Benson, R. | bioRxiv Science

bioRxiv2023

A whole-body micro-CT scan library that captures the skeletal diversity of Lake Malawi cichlid fishes

Here we describe a dataset of freely available, readily processed, whole-body CT-scans of 56 species (116 specimens) of Lake Malawi cichlid fishes that captures a considerable majority of the morphological variation present in this remarkable adaptive radiation. We contextualise the scanned specimens within a discussion of their respective ecomorphological groupings and suggest possible macroevolutionary studies that could be conducted with these data. We also describe a methodology to efficiently CT-scan (on average) 23 specimens per hour, limiting scanning time and alleviating the financial cost whilst maintaining high resolution. We demonstrate the utility of this method by reconstructing 3D models of multiple bones from multiple specimens within the dataset. We hope this dataset will enable further morphological study of this fascinating system and permit wider-scale comparisons with other cichlid adaptive radiations.

evolutionary biology↗

bioRxiv2023

Macroevolutionary drivers of morphological disparity in the avian quadrate

In birds, the quadrate bone acts as a hinge between the lower jaw and the skull, playing an important role in cranial kinesis. As such, the evolution of avian quadrate morphology may plausibly be assumed to have been influenced by selective pressures related to feeding ecology. However, variation in quadrate morphology across living birds and its potential relationship with ecology have never been quantitatively characterised. Here, we used three-dimensional geometric morphometrics and phylogenetic comparative methods to quantify morphological variation of the quadrate and its relationship with an array of key ecological features across 200 bird species covering all major extant lineages. We found non-significant associations between quadrate shape and several aspects of feeding and foraging ecology across different scales of phylogenetic comparison. By contrast, allometry and phylogeny exhibit stronger relationships with quadrate shape than other ecological features. We show that the avian quadrate evolves as an integrated unit and exhibits strong associations with the morphologies of neighbouring bones. Our results collectively suggest a macroevolutionary scenario in which the shape of the quadrate evolved jointly with other elements of the avian kinetic system, with the major lineages of birds exploring alternative quadrate morphologies--highlighting the potential diagnostic value of quadrate morphology in investigations of fossil bird systematics.

paleontology↗