DOI: 10.5061/dryad.66t1g1k97
title: Viviparity is associated with larger female size and higher sexual size dimorphism in a reproductively bimodal lizard

description: Squamate reptiles are central for studying phenotypic correlates of
 evolutionary transitions from oviparity to viviparity because these
 transitions are numerous, with many of them being recent. Several models
 of life-history theory predict that viviparity is associated with
 increased female size, and thus more female-biased sexual size dimorphism
 (SSD). Yet the corresponding empirical evidence is overall weak and
 inconsistent. The lizard Zootoca vivipara, which occupies a major part of
 Northern Eurasia and includes four viviparous and two non-sister oviparous
 lineages, represents an excellent model for testing these
 predictions.  We analysed how sex-specific body size and SSD is
 associated with parity mode, using body length data for nearly 14,000
 adult individuals from 97 geographically distinct populations, which cover
 almost the entire species’ range and represent all six lineages. Our
 analyses controlled for lineage identity, climatic seasonality (the
 strongest predictor of geographic body size variation in previous studies
 of this species), and several aspects of data heterogeneity. 
 Parity mode, lineage, and seasonality are significantly associated with
 female size and SSD; the first two predictors accounted for 14–26% of the
 total variation each, while seasonality explained 5–7%. Viviparous
 populations exhibited a larger female size than oviparous populations,
 with no concomitant differences in male size. Variation of male size was
 overall low and poorly explained by our predictors.  Albeit fully
 expected from theory, the strong female bias of the body size differences
 between oviparous and viviparous populations found in Z. vivipara is not
 evident from available data on three other lizard systems of closely
 related lineages differing in parity mode. We confront this pattern with
 the data on female reproductive traits in the considered systems and the
 frequencies of evolutionary changes of parity mode in the corresponding
 lizard families and speculate why the life-history correlates of
 live-bearing in Z. vivipara are distinct.  Comparing conspecific
 populations, our study provides the most direct evidence for the predicted
 effect of parity mode on adult body size but also demonstrates that the
 revealed pattern may not be general. This might explain why across
 squamates, viviparity is only weakly associated with larger size.
description: The body size data come from museum samples or from previous
 studies performed for other purposes (e.g., Bauwens & Verheyen
 1987; Arribas 2009; Recknagel & Elmer 2019). Additional data were
 extracted from published histograms or individual values.
 Climate data were extracted from the Worldclim
 resource.
description: # Viviparity is associated with larger female size and higher sexual size
 dimorphism in a reproductively bimodal lizard
 [https://doi.org/10.5061/dryad.66t1g1k97](https://doi.org/10.5061/dryad.66t1g1k97) ## Description of the data and file structure Data are presented in excel files, each data file is accompanied with extensive comments given in a corresponding MS Word file; Empty cells mean that the data are not available (=n/a) Files Roitberg_et_al_2024_SVL_data.xls and Roitberg_et_al_2024_SVL_data_ReadMe.doc relate to body-sizedata; Files Roitberg_et_al_2024_physical_characteristics_of_study populations.xls and Roitberg_et_al_2024_physical_characteristics_of_study populations_ReadMe.doc relate to latitude, longitude, altitude, and climatic data (averaged for study populations); Files Roitberg_et_al_2024_physical_characteristics_of_individual_sites.xls and Roitberg_et_al_2024_physical_characteristics_of_individual_sites_ReadMe.doc relate to latitude, longitude, altitude, and climatic data for individual sites