Poison Frog Colors Are Honest Signals Of Toxicity, Particularly For Bird Predators

Antipredator defenses and warning signals typically evolve in concert. However, the extensive variation across taxa in both these components of predator deterrence and the relationship between them are poorly understood. Here we test whether there is a predictive relationship between visual conspicuousness and toxicity levels across 10 populations of the color-polymorphic strawberry poison frog, Dendrobates pumilio. Using a mouse-based toxicity assay, we find extreme variation in toxicity between frog populations. This variation is significantly positively correlated with frog coloration brightness, a viewer-independent measure of visual conspicuousness (i.e., total reflectance flux). We also examine conspicuousness from the view of three potential predator taxa, as well as conspecific frogs, using taxon-specific visual detection models and three natural background substrates. We find very strong positive relationships between frog toxicity and conspicuousness for bird-specific perceptual models. Weaker but still positive correlations are found for crab and D. pumilio conspecific visual perception, while frog coloration as viewed by snakes is not related to toxicity. These results suggest that poison frog colors can be honest signals of prey unpalatability to predators and that birds in particular may exert selection on aposematic signal design.Integrative Biolog

Sexual conflict over breeding substrate causes female expulsion and offspring loss in a cichlid fish

Females of the Lake Tanganyika cichlid Lamprologus callipterus exclusively breed in empty snail shells that males collect in their territories. Male-male competition for shells is severe, leading to frequent shell stealing and territory takeover. As a consequence, males have breeding females in their shells that spawned with competitors. In this field study, we investigated both naturally occurring and experimentally induced encounters of territorial males with females that had spawned with other males. We found that the breeding success of females that were taken over by a different male was significantly reduced. Behavioral observations after experimental shell relocation further showed that males recognized females that they had not spawned with: males directed more exploration and manipulation behavior toward such shells compared with controls. Reoccupation rate of emptied experimental shells was significantly higher than that of unmanipulated empty shells. This indicates that shell stealing and nest takeover, followed by female expulsion, contribute to the reproductive success of L. callipterus males. We also found that female mate choice reduces expulsion risk: females preferred to mate with large males, and male size correlated with dominance. We conclude that the limited availability of breeding substrate is a key determinant of both intrasexual competition and intersexual conflict in this specie

Wildlife pathogen detection:Evaluation of alternative DNA extraction protocols

Accurate detection of wildlife pathogens is critical in wildlife disease research. False negatives or positives can have catastrophic consequences for conservation and disease-mitigation decisions. Quantitative polymerase chain reaction is commonly used for molecular detection of wildlife pathogens. The reliability of this method depends on the effective extraction of the pathogen's DNA from host samples. A wildlife disease that has been in the centre of conservationist's attention is the amphibian disease Chytridiomycosis, caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd). Here, we compare the efficiency of a spin column extraction kit (QIAGEN), commonly used in Bd DNA extraction, to an alternative spin column kit (BIOKÈ) used in extractions from other types of samples, which is considerably cheaper but not typically used for Bd DNA extraction. Additionally, we explore the effect of an enzymatic pre-treatment on detection efficiency. Both methods showed similar efficiency when extracting Bd DNA from zoospores from laboratory-created cell-cultures, as well as higher efficiency when combined with the enzymatic pre-treatment. Our results indicate that selecting the optimal method for DNA extraction is essential to ensure minimal false negatives and reduce project costs

Lack of alignment across yeast-dependent life-history traits may limit <i>Drosophila melanogaster</i> dietary specialization

Heterogeneity in food resources is a major driver of local adaptation and speciation. Dietary specialization typically involves multiple life-history traits and may thus be limited by the extent to which these traits adapt in concert. Here, we use Drosophila melanogaster, representing an intermediate state in the generalist-specialist continuum, to explore the scope for dietary specialization. D. melanogaster has a close association with yeast, an essential but heterogeneous food resource. We quantify how different D. melanogaster strains from around the globe respond to different yeast species, across multiple yeast-dependent life-history traits including feeding, mating, egg-laying, egg development and survival. We find that D. melanogaster strains respond to different yeast species in different ways, indicating distinct fly strain-yeast interactions. However, we detect no evidence for trade-offs: fly performance tends to be positively rather than negatively correlated across yeast species. We also find that the responses to different yeast species are not aligned across traits: different life-history traits are maximized on different yeast species. Finally, we confirm that D. melanogaster is a resource generalist: it can grow, reproduce and survive on all the yeast species we tested. Together, these findings provide a possible explanation for the limited extent of dietary specialization in D. melanogaster.</p

Differential survival between visual environments supports a role of divergent sensory drive in cichlid fish speciation

Identifying the selective forces that initiate ecological speciation is a major challenge in evolutionary biology. Sensory drive has been implicated in speciation in various taxa, largely based on phenotype-environment correlations and signatures of selection in sensory genes. Here, we present a reciprocal transplant experiment revealing species differences in performance in alternative visual environments, consistent with speciation by divergent sensory drive. The closely related cichlids Pundamilia pundamilia and Pundamilia nyererei inhabit different visual environments in Lake Victoria and show associated differences in visual system properties. Mimicking the two light environments in the laboratory, we find a substantial reduction in survival of both species when reared in the other species’ visual environment. This implies that the observed differences in Pundamilia color vision are indeed adaptive and substantiates the implicit assumption in sensory drive speciation models that divergent environmental selection is strong enough to drive divergence in sensory properties