Factors determining the dorsal coloration pattern of aposematic salamanders

Abstract

Aposematic bright colors have a key role for animal defense and can be expressed through metabolic production or by acquiring pigments from diet. Aposematic coloration can be related to both local adaptations and availability of trophic resources. The European fire salamander (Salamandra salamandra) shows significant color variability and occurs across a broad range of habitats. Here we combined field observations with common rearing experiments to disentangle the role of environmental conditions and local adaptations in determining aposematic coloration of salamander populations. We assessed color variation and measured habitat features and food availability in adults from 25 populations. Furthermore, we reared newborn larvae from 10 populations under different food availability and analyzed color of metamorphs. To assess color pattern, we measured the percentage of yellow covering the body, and the Hue, Saturation and Value of yellow coloration. Adult showed strong variation of color pattern; variation was strongly related to the individual's size, to habitat productivity and to food availability. Under common garden conditions, differences between populations were not anymore evident, and coloration was only affected by resource availability during larval development. Our results suggest that environmental conditions and food availability are more important than local adaptations in determining differences in aposematic color pattern.

Antioxidant availability trades off with warning signals and toxin sequestration in the large milkweed bug (Oncopeltus fasciatus)

“…This is after what Agrawal et al (2022) describe as "a long history of finding no costs of cardenolide exposure or sequestration" (Chaplin & Chaplin, 1981;Isman, 1977;Vaughan, 1979). Our results also add to the growing literature that the production and maintenance of warning signals and chemical defenses are affected and limited by resource availability (Barzaghi et al, 2022;Blount et al, 2009Blount et al, , 2012Blount et al, , 2023Burdfield-Steel et al, 2019;Lindstedt et al, 2010Lindstedt et al, , 2020Ottocento et al, 2023).…”

“…This is in line with research showing that resource availability can influence the expression of melanic signals in other aposematic species (Lindstedt et al, 2020 ). Investigating how resource availability affects the defenses of aposematic animals is important for understanding which factors drive variation in warnings signals and chemical defenses (Barzaghi et al, 2022 ; Blount et al, 2009 , 2012 ; Davis, 2009 ; Lindstedt et al, 2020 ; Ottocento et al, 2023 ).…”

Larval development and poor trophic resource availability: Local adaptations and plasticity in a widespread amphibian species

“…The duration of post‐metamorphosis rearing was the same for all the individuals. We took measurements at 30 days because the first month after metamorphosis is a critical period for the survival of juveniles, and because the morphological patterns of fully terrestrial individuals are reached around after this period (e.g., aposematic coloration and shape) (Barzaghi et al, 2022). Considering subsequent periods posed ethical and practical issues (salamanders needed to be released in their environment).…”

Color morphs of the fire salamander are discriminated at night by conspecifics and predators

“…Dorsal color morphs in S. salamandra result from the combination of yellow, black, brown, red and/or gray patches (Beukema et al., 2016; Burgon et al., 2020; Velo‐Antón & Buckley, 2015). Recent studies suggest that the proportion of yellow in this species is influenced by food availability and environmental conditions (Barzaghi et al., 2022; Caspers et al., 2020). Furthermore, Caspers et al.…”

“…Dorsal color morphs in S. salamandra result from the combination of yellow, black, brown, red and/or gray patches (Beukema et al, 2016;Burgon et al, 2020;Velo-Antón & Buckley, 2015). Recent studies suggest that the proportion of yellow in this species is influenced by food availability and environmental conditions (Barzaghi et al, 2022;Caspers et al, 2020). Furthermore, Caspers et al (2020) found that clay models with higher proportions of yellow (vs. black) were subjected to fewer predation attempts, suggesting that yellow-black coloration in S. salamandra might function as an aposematic signal.…”