Anurans of Sete Cidades National Park, Piauí state, northeastern Brazil

: The Sete Cidades National Park is located in the Brazilian municipalities of Piracuruca and Brasileira, Piauí state, in a transitional zone between the Caatinga and Cerrado biomes. Studies on its herpetofauna were limited to anuran distribution notes and a snake checklist. Thus, here we present an unpublished species list of anurans from Sete Cidades National Park, Piauí state, northeastern Brazil. We recorded one of the two highest species richness for all northeastern National Parks, and also increased the geographic distribution of one species in the state of Piauí. Most species observed are common of both Caatinga and Cerrado biomes or have wide distribution in Brazil. The anuran assemblage of Sete Cidades National Park is more similar to those registered at the Delta do Parnaíba Environmental Protection Area, Ceará, Piauí and Maranhão states, and Ubajara National Park, Ceará state. These results increase our knowledge on anuran diversity in northeastern Brazil, providing basic information for management and conservation actions of an important Brazilian National Park.


Introduction
The Brazilian Conservation Units system has 73 National Parks (PARNAs), covering about 75 million hectares, almost 10% of the Brazilian territory (ICMBio 2016). These National Parks are fundamentally important for biodiversity conservation because they protect natural environments and their resources, fauna, and flora. In addition, they provide subsidies to scientific research, environmental education and sustainable tourism (Brito & Câmara 1998).
There are 20 National Parks in Northeastern Brazil, of which four (Serra da Capivara National Park -SCaNP, Sete Cidades National Park -SCNP, Serra das Confusões National Park -SCoNP and Nascentes do Rio Parnaíba National Park -NRPNP) are located in the state of Piauí (ICMBio 2016). These four national parks have a total area of approximately 11.817,46 km², representing about 4.7% of the state of Piauí, and present environments with characteristics of different biomes, forming a complex landscape with high biodiversity (Matos et al. 2010).
The state of Piauí has extensive transition areas covered with ecotonal formations (about 20% of the state). In the state's northern portion transitional areas between the Amazon rainforest and Caatinga are found, represented by deciduous and semi-deciduous forests, and babassu and carnaúba palm forests. The south-central portion is characterized by the contact between Caatinga (about 37% of the state) and Cerrado (around 33% of the state), represented by typical open area vegetation adapted to water deficits (Farias & Castro 2004). The ecotones or transitional zones in northeastern region of Brazil harbor rich anuran faunas, despite these areas having been studied only recently (e.g. Magalhães et al. 2013, Benício et al. 2014, Dal Vechio et al. 2016, Matavelli et al. 2019). This diversity of contrasting environments from neighboring biomes likely allow the coexistence of high faunistic and floristic diversities that need to be studied further.
Recently, there has been an increase in studies of amphibians from Piauí state, such as the description of new species (e.g. Maciel et al. 2015), distributional records (e.g. Andrade et al. 2011, Benício et al. 2011, Leite Jr. et al. 2008, Macedo et al. 2011, Vasconcelos et al. 2014, ecological relations and checklists (i.e. Loebmann & Mai 2008, Dal Vechio et al. 2013, Benício et al. 2014, Araújo et al. 2018. Despite the availability of a compilation of amphibian species published for Piauí state (Roberto et al. 2013), there is still a lack of studies in some regions. For example, inventories evaluating species richness of anurans have been published for only half of the National Parks from Piauí (i.e. Serra das Confusões and Serra da Capivara National Parks) (Cavalcanti et al. 2014, Dal Vechio et al. 2016. The Sete Cidades National Park (SCNP) was created in 1961 for the preservation and conservation of natural resources, flora, and fauna of this ecotonal region. However, herpetofaunal studies in the region were limited to amphibian distribution notes (Annunziata et al. 2007, Vasconcelos et al. 2014) and a snake checklist (Rocha & Prudente 2010). Thus, even after nearly 60 years of its creation, the distribution pattern of amphibians (or even a list of species) remains mostly unknown in this region. Herein, we provide a checklist of anuran species from the Sete Cidades National Park, comparing its richness and composition with other Protected areas in Caatinga and Cerrado biomes.

Study area
We conducted the study in Sete Cidades National Park (SCNP), located in the northern region of the state of Piauí, northeastern Brazil (04°05'-04°15'S and 41°30'-41°45'W, WGS84 datum, Figure 1). Covering approximately 6.221 ha between the Brazilian municipalities of Piracuruca and Brasileira, the SCNP is located in a transitional area between the Ibiapaba plateau and the coastal plain, with a relief formed by sedimentary basins and altitudes ranging from 100 to 300 m above sea level (Afonso et al. 2008). Its vegetation is typical of a transition zone, with Caatinga patches inserted in Cerrado vegetation, on different soil types: Red Latosols, Quartzerenic Latosols, Lithic Latosols and Planosols (Della-Favera 2002, Oliveira et al. 2010, Lopes 2011. These physical-natural aspects allow the formation of six different vegetation types at SCNP: typical cerrado, covering 37.6% of the total area, cerradão with 24.3%, campo limpo with 14.3%, cerrado rupestre with 10.5% of SCNP area, semi-deciduous forest with 8.4%, and flooded gallery forest covering only 3.3% of the area (Ribeiro & Walter 1998). The SCNP region has a dry semi humid tropical climate (Aw' type), with average annual rainfall ranging from 1.300 mm to 1.500 mm. It has an average annual temperature of 33.6°C, with minimum temperatures of 21.8°C in February, and maximum temperatures of 35.0°C in October (Castro & Costa 2007).

Anuran sampling
We conducted fieldwork in two distinct rainy periods distributed in 2018 and 2019, totaling 19 sampling days. Two sampled methods were performed: the first sampling campaign was carried out for 11 consecutive days in May 2018, from the 16 th to the 26 th , while the second campaign consisted of monthly visits between January and May 2019, lasting two consecutive days each. It is important to point out in both campaigns we used auditory census and active visual searches (Crump & Scott Jr. 1994) in different environments used by anurans within SCNP (Table 1; Figure 2), searching species on soil, water, and terrestrial and aquatic vegetation. These methods are indicated for inventory studies because are inexpensive and efficient to record the largest species number in the shortest time (Valdujo et al. 2009, Andrade et al. 2017. In both campaigns four researchers carried out field activities, starting around 18:00 h and ending at 00:00 h, resulting in the total sampling effort of 108 h/person. The collection locations were random and chosen according to the species' vocalization activities. We deposited voucher specimens in the Herpetological collection of the Universidade Regional do Cariri (URCA-H) and the Coleção Biológica of the Instituto Federal de Educação, Ciência e Tecnologia do Piauí, Campus Pedro II (CBPII) and tissue samples in Tissue collection of the Universidade Regional do Cariri (URCA-G). Anuran nomenclature follows Carvalho et al. (2020), Frost (2020), and Mângia et al. (2020).

Statistical analyses
We evaluated the efficiency of anuran sampling methods in SCNP by using sample-based accumulation curves (Gotelli & Colwell 2001) with 1000 randomizations from an incidence matrix. Each night of observation corresponded to a sample, resulting in 19 samples. In addition, we calculated the expected species richness using the nonparametric estimators Chao 2 and Jackknife 1 (Magurran & McGill 2011), with 100 randomizations.
Considering SCNP is located in a transitional zone between Caatinga and Cerrado, we compared its anuran species richness with other protected areas located in both biomes and calculated the Local Contribution to Beta Diversity -LCBD (sensu Legendre & De Cáceres 2013) to evaluate the variation in species composition among different sites. The LCBD allows us to evaluate which component of beta diversity (turnover or nestedness) best explain the variation in species composition (Legendre 2014). For this analysis, we constructed a matrix with presence and absence data for 181 anuran species, excluding species without specific identification ("gr.", "aff." and "sp.") and considering only species with identification to be confirmed ("cf."). We obtained the LCBD values using the Jaccard dissimilarity index of the Baselga family for presenceabsence data (Legendre 2014). In addition, we performed the Jaccard Similarity coefficient (J'; Magurran & McGill 2011) with a subsequent cluster analysis by Unweighted Pair Group Average Method (UPGAM), to illustrate the similarity between anurans richness of SCNP and other protected areas from Caatinga and Cerrado biomes. To investigate the relationship between the amphibian species richness similarity and the protected areas geographical distance, we measure the geographical distances between the above-cited areas using ArcGIS software (Esri 2008) and performed a Mantel test (Manly 1994), with 10.000 permutations. Table 1. Environmental description of the sampled habitats in the Sete Cidades National Park (SCNP), Piauí state, northeastern Brazil. The vegetation was classified according to Oliveira et al. (2010).

P3
4°06'36.10" 41°42'04.70" Large temporary lake formed in an area of cerrado sensu stricto (cerrado típico) on the side of the access road to the park.

P10
4°05'32.18" 41°40'48.56" Natural pool formed next to the north access road to the park in a mesophytic cerradão area (cerradão mesofítico).  (Andrade et al. 2017). Due to the low representativeness of amphibians in the Serra da Capivara National Park, we did not include in our analysis the checklist carried out by Cavalcanti et al. (2014) to avoid a trend in the comparison among species composition caused by the large difference in the number of species. We evaluate anuran species distribution and association with Brazilian biomes (IBGE 2019) from literature records (i.e. Roberto et al. 2013, Andrade et al. 2017, Araújo et al. 2018, Frost 2020) and the amphibian conservation status is according to IUCN (2020). All diversity metrics and similarity analysis were performed using the packages adespatial (Dray et al. 2019), BiodiversityR (Kindt and Coe 2005), and Vegan (Oksanen et al. 2016) for R 5.6.1 (R Core Team 2019).
The species accumulation curve presented a strong tendency towards stabilization (Figure 6), which suggests that the sampling effort was appropriate for species richness and that the number of species will remain constant regardless of an increase in sampling effort. Furthermore, the observed species richness represented 95.2% of the richness estimated by Chao 2 (31.51 ± 1.27) and 88.8% of the richness estimated by Jackknife 1 (33.79 ± 0.93).
We observed low similarities in species composition between different protected areas compared in this study, which was mainly determined by species turnover among areas (93.27% of total beta diversity). Species loss contributed only 6.72% of total beta diversity (Figure 7).
In general, we also observed the formation of two clusters, one formed by the Caatinga biome protected areas and another by Cerrado biome protected areas (Figure 8). No single species was common in all protected areas analyzed. However, Rhinella jimi and Leptodactylus troglodytes were common in all Caatinga biome protected areas and Physalaemus cuvieri was common in all Cerrado biome protected areas. Among the 28 protected areas of these biomes, the differences in species None of the species registered here were exclusive to Sete Cidades National Park, being recorded in other protected areas of Caatinga and Cerrado biome. We observed that the anurofauna recorded in Sete Cidades National Park is more similar to that recorded in Delta do Parnaíba Environmental Protected Area (J' = 0.68), with 21 species in common, in Ubajara National Park (J' = 0.56), with 18 species in common, and in Lençóis Maranhenses National Park (J' = 0.54), with 15 species in common. Whereas anuran richness registered in Santuário do Caraça RPPN (J' = 0.07) and Peti Environmental Station (J' = 0.11), both in state of Minas Gerais, with four and five species in common respectively were more distinct from our study (Figure 7). Furthermore, the geographical distance between the protected areas was able to explain the amphibian species composition dissimilarity in the areas investigated (r = 0.68, p = 0.001), where the further away are two areas more dissimilarity is their anuran composition.   (IUCN 2020). Conservation status for Scinax gr. ruber was not provided since we did not identify it at the specific level. Rhinella mirandaribeiroi and Adenomera juikitam do not present data on abundance and/or distribution, being classified as data deficient (DD), although the lack of data is not a category of threat.

Discussion
About 55 amphibian species are found in the state of Piauí (Roberto et al. 2013), of which we recorded approximately 54% in Sete Cidades National Park. This richness was higher than other protected areas of the state, such as Uruçuí-Una Ecological Station (Dal Vechio et al. 2013;26 species), Delta do Parnaíba Environmental Protection Area in the coastal zone of states of Piauí and Maranhão (Loebmann & Mai 2008, Andrade et al. 2016, Araújo et al. 201826 species), Serra das Confusões National Park (Dal Vechio et al. 2016;18 species), and Serra da Capivara National Park (Cavalcanti et al. 2014;eight species). The largest number of species recorded here is probably caused by the location of Sete Cidades National Park, within an area of ecological tension, under the influence of different phytogeographic elements (Cerrado-Caatinga) (Rocha & Prudente 2010). The ecotonal areas of Caatinga and Cerrado biomes harbor high biodiversity in the state of Piauí, and the anurofauna from these environments is characterized by species typical from each of these domains (Dal Vechio et al. 2016).
Although there are extensive areas of contact between the two biomes in the state of Piauí, few studies have been conducted in these transitional areas in the state (e.g. Benício et al. 2014, Dal Vechio et al. 2016. Therefore, we highlighted the importance of this study and the Sete Cidades National Park for anuran conservation and preservation.

Despite the differences in phytogeographic units between Sete
Cidades National Park and Serra da Capivara National Park (CapNP), we believe that the great difference observed in the number of species is caused mainly due to sampling problems in SCapNP (Cavalcanti et al. 2014). Only eight amphibian species were recorded in SCapNP, of which seven anurans (Rhinella granulosa, R. jimi, Scinax x-signatus, Leptodactylus syphax, L. troglodytes, L. vastus, Physalaemus cuvieri) and one caecilian (Siphonops sp.), all of them are common of semiarid and open areas of the state of Piauí (Dal Vechio et al. 2013, Andrade et al. 2016, Araújo et al. 2018, including SCNP. According to Cavalcanti et al. (2014), the low number of species recorded in SCapNP possibly results from the atypical climatic conditions in the region during fieldwork. Seasonal patterns of precipitation, observed in the tropical region, are closely related to the increase in amphibian richness and to the greater number of species in reproductive activity (Vasconcelos & Rossa-Feres 2005, Vieira et al. 2007. Therefore, it is essential for an efficient anuran sampling, mainly in semiarid regions, that the sampled takes place during the all rainy season. We identified 181 species of anurans in Caatinga and Cerrado biomes protected areas. This richness is likely higher, considering we only counted species published in the above-cited checklists, and we excluded species without specific identification ("gr.", "aff." and "sp."). Therefore, we would like to underline once again the expressive anuran diversity in these protected areas and in Sete Cidades National Park, since we registered about 17% of these species. Although direct comparison of species composition might be difficult in some cases due to the use of different collection methods and sampling efforts, SCNP is undeniably a key area of high biological diversity and of central interest for biodiversity protection.
Sete Cidades National Park was more similar to nearby protected areas in Piauí and Maranhão states, in the transition zone between Caatinga and Cerrado biomes. Besides the geographical distance between these areas, the concomitant presence of floristic elements of Caatinga and Cerrado and the similar sampling efforts used may account for their high anuran similarity. Despite most species registered in the present study being widely distributed or occurring in both Caatinga and Cerrado biomes, the formation of two clusters (Caatinga biome protected areas and Cerrado biome protected areas), and the result of our Mantel test suggests that geographic distance might help explain anuran dissimilarity between more distant.
In addition, we filled the distribution gap between the Ibiapaba Plateau, state of Ceará (Loebmann & Haddad 2010), about 100 km northeast of the Sete Cidades National Park, and the populations recorded in Mirador State Park, state of Maranhão (Andrade et al. 2017), about 539 km southwest of SCNP.
Although no SCNP amphibian species has been assessed as "threatened", three species deserve attention. Appropriate data on abundance and/or distribution is lacking for R. mirandaribeiroi and Adenomera juikitam, while it is impossible to attribute a conservation status for Scinax gr. ruber, as it was not identified to the specific level and likely correspond to one new species. In addition, an important revision about the species diversity and relationships in the Leptodactylus mystaceus complex reveled as candidate new species L. cf. mystaceus from localities near to SCNP (Silva et al. 2020). Therefore, we encourage taxonomic studies addressing these taxa in order to elucidate these questions about possible new anuran species in this protected area.
Habitat loss and fragmentation are important threats to biodiversity (Leal et al. 2005), and the maintenance of preservation areas is critical for environmental protection. Herein, we found a high species diversity in the ecotonal area of the SCNP in Piauí state, with the presence of both widely distributed common species and others predominantly to certain biomes. Although, in theory, amphibian fauna is safe within a protected area, this alone does not prevent population declines from occurring. The increase of amphibian declines worldwide has been attributed to various diseases, including infection by the fungus Batrachochytrium dendrobatidis (Scheele et al. 2019). It is important to highlight this fungus was already detected in northeastern Brazil, sometimes inside some protected areas (e.g. Carvalho et al. 2017, Amorim et al. 2019, close localities to near SCNP in Piauí state (Benício et al. 2019). Therefore, it is also important to investigate the anuran diversity in this protected area considering the amphibian declines worldwide.
This work contributes to the increase in our knowledge of amphibian diversity in the Northeastern region of Brazil. Our results show that SCNP when compared to other protected areas presents the highest anuran species richness in the state of Piauí and one of the two highest among all northeastern National Parks. We reinforce the need for further studies on the natural history, ecology and conservation of amphibians both inside and outside protected areas in Piauí state.