INTRODUCTION
The high species diversity of anurans on the planet is a result of multiple evolutionary processes (Pyron & Wiens, 2013). However, we still lack robust information on how specific traits have emerged and which evolutionary forces have shaped them, such as behaviors and coloration patterns. The role of amphibian coloration remains poorly understood, considering the extensive array of colors and patterning with widespread polymorphism (Toledo & Haddad, 2009). The occurrence of multiple color morphs within a single species has intrigued researchers, leading to the exploration of various mechanisms underlying this polymorphism. Such mechanisms may be explained by genetic drift, natural selection, sexual selection, or a combination of these factors (Tazzyman & Iwasa, 2010; Rojas et al., 2015; Rojas et al., 2020).
Species coloration can play an important role to camouflage, solar radiation protection, thermoregulation and aposematism (Duellman & Trueb, 1986; Wells, 2007; Toledo & Haddad, 2009). Aposematism is a defensive strategy strongly linked to color polymorphism in poison anurans, in which colors function as signals to visually oriented predators, such as birds, to convey a clear message regarding unpalatability or the presence of toxic substances (Rojas et al., 2015). Additionally, for certain species, color patterns are useful for communicating about individual’s health status or even physical fitness (Zamora-Camacho & Comas, 2019).
Intraspecific color variation in amphibians has been documented in several species (Richards-Zawacki et al., 2013; Gehara et al., 2013; Amézquita et al., 2017), providing an excellent opportunity to investigate the evolutionary mechanisms that drive the selection and fixation of such variability in certain populations across a species’ geographic range. Cryptic coloration with dull colors is widely observed within the Bufonidae family and is likely the ancestral condition of this lineage (Loeffler-Henry et al., 2023). However, the emergence of species with conspicuous and vibrant coloration throughout the body or in specific parts has occurred in certain species, such as the generaAtelopus and Melanophryniscus (Baldo et al., 2012). Typically, these aposematic color patterns are associated with defensive mechanisms against predators and a warning for the presence of toxic alkaloids and tetrodotoxins of exogenous origin (Rueda Almonacid et al., 2005; Daly et al., 2008; Yotsu-Yamashita & Tateki, 2010; Mebs et al., 2018).
Toads of the genus Atelopus , distributed in the Neotropics, are well known for their bright coloration and large variation in color pattern, especially in populations from the Guiana Shield (Noonan & Gaucher, 2005; Lötters et al., 2022). Also, they are known to possess tetrodotoxin, which is an effective defense mechanism against predation (Mebs et al., 2018). Most species are restricted to the highlands of Andean zones while a few species alongside the Amazon River and Guiana Shield present wider distributions (La Marca et al., 2005; Lötters et al., 2011). The harlequin toad Atelopus spumarius sensu lato displays a cis -Andean distribution ranging from Ecuador and Peru, along the Amazon River, to the Guianas and the Brazilian states of Amapá and Pará. The species exhibit high color polymorphism along its distribution (Noonan & Gaucher, 2005). However, the Atelopus spumarius sensu lato encompasses at least two nominal species along its distribution, namely A. hoogmoedi , A. manauensis (Jorge et al., 2020b), and one candidate species in the south margin of the Amazon River (Silva et al., 2020). These populations have exhibited a complex and highly variable color pattern within and among populations.
The bufonid Atelopus hoogmoedi is a colorful small toad that until recently was known as Atelopus spumarius or A. spumarius hoogmoedi (Frost, 2022). The distribution of A. spumarius was supposed to range from the Andes to the Guianas, with a gap in between those two extremes in western Amazonia. Since the beginning of the century A. spumarius hoogmoedi was elevated to full species (Lötters et al., 2002, 2005). Atelopus hoogmoedi was described from French Guiana and is known to occur throughout the three Guianas and adjacent Brazil (Noonan & Gaucher, 2005).
In the Brazilian state of Pará the species was known from one small area in Monte Dourado and from a rather undefined locality “Brazil, 30 km S of the Suriname border” (material in RMNH), with outlying populations in Tucuruí, Serra de Carajás, Itaituba and near Santarém all four localities in Pará South of the Amazon River (Ávila-Pires et al., 2010). It was also recorded in the south margin of the Amazonas river in the Virola-Jatobá Sustainable Development Project (PDS) in the Xingu river basin which is a candidate species (Silva et al., 2020). The species is also known from several localities in Amapá (Lima, 2008; Silva-e-Silva & Costa-Campos, 2018) and from Uatumã river basin in Central Amazon (Jorge et al., 2020a). The typical color pattern of Brazilian populations mentioned are rather uniform in dorsal pattern (dark brown with vermiculate yellow to pale greenish lines on the back). On the other hand, individuals from different populations in Amazonia presented a great variation in color pattern with a significant differentiation from the typical pattern (Lötters et al., 2022).