DISCUSSION
Polychromatism has been recorded in several anuran species and may serve
distinct functions such as disruptive camouflage, aposematism, sexual
identification, and others (Hoffman and Blouin 2000; Wells 2007).
Although in the present study we observed multiple coloration patterns
in individuals from the same locality, no studies have been conducted to
assess the evolutionary mechanisms that have selected for these
characteristics in the different populations of A. hoogmoedi . The
diurnal activity displayed by species within this genus, coupled with
their specific habitat in stream environments characterized by
background noise, likely played a role in the evolution of visual
communication signals (Heyer et al., 1990; Hödl & Amézquita, 2001).
Geographic isolation can generate phenotypic diversity in certain
amphibian species (Rudh et al., 2007). However, this does not seem to be
the case in A. hoogmoedi , as populations in close proximity
exhibit distinct color patterns. Color variation among individuals in
different populations has been described as a consequence of genetic
drift associated with geographic features in Adelphobates
galactonotus (Rojas et al., 2020). Furthermore, for some species dorsal
coloration in males may play a role in female mate preferences (Maan &
Cummings, 2008), although differences in coloration may not be
sex-related for others (Ávila-Pires et al., 2010). The use of visual
displays in Atelopus is described in the literature, both for the
defense of territory and for aggression between individuals (Crump 1988,
Lindquist and Hetherington 1996, 1998). Examining how the various color
patterns of A. hoogmoedi may influence sexual selection or
reproductive territory defense can provide insights into the selective
pressures acting on this trait.
In certain polychromatic anuran species, color variation can lead to
varying predation rates (Noonan & Comeault, 2009; Chouteau & Angers,
2011; Hegna et al., 2013; Amézquita et al., 2013; Willink et al., 2014).
This can be attributed to the search image and prior predator experience
exposed to different color patterns. In terms of parsimony, it would be
expected that a monomorphic color pattern within a species facilitates
easier learning of the signal by predators (Rojas et al., 2015). This
phenomenon is observed in Mullerian mimicry organisms (Chatelain et al.,
2023). Polychromatism has been extensively studied in the context of
predator-prey relationships, particularly when the models are
geographically isolated, such as on islands (Hegna et al., 2013) or
separated by rivers that act as a geographic barrier (Rojas et al.,
2015; Jeckel et al., 2019). Populations exhibiting distinct color
patterns that are geographically isolated may arise as a response to
different predators in each locality. However, in the case of A.
hoogmoedi which is distributed within a continuous forest landscape,
the explanations may not be as straightforward.
Hence, the advantage of the polychromatic pattern in Atelopus
hoogmoedi remains a mystery, prompting the need for further research
encompassing genetic, behavioral, sexual and environmental selection.
This characteristic provides an excellent opportunity to elucidate how
evolutionary mechanisms such as selection, drift, or geographic
isolation may operate to select for these patterns. Despite A.
hoogmoedi being widely distributed in the Eastern Amazon and being one
of the few species within the genus Atelopus that does not show
strong evidence of population reduction (Valencia & Fonte, 2022), there
are still significant gaps in our understanding of the species’ biology
and even its taxonomic delimitation (Silva et al., 2020).
We strongly encourage further investigations to elucidate the factors
influencing color variation in this species. Scientific research on the
biodiversity of the Amazon Rainforest has recently faced significant
challenges due to funding cuts in the scientific budget implemented by
the previous Brazilian government (Angelo, 2019; Fernandes et al., 2017;
Escobar, 2019). Additionally, the increase in losses of natural areas in
the last years (Peres et al., 2023) highlights the need to accelerate
studies in the region before the loss of basic information. This
jeopardizes the study and understanding of Neotropical biodiversity,
particularly concerning a highly endangered group of vertebrates such as
the anurans of the genus Atelopus . Therefore, it is imperative to
allocate investments toward integrative research on the evolution and
ecology of this genus of anurans.