Scinax, Wagler, 1830

Silva, Helio Ricardo Da & Alves-Silva, Ricardo, 2013, Predictive-like distribution mapping using Google Earth: Reassessment of the distribution of the bromeligenous frog, Scinax v-signatus (Anura: Hylidae), Zootaxa 3609 (2), pp. 213-222 : 214-216

Distribution of Scinax v-signatus: Historical Background

Scinax v -signatus ( Lutz, 1968) is a hylid frog endemic to the Atlantic Forest in southwestern Brazil ( Peixoto and Carvalho-e-Silva 2004). This small frog belongs to a group of species know as the Scinax perpusillus group ( Peixoto 1987). This non-ranked species-group name is used to refer to a demonstrably monophyletic group of tree frogs, which are unique among congeners because of their tight relationship with bromeliads ( Faivovich 2002). All species in the group use bromeliads for hiding, reproducing, and raising tadpoles ( Peixoto 1987; Faivovich 2002; Alves-Silva and Silva 2009; Faivovich et al. 2010). Currently, there are 13 recognized species belonging to this group ( Silva and Alves-Silva 2011; Lacerda et al. 2012), many of them known only from their type locality (Alves- Silva & Silva 2009).

Scinax v-signatus was described from Parque Nacional da Serra dos Órgãos in the mountains of the State of Rio de Janeiro, in the Municipality of Teresópolis, at an elevation of about 980 m. At the time of its description Bertha Lutz had already recognized the dependency of S. v-signatus on bromeliads and its relatedness to Scinax perpusillus (originally described as Hyla perpusilla ), a species she co-authored earlier ( Lutz and Lutz 1939). However, it was Peixoto (1987) who first suggested that a larger cluster of species, all bromeliad dependent (bromeligenous, sensu Peixoto 1995), should be recognized as a group within the genus. He referred to this assemblage as the “ perpusillus group” indicating its distinctiveness among congeners. Later, Peixoto (2002) described another species for the group, Scinax arduous , from the mountainous region of the Municipality of Santa Teresa, in the State of Espírito Santo, northwest of the State of Rio de Janeiro ( Fig. 1 ). In the same paper Peixoto stated that a population of S. v -signatus occurred in sympatry with S. arduous in Santa Teresa. Besides that report ( Peixoto 2002), no other samples of bromeligenous Scinax from Santa Teresa included specimens of S. v - signatus —we have examined specimens from Museu Nacional/UFRJ (Rio de Janeiro) and Museu Melo Leitão (Santa Teresa, Espirito Santo) collected in the area of the type locality in Santa Teresa and found only S. arduous . When this particular distribution was described, there was no evidence of the occurrence of Scinax v -signatus outside these two localities (Teresópolis, RJ and Santa Teresa, ES), leaving a gap between the two putative populations of about 370 km in a straight line (measured using the ruler tool in GE).

Most frogs in this group, especially Scinax v-signatus, have yellow flash coloration on the hidden parts of their body and limbs (axillary and inguinal regions, thighs, shank, or feet). Variation in this color pattern facilitates identification of the species in the group (see Faivovich et al. 2010; Lacerda et al. 2012; Silva and Alves-Silva 2011). The occurrence of a unique pattern is quite evident in S. v -signatus which, besides having a distinctive orange coloring on the foot, lower leg, anterior and posterior thigh, and inguinal and axillary regions (it is never orange, but yellow in other species), also has dark pigmentation on the mental region which is organized in the form of a Y or V ( Lutz 1968; Peixoto 2002). However, after euthanasia and fixation the bright colors in many specimens tend to wash out and vanish (personal observation), and the yellow or orange color of the specimens may vanish in just a few days after they are stored in 70 % alcohol. This is particularly relevant because all six adult specimens identified as Scinax v -signatus by Peixoto (2002) from Santa Teresa, ES, were already in collections, having been collected between 1968 and 1984. Therefore, it is reasonable to assume that the samples he observed had already lost the yellow coloration when he studied them, potentially compromising the possibility of proper identification. Additionally, Peixoto may have also relied on the identification given earlier by Werner C. A. Bokermman ( Santos, 1995) who had collected these specimens ( Peixoto 2002), and who may have misidentified the first specimens obtained from the site as S. v-signatus (which at the time was the only species of the group know from higher elevations).

When surveying areas between the two type localities in northern Rio de Janeiro (RJ) and southern Espírito Santo (ES), we collected specimens that fit neither the description of S. v-signatus nor that of S. arduous , and may represent at least two new species for the group ( Fig. 1 ). We also have collected specimens we identified as Scinax arduous from two other localities in the State of Espírito Santo ( Fig. 1 ). Recently, Pertel et al. (2010) reported collecting specimens of Scinax arduous (and no other bromeligenous species of Scinax ) from the Municipality of Afonso Claudio, about 50 km southwest of Santa Teresa. Also, Scinax belloni Faivovich, Gasparini, and Haddad, 2010 , was described from the Municipality of Castelo, Espírito Santo ( Fig. 1 ), about 85 km southwest of Santa Teresa ( Faivovich et al. 2010). Scinax v -signatus was recorded at none of these new localities. All this evidence poses question on the validity of the record of S. v-signatus from Santa Teresa. Even Peixoto himself cast some doubts on his earlier identification of the material from Santa Teresa as S. v-signatus in the more recent IUCN Red List, “specimens from Espírito Santo might belong to a separate species.” (as personal communication in Peixoto and Carvalho-e-Silva 2004). Nevertheless, the IUCN map of the distribution of S. v-signatus (and AmphibiaWeb as well) still depicts it as occurring in Santa Teresa, ES. Additionally, the map presents two problems: (1) it suggests a continuous distribution of about 372 km for S. v- signatus ( Peixoto and Carvalho-e-Silva 2004), assuming the occurrence of the species even in areas where no bromeliads may occur; and (2) the southernmost limits of the maps do not include the type locality for the taxon, which is left out of the area outlined by about 40 km ( Fig. 2 ). Needless to say, a better method for describing the distribution of this species is needed.

Figures

FIGURE 1. Map of southeastern Brazil highlighting the area of the States of Minas Gerais, Rio de Janeiro, and Espírito Santo. Symbols indicate the type localities for Scinax v-signatus (white circle), the type locality for S. arduous (white square) and S. belloni (black square). The white hexagons indicate three new localities for S. arduous. The star indicates two localities where an undescribed species was collected in the south of the State of the Espírito Santo, and the black circle indicates the locality for another undescribed species collected in the north of the State of Rio de Janeiro.

FIGURE 2. Map from GAA depicting the distribution of Scinax v-signatus. Note that the type locality (Black circle) was not included in distribution area.