Linear Morphometrics
We modified our recent approaches (Pyron and Beamer 2023) based on Bingham et al. (2018)’s strategy for multivariate assessment of salamanders. We recorded 17 measurements at 0.01mm precision for 89 specimens from the 31 sites: SVL (snout-vent length), TL (tail length), AG (axilla-groin length), CW (chest width), FL (femur length), HL (humerus length), SG (snout-gular length), TW (tail width at rear of vent), TO (length of third toe), FI (length of third finger), HW (head width), ED (eye diameter), IN (internarial distance), ES (eye-snout distance), ON (orbito-narial distance), IO (inter-orbital distance), and IC (inter-canthal distance). We implemented the general recommendations and statistical approaches of (Onn and Grismer 2021; Chan and Grismer 2022) for linear morphometrics, allometric size-correction, and quantitative analyses. We employed the “common within-group pooling” strategy, wherein distinct populations or localities within a species (e.g., geographic lineages) have separate slopes but a shared intercept representing overall body-size for the whole species. We tested both pooled-group and multi-species approaches; they were qualitatively identical, and we therefore present the more conservative pooled-group analyses. After allometric size-correction, we performed Linear-Discriminant Analysis (LDA to examine phenotypic differentiation of populations. We identified variables with the heaviest loading across the discriminant axes as a preliminary indicator of the morphological trait with the greatest importance in differentiating populations.