TRABAJO

Diversity and conservation status of the herpetofauna for an area from north of Hidalgo, Mexico

Luis M. Badillo-Saldaña, Aurelio Ramírez-Bautista, Daniel Lara-Tufiño, Christian Berriozabal-Islas

Universidad Autónoma del Estado de Hidalgo. Centro de Investigaciones Biológicas. Laboratorio de Ecología de Poblaciones. Apartado Postal 1-69, Plaza Juárez, 42001 Pachuca, Hidalgo, México.

Recibido: 27/02/15
Revisado: 14/05/15
Aceptado: 09/06/15

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ABSTRACT

Conservation measures currently lack adequate information to assign some species of amphib­ians and reptiles in the categories of protection. In this study we analyzed and compared the herpetofauna of mountain cloud forest (MCF) and tropical evergreen forest (TEF) in an area north of Hidalgo. For this study, we conducted fieldwork (24 sites) and a literature review. In addition, the conservation status of species was analyzed. The herpetofauna of the municipal­ity of Tepehuacan de Guerrero, Hidalgo, Mexico consists of 70 species (20 amphibians and 50 reptiles), nine of which are historical records that were not found in the present study. Cloud forest was more diverse (39 species) than TEF (37 species). There are discrepancies between national and international agencies of conservation regarding the threatened status of these spe­cies. The high biodiversity recorded in MCF and TEF in the study area indicates the importance of this area for conservation. In this study, we propose to reassess the conservation category of Hidalgo state herpetofauna.

Key words: Amphibians; Reptiles; IUCN; SEMARNAT; Sierra Madre Oriental.

RESUMEN

Diversidad y estado de conservación de la herpetofauna para un área del norte de Hidalgo, México. Actualmente las medidas de conservación carecen de información adecuada para asignar algunas especies de anfibios y reptiles dentro de las categorías de protección. En este estudio se analizó y comparó la herpetofauna de bosque mesófilo de montaña (BMM) y bosque tropical perennifolio (BTP) de un área al norte de Hidalgo. Para este estudio, se realizó trabajo de campo (24 sitios) y revisión de la literatura. Además, se analizó el estado de conservación de las especies. La herpetofauna del municipio de Tepehuacán de Guerrero, Hidalgo, México consta de 70 especies (20 anfibios y 50 reptiles), nueve de estas especies son registros históricos que no fueron encontrados en el presente estudio. El BMM fue más diverso (39 especies) que el BTP (37 especies). Existen discrepancias entre las agencias nacionales e internacionales de conser­vación con respecto al estado de amenaza de estas especies. La alta biodiversidad en el BMM y BTP podría sugerir que este sitio es un área importante para la conservación. En este estudio, proponemos reevaluar las categorías de conservación de la herpetofauna del estado de Hidalgo.

Palabras clave: Anfibios; Reptiles; IUCN; SEMARNAT; Sierra Madre Oriental.

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INTRODUCTION

The high biological diversity of Mexico is the result of its geographic location and its complex geological history, characteristics that give rise to a patchwork of environmental and microenvironment condi­tions for the establishment and development of a wide variety of habitats and species (Challenger and Soberón, 2008). This high diversity is also reflected on the high diversity and endemism of amphibians and reptiles of Mexico (Wilson and Johnson, 2010; Wilson et al., 2013a, 2013b). Despite efforts to conserve the high diversity of Mexican amphibians and reptiles, current conservation measures may not be effective, because of the lack of knowledge about the status and distribution of species and populations (Howard and Bickford, 2014).

Among the first studies on herpetofauna from Mexico are those by Francisco Hernández in 1570-1577, who recorded 68 species (9 amphibians and 59 reptiles) and Dugès that on 1896 reported 218 species (37 amphibians and 181 reptiles; Flores-Villela, 1998; Vite-Silva et al., 2010). Later, Martín del Campo (1937) and Smith and Taylor (1966) carried out studies on species accounts and their distribution, which increased significantly the knowledge of herpetofauna from Mexico. Currently, there are 1,227 species (378 amphibians and 849 reptiles; Wilson et al. 2013a, 2013b) registered in the country, of which more than half are listed as species in risk by Mexican legislation (52%; NOM-059-2010). The IUCN considers less than a quarter of these species to be threatened (see Wilson et al., 2013a, 2013b).

During the years 1937-1966, explorations to register the herpetofauna of Hidalgo State were initi­ated in an inconsistent way (Ramírez-Bautista et al., 2010; Gual-Díaz and Goyenechea, 2014). In the last two decades, studies on amphibians and reptiles in Hidalgo have increased substantially (Fernández-Badillo and Goyenechea, 2010; Ramírez-Bautista et al., 2010, 2014; Vite-Silva et al., 2010; Huitzil and Goyenechea, 2011; Cruz-Elizalde and Ramírez-Bautista, 2012; Hernández-Salinas and Ramírez-Bautista, 2012; Ramírez-Bautista and Cruz-Elizalde, 2013). However, there are regions and vegetation types in the state that are poorly explored, from which new records have been recently registered (Berriozabal-Islas et al., 2012; Ramírez-Bautista et al., 2013; Badillo-Saldaña et al., 2014; Lara-Tufiño et al., 2014) and new species have been described (Woolrich-Piña et al., 2012).

Currently, the herpetofauna of Hidalgo State is comprised by 195 species (Ramírez-Bautista et al., 2014; Lemos-Espinal and Smith, 2015). This species richness represents almost 15% of the entire country’s herpetofauna. In a biogeographic context, this high level of diversity is a result of the location of Hidalgo within the Sierra Madre Oriental, Transmexican Volcanic Belt, Mexican Plateau, and Gulf Coastal Plain, which present a high number of vegetation types (Ramírez-Bautista et al., 2010).

The herpetofauna from Tepehuacán de Guerrero, Hidalgo, Mexico has been previously studied by Mendoza-Quijano et al. (2006) and Ramírez-Bautista et al., (2010). However, these studies were carried out in a single vegetation type and conse­quently provided isolated records for this municipality. Nonetheless, both studies reported a significant number of 44 species. In spite of the reported species richness for the municipality, it is expected that a systematic study may show a higher diversity of amphibians and reptiles due to the expected increase in number of microhabitat types, as a result of the convergence of tropical evergreen forest (TEF) and mountain cloud forest (MCF). The primary goal of this study was to assess the amphibian and reptile species composition in two dominant vegetation types from the municipality of Tepehuacán de Guerrero, Hidalgo, Mexico, and evaluate the conservation status of these species according to national and international conservation systems, which are compared with the Environmental Vulnerability Score (see Wilson et al., 2013a, 2013b).

MATERIALS AND METHODS

The municipality of Tepehuacan de Guerrero is located in northern Hidalgo, entrenched in the Sierra Madre Oriental (between 20° 56’ and 21° 12’ N; 98° 44’ and 98° 58’ W; Fig. 1), and located at an elevation range from 200 to 2000 m a.s.l. It has a territorial extension of 426.6 km2, which corresponds to 1.7% of the entire state. Dominant vegetation types are TEF and MCF (Rzedowski, 2006; INEGI, 2009). The TEF is distributed in lowlands and MCF is present in highlands, MCF is characterized by the presence of fog throughout the year. The region shows a semiwarm-humid climate, with a mean annual temperature of 24°C at low elevations and 18°C in high places (INEGI, 2009), while annual precipitation varies between 1000 and 2200 mm3, and rains are seasonal, being dry from December to May, and wet from June to November.

Figure 1. Study area. The triangles represent the surveys sites of tropical evergreen forest and squares correspond to mountain cloud forest.

We visited the studied area 12 times between 2011 and 2012; six during the rainy season, and six during the dry season. Each visit consisted of two sampling days, one day per vegetation type. Surveys were made during the day (09:00-14:00 h) and night (18:00-23:00 h) by a team of four people. Thus, a total of 120 h by person of search effort was dedicated to each vegetation type. We selected 12 sites in MCF and 12 in TEF, all sites were separated by 1.5 km (airline). Four transects of 900 m were conducted at each site during the morning, and each of these transects was conducted by one person. Additionally, two transects were selected at night, and each was conducted by two people. We used the method of direct sampling, which takes into account checking all potential microhabitats occupied by amphibians and reptiles according to their natural history (Casas-Andreu et al., 1991; Manzanilla and Péfaur, 2000; Amador, 2010). To assess abundance, we counted all individuals of each species observed at each site.

Most species were identified directly in the field with the use of identification keys for amphibians and reptiles; however, when specimens were not recognized in the field, they were collected in order to identify them in the Laboratorio de Ecología de Poblaciones (LEP) of the Centro de Investigaciones Biológicas (CIB) of the Universidad Autónoma del Estado de Hidalgo (UAEH). Specimens were collected under scientific permit SGPA/DVGS/02419/10 issued by SEMARNAT (Secretaría del Medio Am­biente y Recursos Naturales), and then euthanized and preserved using the method proposed by Casas-Andreu et al. (1991).

Scientific names were updated according to the most recent taxonomic changes (Ramírez-Bautista et al., 2010; Wilson et al., 2013a, 2013b; Streicher et al., 2014; Ramírez-Bautista et al., 2014; Mesa-Lázaro and Nieto-Montes de Oca, 2015). The verification of species assignment was made by Uriel Hernández-Salinas. In addition to the field work, a literature search was made to identify historical records for the study area and generate in conjunction with the field data an updated list of the herpetofauna of the study area.

We developed a species list for each vegetation type, and to obtain an approximation to the level of conservation risk that these species are confronting, we included the protection category for each species according to national (NOM-059-SEMARNAT-2010) and international (Redlist-IUCN) conservation assessment systems and compared these systems with the Environmental Vulnerability Score (EVS) in which a score of 3-9 corresponds to the low threat category, 10-13 corresponds to medium threat, and 14-20 corresponds to the high threat category (see Wilson et al., 2013a, 2013b).

To obtain the completeness of the inventory, we generated a species accumulation curve. The completeness was measured by Bootstrap estimator, because this estimator does not consider the rare species of the sample, and it has been proposed as one of the most accurate estimators to assess the herpetological communities under a more realistic scenario, especially when working with reptiles, because, populations of this group of vertebrates often have low densities (Carbajal-Cogollo and Urbina-Cardona, 2008; Urbina-Cardona et al., 2008). For completeness analysis of the inventory only the data obtained during the fieldwork was used.

 

RESULTS

As a result of fieldwork, we report 61 species (18 amphibians and 43 reptiles). Of these, 26 species are new records for this municipality. In the literature review we found only two studies of amphibians and reptiles for the region, which provide a list of 42 species. Of these 42 species, in the field work we did not find nine species (Incilius occidentalis, Eleutherodactylus guttilatus, Corythophanes hernandesii, Oxybelis aeneus, Geophis latifrontalis, G. mutitorques, Imantodes gemmistratus, Pliocercus elapoides, and Rhadinaea marcellae). Therefore, the entire herpetofauna for the municipality of Tepehuacán de Guerrero is composed of 70 species. Twenty species are amphibians (6 families and 11 genera), and 50 species are reptiles (15 families and 34 genera). The family Hylidae was the most diverse for amphibians, and the family Dipsadidae was the most diverse for reptiles. Forty percent of the species found in this study are endemic to Mexico (Table 1).

Table 1. Species distribution by vegetation types from the municipality of Tepehuacan de Guerrero. Vegetation type: MCF= mountain cloud forest, TEF= tropical evergreen forest. Conservation status according to NOM-059-SEMARNAT-2010: Am= threatened, Pr= special protection, P= endangered, Nc= not considered; Red list-IUCN: NT= near threatened, V= vulnerable, CE= critically endangered, LC= least concern, EN= endangered, DD= data deficient, NE= not evaluated. * Species reported from literature not found in field work. EM= endemic of Mexico, NEM= not endemic of Mexico.

According to vegetation type, MCF showed the highest richness, with 39 species of amphibians and reptiles (Table 1). The completeness of the inventory for this environment was 86% (Bootstrap, 45 species). In TEF, the species list included 37 amphibians and reptiles (Table 1), with a completeness of the inventory of 84% (Bootstrap, 44 species). MCF was richer in amphibians than TEF, whereas TEF showed a higher diversity of reptiles (Table 1).

According to NOM-059-2010 of Secretaría del Medio Ambiente y Recursos Naturales, of the 70 recorded species from this municipality, Lithobates johni is the only species (1.4%) that is regarded as endangered (P), 18 species (25.7%) are in the category of special protection (Pr), and 13 species (18.6%) under the status of threatened (Am), whereas, 38 (54.3%) are not given a conservation status (Nc) by this system. According to the IUCN Red list (2014), Pseudoeurycea gigantea (1.4% of species) is considered critically endangered, four species (5.7%) are regarded as endangered, three (4.3%) as near threatened, eight (11.4%) as vulnerable, 39 (55.7%) are in the category of least concern, 13 (18.6%) are not evaluated and the remaining two species (2.9 %) are not assigned to any category due to insufficient information (Table 1). Finally according to the EVS system, the species are distributed in three categories, 33 species (47.2%) low risk, 22 (31.4%) medium risk, and 15 (21.4%) high risk (Table 1).

DISCUSSION

In this study we report a high diversity of amphibians and reptiles for the municipality of Tepehuacán de Guerrero, which is the result of the significant topographic complexity of the region. In this area, elements of different origins converge, mainly Neartic and Neotropical, and also from the Sierra Madre Oriental that is regarded as a diversity hotspot in Mexico (Canseco-Márquez et al., 2004; Mendoza-Quijano et al., 2006).

The herpetofauna of the study area is repre­sented by 70 species, which correspond to 35.9% of the total herpetofauna of Hidalgo State (Ramírez-Bautista et al., 2014), and 33.8% of the herpetofauna recorded for the Sierra Madre Oriental. Of the 70 species registered, 15% corresponds to endemic species (Canseco-Márquez et al., 2004). These re­sults highlight the relevance of the study area for the conservation of an important portion of the Mexican herpetofauna (Vite-Silva et al., 2010; Cruz-Elizalde and Ramírez-Bautista, 2012). The notable high richness in the region may be partly due to the array of environmental conditions (temperature, humidity, and heterogeneity of microhabitats) present in each forest type (TEF and MCF) which in turn help to maintain a high diversity of this group of vertebrates (Pineda and Halffter, 2003; Urbina-Cardona et al., 2008). Regarding species richness by vegetation types, MCF showed the highest amphibians richness compared to TEF (Table 1), and this might be explained by the importance of water and humidity conditions for the distribution of this biological group (Jansen and Healey, 2003; Cushman, 2006; Vitt and Caldwell, 2009), in this forest the pres­ence of ambient humidity is constant throughout the year (CONABIO, 2010). On the contrary, TEF showed higher reptile richness than MCF (Table 1). This pattern could be the result of physiological requirements of this group since reptiles are closely linked to the specific environmental variables such as heat sources (Urbina-Cardona and Reynoso, 2009; Ramírez-Bautista and Cruz-Elizalde, 2013); for instance, higher ambient temperatures that occur in TEF allow for better thermoregulation activity by reptiles than in MCF (Urbina-Cardona et al., 2008; Vitt and Caldwell, 2009).

The twenty six species registered during field work suggests that more field work is required to determine the current distribution and diversity of amphibians and reptiles in Hidalgo State (Ramírez-Bautista et al., 2014). However, notwithstanding of these new records, in this study nine species reported previously for the study area were not found. This finding indicates to the possibility that these species could be locally extinct. Perhaps, due to the fact that these species may need specific requirements for living and thrive in, and in this way to establish in this area. The species loss could be a consequence of the high rate by change of land use in the region, which could be exerting a strong pressure on populations of these species, and therefore, on reducing diversity of amphibians and reptiles of the region.

A high number of species was found to be listed under some conservation category in accordance to the national (32 species, 45.7%; NOM-059) and international (16 species, 22.8%; IUCN) organizations that categorize species according to extinction risk. However, there are discrepancies when comparing national and international conservation assess­ment systems. For instance, IUCN (2014) regards Pseudoeurycea gigantea as critically endangered, but the same species is not assessed by the NOM-059-2010, and according to the EVS system, this species presents a score of 16, which corresponds the high threat category (Table 1). The primary reasons by the IUCN and the EVS to place this species within the category of critically endangered are the decline in its populations and its restricted distribution, both ecologically and geographically. A possible reason of the absence of this species in the NOM-059-2010 is that for decades this species was considered a synonymy of P. bellii species listed by this evaluation system. Therefore, natural history data between these two species may have been confused (Badillo-Saldaña et al., 2015).

Furthermore, in the national evaluation system (NOM-059-SEMARNAT-2010), 11.5% of the species reported in this study are overvalued according to the EVS system, so that, the category of these species probably should be reconsidered. For example, Sceloporus serrifer (Pr, NOM-059; LC, IUCN; 6 EVS) is a species with a widespread distribution within and outside the country, with populations moderately abundant (Lee, 1996). In this sense, we advocate the conservation status reassessment of the risk category for this by the NOM-059, considering some criteria such as geographic distribution, vegetation types, reproductive characteristics, and human related pressures, as those encompassed in the EVS system (see Wilson et al., 2013a, 2013b).

Therefore, using the EVS system, species that are not considered in a risk category by the other systems (NOM-059 and IUCN) may be relevant for conservation actions, and the risk category of species listed in the NOM-059 and IUCN systems could be corroborated. This is important, since the conservation status of many species is unknown due to the lack of populations data (Howard and Bickford, 2014), as well as on information on the anthropic effects on species and communities from areas with high biological richness and the consequent implementation of appropriate strategies and areas of conservation (Porter-Bolland et al., 2012). Therefore, we could be implementing inappropriate conservation actions for some species that might be threatened and that there are not considered within national or international law because of lack of data (Howard and Bickford, 2014). Therefore, it is important to conduct natural history studies (Vitt, 2013) to provide an adequate risk assessment (Howard and Bickford, 2014).

These ideas are deemed important for the her­petofauna of MCF and TEF, with their high values of species richness and endemism. The main concern is that these forests are disappearing at an accelerating rate in the region, as a result of human related activities such as increasing farming, ranching, mining, and settlements (Challenger and Soberón, 2008; Mass et al., 2009; Gual-Díaz and Goyenechea, 2014a, 2014b), Nonetheless, in spite of the important efforts that have been invested addressing wildlife conservation in the state of Hidalgo and Mexico as a whole, more adequate legislation is highly desirable for enhancing protection of wildlife.

Acknowledgements

We thank projects CONABIO FB1580/JM001/12 and FOMIX-2012/191908. We also thank J. E. Tomas Villegas and U. Hernández-Salinas for their help in the field, and all the staff of the LEP of CIB, UAEH; to V. Mata-Silva for his help in reviewing this paper and the people from the municipality of Tepehuacán de Guerrero for their logistic help; and SEMAR­NAT by the permission granted us. We also want to thank the two anonymous reviewers for comments received in this paper.

 

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