DOI: 10.5061/dryad.pvmcvdnmf
title: Dataset and script to: Morphometric variance, evolutionary constraints and their change through time in Late Devonian Palmatolepis conodonts

description: Phenotypic variation is the raw material of evolution. Standing variation
 can facilitate response to selection along “lines of least evolutionary
 resistance”, but selection itself might alter the structure of the
 variance. Shape was quantified using 2D geometric morphometrics in
 Palmatolepis conodonts through the Late Devonian period. Patterns of
 variance were characterized along the record by the variance-covariance
 matrix (P-matrix) and its first axis (Pmax). The Late Frasnian was marked
 by environmental oscillations culminating with the Frasnian/Famennian mass
 extinction. A shape response was associated with these fluctuations,
 together with a deflection of the Pmax and the P-matrix. Thereafter, along
 the Famennian, Palmatolepis mean shape shifted from broad elements with a
 large platform to slender elements devoid of platform. This shift in shape
 was associated with a reorientation of Pmax and the P-matrix, due to
 profound changes in the functioning of the elements selecting for new
 types of variants. Both cases provide empirical evidences that moving
 adaptive optimum can reorient phenotypic variation, boosting response to
 environmental changes. On such time scales, the question seems thus not to
 be whether the P-matrix is stable, but how it is varying in response to
 changes in selection regimes and shifts in adaptive optimum.
description: Platform elements of the conodont
 genus <em>Palmatolepis</em> have been collected in seven
 Frasnian and twelve Famennian levels of the Col des Tribes section
 (Montagne Noire, France). Age was estimated for each level using a
 biostratigraphic analysis (Girard et al. 2014). The study focused on four
 well-represented subgenera: <em>Manticolepis, Panderolepis,
 Deflectolepis</em> and <em>rhomboidea</em>. 2D pictures
 of the elements were taken, the oral surface facing the camera. The
 outline of the element was described with 64 equidistant points. Based
 from the corresponding coordinates, radii (e.g. distance from each point
 to the centroid) were calculated and analysed using a Fourier-based
 morphometric method. The coefficients of nine harmonics were retained,
 thus delivering 18 shape variables (coefficients A1 to B9). These
 coefficients have been standardized by size, estimated by the zeroth
 harmonic (A0). A total of 1535 elements have been included in the
 analysis. 
description: <b>Renaud_Girard_Dufour_2021_Rcode.R </b> This file contains the script of the multivariate analyses used in the study. <b>Palm_CTselect_2021.txt </b> This file contains the dataset. Successive columns correspond to the following variables. Section: CT outcrop; level: numbering of the level along the section; depth: depth in the section in cm; agemodel: estimated absolute age of the level according to Girard et al. (2020) updated after Becker et al. (2020); LevSide: code combining level, subgenus and side; Zone: biostratigraphic zones, numbered according to their temporal order; Side: right/left side; collage and photo: person responsible for orienting and picturing the elements (CG: Catherine Girard); species: tentative specific identification; Subgenus: subgeneric attribution; ssgleve: code combining subgenus and level; A0: zeroth harmonic (size); A1 to B9: Fourier coefficients (shape variables).