Anuran composition in a Brazilian semi-arid environment with notes on reproductive activity

1 Universidade Federal Rural do Semi-Árido. Av. Francisco Mota, 572, Costa e Silva, 59625-900, Mossoró, RN, Brasil. 2 Instituto Federal do Maranhão, Campus Avançado Carolina. Praça Santo Antônio, 93, Centro, 65980-000, Carolina, MA, Brasil. 3 Universidade Federal de Campina Grande, Unidade Acadêmica de Biologia e Química. Sítio Olho D’Água da Bica, 58175-000, Cuité, PB, Brasil. 4 Universidade Federal de Mato Grosso do Sul. Instituto de Biociências. Av. Costa e Silva, s/n, 79070-900, Cidade Universitária, Campo Grande, MS, Brasil. Jean Carlos Dantas de Oliveira1 jeancarlosdo@hotmail.com


Introduction
Studies on the biology and distribution of amphibians can generate important information about the quality of the environment itself, mainly in natural areas, working as a basis for the elaboration of effective management and conservation measures (Pereira et al., 2015).The Neotropical region comprises the largest diversity of anuran amphibians, with approximately one-third of the species known in the world (Duellman, 1999).However, mostly of the Caatinga amphibian inventories published to date have been conducted within protected areas and/or in humid areas of high altitude, being in fact areas that are better characterized as Rain Forest and/or Cerrado enclaves (Santana et al., 2015).
The Brazilian territory comprises 1080 known species of amphibians (Segalla et al., 2016), and this high diversity may be explained by the extensive domain of the landscape, formed by very heterogeneous ecosystems.Nevertheless, the knowledge about amphibian diversity in Brazilian biomes is scarce (Vieira, 2007), and this animal group has one of the highest rates of decline in several places in the world (Stuart et al., 2004).The main reasons for these declines are the increasing climate change, the intense destruction of their natural habitats, infectious diseases from the high degrees of pollution, invasive species, ultraviolet radiation and illegal trade (Young et al., 2004).
Among the Brazilian morphoclimatic domains, the Caatinga biome is represented by a mosaic of xerophilous, thorny and shrub vegetation, inserted in a semi-arid region, covering an area of 844,453 square kilometers, corresponding to 11% of the Brazilian territory, but little protected and studied (Leal et al., 2003).Despite being neglected with a small parcel protected by conservation units, the Caatinga has a diverse biological heritage, in which recent studies (Arias et al., 2001(Arias et al., , 2011;;Passos et al., 2011;Magalhães et al., 2014;Santana et al., 2015) have described new species in the semi-arid regions, demonstrating that, contrary to that many stated previously, this domain is not poor in species or endemism, although still poorly sampled (Pessoa et al., 2012).
The Caatinga has regional characteristics, such as backwoods areas, a term used in the northeastern states to designate the driest part of the biome where vegetation reflects these environmental conditions.The Brazilian semiarid region has shallow soils, irregular pluviometrical precipitations, contrasting with prolonged droughts and ephemeral torrential rains (Araújo et al., 2016).The species of anurans that present reproductive modes dependent on accumulated water gather in these aquatic habitats suitable for oviposition and larval development, forming aggregations with high inter and intraspecific potential (Bertoluci and Rodrigues, 2002).The use of different microhabitats as reproductive sites facilitates spatial partitioning by anu-rans, and the reproductive activity of these individuals is strongly influenced by the availability of water bodies and mild temperatures (Ferreira-Silva et al., 2016).
There are large gaps in relation to the distribution of species of anurans amphibians in the northeastern semiarid region and few studies are developed in this environment, avoiding better directions in conservation and management actions for the amphibian fauna of this region.About the knowledge of the anurans of the semi-arid region of the state of Paraíba, few studies were held, highlighting Vieira et al. (2007), Protázio et al. (2015) and Costa et al. (2016).Within this context, our aim in this work was to analyses the community composition of anuran amphibians in an area inserted in the Caatinga biome, in Northeast Brazil, evaluating also whether there is a relationship between number of species and vocal activity vs. precipitation.Observations on reproductive activity and use of microhabitats are also reported.

Study area
The Cajueiro Farm (6°20'38"S, 37°44'48" W) belongs to the Human and Agrarian Sciences Center of the State University of Paraíba (UEPB), Campus IV, located in the municipality of Catolé do Rocha, Paraíba, located in the semi-arid region of the Brazilian Northeast, with an average altitude of 270 m above the sea level.It has a hot semi-arid climate, with summer rains, and a dry weather predominating in an average of five to seven months.According to the Köppen-Geiger classification, it is a tropical savanna climate with dry winter (Aw) (Kottek et al., 2006).The average annual rainfall is approximately 850 mm and its average temperature ranges from 26 to 27ºC.The vegetation is of the Caatinga-Backwood type (Beltrão et al., 2005).
The study site has an area of 112 hectares, is covered by Caatinga physiognomy of the type tree and shrub rich in thorny plants, cactaceous and several fruit species, with the presence of streams, reservoirs, wetlands and hillside areas.We collected the specimens in the farm pond, which presented water throughout the study period.The vegetation in its surroundings is represented by arboreal-shrub Caatinga besides the presence of grasses and sandy soil with the presence of rocks.We obtained the values of rainfall (Table 1) through the Executive Agency of Water Management of the State of Paraíba (AESA, n.d.).
We conducted the field samplings monthly, from November 2013 to June 2014, for two consecutive days.Species were recorded through active visual and auditory search limited by time (Heyer et al., 1990)

Data analysis
To evaluate the efficacy of the capture methodology, a sample-based rarefaction (species accumulation curve) was generated, based on a presence-absence data matrix.We performed a Pearson regression analysis between number of recorded species and vocal activity and rainfall.
Regarding reproductive activities, we recorded 13 species by vocalizing.This behavior was observed in all months of research, with high variation in the number of vocalizing species (Table 2).The lowest number was recorded in November 2013, with the vocalizing of only Pseudopaludicola pocoto.The maximum registered number of vocalizing species occurred in February 2014 (Table 2).Individuals of P. pocoto showed the higher activity of vocalization, presenting the behavior in seven of the eight months of collection, followed by B. raniceps and D. nanus who vocalized in six of the eight months (Table 2).In relation to the use of microhabitats, two species (L.macrosternum and R. jimi) were the ones with the highest distribution, with records on three types of microhabitats (sand, water and stone).Seven species used two microhabitats (Table 2).The microhabitats used by these species were: (i) shrubs and aquatic vegetation, for D. nanus and B. raniceps; (ii) sand and stone by S. x-signatus and P. pocoto and (iii) sand and water by P. albifrons, P. kroyeri and P. diplolister.We also recorded eight species in only one microhabitat.The substrates used by these species were: (i) sand (R. granulosa, L. fuscus, L. troglodytes and P. cristiceps) and (ii) shrub (P.nortestina) and water (L.vastus and P. cicada) (Table 2).
Even with rain during all the months of collection, the highest number of species, with higher intensity of vocalization activity among the anurans was observed in the period with the highest rainfall values, mainly in the months of February and March.However, there is no relationship between vocalization and rainfall (r = 0.23; p = 0.56) (Figure 5a).In this period, we also recorded a high number of species, with 14 of the 17 anurans recorded.However, there is no relationship between the number of species recorded and rainfall (r = 0.18; 0.67) (Figure 5b).

Discussion
A total of 19 species registered at the Cajueiro Farm are considered typical of occurrence in the Caatinga (Rodrigues, 2003), including a species recently described (Pseudopaludicola pocoto) (Magalhães et al., 2014).In the semi-arid region of Paraíba Cariri, 16 species are known (Vieira et al., 2007), of which 13 were recorded in the present study.A similar richness (17 species) was recorded in another area of Caatinga (Abrantes et al., 2011), of which 11 occur in Cajueiro Farm.Comparisons with the anurans recorded in a remnant of Caatinga in the Pernambuco semi-arid region, with 23 recorded species (Pereira et al., 2015), and another work in an ecotone of Atlantic-  Caatinga Forest in the state of Rio Grande do Norte, with a total of 34 species of anurans (Magalhães et al., 2013), 16 species of our study are shared.However, the species P. kroyeri recorded here was not found in any of the studies cited previously.This sharing of species in these areas demonstrates a similar fauna in regions under the Caatinga domain, while the greatest richness found by Magalhães et al. (2013) is probably related to the location of the area studied by them in a transition region with the Atlantic Forest domain.Despite the fact that all these inventories have different sampling effort (e.g.area, time), such comparison is imperative to better understanding geographic patters of anurans in this poorly sampled domain.
The prevalence of the Leptodactylidae and Hylidae families regarding the other anuran families is recurrent in studies in the semi-arid region (e.g.Vieira et al., 2007;Cunha et al., 2010;Pereira Jr et al., 2003;Magalhães et al., 2014;Pereira et al., 2015), demonstrating that these families are more abundant and diversified in this area.The abundance of L. macrosternum and P. pocoto recorded in most of the samplings also occurred in other studies performed in the region (Magalhães et al., 2013;Pereira et al., 2015), explaining their dominance in relation to the others.
The concentration of rainfall in season of semi-arid regions, causes oscillations in water volumes of water bodies used by anurans, thus affecting, the number of species that breed in these environments (Abrantes et al., 2011) and, consequently, the dynamics of seasonal distribution of the anurans present in these areas.In this context, the non-relation between reproductive/vocalization activity and species richness with rainfall may be related to the constant presence of water in the study area, due to the reservoir that presented water throughout the sample period, which facilitates the permanence of the species in the environment.
The range of the Hylidae family in the use of the different microhabitats may be related to the fact that the hylids present a greater vertical segregation in relation to the families with representatives of terrestrial habits (e.g.Bufonidae, Leptodactylidae and Microhylidae) (Pereira Jr et al., 2013).Usually, the choice of diverse microhabitats allows species coexistence (Melo et al., 2003(Melo et al., , 2007;;Conte and Rossa-Feres, 2007).The overlap in the use of microhabitats is possibly associated with the reproductive mode of the anuran species from the Caatinga biome, which present behavioral specializations to avoid excessive loss of water.These factors may explain not only the overlap of microenvironments, but also the greater species diversity for periods with higher rainfall concentrations.
Studies of this nature, developed outside a protected area, are of extreme importance.Besides, the studied re-gion is poorly sampled, and with strong anthropogenic pressures, in many cases due to the lack of knowledge of the composition and richness of the species that inhabit these localities.Thus, the enhancement of the basic knowledge is essential to draw up plans for the conservation of the biota.

Figure 4 .
Figure 4. Anuran accumulation curve at Cajueiro Farm, Paraíba semi-arid region, Northastern Brazil.The black line represents the accumulation curves, the red line represents estimates of species based on Jacknife1 and the red dashed lines represent their confidence interval (95%).

Table 1 .
, starting at 6h p.m. until 9h p.m., totaling 96 hours/man of sample effort.Data on reproductive activity of individuals were also recorded, including vocalization and/or amplexus, calling season, as well as types and use of microhabitat(shrub, water, sand, stone, aquatic vegetation).Voucher specimens were killed following the resolution 714 of the Federal Council of VeterinaryMedicine (2002), by means of hyper doses of anesthetic lidocaine 5%, fixed with 10% formaldehyde and preserved in alcohol 70%.All voucher specimens are housed in the didactic collection of the Laboratory of Zoology of the Federal University of Campina Grande (UFCG/Cuité, PB) (Collection License Nº. 82872297, Chico Mendes Institute for Biodiversity Conservation).Accumulated rainfall values at Cajueiro Farm, Catolé do Rocha, Paraíba semi-arid region, Northeast Brazil, in the period from November 2013 to June 2014.List of anuran species recorded at the Cajueiro Farm, Paraíba semi-arid region, Northastern Brazil, from November 2013 to June 2014.

Table 2 .
Reproductive patterns of the 17 anurans species recorded in the sampling period from November 2013 to June 2014 at the Cajueiro Farm, Paraíba semi-arid region, Northastern Brazil.