Herpetofauna of the Northwest Amazon forest in the state of Maranhão, Brazil, with remarks on the Gurupi Biological Reserve

Abstract Understanding the biodiversity of an area is the first step for establishing effective interventions for conservation, especially when it comes to herpetofauna, since 4.1% and 9.2%, respectively, of Brazilian amphibians and reptiles are endangered. The aim of this study is to identify the composition of the herpetofauna occurring in the Northwest Amazonian state of Maranhão, with a focus on the Gurupi Biological Reserve and surrounding areas. Samples were collected between May 2012 and October 2013 (18 months), through pitfall traps, time constrained active search, and opportunistic encounters, and these records were supplemented by specimens collected by third parties and by bibliographic records. A total of 131 species were recorded: 31 species of amphibians and 100 species of reptiles (six testudines, 30 lizards, two amphisbaenas, 60 snakes and two alligators), including some species new to the state of Maranhão and the northeast region of Brazil. This inventory contributes to the knowledge of the herpetofauna for the Belém Endemism Center, the most devastated region of the Brazilian Amazon, and considered poorly sampled.


Introduction
Conservation units in the Amazon (National Parks, ecological stations, extractive reserves, national forests, biological reserves, etc.) are of fundamental importance for the conservation of biodiversity in this biome (Peres 2005;Silva 2005).
With regard to formulating effective management plans, it is of fundamental importance for biodiversity conservation to know the composition of the fauna and flora. Faunal lists, especially in regions that represent sampling gaps and that refer to groups with a high percentage of endangered species should be emphasized (Peres 2005).
In this context, regarding the herpetofauna, there are in Brazil 1080 known species of amphibians and 773 species of reptiles of which 4.1% and 9.2% are endangered, respectively (Costa and Bérnils 2015;Segalla et al. 2016).
Biodiversity inventories enable us to identify the degree of regional endemism, new trigger points, new species and the actual conservation status of the species recorded, besides enriching regional and national scientific collections (Moura et al. 2014).
It is noteworthy that species lists are highly important for our understanding of the environmental conservation, since the occurrence of bioindicator species (either opportunistic or vulnerable) can be used to determine the effects of environmental disturbance in the area, and therefore, pave a way to efficient interventions and conservation policies (Brown and Freitas 2002).
The state of Maranhão is known for its rich biodiversity (Martins and Oliveira 2011), lack of researchers and extensive sampling gaps, especially regarding the herpetofauna in the Amazon biome of northwestern Maranhão.
This study aims to record the composition of amphibians and reptiles of the RE-BIO Gurupi and adjacent regions of the northwest Amazon of Maranhão state, a conservation unit of utmost importance, composing the largest and last block of continuous forests in the Belém Endemism Center (Martins and Oliveira 2011).

Materials and methods
Study Area: The Gurupi Biological Reserve (03°58'32"S 46°46'52"W) (Figure 1), was created by Law 95 614 1988 and occupies an original area of 341,650 hectares in the municipalities of Bom Jardim, Centro Novo do Maranhão and São João do Caru, in the state of Maranhão (IBAMA 2006). The climate is humid type B2, with moderate water deficit in the summer, average annual rainfall exceeding 2,000 and average temperature greater than 24°C, with the soil type being argisoil (Martins and Oliveira 2011). This work was performed and focused only in Gurupi and the adjacent rainforests of the State of Maranhão, northwest Amazon.
Sampling: Samples were collected between May 2012 and October 2013 (18 months), with pitfall traps, time constrained active search, and opportunistic encounters in the forested areas and access roads to REBIO (road killed individuals). They also included those collected by third parties and bibliographic records.
The time-constrained active search was conducted over three campaigns for three nights in December 2012, January and May 2013, by a team made up of five collectors, totaling an effort of 135 man hours according to the methodologies of Martins and Oliveira (1998), and Bernarde and Abe (2006). The search was concentrated in the area adjacent to aquatic environments near the southern tip of REBIO Gurupi (04°00'20"S, 46°46'41"W).
The collected amphibians were euthanized by applying lidocaine ointment (lidocaine) on the ventral region and the reptiles through overdosing with ether (Callefo, 2002;Franco and Salomão 2002). All specimens were fixed with 10% formalin and then preserved in 70% ethanol.
Voucher specimens were deposited in the collection of Herpetology and Paleontology of the Federal Rural University of Pernambuco CHP-UFRPE (tumble numbers in Appendix 1) and the University of São Paulo Museum of Zoology MZUSP (tumble numbers in Appendix 1). Important bibliographic databases added to this work were Cunha and Nascimento (1993) for snakes, Avila-Pires (1995) for lizards and Barreto et al. (2011) for amphibians and reptiles.
Data analysis: In order to evaluate the efficiency of the collection effort in the analyzed fragment, species rarefaction curves were constructed with 1000 randomizations generated based on the data matrix of the relationship between richness and abundance (ICE index) through the statistical program Ecosim version 7.0 (Gotelli and Enstminger 2003).

Results
A total of 131 species composing the local herpetofauna was recorded: 31 species of amphibians (seven families) and 100 species of reptiles, which included six testudines, 30 lizards, two amphisbaenians, 60 snakes and two crocodylians (Figure 3, 4).
Of the 131 species recorded for the northwest Amazon in Maranhão, 78 species (62%) were recorded in this study and 53 (38%) included results from previously published data (Cunha and Nascimento 1993;Avila-Pires 1995;Barreto et al. 2011).

Discussion
The Belém Endemism Center (EC) is the smallest among the eight EC in the Amazon region, and has the largest loss of forest cover, with about 70% of its total area already destroyed Fearnside 2006).
The species richness of REBIO Gurupi is second only to the richness sampled in the National Forest of Saracá-Taquera in northern Pará, located in the Guyana Endemism Center, more than 1000 km from REBIO Gurupi (Morato et al. 2014).
Regarding sampling efficiency, the collection effort and methods used were not effective, as not all niches were sampled. As a result, the curve implied 33 amphibian species and 78 reptile species at the site. As the curves did not reach an asymptote, we believe that site has potential for species that have not yet been recorded. This is borne out by the additional 58 species not found during the field work but recorded in the literature for the area (Cunha and Nascimento 1993;Avila-Pires 1995;Barreto et al. 2011) (Figure 2). Regarding collection methods, pitfall traps yielded only 33 species of the 78 found in the field, chiefly amphibians, frogs, and fossorial lizards.

Conclusion
Since only 38% of the recorded species included in this inventory were obtained from literature (Table 1), it is possible to ascertain that our sampling reflects a great share of the total herpetofauna from Northwestern Maranhão. With this richness, the Gurupi Biological Reserve stands out as a biodiversity hotspot in the Amazon, reinforcing the need for its protection, and its position as the most important restricted use conservation unit of the Belém Endemism Center.