How to render species comparable taxonomic units through deep time: A case study on intraspecific osteological variability in extant and extinct lacertid lizards
Creators: name: Tschopp, Emanuel
name: Napoli, James
name: Wencker, Lukardis
name: Delfino, Massimo
name: Upchurch, Paul
Publisher: name: Zenodo
Year: 2021
Subjects: subject: morphological disparity
subject: Osteology
subject: intraspecific variation
subject: Lacertidae
subject: taxonomic bias
subject: species
subject: Genetics
subject: FOS: Biological sciences
subject: Ecology, Evolution, Behavior and Systematics

description: Generally, the species is considered to be the only naturally occurring taxon. However, species recognized and defined using different species delimitation criteria cannot readily be compared, impacting studies of biodiversity through Deep Time. This comparability issue is particularly marked when comparing extant with extinct species because the only available data for species delimitation in fossils are derived from their preserved morphology, which is generally restricted to osteology in vertebrates. Here, we quantify intraspecific, intrageneric, and intergeneric osteological variability in extant species of lacertid lizards using pairwise dissimilarity scores based on a data set of 253 discrete osteological characters for 99 specimens referred to 24 species. Variability is always significantly lower intraspecifically than between individuals belonging to distinct species of a single genus, which is in turn significantly lower than intergeneric variability. Average values of intraspecific variability and associated standard deviations are consistent (with few exceptions), with an overall average within a species of 0.208 changes per character scored. Application of the same methods to six extinct lacertid species (represented by 40 fossil specimens) revealed that intraspecific osteological variability is inconsistent, which can at least in part be attributed to different researchers having unequal expectations of the skeletal dissimilarity within species units. Such a divergent interpretation of intraspecific and interspecific variability among extant and extinct species reinforces the incomparability of the species unit. Lacertidae is an example where extant species recognized and defined based on a number of delimitation criteria show comparable and consistent intraspecific osteological variability. Here, as well as in equivalent cases, application of those skeletal dissimilarity values to paleontological species delimitation potentially provides a way to ameliorate inconsistencies created by the use of morphology to define species.
description: The complete character matrix is also available on MorphoBank (http://morphobank.org/permalink/?P4084), where sources for characters and character scores are marked within the matrix as comments.Funding provided by: Seventh Framework Programme<br>Crossref Funder Registry ID: http://dx.doi.org/10.13039/100011102<br>Award Number: Marie Skłodowska–Curie grant agreement No. 609402-2020 researchers: Train to Move (T2M)Funding provided by: FP7 Research infrastructures<br>Crossref Funder Registry ID: http://dx.doi.org/10.13039/100011260<br>Award Number: FR-TAF-5839Funding provided by: FP7 Research infrastructures<br>Crossref Funder Registry ID: http://dx.doi.org/10.13039/100011260<br>Award Number: AT-TAF-5725Funding provided by: Erasmus+<br>Crossref Funder Registry ID: http://dx.doi.org/10.13039/501100010790<br>Award Number: 2 Traineeships for LCM WenckerFunding provided by: Richard Gilder Graduate School**<br>Crossref Funder Registry ID: <br>Award Number: PhD fellowship for JG NapoliFunding provided by: American Museum of Natural History<br>Crossref Funder Registry ID: http://dx.doi.org/10.13039/100005835<br>Award Number: Newt and Callista Gingrich endowmentFunding provided by: Università degli Studi di Torino<br>Crossref Funder Registry ID: http://dx.doi.org/10.13039/501100006692<br>Award Number: PhD fellowship for LCM WenckerFunding provided by: Università degli Studi di Torino<br>Crossref Funder Registry ID: http://dx.doi.org/10.13039/501100006692<br>Award Number: Fondi di Ricerca Locale UNITO 2017-2019Funding provided by: H2020 Marie Skłodowska-Curie Actions<br>Crossref Funder Registry ID: http://dx.doi.org/10.13039/100010665<br>Award Number:
description: Personal visits to scientific collections by Emanuel Tschopp and Lukardis Wencker. Some specimens were scored based on figures in published literature. Python and R scripts were developed by Lukardis Wencker and James Napoli, respectively.