Poison frog dietary preference depends on prey type and alkaloid load

Abstract

The ability to acquire chemical defenses through the diet has evolved across several major taxa. Chemically defended organisms may need to balance chemical defense acquisition and nutritional quality of prey items. However, these dietary preferences and potential trade-offs are rarely considered in the framework of diet-derived defenses. Poison frogs (Family Dendrobatidae) acquire defensive alkaloids from their arthropod diet of ants and mites, although their dietary preferences have never been investigated. We conducted prey preference assays with the Dyeing Poison frog (Dendrobates tinctorius) to test the hypothesis that alkaloid load and prey traits influence frog dietary preferences. We tested size preferences (big versus small) within each of four prey groups (ants, beetles, flies, and fly larvae) and found that frogs preferred interacting with smaller prey items of the fly and beetle groups. Frog taxonomic prey preferences were also tested as we experimentally increased their chemical defense load by feeding frogs decahydroquinoline, an alkaloid compound similar to those naturally found in their diet. Contrary to our expectations, overall preferences did not change during alkaloid consumption, as frogs across groups preferred fly larvae over other prey. Finally, we assessed the protein and lipid content of prey items and found that small ants have the highest lipid content while large fly larvae have the highest protein content. Our results suggest that consideration of toxicity and prey nutritional value are important factors in understanding the evolution of acquired chemical defenses and niche partitioning.

Passive accumulation of alkaloids in inconspicuously colored frogs refines the evolutionary paradigm of acquired chemical defenses

“…Sympatric populations of the undefended H. awa and defended E. espinosai (formerly E. darwinwallacei [65]) are both diet specialized, with the former consuming mostly ants and beetles and the latter consuming mostly mites and springtails [66]. In a lab experiment, the defended species D. tinctorius was shown to prefer fruit fly larvae over ants when given the choice [67], suggesting that even in defended species, consumption of possible alkaloid-containing prey is not necessarily a preference. One study found that O. sylvatica alkaloid quantity is inversely correlated with ant and mite stomach contents; however, this species consumed more mites and ants than sympatric H. infraguttatus [46].…”

“…Sympatric populations of the undefended H. awa and aposematic E. espinosai (formerly E. darwinwallacei [65]) are both diet specialized, with the former consuming mostly ants and beetles and the latter consuming mostly mites and springtails [66]. In a lab experiment, the aposematic species D. tinctorius was shown to prefer fruit fly larvae over ants when given the choice [67], suggesting that even in aposematic species, consumption of possible alkaloid-containing prey is not necessarily a preference.…”

Eco-Metabolomics Applied to the Chemical Ecology of Poison Frogs (Dendrobatoidea)

“…For univariate analysis they have compared quantities or chromatographic peak intensities/areas and performed parametric or non-parametric tests for measuring the significance of this differentiation employing ANOVA and Kruskal–Wallis analysis, respectively (Mina et al 2015 ; Moskowitz et al 2020 ), depending on the data-normality. For multivariate analysis, the main type of analysis used has been Non-metric multidimensional scaling (NMDS) accompanied by ANOSIM or PERMANOVA analysis for testing the significance of different metavariables in differentiating alkaloid profiles (Saporito et al 2006 , 2007 , 2010 ; Stuckert et al 2014 ; Mina et al 2015 ; Moskowitz et al 2022 ). Correlation analysis have also been tested for measuring the strength of the correlation between total amount of alkaloids and diversity of alkaloids (Saporito et al 2010 ), a common pattern found on different species.…”