes, bromeliads, orchids, vines (lianas) and fern Acrostichium aureum, characteristic of the area (^{CONABIO, 2008}).

Within the mangrove, there is a great diversity of fauna such as crustaceans, including mud crab (Rhithropanopeus harrisii), the mangrove crab (Ucides cordatus), blue crab (Cardisoma guanhumi ) and white shrimp (Litopenaeus setiferus). We can also find some turtles and reptiles like the iguana ( Iguana iguana), birds like the egret (Ardea alba); diver duck or cormorant (Phalacrocorax auritus) and Kingfisher (Chloroceryle Aenea). Just as a lot of fish like snook (Centropomus undecimalis) and crappie (Chichlasoma sp.), like some mammals such as raccoons (Procyon lotor shufeldti) as well (^{CONABIO, 2008}). This richness and diversity gives it great importance for nature tourism, because in them can be made and interpretive activities such as hiking, wildlife watching, fishing, hunting and photographic walk.

Epidendrum rigidum Jacq.: Orchids recorded in the study area are common name unknown. Sympodial orchid growing 8-30 cm long, 2-7 alternate, elliptical, enveloping, basal, simple leaves, arranged in different planes (^{Ruizet al., 1985}) elongated, soft and incurved towards the back (^{López-Ruiz, 2005}), soft texture, waxy, with a midrib, smooth edge and obtuse apex, 7 -9 cm long x 1- 2 cm wide. The basal parts of the stems are joined to form a rhizome, upper stem grows up straight and horizontal, reaching up to 20 cm high. Their roots grow on both sides of creeping rhizome, between nodes, on the same plane. These are abundant cylindrical, 15 cm long and brown colour with green tones (Ruiz et al., 1985).

Green flowers, not showy, partially covered by fleshy bracts; 5 to 8 cm in length and has oval sepals of 5 mm long, the lateral sepals are larger than the dorsal sepal. The petals are also 5 mm long and the same colour, the lip or lip-shaped heart. The plant blooms 2-3 times a year and the flowers are open from 4-5 days. Found in trees 12 m tall, distributed in the basal part of the tree (2 m), where the highest roots of red mangrove (Rhizophora mangle L.) emerge. Just as, in the middle, about 6 m high, in the face of the tree where it receives more sunlight. Also, found on dead trunks of trees of the same species to 1.20 m above the ground. This species is found in clusters of up to 60 individuals.

Encyclia boothiana Lindl. Commonly known as dollar orchids, because the shape of their bulbs, which are oval and flattened 1-2 cm in diameter, rough texture. Elliptic, simple, oblong sheathing leaves with acute apex and entire margin, centre rib, rigid, soft, waxy texture. These emerge from the apex of the bulb (Ruiz et al., 1998), incurved towards the back (López-Ríos, 2005), 5 to 8 cm long x 1 cm wide, 2 leaves per bulb. Single dicasio inflorescence (López-Ríos, 2005) of 11 cm long with 2 or 3 flowers with sepals and petals oval green-yellow colour, with brown shades, white lip shaped as a mouth. The plant blooms only once a year and the flowers are open from 3-5 days.

In the study area, this species was recorded on trees of red mangrove (Rhizophora mangle L.) from the roots to the top of the red mangrove trees. The populations found were 3 to 113 individuals per cluster and usually on the side where they receive more sunlight.

Brassavola nodosa L. Lindl. Orchid called "dama de noche" or "smells at night," because at night, filling the air with their sweet perfume like scent of gardenia or orange. This species has pseudobulbs 6-30 cm long, with narrow, cylindrical form clearly separated. It has numerous side and round stems.

The stems are robust, elongated, with 4 or 5 nodules with a single leaf of light green, fleshy, straight (López-Ríos, 2005), with a central rib or groove that runs the entire length of the leaf (uninervada), acute apex, entire or smooth edge (Ruiz et al., 1998), 1 cm wide and 10 cm long. Presents an inflorescence (single dicasio) per stem, 3-6 large flowers about 6 cm long, with long narrow sepals and petals (threadlike) (López-Ríos, 2005), light green colour. The lip is tubular at the base, embracing a spine and widely opening in the middle, ending in an acute form, this may be about 5 cm wide, crenate striking edge (López-Ríos 2005) and; white and soft aroma, flower open from 7-9 days. Flowers 2 or 3 times a year.

In the study area it was found on trees of red mangrove (Rhizophora mangle L.) to 12 m tall. Its distribution in the tree was variable but mostly in the forks and lateral branches of the tree and with an orientation toward the side receiving more sunlight. Also, it was found on black mangrove (Avicennia germinans L.) on dead and dried vines or lianas one meter above the ground, in groups of up to 50 or 60 individuals.

Catasetum intergerrinum Hook. Common, unknown name. This species has 2 or 5 pseudobulbs, corrugated and solid spindle, light green, covered by transparent cuticle and pooled from 5 to 10 cm long, with light colored spines at the terminal when the leaves have fallen. Sheathing leaves located in the apical part of the pseudobulbs, large, soft, elliptical, green on you and light green on the underside, 30 to 40 cm long and 11-13 cm wide; parallel veins with 3-5 ribs. Edge whole or smooth, acute apex; deciduous and incurved towards the back (López-Ríos, 2005).

These species produce separate male and female flowers, which is exceptional in this family. Presents an inflorescence in clusters of 35 cm long. It may have 4 or 7 flowers, greenish-yellow and clear uniform appearance (female), cap-shaped, which are open from 5-7 days when they are not pollinated; bloom 2 to 3 times a year. It features thin, cylindrical roots brown about 5 cm long, abundant, such is the amount of roots that this species has that when they are leafless pseudobulbs only plant seems a bird's nest.

In the study area it was found on trees of red mangrove (Rhizophora mangle L.), with a widespread distribution throughout the tree from the base up to 13 high, and oriented toward the side where the tree gets better light sol. Other hosts were lianas or vines dead and alive. Populations were small and two plants per tiller.

Myrmecophylla tibiscinis Bateman: common unknown name. It is an epiphyte and terrestrial occasions large plant with pseudobulbs up to 50 cm long, cylindrical, furrowed by numerous longitudinal wrinkles, yellowish-green colour, hollows, often inhabited by ants, which use it as a shelter. Each pseudobulb has 2 short leaves, sheathing, and elliptical, smooth textures and rigid. With a central rib, sharp edge and apex entire or smooth, 3-5 cm wide by 12 or 20 cm long. Its roots are cylindrical and short of 6-8 cm, abundant, white, with green root apex (photosynthetic).

Its buds are erect, unbranched 1 cm in diameter at the base, apex emerge pseudobulbs. The flowers appear in a cluster at the end of the shoot or flower stalk (inflorescence), measuring up to 1.5 m long, and 5 to 10 flowers of lilac colour in the terminal part. The sepals and petals, and the lip have scalloped edges. The lateral lobes of the lip and tubular form of this dominate the appearance of the flower; which rolls, but do not enclose the column. The plant blooms once a year, the flowers are open from 10 to 15 days. In the study area, it was located on dead tree trunks of black mangrove (Avicennia germinans L.) and lianas, at a height of 1.5 m above the ground, also in the upper canopy of trees of red mangrove (Rhizophora. Mangle L.), 12 m in height. The location of this orchid on trees was on the side of the tree opposite the sun.

Oncidium cavendischianum Bateman: epiphytic plant, commonly called “oreja de burro” by locals, which can grow quite large, measuring up to 80 cm in height when several years old, has small pseudobulbs, subcylindrical, inconspicuous (López-Ríos, 2005). Its leaves are fleshy, elliptic oblong, envelopes; with acute apex (^{Ruiz, 1985}), soft texture, entire margin and incurved towards the back (López-Ríos, 2005). Green coloration and large size 13-70 cm long * 3-15 cm wide. These emerge from the pseudobulbs, which have a single leaf. Its inflorescence is paniculate, rarely racemose, 50 cm long, with 10-20 flowers 3 cm in diameter. Sepals and yellow petals; with reddish brown spots. Lobed lip, yellow with brown spots at the base; presented as a dancer, these remain open for 6-10 days.

Their presence in the study area was recorded on dead trunks at a height of 1 to 2 m high, and the lower or basal part of the red mangrove (Rhizophora mangle L.) on the roots that serve as support plant; well as in dead vines, about 2 m above the ground. It was found in associations of 2 or 4 plants located on the face or where the tree receives little light area.

The value obtained by the Shannon-Wiener index (1.2334) indicated that the distribution of individuals among species is heterogeneous, this may be because most of the individuals belonged to the species Brassavola nodosa (L) Lindl (47) . The value obtained in this study agrees with the results obtained by ^{Sol (1996)}, in a study conducted on the distribution of vegetation in a jungle stronghold in the region of the Chontalpa where the author obtained an index with a value of 1.2334 reflecting irregular distribution of individuals among species; i. e. few species with several individuals within the study area.

The Sörensen index shows that each of the sampled transects have different orchid species and common species between them. Of these transects which are presented more affinity transect C and D, sharing four species in common: Encyclia boothiana Lindl (2 and 1 individuals), Brassavola nodosa L. Lindl (12 and 10 individuals), Onciduim cavendischianum Bateman (3 and 1 individual) and Catasetum intergerrinum Hook (7 and 2 individuals). While in transects A and B are the least related sharing a common species Brassavola nodosa L. Lindl (4 and 9 individuals).

When comparing transects A and B, the Sorensen similarity index obtained from (0.4) indicated that 40% of the species are common between the two sampling units may be impacted with less coverage, substrate and humidity. While in transects A and C an index of similarity (0.57) was obtained, i. e. 57% of the species are common in both monitoring sites, the conditions in the area are more favourable for the development of some orchids, with an acceptable degree of conservation, with good coverage, substrate and humidity.

Regarding transects A and D, showed the lowest value, i.e. 0.28, indicating that only 28% of individuals present in both monitoring sites. This is an altered with large open spaces and increased sun exposure, less humidity and a substrate area. This indicates that it is not suitable for the development of some species of orchids. ^{Murguía (2007)} mentioned that, the distribution of a species is related to the presence of vegetation, and associated fauna favourable environmental variables, such as weather, temperature, soil, sun exposure, topography and altitude, which create specific microhabitats for development of restricted species.

In B and C transects similarity index of 0.5 was obtained, as in the transects A and C, indicating that they share the largest similarity, since 50% of the species are present in both monitoring units. Being good substrate areas, vegetation cover and moisture. The transect B and D record a value of 0.75 in the Sorensen similarity index, indicating a high value, so the 75 orchid species recorded are common to both monitoring sites. This area has excellent condition with few open spaces, and has good moisture and substrate.

The similarity index for transects C and D was 0.80 represented the highest value in relation to the number of species present in the transects. This was one of the best preserved areas, no open spaces with high moisture concentration probably due to its proximity to one of the bodies of water in the area and abundant and diverse substrate decomposition. Toribio-Díaz (2009) notes that these requirements are necessary for the development and growth of orchids.

Of the six species of orchids recorded through morphological variables, species that stood out in terms of inflorescence size (length), number and size of flowers, striking (color and shape) and Life of Flowers (days) were Oncidium cavendischianum Bateman, Catasetum intergerrinum Hook and Myrmecophylla tibiscinis Bateman. The results of this study agree with those pointing ^{Hágsater et al. (2005)} who found in the mangrove area the same species because this is their natural habitat.

Of the 70 surveys conducted for the assessment of the tourism potential (attractive), the species that received the highest numerical in the total visual value (TVV) was Myrmecophylla tibiscinis Bateman orchid with 1385.05 and a final visual value (FVV) of 19.78. The values obtained from FVV of each species was compared with the values of adjectives, adjective and give your category.

Orchid Myrmecophylla tibiscinis Bateman presented the highest numerical value (19.78) in the FVV and the adjective great and with a spectacular category. While followed in order of importance Brassavola nodosa L. Lindl, with the value of 13.29 Catasetum integerrinum Hook, Onciduim cavendischianum Bateman and showed a high numeric value to its final visual value, accounting category of fantastic and spectacular respectively, this indicates that these four species have a high tourism potential (attractive). Mentioning that these species could be used for tourism-related activities in the area.

The interpretive trails in the form of ecotourism had the highest percentage of units evaluated (32). With respect to wildlife watching activities, hunting and photographic reproduction and display, but received lower percentage 17, 5 and 15 respectively, and can be used as complementary activities within own interpretive trails.

Conclusions

Mangroves from the Ejido Aquiles Serdán, Paraíso, Tabasco had mangrove floristic similarities with other sites, as some of the species listed for other sites were present in this paper.

Taking as reference the diversity indices, the data are similar to other tropical regions of the planet; flora is heterogeneous, with some degree of inter-specific similarity as the Sörensen index showed.

The initial proposal on the tourism potential of the study area is met by the species Brassavola nodosa L. Lindl, Catasetum integerrinum HooK, Oncidium cavendischianum Bateman and Myrmecophylla tibiscinis Bateman, which presented the highest values for this purpose.