Acta Herpetologica 11(1): 47-52, 2016 ISSN 1827-9635 (print) © Firenze University Press ISSN 1827-9643 (online) www.fupress.com/ah DOI: 10.13128/Acta_Herpetol-16940 Population structure and activity pattern of one species of Adenomera Steindachner, 1867 (Anura: Leptodactylidae) in northeastern Brazil Maria Juliana Borges-Leite1,*, João Fabrício Mota Rodrigues2, Patrícia De Menezes Gondim1, Diva Maria Borges-Nojosa1 ¹ Programa de Pós-Graduação em Ecologia e Recursos Naturais, Departamento de Biologia, Universidade Federal do Ceará – UFC, Campus do Pici, CEP 60455-760, Fortaleza, CE, Brazil. *Corresponding author. E-mail: jborgesleite@gmail.com 2 Programa de Pós-Graduação em Ecologia e Evolução, Departamento de Ecologia, Centro de Biociências, Universidade Federal de Goiás – UFG, Campus Samambaia, CEP 74001-970, Goiânia, GO, Brazil Submitted on 2015, 23rd September; revised on 2015, 8th November; accepted on 2015, 16th November Editor: Fabio Maria Guarino Abstract. We analyzed the population structure and sexual size dimorphism of an Adenomera species occurring in the municipality of São Gonçalo do Amarante, from September 2010 to August 2011, using pitfall traps and active search- es. We captured 116 individuals; 36 males, 23 females and 57 juveniles. Sexual size dimorphism was not observed. The smallest individuals were found in the middle of the rainy season, and the higher abundance of juveniles during this period may be related to recruitment. Females were captured in pitfall traps more often than males, while males were captured during active searches more often than females due to their calling behavior. We provide basic information regarding this Adenomera population, located in a region of severe environmental degradation, which may serve as a source of information for future studies of the area aiming to evaluate how the construction of industrial complexes affects anuran populations. Keywords. Amphibian, Ceará, Leptodactylus marmoratus group, sexual size dimorphism. Constant environmental degradation, mainly caused by human action, has brought about serious changes in global diversity, with habitat loss being the greatest threat to biodiversity (Vitousek et al., 1997). Elimina- tion or modification of specific anuran microhabitats has been considered the main factor responsible for popula- tion declines of several species of this taxonomic group (Young et al., 2001; Becker et al., 2007). Basic information studies detailing the popula- tion structure of anurans have increased over the years, but they are concentrated in biomes such as the Cerrado (Giaretta and Menin, 2004; Kokubum and Giaretta, 2005; Giaretta et al., 2008), Neotropical rainforest (Sá et al., 2014) and Amazon forest (Menin et al., 2007; Kokubum and Sousa, 2008; Waldez et al., 2011). Some studies report data on the abundance, size classes and population recruitment (which mainly occurs in the wet period) of amphibian species, and sexual dimorphism, with females typically larger than males (e.g., Giaretta and Menin, 2004; Kokubum and Giaretta, 2005; Kokubum and Sousa, 2008; Waldez et al., 2011). In addition, adult and juvenile size, and sex-ratio data are important to better under- stand the population structure, expanding on knowledge that generally focuses on reproduction and diet. Members of the genus Adenomera are recognized by their small size (snout vent length average is 18-25mm), have terrestrial habits and some species lay their eggs in underground chambers with tadpoles completing devel- opment in foam nests (Angulo et al., 2003; Kokubum and Giaretta, 2005; Kok et al., 2007; Kokubum and Sousa, 2008), or in pools originated by flooding of the nest (De la Riva, 1995; Almeida and Angulo, 2002; Carvalho and 48 Maria Juliana Borges-Leite et alii Giaretta, 2013) or in holes in fallen tree trunks (Menin and Rodrigues, 2013). In this paper, we aim to analyze the population structure, the activity pattern, and sexual size dimorphism of one species of Adenomera in an area that suffers strong disturbance due to the installation of an industrial complex. Furthermore, we aim to expand the knowledge of the Adenomera group, and provide data for future studies that seek to resolve its current taxo- nomic confusion. We performed the fieldwork in the municipality of São Gonçalo do Amarante, Ceará state, Brazil (Fazenda Maceió da Taíba: 03°30’54”S, 38°55’07”W) from Septem- ber 2010 to August 2011. The climate is defined by two periods: dry (July-December) and rainy (January-June). Mean annual rainfall is 1,026 mm and mean annual tem- perature is 27°C (FUNCEME–Fundação Cearense de Meteorologia e Recursos Hídricos). The study area is a forest fragment mostly composed of coastal, inter-dune, semi-deciduous forest (mata de tabuleiro), where approxi- mately 382 plant species have been recorded (Castro et al., 2012), largely consisting of small trees. The nearest water source is an inter-dune pond located approximately 500 to 1000 meters from the sampling point. We conducted samplings once a month lasting three days per field trip to observe a population of Adenomera sp. This undescribed species has been recorded until now only from São Gonçalo do Amarante (Borges-Leite et al., 2014), and has been analyzed and confirmed by experts as a new species (Kokubum, pers. comm.). This species has a seasonal reproductive pattern with breeding occur- ring only in wetter months, and tadpole development has no aquatic stage (Borges-Leite et al., 2015). Active searches, unlimited by time, were performed by two people mainly in areas of forest without a water source, from 3 p.m to 12 a.m. Pitfall traps were also dis- posed in a forest fragment of semi-deciduous forest (mata de tabuleiro), but in a different location to those used for active searches. Pitfall traps were composed of a five-station line; each station (trap) consisting of four plastic buckets of 60 L arranged in a “Y” (Heyer et al., 2001), totaling five traps per day of effort. We sexed all captured individuals based on external morphology (shovel-shaped snout on males) and meas- ured snout-vent length (SVL) with a digital caliper (accu- rate to 0.01 mm) to ascertain the presence of sexual size dimorphism. To classify individuals as juvenile or adult, we used the method of Waldez et al. (2011), in which the size of the smallest calling male is used to classify juve- nile individuals (juveniles had SVL < 18.8 mm in our study). Individuals larger than 18.8 mm were classified in males or females according to the external morphology described above. We used Welch’s t test to analyze sexual dimorphism in snout-vent length, since this variable had a normal distribution. We used the Kruskal-Wallis (K-W) test to evaluate variation in SVL of juveniles, males, females, and the total population between the months in which they were sampled. We used Chi-Squared tests to evaluate the number of males and females captured in each sampling method used in this study (active searches and pitfall traps). All statistical analyses were performed using stats packages available in R, version 2.13.2 (R Development Core Team, 2014). The alpha value was set to 5% for all statistical tests. Descriptive statistics are presented in this paper as mean ± standard deviation. After 12 months of sampling, the applied effort was 180 traps × days (five pitfall traps × three days × 12 months) and 720 hours of active searches (10 hours × three days × 12 months × two persons). We captured 116 individuals: 36 males, 23 females and 57 juveniles (Fig. 1-2 and Table 1). Adult females were captured in all sam- plings during the rainy season (January-June) and adult males were captured between January and April. We cap- tured juveniles from February to June, with a peak in number in May. Juveniles were sampled throughout the rainy season, except at its onset, in January, and their size varied during the sampling period (K-W test, H = 37.68, df = 4, P < 0.001, Fig. 3A), being small at the beginning of the rainy season and larger close to the dry season. Males had SVL ranging between 18.8-22.6 mm (mean = 20.77 ± 0.87 mm, n = 36), while females ranged between 18.8-25.5 mm (mean = 21.46 ± 1.94 mm, n = 23). The size of males did not change during the study (K-W test, H= 2.38, df = 3, P = 0.50, Fig. 3B), but SVL of females (K-W test, H = 11.49, df = 4, P = 0.04, Fig. 3C) and the total population (K-W test, H = 43.81, df = 4, P < 0.001, Fig. 3D) were larger at the beginning of the rainy season. There was no evidence of sexual dimorphism in size (t = 1.62, df = 27.66, P = 0.11). Morphological dif- ferences between males and females were observed, with males having a more shovel-shaped snout. The propor- tion of males and females captured in pitfall traps was significantly different with a higher number of females than males captured (χ2 = 17.19, df = 1, P < 0.001; Table 1). The captures were also sex-biased in active searches, with a higher number of males than females (χ2 = 26.95, df = 1, P < 0.001; Table 1). Significant differences in sex ratio with a male-biased sample may result from behavioral differences between the sexes (Giaretta and Menin, 2004) or even the choice of sampling method (Fogarty and Vilella, 2002). Active search, for example, may bias the result of the sex ratio towards males (Fogarty and Vilella, 2002; Waldez et al., 2011). The male-biased capture in active search may be 49Population structure and activity pattern of one species of Adenomera Fig. 1. Snout-vent length (SVL) class-size distribution in Adenomera sp. females, males and juveniles. Fig. 2. Number of Adenomera sp. males, females and juveniles sampled each month from January – June 2011 at São Gonçalo do Amarante, Ceará, Brazil. 50 Maria Juliana Borges-Leite et alii due to researchers being guided by the calling behavior of males, while females go unnoticed. This bias was also found in our results for active searches (Table 1). In most anurans, there is no difference in activ- ity pattern between males and females (Lemckert, 2004). However, we found that females were captured in pit- fall traps more frequently than males, suggesting higher mobility for this sex because active animals are more captured by this trap than inactive ones. Females usual- ly use larger areas than males due to increased energetic demands and nutritional requirements (Muths, 2003). This difference in movement pattern was not observed by Kokubum and Giaretta (2005), who found a non-signifi- cant difference in the number of individuals of each sex captured in pitfall traps in Uberlândia, Minas Gerais. Amphibians that have a long reproductive period can recruit juveniles during most of the year (López et al., 2011). Some studies of species with terrestrial repro- duction showed that a peak in reproductive activity and juvenile growth occurs in the rainy season (Moreira and Lima, 1991; Ovaska, 1991; Kokubum and Giaretta, 2005; Borges-Leite et al., 2015). Once the number of juveniles is increasing in the population, a decrease in the aver- age body size of the population is expected, as previ- ously observed in other genera, suggesting the occur- rence of recruitment events (Menin et al., 2007; Waldez et al., 2011). In our study the rainy season was marked by a variation in the size and number of captured juve- niles, and by the occurrence of a greater abundance of juveniles than adults in the last months of the season. These characteristics suggest the existence of recruit- ment events in this population in the rainy period, begin- ning in February and peaking in May. This recruitment can also be observed by the decrease in SVL of the total population during the study (Fig. 3D). It can also be seen that in May, three months after recruitment started, the size of females is smaller than in previous months, indi- cating that some of the individuals previously classified as juveniles have already become adult. This observa- tion in females supports the results of Sá et al. (2014), with regard to adult body size variation in anurans with prolonged reproduction, although we did not find the same variation in males. Although there are some stud- Table I. Number and sex of Adenomera sp. individuals captured using pitfall traps and active search methods. Categories Method of capture Pitfall traps Active searches Male 1 35 Female 20 3 Fig. 3. Variation in snout-vent length of Adenomera sp. from Janu- ary – June 2011. A) Juveniles; B) Males; C) Females; and D) Total population (1 = January, 2 = February, 3 = March, 4 = April, 5 = May and 6 = June). 51Population structure and activity pattern of one species of Adenomera ies in Brazilian coastal regions focusing on reproductive patterns and sexual dimorphism of anurans (e.g. Gias- son and Haddad, 2007), to our knowledge, our study is the first to explore the population structure of a coastal anuran. Our study showed that in this population of Adenomera there is no sexual size dimorphism, contrary to 90% of frog species in which females are larger than males (Shine, 1979) and also to other species of the genus Adenomera (e.g. Kokubum and Giaretta, 2005; Kok et al., 2007). This sexual difference in anurans may arise, for example, because females delay their reproduction and invest more time in growth than males, which grow up fast and start reproductive activity early (Zhang and Lu, 2013). However, in an environment where the rainy season is reduced, such as in our study area, it may be advantageous for females not to delay reproduction. We conclude that juvenile recruitment in this popu- lation of Adenomera occurs in the rainy season, and there was no sexual size dimorphism. Hence, we add new important data to the problematic Adenomera group. The taxonomic problems of this group, which include great intra- and inter-population morphological variation and cryptic species (De la Riva, 1996; Angulo et al., 2003), need more population studies in order to help under- stand its variation. Regarding the population from São Gonçalo do Amarante, this study may be a starting point for future studies aiming to evaluate the impact of the Port and Industrial Complex over a year-long interval in an anuran population. At the current moment, the Ade- nomera population has a high recruitment, favoring its maintenance, but only future detailed studies will be able to evaluate its ability to co-occur alongside strong human disturbance. ACKNOWLEDGEMENTS We thank Mr. and Mrs. Borges for accommodation and permission to use their property for research; the Instituto Chico Mendes de Conservação da Biodiversi- dade (ICMBio) for collection permits (authorization # 25935-1 - SISBIO); and Daniel Cassiano, Rafael Carval- ho and James Harris for reviewing the manuscript and providing interesting suggestions. M.J. Borges-Leite and J.F.M. Rodrigues thank CAPES for a graduate fellowship. REFERENCES Almeida, A.P., Angulo, A. (2002): Adenomera aff. marm- orata (NCN). Reproduction. Herpetol. 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