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Data from: Flexible oviposition behavior enabled the evolution of terrestrial reproduction

Cite this dataset

Touchon, Justin; McMillan, Owen; Ibañez, Roberto; Lessios, Harilaos (2024). Data from: Flexible oviposition behavior enabled the evolution of terrestrial reproduction [Dataset]. Dryad. https://doi.org/10.5061/dryad.pvmcvdnv1

Abstract

In vertebrates, nearly all oviparous animals are considered to have either obligate aquatic or terrestrial oviposition, with eggs that are specialized for developing in those environments. The terrestrial environment has considerably more oxygen but is dry and thus presents both opportunities and challenges for developing embryos, particularly those adapted for aquatic development. Here, we present evidence from field experiments examining egg-laying behavior, egg size and egg jelly function of 13 species of Central and South American treefrogs in the genus Dendropsophus, which demonstrates that flexible oviposition (individuals laying eggs both in and out of water) and eggs capable of both aquatic and terrestrial development are the likely factors which enable the transition from aquatic to terrestrial reproduction. Nearly half of the species we studied had previously undescribed degrees of flexible oviposition. Species with obligate terrestrial reproduction have larger eggs than species with aquatic reproduction, and species with flexible reproduction have eggs of intermediate sizes. Obligate terrestrial breeding frogs also have egg masses that absorb water more quickly than those with flexible oviposition. We also examined eight populations of a single species, Dendropsophus ebraccatus, and document substantial intraspecific variation in terrestrial oviposition; populations in rainy, stable climates lay fewer eggs in water than those in drier areas. However, no differences in egg size were found, supporting the idea that the behavioral component of oviposition evolves before other adaptations associated with obligate terrestrial reproduction. Collectively, these data demonstrate the key role that behavior can have in facilitating major evolutionary transitions.

README: Data for "Flexible oviposition behavior enabled the evolution of terrestrial reproduction"

https://doi.org/10.5061/dryad.pvmcvdnv1

There are three data files that accompany this manuscript. 

  1. oviposition.csv
  2. hydration.csv
  3. diameter.csv

File name: oviposition.csv

Description: Oviposition decisions of Dendropsophus treefrog females in breeding assays. Females were given access to both aquatic and terrestrial oviposition sites inside shaded or unshaded breeding enclosures and were allowed to lay their eggs in sites of their choosing.  T

Site: The name of the population where the frogs were studied. There were 12 different sites visited during the study.

Species: One of 13 species of Dendropsophus treefrogs that were studied.

Date: Date that the photo was taken. Dates are recorded as YYYYMMDD.

Pair: A unique ID for each pair of frogs mated during the behavioral assays.

Treatment: The shade treatment of the breeding enclosure for the particular trial, either shaded ("shade") or unshaded ("sun").

NumMasses: The total number of discrete egg masses the female laid.

TerrMasses: The number of egg masses that were laid only in air, i.e., having no contact with water at all. These masses are dubbed “terrestrial”.

AWSMasses: The number of egg masses that were laid containing both eggs fully in contact with the water and fully in contact with air. These masses are dubbed “at the water surface”.

AqMasses: The number of egg masses that were laid with only eggs fully in contact with the water. These masses are dubbed “aquatic”.

NumEggs: The total number of eggs laid by the female.

TerrEggs: The number of terrestrial eggs laid. Terrestrial eggs are those that have no contact with water.

AqEggs: The number of aquatic eggs laid. Aquatic eggs are those that have at least some contact with water.

PropTerr: The proportion of a females' oviposited eggs that were terrestrial.

PropAq: The proportion of a females' oviposited eggs that were aquatic.

File name: hydration.csv

Description: Measurements of egg jelly hydration rate for treefrogs in the genus Dendropsophus, measured via mass in the field. Clusters of 10 eggs with their surrounding jelly were transferred from their terrestrial oviposition site in a behavioral assay to a small piece of plastic (approximately 5 cm X 5 cm), were submerged in clean water. Periodically, the eggs and plastic were removed from the water, blotted dry with a paper towel and were weighed to the nearest 10th of a gram.

Site: The name of the population where the frogs were studied. There were 12 different sites visited during the study.

Species: One of 13 species of Dendropsophus treefrogs that were studied.

Date: Date that the photo was taken. Dates are recorded as YYYYMMDD.

Pair: A unique ID for each pair of frogs mated during the behavioral assays.

Time: The time, in minutes, since being submerged.

PlasticMass: The mass of the plastic that the cluster of eggs were adhered to. Data are recorded in grams.

MassW.Plastic: The mass of the eggs and the piece of plastic they are attached too over time.  Data are recorded in grams.  

EggMass: The mass of the eggs and the piece of plastic, minus the weight of the plastic itself, at each time point during the assay.  Data are recorded in grams.

File name: diameter.csv

Description: Measurements of egg diameter of eggs of treefrogs in the genus Dendropsophus, measured via digital photographs in ImageJ. Five eggs per female were removed from the egg mass and placed onto grid paper where they were photographed. Diameter was measured in two perpendicular directions and averaged to calculate the diameter for each eggs.

Site: The name of the population where the frogs were studied. There were 12 different sites visited during the study.

Species: One of 13 species of Dendropsophus treefrogs that were studied.

Date: Date that the photo was taken. Dates are recorded as YYYYMMDD.

Pair: A unique ID for each pair of frogs mated during the behavioral assays.

PhotoTime: Time of day that the photo was taken. Time is recorded on a 24hr clock.

Egg: Which of five eggs was measured.

Diameter: The diameter of the egg in mm. Values of "NA" refer to eggs that were not measured, either because they were not round or the image of them was distorted.

Methods

Data are field collected behavioral assays, egg jelly hydration rates, and egg diameters.

Funding

National Science Foundation, Award: 1064566

Smithsonian Tropical Research Institute