A new species of Chaunus from Central Brazil : Anura; Bufonidae

A new species of Chaunus, apparently related to Chaunus arenarum, Chaunus rubescens, and Chaunus achavali is described. The new species occupies Cerrado habitats in southwestern Piauı´ and Bahia states and in northwestern Minas Gerais state, Brazil. The species is characterized by anterior interruption of the supraocular crest; weakly developed cranial crests; short and robust limbs; several pointed spiculae on dorsum, head, and limbs; male coloration; small to medium size; and by the short and narrow head

Evolution in the Genus Rhinella: A Total Evidence Phylogenetic Analysis of Neotropical True Toads (Anura: Bufonidae)

True toads of the genus Rhinella are among the most common and diverse group of Neotropical anurans. These toads are widely distributed throughout South America, inhabiting a great diversity of environments and ecoregions. Currently, however, the genus is defined solely on the basis of molecular characters, and it lacks a proper diagnosis. Although some phenetic species groups have traditionally been recognized within Rhinella, the monophyly of some of them have been rejected in previous phylogenetic analyses, and many species remain unassigned to these poorly defined groups. Additionally, the identity and taxonomy of several species are problematic and hinder the specific recognition and description of undescribed taxa. In this work, we first perform phylogenetic analyses of separate mitochondrial and nuclear datasets to test the possible occurrence of hybridiza-tion and/or genetic introgression in the genus. The comparative analysis of both datasets revealed unidirectional mitochondrial introgressions of an unknown parental species into R . horribilis (“ghost introgression”) and of R . dorbignyi into R . bernardoi; therefore, the mitochondrial and nuclear data-sets of these species were considered separately in subsequent analyses. We performed total-evidence phylogenetic analyses that included revised molecular (four mitochondrial and five nuclear genes) and phenotypic (90 characters) datasets for 83 nominal species of Rhinella, plus several undescribed and problematic species and multiple outgroups. Results demonstrate that Rhinella was nonmono-phyletic due to the position of R . ceratophrys, which was recovered as the sister taxon of Rhaebo nasicus with strong support. Among our outgroups, the strongly supported Anaxyrus + Incilius is the sister clade of all other species of Rhinella. Once R . ceratophrys is excluded, the genus Rhinellais monophyletic, well supported, and composed of two major clades. One of these is moderately supported and includes species of the former R . spinulosa Group (including R . gallardoi); the mono-phyletic R . granulosa, R . crucifer, and R . marina Groups; and a clade composed of the mitochondrial sequences of R . horribilis. The other major clade is strongly supported and composed of all the spe-cies from the non-monophyletic R . veraguensis and R . margaritifera Groups, the former R . acrolophaGroup, and R . sternosignata. Consistent with these results, we define eight species groups of Rhinella that are mostly diagnosed by phenotypic synapomorphies in addition to a combination of morpho-logical character states. Rhinella sternosignata is the only species that remains unassigned to any group. We also synonymize nine species, treat three former subspecies as full species, and suggest that 15 lineages represent putative undescribed species. Lastly, we discuss the apparently frequent occurrence of hybridization, deep mitochondrial divergence, and “ghost introgression”; the incomplete phenotypic evidence (including putative character systems that could be used for future phy-logenetic analyses); and the validity of the known fossil record of Rhinella as a source of calibration points for divergence dating analyses.Peer reviewe

On the taxonomic status of Bufo brasiliensis Laurenti, 1768

Valencia-Zuleta, Alejandro, Caramaschi, Ulisses, Maciel, Natan M. (2018): On the taxonomic status of Bufo brasiliensis Laurenti, 1768. Zootaxa 4392 (3): 598-600, DOI: https://doi.org/10.11646/zootaxa.4392.3.1

Rhinella cerradensis Maciel, Brandão, Campos & Sebben, 2007, sp. nov.

Rhinella cerradensis sp. nov. (Figs. 1–3) Holotype: Coleção Herpetológica da Universidade de Brasília (CHUNB 49573), adult male collected at Centro de Instrução e Adestramento de Brasília, Brasília, Distrito Federal, Brazil (14 ° 49 'S; 45 ° 58 'W) in November 2002, by N.M. Maciel, R.H. Matsushita, A.Q.Teixeira Jr., and B. A. Duar. Paratypes: CHUNB 40276, 40277, 40280, 49281 (males), 40278, 40279 (females), collected along with the holotype; CHUNB 40273–40275 (females), collected at Rio Pratudão Farm, Correntina Municipality, Bahia State, in October 1996 by R.A. Brandão; CHUNB 13790–13791 (females), collected at Emas National Park, Mineiros Municipality, Goiás State, in November 1998 by R.A. Brandão; CHUNB 38669 (male), collected at Jardim Botânico, Brasília, Distrito Federal, in January 2001 by B.A. Duar; CHUNB 25043 (female), collected at Brasília, Distrito Federal, in September 2001 by O. R. Pires Jr.; CHUNB 38655, 38656 (females), 38658 (juvenile), collected at Trijunção Farm, Cocos Municipality, Bahia State, in October 2001, by R.A. Brandão; CHUNB 29386 (male), collected at Brasília, Distrito Federal, in August 2002 by D.S. Diniz; CHUNB 39979–39980 (females), collected at Trijunção Farm, Cocos Municipality, Bahia State, (data not recorded) by R.A. Brandão; CHUNB 39953 (female), collected at Centro de Instrução e Adestramento de Brasília, Brasília, Distrito Federal, in January 2003, by N.M. Maciel; CHUNB 38668 (male), collected at Centro de Instrução e Adestramento de Brasília, Brasília, Distrito Federal, in August, 2003, by N.M. Maciel, R.H. Matsushita, and R.A. Brandão (advertisement call recorded); CHUNB 38667 (female), 38670–38671 (males), collected at Trijunção Farm, Cocos Municipality, Bahia State, in October 2004, by R.A. Brandão, N.M. Maciel and A. Sebben; CHUNB 43864 (female), collected at São Domingos Municipality, Goiás State, in November 2004. Species measurements are provided in Table 1. Diagnosis and comparisons with other species: A medium to large sized species, similar to R. icterica, R. marina, R. poeppigii, R. schneideri, and R. jimi mostly by the well developed cranial crests, long and broad parotoid gland, head wider than long, and morphometric features (see morphometric analysis section). Rhinella cerradensis has the following unique combination of features within the R. marina group: medium to large size, (males 120.4 (± 13.4) mm, ranging 103.3–147.1 mm and females 114.5 (± 20.1) mm, ranging 82.1– 139.8 mm); head wider than long; well developed cranial crests, with evident spicules; snout in dorsal view mucronate to truncate and obtuse in lateral view; a medium sized parotoid gland, parotoid gland elliptical, yellowish, with a high density of keratinous pointed spicules; pointed spicules present on dorsal glands, fore, and hind limbs; tibial gland absent; dorsum uniform brownish to dark green and venter brownish white in males; females with brownish green dorsum, but with black coloration in many areas (sometimes also in hind limbs), resembling R. icterica female coloration; a jagged or “scalloped” suture formed by the articulation between the medial ramus of the pterygoid and the parasphenoid alae. The new species can be quickly distinguished from R. schneideri and R. jimi by the smaller body and parotoid gland size and by the absent of tibial gland (PGL in R. schneideri 28.9 (± 9.8) mm (n= 27), R. jimi 34.8 (± 11.8) mm (n= 9), and R. cerradensis 27.5 (± 7.7) mm (n= 18)). From R. icterica the new species can be distinguished by size of parotoid gland (larger and rounded in R. icterica, PGL = 29.7 (± 9.6) mm (n= 29)); by a less developed preocular crest; by narrow head (wide in R. icterica); by tympanum without folded skin (present in R. icterica); and by smaller hand (HAL in R. cerradensis 25.7 (±6.0) mm (n= 18) and in R. icterica 26.7 (± 6.1) mm (n= 29)). From R. marina, R. cerradensis can be distinguished by shape of parotoid gland (almost rounded in R. marina); by narrower and longer head (wider in R. marina). From R. veredas, it can be easily distinguished by complete supraocular crest and by dorsal coloration of the male. From R. rubescens, it can be distinguished by its larger size (SVL= 115.5 (± 26.4) mm (n= 18) in R. cerradensis and 69.1 (± 23.4) mm in R. rubescens (n= 49)); shape of parotoid gland (long and narrow in R. rubescens); wider head (LC= 23.2 (± 7.4) mm in R. rubescens (n= 49)); snout profile (sub-elliptical in dorsal view in R. rubescens), cranial crests developed (weakly developed in R. rubescens); and dorsal glands with keratinous spicules on body (smooth in R. rubescens). From R. arenarum, it can be distinguished by larger size (SVL= 87.3 (±11.0) mm in R. arenarum (n= 25)); parotoid gland shape (long and narrow in R. arenarum), by more developed cranial crests (weakly developed in R. arenarum); tongue long and narrow (rounded and short in R. arenarum); and by dorsal male coloration. From R. achavali it can be distinguished by larger size (SVL= 95.4 (± 6.2) mm in R. achavali (n= 5)), shape of parotoid glands (long and narrow in R. achavali); by dorsal male coloration; by pointed spiculae on body glands; and by the rough skin. Description of the holotype: General aspect robust (Fig. 1 A). Head wider than long; SVL approximately 2.7 × head width; snout mucronate to truncate in dorsal view and obtuse in lateral view (Figs. 3 A and 3 B); almost all cranial crests present and developed, parietal crest absent; pre-tympanic and rostral crests well developed; supranasal crest evident with rugosites, produced by cranial striations; supratympanic crest developed, in contact with the parotoid gland; cranial crests keratinized, especially the supraocular crest; loreal region smooth; nostrils large, with lateral elliptic openings directed upward; interorbital distance and eye diameter equal in length; eye diameter about 1.5 × tympanum diameter; eyelid large, with small keratinous spicules; tympanum visible, well developed, rounded; dorsum of head flat, with small rounded spicules. Parotoid gland evident, elliptical, with keratinous spicules; parotoid length about 2.6 × its width. Tongue longer than wide, smooth, with one single superficial central fold, free in its posterior end, attached to jaw; vomerine teeth absent; choanae elliptical. Fingers thin and developed (Fig. 3 C); forearm and arm robust; relative finger length II <IV <I <III; fingers without webbing; tips of fingers keratinized and dark in dorsal view; subarticular tubercles at base of all fingers; subarticular tubercles present between phalanges II and III of finger III, subarticular tubercles on phalange III of finger III; outer palmar tubercle large and rounded; inner palmar tubercle rounded at base of finger I. Nuptial pads evident, dorsally visible on fingers I and II. Toes with broad lateral fringes, toe tips keratinized and dark, relative toe lengths I <V <II <III<IV; small subarticular tubercles present on toes, between phalanges II and III on toes III, IV and V. Foot webbing present and well developed; foot webbing formula I 2 - 2 / 2 II 1- 3 III 2-3 / 2 IV 3 / 2 - 2 V; outer metatarsal tubercle small oval; inner metatarsal tubercle well developed and elongate, weakly keratinized. Metatarsal fringe present, beginning at tip of toe I, covering 2 / 3 of metatarsal length (the fringe is interrupted by inner metatarsal tubercle); plantar surface with small, conical callosities. Dorsal skin rough; dorsum covered by rounded and oval glands of different sizes; all glands with black and pointed keratinized spicules; spicule number varies with gland size; glands are smaller and more dense on anterior and posterior limbs. Measurements of holotype (in mm): SVL 109.9; HL 32.8; HH 21.0; HW 40.6; PGL 28.9; PGW 10.8; TD 8.8; ED 13.3; END 4.9; IOC 14.1; IOD 15.0; IND 7.5; FN/DFN 4.1; HAL 26.6; FAR 20.5; UAR 17.3; TIL 47.5; THL 49.8; TL 27.7; and FL 50.2. Morphometric analyses: The PCA suggests the presence of two morphological subgroups in species of R. marina group (Fig. 4). A subgroup of species represented by the white symbols, composed by R. marina, R. icterica, R. schneideri, R. jimi, and R. cerradensis and another represented by the black symbols, consisting of R. arenarum, R. rubescens, R. achavali, and R. veredas. The first two scores account for a total of 94.8 % of the variance. The first component accounts for 88.4 % of the variance and showed high and positive scores. The second component accounts for 6.4 % of the variance and showed positive higher values for tympanum diameter and foot and leg lengths, and negative values for parotoid gland length (Table 2). Examination of factor loadings suggested the formation of two subgroups. The first subgroup (white symbols) is composed of the larger sized species, with developed and marked cranial crests, relatively smaller tympanum, and shorter limb length. The second subgroup (black symbols) is formed by the smaller species with less developed cranial crests and relatively longer parotoid glands (Fig. 4). Coloration: Sexual dimorphism is well marked in coloration (Fig. 2). In life, males have a brownish green dorsum (sometimes a dark green dorsum) and a brownish white venter. Females have the same brownish green dorsum and brownish white venter of the male, but show black coloration in many areas of dorsum (sometimes also on hind limbs). In this respect, the females of this species resemble R. icterica females. The coloration of preserved specimens resembles the coloration of males and females in life, but the parotoid glands turn yellowish. Description of the tadpole: Descriptions are based on a tadpole series (CHUNB 49574) collected at Estação Rádio, Centro de Instrução e Adestramento de Brasília, Brasília Municipality, Distrito Federal on 31 August 2002, by N.M. Maciel and R.H. Matsushita. Tadpole series measurements are provided in Table 3. Measurements of the specimen used for description (Fig. 5) (in mm): BL 9.72; IND 1.30; IOD 2.90; MTH 4.30; TAL 12.64; TL 21.76; TMH 1.50; TMW 1.65. The specimen used for description is in stage 40 (Gosner, 1960) (Fig. 5). Body elliptical in lateral (Fig. 5 A) and dorsal views (Fig. 5 B). Body 76 % of tail length and 45 % of total length; body wider than deep; snout rounded in lateral and dorsal views; eyes dorsal, directed laterally; distance between eyes 2.2 × the distance between nostrils; nostril opening kidney shape; spiracle sinistral, near to midbody axis, opening in the body wall, without external tube. Vent tube medial (easily visible in tadpoles in early stages). Tail musculature gradually tapering to rounded tip. Caudal fin fusiform; dorsal fin about same height as ventral fin. Color in preservative uniform, dark brown. Oral disc anteroventral, and emarginated laterally in lower and upper jaw. LTRF 2 (2)/ 3 (1); A 2 slightly longer than A 1, P 1 slightly shorter than A 1 and longer than P 2 and P 3. Lower jaw serrate and shallowly V-shaped. The majority of tadpole specimens are in stages 40–42. The tadpoles in stage 42 differed from those in stage 40 mainly by the development of hindlimbs, presence of emerged forelimbs, more rounded snout, and shorter body. The tadpoles described from species of the R. marina group and those of the new species are similar in general shape (Rosa, 1951; Savage, 1960; Rosa, 1965; Cei, 1980; Heyer et al., 1990; Eterovick & Sazima, 1999). According to Eterovick & Sazima (1999) the tadpoles of R. rubescens are more similar to those of R. schneideri in body proportions and spiracle position, while the tadpoles of R. arenarum more closely resemble those of R. icterica. The tadpoles of the new species resemble R. rubescens and R. schneideri in body proportions and spiracle position. The tadpole of R. cerradensis can be diagnosed by body proportions, spiracle position, and the absence of an external spiracular tube, with the opening in the body wall (Fig. 5 A). The absence of an external tube is unique among the tadpoles described of the R. marina group. Osteological features: Skull with the robust general aspect of the species of Rhinella marina group (sensu Pramuk, 2006). The specimens analyzed have extremely well-ossified and exostosed crania that are ornamented with deep striations, pits, and rugosities. The cranium is wider than long, with the greatest width at the level of the quadratojugals, as it is characteristic of other species of the group. All cranial crests present, with the exception of the parietal crest (Fig. 6). The Arabic numbers between quotations marks in the text indicate skull features of the new species (see Fig. 6). A detailed description of cranial features follows. Alary process of premaxilla postero-lateraly positioned; premaxilary bones are miss in the figure, frequently split during osteological bufonid preparations; vertical process of maxilla flattened laterally but dilated medially, maxillary crest well developed (5) (Fig. 6 B and C); nasals in contact medially (1), anterior tips of nasals ventrally projected, ornamentations along edges forming the canthal (3) and supraorbital crests (4) (Fig. 6 A); vertical arm of nasals robust on top and flattened on bottom; anterior portion of frontoparietal with rectangular shape, posterior portion projected at posterior end of skull, composing apical part of foramen magnum (2); frontoparietal not contacting prootic process (2) (Fig. 6 A); medial area of frontoparietal large, with a portion that does not compound cranial box; this lateral portion bends in a plane approximately 90 ° relative to roof of skull, forming supraorbital crests; in this configuration there is no ventral groove for occipital artery. Supraorbital crests ornamented, composing a continuum with canthal crest; squamosal with a great mosaic of planes and processes, formed mainly by dorsal, vertical, and medial planes, medial plane blade-shaped, poorly developed, and projected to maxillary bone, horizontally oriented and poorly developed posteriorly; a large medial projection (otic plate) on top of squamosal; exoccipitals not fused one with another; a well developed prootic process that does not touch frontoparietal; a jagged or “scalloped” suture formed by articulation between pterygoid medial ramus (8) and the parasphenoid alae (7) (Fig. 6 B and 6 C; sensu Pramuk, 2006); neopalatine bone bearing a blade-like projection (Fig. 6 B and 6 C); dorsal surface of sphenethmoid covered completely by medial articulation of nasals and frontoparietals (6); nasals not expanded dorsolaterally (as they are in R. granulosa species group), and forming a transverse suture with frontoparietals; jaw articulation lies posterior to level of the fenestra ovalis; and with a complete temporal arcade (sensu Pramuk, 2006). Advertisement call: The recording was made at Centro de Instrução e Adestramento de Brasília, Brasília, Distrito Federal in August 15 2003, 22: 30 h. The air temperature was 17.1 ºC, with 73 % relative humidity. The specimen has SVL= 117.7 mm. The advertisement call graphics are shown in Figure 7. The calls were variable in duration (1.9– 12.4 s). Mean call rate was 9.8 ± 0.6 notes per second. (19–129 notes per call). Note rate and note interval were based on the means of 10 notes of the calls. The mean note rate was 44.7 (± 2.41) ms and the interval among note average 66.5 (± 2.17) ms; each note was formed by three pulses (Fig. 7 B). Dominant and fundamental frequencies were also determined from five notes from various parts of the calls. Mean dominant and fundamental frequencies were 839.0 (± 8.9) Hz and 421.0 (± 3.3) Hz, respectively. The advertisement call of R. cerradensis resembles that of other species in the R. marina group. Although the calls of the Rhinella marina species group are conservative, they present some differences. The notes per advertisement call of R. cerradensis is more variable than R. schneideri (33–40; Köhler et al., 1997), R. icterica (4–20; Heyer et al., 1990), R. poeppigii (10–45; De La Riva et al., 1996), R. arenarum (61–107; Straneck et al., 1993), R. marina (19–25; Crocroft et al., 2001), and R. rubescens (5–25) (present work). The number of pulses per note of the new species (three) is equal to those of R. schneideri (Köhler et al., 1997), and R. arenarum (Straneck et al., 1993), while in R. icterica they range from one to three (Heyer et al., 1990), three to five in R. poeppigii (De La Riva et al., 1996), five pulses in R. marina (Crocroft et al., 2001), and two pulses in R. rubescens (present work). The advertisement call of R. schneideri has a second power peak of 2100 Hz above the dominant frequency (Köhler et al., 1997). Rhinella icterica (Heyer et al., 1990), R. rubescens (Haddad et al., 1988), R. marina (Crocroft et al., 2001), R. poeppigii (De La Riva et al., 1996), R. arenarum (Straneck et al., 1993), and the new species lack the second power peak. However, the spectrogram of R. arenarum provided by Martin (1972) showed a second power peak above the dominant frequency. The re-analyzed call of R. icterica (Heyer et al., 1990) presented a lower fundamental and dominant frequencies of 324.9 (± 4.5) and 646.0 (± 0.2) Hz than R. cerradensis 421.0 (± 3.3) and 839.0 (± 8.9) Hz. Conversely, R. marina (Crocroft et al., 2001) showed higher fundamental and dominant frequencies of 559.9 and 1119.7 Hz (with no frequency variation among notes) among these three species (R. icterica, R. cerradensis, and R. marina). The advertisement call of R. arenarum (Straneck et al., 1993) presented a dominant frequency of 1348 (± 18.3) Hz, similar to R. rubescens, dominant frequency of 1015.6 (± 41.1) Hz. Etymology: “Cerrado” is the second largest South American biome and nearly restricted to Brazil. It can be characterized as a complex mosaic landscape composed of savanna, grassland and forest physiognomies, determined by soil fertility, natural fires, and water availability (Ribeiro & Walter, 2001). Despite the great number of endemic and rare species, the Cerrado is severely threatened by increasing deforestation, charcoal production, and large hydroelectric dams. As a result the Cerrado was recognized as one of the world’s biodiversity hotspots (Myers et. al., 2000). The known distribution of R. cerradensis is restricted to the Brazilian Cerrado biome. So, the specific name is in recognition of this important, poorly known and endangered biome; it is used as a noun in apposition. Distribution: Rhinella cerradensis has a large distribution in the Cerrado, occurring in the Brazilian states of Piauí, Bahia, Goiás, Minas Gerais, and Distrito Federal (Fig. 8). Natural history notes: Field observations were made in the states of Distrito Federal, Bahia, and Goiás. We have carried out studies at Centro de Instrução e Adestramento de Brasília (CIAB) since 2001. Rhinella cerradensis was observed in March (end of the rainy season), and August to October of 2002 (from dry season to just before the beginning of the rainy season), when periodical visits were made to the area. Adults were always found in open Cerrado physiognomies (Cerrado and Campo Sujo; see Ribeiro & Walter 2001 for an account of the Cerrado physiognomies). We observed the reproductive activity, recorded the advertisement call, and collected tadpoles. We found a carcass of an adult male of R. cerradensis completely eviscerated with untouched secretory parotoid glands. R. schneideri and R. rubescens were also found breeding in the same permanent pond at Brasília. In Emas National Park we recorded a Conepatus striatus (Mammalia: Mustelidae) feeding upon an adult R. cerradensis. The new species is sympatric with R. schneideri and R. veredas in western Bahia and Piauí states, and with R. schneideri, and R. rubescens in the states of Distrito Federal and Goiás. Until now few observations on the natural history of the new species exist, and only four advertisement calls have been recorded. The elongate and well developed inner metatarsal tubercle suggests that C. cerradensis might bury itself during the dry Cerrado season as do other Neotropical species (e.g., Eupemphix nattereri, Pleurodema diplolistris, and Odontophrynus cultripes).Published as part of Maciel, Natan M., Brandão, Reuber A., Campos, Leandro A. & Sebben, Antonio, 2007, A large new species of Rhinella (Anura: Bufonidae) from Cerrado of Brazil, pp. 23-39 in Zootaxa 1627 on pages 25-33, DOI: 10.5281/zenodo.17931

A large new species of Rhinella (Anura: Bufonidae) from Cerrado of Brazil

Maciel, Natan M., Brandão, Reuber A., Campos, Leandro A., Sebben, Antonio (2007): A large new species of Rhinella (Anura: Bufonidae) from Cerrado of Brazil. Zootaxa 1627: 23-39, DOI: 10.5281/zenodo.17931

Tadpoles of Three Species of the Rhinella granulosa Group with a Reinterpretation of Larval Characters

The Rhinella granulosa group currently comprises 14 species of Neotropical toadswhose monophyly is strongly supported by several synapomorphies, including adistinctive set of larval characters. Recently, the identity of specimens used in tadpole description of R. major and R. mirandaribeiroi was questioned. In this work, we revise the larval external morphology of these species based on tadpoles properly identified, and examine for the first time the tadpoles of R. bernardoi. Tadpoles of R. major have the labial tooth row formula 2/2 and the tail striped pattern recovered as synapomorphies of the group. Tadpoles of R. mirandaribeiroi show instead a third posterior labial ridge arranged on a medial flap, a condition suggested as synapomorphy of a derived subclade of the R. granulosa group. Lastly, tadpoles of R. bernardoi differ from the remaining tadpoles within the group by lacking the typical striped tail muscle pigmentation.Fil: Grosso, Jimena Renee. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - Tucumán. Unidad Ejecutora Lillo; ArgentinaFil: Pereyra, Martín Oscar. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas | Universidad Nacional de Misiones. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas; ArgentinaFil: Vera Candioti, María Florencia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico - Tucumán. Unidad Ejecutora Lillo; Argentina. Universidad Nacional de Tucumán. Facultad de Ciencias Naturales e Instituto Miguel Lillo; ArgentinaFil: Maciel, Natan M.. Universidade Federal de Goiás; BrasilFil: Baldo, Juan Diego. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas | Universidad Nacional de Misiones. Instituto de Biología Subtropical. Instituto de Biología Subtropical - Nodo Posadas; Argentin

Data from: Biophysical model of water economy can explain geographic gradients in body size in anurans

Geographical gradients of body size express climate-driven constraints on animals, but whether they exist and what cause them in ectotherms remains contentious. For amphibians, the water conservation hypothesis posits that larger bodies reduce evaporative water loss (EWL) along dehydrating gradients. To address this hypothesis mechanistically, we build upon well-established biophysical equations of water exchange in anurans to propose a state-transition model that predicts an increase of either body size or resistance to EWL as alternative specialization along dehydrating gradients. The model predicts that species whose water economy is more sensitive to variation in body size than to variation in resistance to EWL should increase in size with response to increasing potential evapotranspiration (PET). To evaluate the model predictions, we combine physiological measurements of resistance to EWL with geographic data of body size for four different anuran species. Only one species, Dendropsophus minutus, was predicted to exhibit a positive body size–PET relationship. Results were as predicted for all cases, with one species – Boana faber – showing a negative relationship. Based on a mathematical model verified empirically, we show that clines of body size among anurans depend on the current values of those traits and emerges as an advantage for water conservation. Our model offers a mechanistic and compelling explanation for the cause and the variation of gradients of body size in anurans