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).