DOI: 10.5061/dryad.ttdz08m9g
title: Data and code from: Interspecific allometry of sexual shape dimorphism in small-bodied and large-bodied geckos

description: At macroevolutionary scales and across species, levels of sexual
 dimorphism often covary with body size, generating allometric trends.
 While such patterns are most evident for sexual size dimorphism,
 interspecific trends in sexual shape dimorphism (SShD) remain
 underexamined. Furthermore, how such patterns are affected by the
 evolution of small body size (miniaturization) is largely unknown. In this
 study, we evaluated trends in SShD across 99 gecko species from two
 families to determine whether small body sizes were associated with
 increased shape dimorphism in the group. Head shape was characterized
 using geometric morphometrics from surface scans of nearly 600
 individuals, and levels of SShD were quantified for each species.
 Phylogenetic comparative analyses were then used to evaluate evolutionary
 patterns of shape dimorphism relative to body size across species. We
 found considerable variation in the magnitude of SShD across taxa, with
 some species displaying little dimorphism and others exhibiting large
 sexual shape differences. Interspecific allometry of SShD differed between
 the two families, with strong negative allometry observed in
 Sphaeorodactylidae (a family with many small-bodied species), while in
 Phyllodactylidae (a family containing few small-bodied species) patterns
 were more isometric with no discernable trend. Notably, the greater SShD
 displayed by small-bodied species corresponded with females exhibiting
 more robust heads, which was consistent with sex-specific foraging
 strategies and dietary differences observed in this group. Our study
 reveals that interspecific allometry in traits other than body size can
 have a pervasive influence on patterns of phenotypic diversity across the
 tree of life.
description: # Data and code from: Interspecific allometry of sexual shape dimorphism
 in small-bodied and large-bodied geckos Dataset DOI:
 [10.5061/dryad.ttdz08m9g](https://doi.org/10.5061/dryad.ttdz08m9g) ##
 Description of the data and file structure This dataset was generated to
 examine macroevolutionary patterns of sexual shape dimorphism (SShD) in
 geckos in relation to extreme body size. Three-dimensional head shape data
 were collected from 3D photogrammetry scans of nearly 600 adult geckos
 representing 99 species across two families: Sphaerodactylidae and
 Phyllodactylidae. Landmark coordinates were digitized and aligned using
 geometric morphometric methods to quantify variation in cranial shape.
 Associated metadata include species identity, sex, family, and body size
 (snout–vent length). A time-calibrated phylogeny, trimmed from the Tonini
 et al. (2016) squamate trees, provides evolutionary context for all
 comparative analyses. These data were used to evaluate interspecific
 allometry of sexual shape dimorphism and to test whether miniaturization
 is associated with shifts in dimorphism magnitude or direction. ### Files
 and variables #### File: Analyses.R **Description:** R script reproducing
 all analyses presented in *Glynne & Adams (2025).* The script includes
 data import, shape alignment, species and sex-specific mean calculations,
 computation of sexual size and shape dimorphism (SSD, SShD), and all
 phylogenetic comparative analyses (E-PGLS, family-specific allometry,
 SSD–SShD regression, and phylogenetic ANOVA).\ All analyses were run in R
 v4.3+ using the packages geomorph, ape, phytools, and RRPP. #### File:
 JetzTree.tre **Description:** Time-calibrated ultrametric phylogeny for
 geckos, derived from the Tonini et al. (2016) fully sampled squamate tree.
 This version is trimmed to the 99 species included in the present
 dataset.\ Branch lengths are in millions of years, representing divergence
 times among taxa, and are used as the phylogenetic covariance structure
 for all comparative analyses. #### File: spec.info.csv
 **Description:** Specimen-level metadata linking each individual to
 species identity, sex, body size, and taxonomic family.  Used to match
 individuals to morphometric data and to compute species- and sex-specific
 means for downstream analyses. ##### Variables * *species_id:* Species
 name in the format *Genus_species* matching tree tip labels. - *comb**id:
 *Unique specimen identifier combining species and individual codes. Where
 each one consists of Genusspecies-Museum Specimen Number.  - *Sex:*
 Biological sex of the specimen (m = male, f = female). - *SVL*: Snout–vent
 length (mm). Standard body size measurement. - *Family:* Gecko family
 assignment: Phyllodactylidae or Sphaerodactylidae #### File: shapedata.csv
 **Description:** Three-dimensional landmark coordinate data representing
 head shape for each individual.\ Landmarks were digitized from 3D
 photogrammetric models of gecko specimens using geometric morphometric
 methods.\ Coordinates were Procrustes-aligned prior to analysis, and each
 row corresponds to a single specimen.\ The dataset contains 68 landmarks
 (each with X, Y, Z coordinates), flattened into sequential numeric columns
 (V1–V204). ##### Variables * **Species_ID:** Species identifier matching
 spec.info.csv - **V1–V204:** Flattened 3D coordinates (68 × 3 = 204
 numeric columns representing X, Y, Z positions) of each m and f average
 for each genus species\  - V1–V3 = Landmark 1 (X, Y, Z)\  - V4–V6 =
 Landmark 2 (X, Y, Z)\  - … continuing through V202–V204 = Landmark 68 (X,
 Y, Z). ## Code/software All analyses were performed in R (version 4.3.2)
 using the following packages: * geomorph (version 4.1.4): For Procrustes
 alignment, morphometric analyses, and shape visualization. * ape (version
 5.8): For phylogenetic data handling, tree manipulation, and covariance
 matrix computation. * phytools (version 2.3.0): For continuous trait
 mapping, visualization of phylogenetic patterns, and time-scaled plotting.
 * RRPP (version 1.4.1): For phylogenetic regression, MANOVA, and
 permutation-based hypothesis testing. Morphometric data were derived from
 3D photogrammetric models processed in meshroom (version 2021) and
 landmarked using Checkpoint Stratovan (version 2022). All scripts are
 fully reproducible and included in the file *Analyses.R.* ## Access
 information The time-calibrated phylogeny used in this study is derived
 from the Tonini et al. fully-sampled squamate tree, and is publicly
 accessible via Dryad:
 https://datadryad.org/dataset/doi:10.5061/dryad.db005 License: CC0 /
 public domain (as per Dryad’s terms) Specimen-level morphometric and
 metadata in this dataset were collected from 13 biological collections
 (museums). The institutional codes and catalog numbers are included in
 spec.info.csv (column “combid” or equivalent) to allow tracing back to
 original specimen vouchers. For example, collection abbreviations such as
 “TCWC” appear in the dataset, among others.