DOI: 10.5061/dryad.w6m905qzm
title: Morphometric data to describe phenotypical variation across Pygmy and Marbled newts (genus Triturus)

description: An extensive dataset on the external morphology of pygmy and marbled newts
 was used to explore the static allometry of sexual size dimorphism (SSD)
 and Rensch’s rule (RR). Females were larger in trunk and head
 sizes, whereas males had longer limbs and digits. Divergences in
 trunk and head dimensions between sexes were achieved along a common
 allometric slope rather than by a change in the slope’s direction, most
 often through a shift in the intercept. Sexual dimorphism in
 finger and toe length was unrelated to body size. The change in
 SSD with a change in body size (RR) was confirmed for female-biased
 traits. RR was unrelated to changes in static allometric slopes.
description: Five (sub)species of <em>T. marmoratus</em> species
 group were analysed: two subspecies of the marbled newts – <em>T.
 marmoratus harmannis </em>(338 females and 247 males from 46
 populations) and <em>T. m. marmoratus </em>(80 females and 70
 males from five populations) and three taxa of pygmy newts
 namely<em> T. p. pygmaeus </em>(26 males and 24 females from
 five populations), <em>T. pygmaeus lusitanicus </em>(317
 females and 254 males from 38 populations) and <em>T. rudolfi
 </em>(126 females and 125 males from six populations).  A sample of
 the even larger crested newt <em>T. cristatus</em> (15 males,
 30 females from one population) was included for comparison. Hybrid
 populations were excluded (Arntzen, 2018, 2024ab). All measured
 individuals were adults. The following eight morphometric traits were
 analyzed: snout-vent length (SVl), as representative of overall body size
 was measured from the tip of the snout up to and including to the
 insertion of hind limbs, interlimb distance (ILd), head width (Hw), head
 length (Hl), forelimb length (FLl), third finger length (TFl), hindlimb
 length (HLl) and fourth toe length (FTl). Snout-vent length as here
 measured purposely excludes the cloaca, the size of which is season
 dependent. That measure largely corresponds to the more commonly used
 measure up to the cloacal slit (e.g. Reinhard and Kupfer, 2015). The
 analysed dataset is compilation of published data (2018, 2024b, 2024c) and
 newly collected ones, and cover the entire distribution range (Arntzen,
 2024cd). All statistical analyses were conducted using
 R (R Core Team, 2022). The significance of differences in mean trait size
 between the sexes was tested by t-tests using the <em>t.test
 </em>function. The allometric relationships between females and
 males within (sub)species and among (sub)species, as well as RR were
 explored using SMA with the <em>smatr</em> package (Warton et
 al., 2012; 2018). First, we plotted trait measures versus SVl (all
 log-transformed) for each (sub)species and sex separately using
 <em>sma </em>function. The strength of the association between
 SVl and the specified trait was estimated by the square of Pearson’s
 correlation coefficient (r<sup>2</sup>). The statistical
 significance of the fitted allometric slope for each sex and (sub)species
 was estimated by the sample correlation between residuals and fitted
 values. We subsequently tested whether the allometric slope is
 non-isometric (<em>b</em> ≠ 1). Differentiation of the sexes
 was explored by testing for differences in the direction of allometric
 slopes (Figure 1, pattern A). When no differences were found, we tested
 for lateral shifts that led to a change in elevation (pattern B), shifts
 along the common allometric slope (pattern C), or both (pattern
 D). We tested for RR using again the <em>sma
 </em>function. The log-transformed mean values for specific traits
 in females versus males for each (sub)species were plotted and tested for
 isometry (<em>b</em> = 1). To test for common slopes across
 taxa and between pairs of taxa, we used the <em>slope.com</em>
 function. First, we calculated the common slope for each of traits for all
 six taxa with pooled males and females as these have common slopes (Table
 1) and estimated its statistical significance based on the
 (Bartlett-corrected) likelihood ratio statistic testing for common slope
 (Warton and Weber, 2002; Warton et al., 2006; Taskinen and Warton, 2013).
 We did post-hoc multiple comparisons of slopes by calculating the common
 slope for pairs of taxa for each trait. Interpretation of all statistical
 tests was done using the standard Bonferroni correction for multiple
 comparisons. To calculate 95% confidence intervals for
 the values of allometric slopes in all aforementioned tests we
 used <em>boot </em>package (Davidson and Hinkley, 1997; Canty
 and Ripley, 2024). We defined bootstrap function and than used
 <em>replicate </em>function to create bootstrap samples.
 Confidence intervals were calculated by using
 <em>quantile</em> function.
description: # Morphometric data to describe phenotypical variation across Pygmy and
 Marbled newts (genus Triturus)
 [https://doi.org/10.5061/dryad.w6m905qzm](https://doi.org/10.5061/dryad.w6m905qzm) From the paper **Allometry, sexual dimorphism, and Rensch’s rule in pygmy and marbled newts (Journal of Evolutionary Biology**, voae150, [https://doi.org/10.1093/jeb/voae150](https://doi.org/10.1093/jeb/voae150)) Authors: Ana Ivanović, Faculty of Biology, University of Belgrade, Belgrade, Serbia, [ana@bio.bg.ac.rs](mailto:ana@bio.bg.ac.rs) Tijana Vučić, Naturalis Biodiversity Center, Leiden, The Netherlands, Institute of Biology, Leiden University, Leiden, The Netherlands, Faculty of Biology, University of Belgrade, Belgrade, Serbia, [tijana.vucic@naturalis.nl](mailto:tijana.vucic@naturalis.nl) Jan W. Arntzen, Naturalis Biodiversity Center, Leiden, The Netherlands, Institute of Biology, Leiden University, Leiden, The Netherlands, [pim.arntzen@gmail.com](mailto:pim.arntzen@gmail.com) | Brief summary: | | :---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | --- An extensive dataset on the external morphology of pygmy and marbled newts was used to explore the static allometry of sexual size dimorphism (SSD) and Rensch’s rule (RR). | | --- Females were larger in trunk and head sizes, whereas males had longer limbs and digits. | | --- Divergences in trunk and head dimensions between sexes were achieved along a common allometric slope rather than by a change in the slope’s direction, most often through a shift in the intercept. | | --- Sexual dimorphism in finger and toe length was unrelated to body size. | | --- The change in SSD with a change in body size (RR) was confirmed for female-biased traits. | | --- RR was unrelated to changes in static allometric slopes. | | Data collection: J. W. Arntzen | | Code: T. Vučić | | We have submitted data and R scripts used for each of the analysis in the study “Allometry, sexual dimorphism, and Rensch’s rule in pygmy and marbled newts”, and file that contains morphometric data as well as additional information for geographic information of populations used in the study. | Data files: 1\)    raw data – **newts-SSD_raw_data.txt**; 2\)    mean values per (sub)species and sex – **newts-SSD_mean_values_species_sex.txt**. R scripts: 1\)    T-tests to assess the significance of differences in mean trait size between the sexes – **newts-SSD_ttest.R**; 2\)    Standardized major axis (SMA) analysis to test the allometric relationships between females and males within (sub)species for analyzed traits with bootstrap to calculate 95% CIs for the values of allometric slopes – **newts-SSD_female_male_slope_boot.R** 3\)    Standardized major axis (SMA) analysis to test Rensch’s rule (RR) with bootstrap to calculate 95% CIs for the values of allometric slopes – **newts-SSD_rr_test_boot.R** 4\)    Standardized major axis (SMA) analysis to test for common slopes across taxa and between pairs of taxa with bootstrap to calculate 95% CIs for the values of allometric slopes – **newts-SSD_common_slopes_test_boot.R** Additional information: 1\)    Morphometric data with additional geographic information: Locality and coordinates of populations – **newts-SSD_locality_data.txt** **## Description of the data and file structure**  ### **newts-SSD_raw_data.txt** The dataset contains raw measures of eight morphometric traits (**in mm**) and their log values. This dataset was used to analyse: differences in mean trait size between the sexes (R script: **newts-SSD_ttest.R**), allometric relationships between females and males (R script: **newts-SSD_female_male_slope_boot.R**) and common slopes across taxa (R script: **newts-SSD_common_slopes_test_boot.R**). Species: *Triturus* species Subspecies: subspecies of *Triturus* species Sex: measured individuals were adults – males and females SubspSex: combined information on subspecies and sex **All measures are in milimeters (mm)** SVl: snout-vent length, as representative of overall body size was measured from the tip of the snout up to and including to the insertion of hind limbs Ild: interlimb distance FLl: forelimb length TFl: third finger length HLl: hindlimb length FTl: fourth toe length Hw: head width Hl: head length \### **newts-SSD_mean_values_species_sex.txt** The dataset contains mean values of eight morphometric traits (**in mm**) per (sub)species and sex values. This dataset was used to test Rensch’s rule (R script: **newts-SSD_rr_test_boot.R**). **All measures are in milimeters (mm)** Abberevations: SVl: snout-vent length Ild: interlimb distance FLl: forelimb length TFl: third finger length HLl: hindlimb length FTl: fourth toe length Hw: head width Hl: head length F: female M: male \### **newts-SSD_locality_data.txt** This file contains additional data – geographic information: Locality number: the ordinal number of population Locality name:  geographic information  Country: Country of origin Longitude Latitude Species: *Triturus* species Subspecies: subspecies of *Triturus* species Sex: measured individuals were adults – males and females **All measures are in milimeters (mm)** Abberevations: SVl: snout-vent length Ild: interlimb distance FLl: forelimb length TFl: third finger length HLl: hindlimb length FTl: fourth toe length Hw: head width Hl: head length log values of measurements **## Code/Software** All R scripts were created using R version 4.4.1 (2024-06-14 ucrt). Packages used: 1\)    smatr v. 3.4.8 (Warton, David I., Duursma, Remko A., Falster, Daniel S. and Taskinen, S. (2012) smatr 3 - an R package for estimation and inference about allometric lines Methods in Ecology and Evolution, 3(2), 257-259) 2\)    boot v. 1.3.31 (Canty, A. and Ripley, B. (2024). boot: Bootstrap R (S-Plus) Functions. R package version 1.3-31) \### **newts-SSD_ttest.R** This R script performs a series of t-tests to assess the significance of differences in mean trait size between the sexes. The data file used for analysis is **newts-SSD_raw_data.txt**. No additional packages are required, as the t.test() function is available in base R. \### **newts-SSD_female_male_slope_boot.R** This R script performs a standardized major axis (SMA) analysis to test the allometric relationships between females and males within (sub)species for the analyzed traits, using bootstrap to calculate 95% confidence intervals (CIs) for the values of allometric slopes. The data file used for analysis is **newts-SSD_raw_data.txt**. The analysis utilizes the smatr and boot packages. \###**newts-SSD_rr_test_boot.R** This R script performs a standardized major axis (SMA) analysis to test Rensch’s rule (RR) using bootstrap to calculate 95% CIs for the values of allometric slopes. The data file used for analysis is **newts-SSD_mean_values_species_sex.txt**. The analysis utilizes the smatr and boot packages. \###**newts-SSD_common_slopes_test_boot.R** This R script performs a standardized major axis (SMA) analysis to test for common slopes across taxa and between pairs of taxa using bootstrap to calculate 95% CIs for the values of allometric slopes. The data file used for analysis is **newts-SSD_raw_data.txt**. The analysis utilizes the smatr and boot packages.