bioRxiv preprint doi: https://doi.org/10.1101/2020.07.31.229310; this version posted August 3, 2020. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC-ND 4.0 International license. Anuran assemblage changes along small-scale phytophysiognomies in natural Brazilian grasslands Diego Anderson Dalmolin1*, Volnei Mathies Filho2, Alexandro Marques Tozetti3 1 Laboratório de Metacomunidades, Departamento de Ecologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil. 2 Fundação Universidade Federal do Rio Grande, Rio Grande, Rio Grande do Sul, Brasil 3Laboratório de Ecologia de Vertebrados Terrestres, Universidade do Vale do Rio dos Sinos, Avenida Unisinos 950, 93022-000 São Leopoldo, Rio Grande do Sul, Brazil. * Corresponding author: Email: [email protected] bioRxiv preprint doi: https://doi.org/10.1101/2020.07.31.229310; this version posted August 3, 2020. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC-ND 4.0 International license. 1 Abstract 2 We studied the species composition of frogs in two phytophysiognomies (grassland and 3 forest) of a Ramsar site in southern Brazil. We aimed to assess the distribution of 4 species on a small spatial scale and dissimilarities in community composition between 5 grassland and forest habitats. The sampling of individuals was carried out through 6 pitfall traps and active search in the areas around the traps. We evaluated the existence 7 of these differences by using permutational multivariate analysis of variance and 8 multivariate dispersion. We found 13 species belonging to six families. Leptodactylidae 9 and Hylidae were the most representative families. The compositional dissimilarity was 10 higher between the sampling sites from different phytophysiognomies than within the 11 same phytophysiognomy, suggesting that forest and grassland drive anuran species 12 composition differently. Also, the difference in anuran species composition between the 13 sampling sites within the forest was considerably high. Based on our results, we could 14 assume that the phytophysiognomies evaluated here offer quite different colonization 15 opportunities for anurans, especially those related to microhabitat characteristics, such 16 as microclimate variables. 17 18 19 20 21 Keywords 22 Dissimilarity; anuran; south Brazil; Taim; forest; grasslands 23 24 25 26 27 28 bioRxiv preprint doi: https://doi.org/10.1101/2020.07.31.229310; this version posted August 3, 2020. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC-ND 4.0 International license. 29 Introduction 30 31 The composition of species in communities is a result of a complex interaction between 32 organisms and environmental characteristics. The presence of a singular species in an 33 assemblage depends on intrinsic (such as the individual's physiological needs for 34 homeostatic maintenance) and extrinsic processes (such as competition, predation and 35 other biotic interactions). Combined, both of them determine the possibility of a given 36 species to colonize a habitat, as well their long-term maintenance in there (Schluter & 37 Ricklefs 1993; Ximenez et al. 2014). It is assumed that heterogeneous habitats comprise 38 a richer biota (Semlitsch et al. 2015) since they offer many different microhabitats, 39 which precisely favors the establishment of species without high niche overlap 40 (Barrows & Allen 2010; Oliveira et al. 2013) 41 The concept of habitat heterogeneity is related to much confusion, being frequently used 42 as a synonym of habitat complexity. The process of describing and evaluating the 43 habitat structure is one of the challenges for carrying out ecological studies (Stein & 44 Kreft 2015). In structural terms, environments can be described by (i) their complexity - 45 vertical development of vegetation - and (ii) their heterogeneity - horizontal variation in 46 descriptors such as density, dominance and frequency of plant species that compose 47 them (August 1983). In a review on the topic, Tews et al. (2004) defend the idea that the 48 concept of habitat heterogeneity includes both vertical and horizontal structure of plant 49 community - a concept adopted in the present study. The possibility of assessing the 50 effect of habitat heterogeneity on the structuring of their communities comes up against 51 the huge number of areas never sampled in the Neotropical region (Garcia & 52 Vinciprova 2003). This fact also has implications for the establishment of conservation 53 strategies for potentially threatened species - as is the case with many Brazilian anurans 54 (Silvano & Segalla 2005). 55 The variety of available habitats and the high levels of species endemism throughout the 56 Brazilian biomes makes it an adequate location to assess the role of environmental 57 heterogeneity in the activity patterns and community structure of anurans (Silvano & 58 Segalla 2005). However, most studies on anuran ecology in Brazil are concentrated in 59 forest environments, especially in the Cerrado and the Atlantic Forest biomes (da Silva 60 et al. 2011a; Iop et al. 2012; Prado & Rossa-Feres, 2014; Saccol et al., 2017). The bioRxiv preprint doi: https://doi.org/10.1101/2020.07.31.229310; this version posted August 3, 2020. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC-ND 4.0 International license. 61 Pampa grassland formations and the coastal portion of southern Brazil are home to 62 anuran species that are common in open habitats (Núñez et al. 2004, Vasconcelos et al. 63 2019; Dalmolin et al. 2019). Although the landscape of these environments consists 64 predominantly of open areas (Machado et al. 2012), some forest patches can also be 65 observed (such as swamp forests and dry or sandy forests). 66 Studies that describe changes in amphibian assemblages over structural changes in 67 vegetation cover can contribute to propose scenarios of landscape changes (Da Silva et 68 al. 2011a). The process of forests expanding over grasslands under climate change or 69 even converting forested areas into human use would reflect changes in the amphibian 70 composition (Manenti et al. 2013; Oliveira & Rocha 2015). In this sense, our work 71 aimed to: (i) verify the distribution of anuran species on a small spatial scale; (ii) 72 describe the association between the patterns of dissimilarity in anuran composition 73 between communities of different phytophysiognomies (forest and grassland). 74 The study design on a small spatial scale is interesting to assess adjacent habitats whose 75 probability of colonization is theoretically the same for all species in the region 76 (Ximenez et al. 2014). In addition, the habitat elements linked to the micro-habitat scale 77 are important descriptors of the spatial partition of species (Freitas et al. 2002, Oliveira 78 & Rocha 2015) in particular because they deal with transition zones in a refined way 79 (Bersier et al. 2007). The detection of differences in anuran assemblages between 80 habitats provides a strong indication of the segregation process of these species along a 81 vegetation gradient (Da Silva et al. 2011a; Prado & Rossa-Feres 2014). We expected to 82 find greater differences in composition in places belonging to different 83 phytophysiognomies than between areas belonging to the same phytophysiognomies, 84 since the environmental and microenvironmental conditions must be similar in these 85 areas, thus reducing their composition dissimilarity (Da Silva et al. 2011). 86 87 Material and Methods 88 89 Study site 90 bioRxiv preprint doi: https://doi.org/10.1101/2020.07.31.229310; this version posted August 3, 2020. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY-NC-ND 4.0 International license. 91 The study was carried out at the Estação Ecológica do Taim (ESEC Taim; S 92 32°32'16.6" W 052°32'16.7"), located in the municipality of Rio Grande, Brazil’s 93 extreme south (Figure 1). ESEC Taim encompasses ecosystems of great relevance and, 94 since 2017, was recognized as a Ramsar site (Ramsar Wetland of International 95 Importance; Ramsar, 2018). The landscape consists of wetlands and grasslands in 96 association with remnants of “restinga” and flooded forests, which are dominated by 97 cork trees (Erythrina crista-galli) and fig trees (Ficus organensis; Waechter & 98 Jarenkow 1998). 99 The climate of the region is humid sub-temperate, with an annual average temperature 100 of 18.1º C and average temperature of the coldest month of 12.7° C. The annual rainfall 101 is 1162 mm, with periods of drought in the spring and a higher incidence of rain in the 102 winter (Maluf 2000). The maximum temperature varied between 9.1° C and 39.3° C 103 during the study period (May 2011 to April 2012), with the hottest months being 104 February and March 2012; the minimum temperature varied between 0.9 ° C and 28.1 ° 105 C, with the coldest months being July and August 2011. Meteorological data were 106 obtained from the database provided by the Meteorological Station of the Universidade 107 Federal do Rio Grande (FURG), located in the municipality of Rio Grande. 108 109 Figure 1: Geographic location of the study area (Estação Ecológica do Taim) in the 110 state of Rio Grande do Sul, Brazil.