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Dryad

One of these things is not like the other: mixed predator cues result in lopsided phenotypic responses in a Neotropical tadpole

Cite this dataset

Rosenthal, Dean; Deng, Luana; Rose, Tarif; Touchon, Justin (2024). One of these things is not like the other: mixed predator cues result in lopsided phenotypic responses in a Neotropical tadpole [Dataset]. Dryad. https://doi.org/10.5061/dryad.1g1jwsv1g

Abstract

Many organisms have evolved to produce different phenotypes in response to environmental variation. Dendropsophus ebraccatus tadpoles develop opposing shifts in morphology and coloration when they are exposed to invertebrate vs vertebrate predators. Each of these alternate phenotypes is adaptive, conferring a survival advantage against the predator with which tadpoles were reared but imposing a survival cost with the mismatched predator. Here, we measured the phenotypic response of tadpoles to graded cues and mixed cues of both fish and dragonfly nymphs. Prey species like D. ebraccatus commonly co-occur with both of these types of predators, amongst many others as well. In our first experiment, tadpoles increased investment in defensive phenotypes in response to increasing concentrations of predator cues. Whereas morphology only differed in the strongest cue predator, tail spot coloration differed even at the lowest cue concentration. In our second experiment, tadpoles reared with cues from both predators developed an intermediate yet skewed phenotype that was most similar to the fish-induced phenotype. Fish are more lethal than dragonfly larvae and thus tadpoles responded most strongly to the more dangerous predator, even though cues of each predator were evenly mixed. We demonstrate that not only do tadpoles assess predation risk via the concentration of predation cues in the water, but they also produce a stronger response to a more lethal predator even when the strength of cues is identical.

README: One of these things is not like the other: mixed and graded predator cues result in lopsided phenotypic responses in treefrog tadpoles

Authors: Rosenthal, D.M., Deng, L., Rose, T., and Touchon, J.C.

DATA FILES

File name: Expt1_tadpole_landmarks.tps
Description: A TPS file that contains the raw data of 14 landmarks collected for all tadpoles in Experiment 1 using the digitizing app in the StereoMorph R package.

File name: Expt2_tadpole_landmarks.tps
Description: A TPS file that contains the raw data of 14 landmarks collected for all tadpoles in Experiment 2 using the digitizing app in the StereoMorph R package.

File name: Expt1_color_measurements.csv
Description: Measurements of tail spot color and size of Dendropsophus ebraccatus tadpoles raised in low, medium or high concentrations of insect or fish chemical cues or as predator free controls. Also included are principal component scores from geometric morphometric analysis.

Brightness: The average brightness of the tail spot. Values range from 0-255. Lower values indiciate darker colors and increasing values indicate brighter colors. Calculated from the Hue/Saturation/Brightness function in ImageJ.

Hue: The average hue of the tail spot. Values range from 0-255. Lower values indiciate longer wavelength colors (e.g. red) and increasing values indicate colors with shorter\
wavelengths. Calculated from the Hue/Saturation/Brightness function in ImageJ.

Saturation: The average saturation of the tail spot. Values range from 0-255. Lower values indiciate less pure colors and increasing values indicate colors with greater purity. Calculated from the Hue/Saturation/Brightness function in ImageJ.

TSA: The area of the pigmented spot at the posterior end of the tail, in mm2. The area was drawn by eye.

ID: A unique ID for each tadpole that is the randomly assigned number of their photo and the location of the tadpole in the photo. Each photo contained up to 5 tadpoles.

Tank: Unique ID for each tank tadpoles were raised in.

Family: Original code for family. Corresponds solely to the order that adult frogs were bred.

Predator: Predator of origin for cues used in the experiment. Either Fish or Dragonfly.

RiskLevel: Denotes the strength of the cue treatment that tadpoles were raised with as a categorical variable. 4 options (low, medium, high or none). 10 tadpoles from each family were raised with each chemical cue for 10 days.

RiskLevel_cont: Denotes the strength of the cue treatment that tadpoles were raised with as a continuous variable, in terms of the number of tadpoles eaten per day per L of water.

Csize: The centroid size resulting from the Procrustes fit of landmark data collected for each tadpole.

relTSA: The relative Tail Spot Area, calculated as the square root of tail spot area divided by the centroid size.

PC1: The first principal component from a PCA of the landmark data from 14 landmarks aligned with a General Procrustes Analysis.

PC2: The second principal component from a PCA of the landmark data from 14 landmarks aligned with a General Procrustes Analysis.

File name: Expt2_color_measurements.csv
Description: Measurements of tail spot color and size of Dendropsophus ebraccatus tadpoles raised in dragonfly nymph or fish chemical cues alone, in mixed fish/dragonfly cues or as predator free controls. Also included are principal component scores from geometric morphometric analysis.

Ind: Unique number for each tadpole.

Tad: Identifies which tadpole is which in each photo.

ID: A unique ID for each tadpole that is the randomly assigned number of their photo and the location of the tadpole in the photo. Each photo contained up to 5 tadpoles.

Tank: Unique ID for each tank tadpoles were raised in.

Family: Original code for family. Corresponds solely to the order that adult frogs were bred.

Treatment: Denotes the predator cue treatment tadpoles were reared with. 4 options. DD: Dragonfly nymph cues only. FF: Fish cues only. DF: Mixed dragonfly nymph and fish cues. CC: Predator-free control.

Brightness: The average brightness of the tail spot. Values range from 0-255. Lower values indiciate darker colors and increasing values indicate brighter colors. Calculated from the Hue/Saturation/Brightness function in ImageJ.

Hue: The average hue of the tail spot. Values range from 0-255. Lower values indiciate longer wavelength colors (e.g. red) and increasing values indicate colors with shorter
wavelengths. Calculated from the Hue/Saturation/Brightness function in ImageJ.

Saturation: The average saturation of the tail spot. Values range from 0-255. Lower values indiciate less pure colors and increasing values indicate colors with greater purity. Calculated from the Hue/Saturation/Brightness function in ImageJ.

TSA: The area of the pigmented spot at the posterior end of the tail, in mm2. The area was drawn by eye.

Csize: The centroid size resulting from the Procrustes fit of landmark data collected for each tadpole.

relTSA: The relative Tail Spot Area, calculated as the square root of tail spot area divided by the centroid size.

PC1: The first principal component from a PCA of the landmark data from 14 landmarks aligned with a General Procrustes Analysis.

PC2: The second principal component from a PCA of the landmark data from 14 landmarks aligned with a General Procrustes Analysis.

Methods

The data are collected from digital photographs taken of anesthetized animals. 14 landmarks are placed around the tadpole to quantify its shape using the StereoMorph package in R. Tail spot coloration is measured using ImageJ.

Usage notes

The data file contains two tps files, which can be analyzed by any software for Geometric Morphometrics. We used the geomorph package in R. .tps files can also be viewed with a standard text editor. 

Funding

Vassar College