Specialist savvy vs generalist grit: elucidating the trade-offs in adaptive dietary ecomorphology amongst African Green and Bush Snakes
Data files
May 16, 2025 version files 1.08 GB
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Additional_Variables.csv
2.99 KB
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Compound_Surface_files.zip
424.15 MB
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Description_-_Landmarks_-_Geometric_Morphometric_.txt
2.34 KB
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hex_files_for_landmarks.zip
1.50 MB
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Maxillae_Surface_files.zip
233.71 MB
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Newick_Tree_by_Engelbrecht_et_al._2021.txt
518 B
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Pterygoid_Surface_files.zip
272.97 MB
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Quadrate_Surface_files.zip
144.62 MB
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README.md
4.83 KB
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Supplementary_Table_1_Diet_Records.txt
49.10 KB
Abstract
Kinetic feeding bones of macrostomatan Afrophidian snakes enable them to consume diverse prey types. While significant research has focussed on functional feeding morphology in snakes, it often emphasises broad taxonomic comparisons or species with distinct dietary ecologies. There is limited knowledge of how small variations in prey type composition may influence feeding morphology among closely related species sharing similar ecological niches. African Green and Bush Snakes (Philothamnus) feed primarily on frogs (anurophagous) and lizards (saurophagous), but the degree of intraspecific dietary generalisation and specialisation remains unclear. Thus, our study had three objectives: 1) to evaluate proportional differences in anurophagy and saurophagy between 14 Philothamnus species, 2) quantitatively assess the shape differences in four of the main cranial bones functional in feeding and 3) explore models of diet evolution. We hypothesised that differences in feeding morphology would reflect the extent of dietary specialisation and/or generalisation. Macroevolution diet analysis results indicated two main diet groups: anurophagous specialists and anuro-saurophagous generalists. Geometric morphometric shape analyses show that the jawbones of anurophagous specialists (P. angolensis and P. hoplogaster) have higher mechanical advantage (MA), pronounced posteriorly curved maxillary teeth, deeper mandibular fossae on a more convex shaped compound, wider proximal quadrates and deeper quadromandibular joint articulations. Conversely, anuro-saurophagous generalists (P. occidentalis, P. natalensis and P. semivariegatus) have longer and thinner jaw bones with lower MA, a more horizontal dorsal quadrate and high shape variation in maxillae and pterygoids. These findings suggest that dietary morphology is malleable and pervasive even amongst congeners with fine-scaled differences in prey type proportions. Dietary specialisation and generalisations amongst the African Green and Bush Snakes appear to exist along a continuum. Dietary ecomorphology appears to be influenced by phylogenetic relationships and may have evolved in dual mode, i.e. gradual specialisation and punctuated shifts in dietary in response to ecological opportunity.
https://doi.org/10.5061/dryad.2jm63xt0g
Description of the data and file structure
The supplementary dataset contains the following files:
File 1: Supplementary_Table_1_Diet_Records.csv
File 2. Additional_Variables.csv
File 3. Compound_Surface_files.zip
File 4. Quadrate_Surface_files.zip
File 5. Maxillae_Surface_files.zip
File 6. Pterygoid_Surface_files.zip
File 7. Description of Landmarks_Geometric Morphometric.txt
File 8. Hex_files_for_landmarks.zip
File 9. Newick Tree from Engelbrecht et al 2021.txt
File Descriptions
File 1: Supplementary Table 1
Supplementary Table 1 contains compiled predation records for the five Philothamnus predator species investigated for geometric morphometric analyses.
Diet data were collected using the Squamatabase R package (Grundler, 2020) and from citizen science and literature records (Maritz and Maritz, 2020). Information provided includes:
- Predator species: P. angolensis, P. hoplogaster, P. natalensis, P. occidentalis and P. semivariegatus
- Prey Type: for example; anurophagous, insectivorous, ornithophagous, piscivorous, rodentivorous and saurophagous
- Prey Taxon: classified as the Taxonomic Family / Class/Order depending on available information
- Observation Type: for example; anecdotal, incidental, direct observation, dissected gut contents, expert validated image, field collection, in captivity, regurgitated by specimen and secondary information
- Locality Description 1: fine-scale location details (e.g. city/neighbourhood/coordinates) when available
- Locality Description 2: broad-scale location context (e.g. country or region) when available
- Primary Data Source: original data collected firsthand through direct methods such as fieldwork, experiments, observations or specimen records
- Database Authority: Authors (Grundler, 2020; Maritz & Maritz, 2020) responsible for generating, curating, and validating the data included in the referenced databases used.
References:
Grundler, M. C. 2020. SquamataBase: A Natural History Database and R Package for Comparative Biology of Snake Feeding Habits. Biodiversity Data Journal, 8. e49943
Maritz, R. A., & Maritz, B. (2020). Sharing for science: high-resolution trophic interactions revealed rapidly by social media. PeerJ, 8, e9485.
File 2: Additional_Variables
This file contains additional variables included and/or explored in the phylogenetic Procrustes regression for snake skull bone shape analyses: head-length(HL), head-width (HW), snout-vent-length (SVL) and tail-length (TL). Body dimensions (HL, HW, SVL and TL) are reported in millimeters (mm). Measurements are associated with individual specimens, each identified by its respective museum (Ditsong National Museum of Natural History, South Africa) ID.
Files 3-6: Surface files
Whole skull ct scans were segmented for snake skull bones of interest (compound, maxillae, pterygoid and quadrate), for which surface files per bone are provided here. Landmarks were placed on these individual surface files per bone. Surface files for each bone (compound, maxilla, pterygoid, quadrate) are saved in separate folders, containing one file per individual. TM numbers refer to museum specimen numbers.
Files 7-8: Hex files & Description of Landmarks for Geometric Morphometric analyses
A set of example hex files—comprising the compound, maxilla, pterygoid, and quadrate bones from a single specimen—prepared for use in Amira (version 5.4.5; Stalling et al. 2005), is provided to visually demonstrate landmark placement. Hex files in this context contain three-dimensional coordinate placements of osteological landmarks per bone, formatted for direct import into Amira. These files enable users to visualize and manipulate landmark placements on the specimen’s 3D surface for geometric morphometric analyses. The additional document titled "Description - Landmarks - Geometric Morphometrics" provides detailed text definitions and descriptions of landmark placements.
Reference;
Stalling, D., Westerhoff, M., & Hege, H. C. (2005). Amira: A highly interactive system for visual data analysis. The visualization handbook, 38, 749-767.
File 9: Phylogenetic tree in Newick format
The phylogenetic tree used is from previously published work by the lead author (Engelbrecht et al., 2019; 2020) and is provided in Newick format. This ultrametric tree served as the framework for macroevolutionary analyses, enabling the reconstruction of ancestral dietary states and the testing of evolutionary models to examine patterns and rates of diet evolution in Philothamnus.
Diet data was collected using the Squamatabase R package (Grundler, 2020) and from citizen science and literature records (Maritz and Maritz, 2020). Compiled prey records are provided here.
Whole skull ct scans were segmented for snake skull bones of interest (compound, maxillae, pterygoid and quadrate), for which surface files per bone are provided here. Geometric morphometric analyses were based on these surface files.
Definitions of 3D landmarks are provided here.
The newick phylogenetic tree is from previously published work by the lead author (Engelbrecht et al 2019; 2020, 2021), and provided here as a newick file. The tree file was used in the macroevolution analysis and testing for models of diet evolution for Philothamnus.
Mechanical advantage was calculated from measured bones as described in the MS, and recorded values per specimen are provided in the "Additional Variables" file.