Morphological diversity, evolution and biogeography of early Pleistocene rabbits (Genus Oryctolagus)

Maxime Pelletier,Lionel Hautier

doi:10.1111/pala.12575

Abstract

AbstractThe early Pleistocene is the key period for understanding the evolutionary history and palaeobiogeography of rabbits (Genus Oryctolagus). In western Europe, many species were endemic, making them a reliable indicator of the evolution of the terrestrial ecosystems in which many species have evolved. However, the morphological variability of rabbit species is still poorly understood and their phylogeny remains a subject of debate. Through both qualitative (morphological description) and quantitative (linear measurements and two‐dimensional geometric morphometrics) approaches, we address here the morphometric diversity of the third lower premolar (p3), a tooth commonly used to distinguish leporid species, in order to assess intra‐ and inter‐regional morphological variations in several early Pleistocene rabbit populations. Our results suggest that the different approaches are complementary and allow, on different levels, a full characterization of the p3 variability of early Pleistocene rabbits and to imply relations between populations. The size and shape variations of this tooth reflect the taxonomic and phylogenetic signals of the different species but were probably also significantly impacted by geographical position and local climatic conditions. In view of the great morphometric variability highlighted in this work, we suggest a careful reconsideration of certain dental criteria previously considered ‘diagnostic’ in the characterization of these species. However, the overall results allowed us to discuss the phylogeny of the genus Oryctolagus and to hypothesize the ecological requirements and different phases of the dispersal of taxa in western Europe, probably associated with global climate changes.

Highlights

Pleistocene rabbits and to imply relations between populations
In view of the great morphometric variability highlighted in this work, we suggest a careful reconsideration of certain dental criteria previously considered ‘diagnostic’ in the characterization of these species
We explore the evolution of morphological diversity in rabbits of the genus Oryctolagus, the most abundant leporids in the Quaternary palaeontological and archaeological records from southwestern Europe

Summary

Introduction

Pleistocene rabbits and to imply relations between populations. The size and shape variations of this tooth reflect the taxonomic and phylogenetic signals of the different species but were probably significantly impacted by geographical position and local climatic conditions. Studies of fossil specimens generally attempt to apprehend the factors responsible for morphometric and phenotypic variations (e.g. environmental and/or evolutionary event), their hypothetical phylogenetic links and the ecological characteristics that would make them valid and distinct species (Mayr 1963) This would prevent the amplification of specific differentiations (i.e. when anatomical characters differ between individuals) and the over complication of taxonomy. To solve these various issues, recent studies have compared these different qualitative and quantitative approaches to highlight whether patterns of morphological variation are congruent or contrasting (Hetherington et al 2015; Hopkins 2017; Mongiardino Koch et al 2017; Ferron et al 2020; Schaeffer et al 2020) To this end, we explore the evolution of morphological diversity in rabbits of the genus Oryctolagus, the most abundant leporids in the Quaternary palaeontological and archaeological records from southwestern Europe. O. cuniculus, the sole and last representative of the genus today (Hoffman & Smith 2005; IUCN 2020), which first appeared at the beginning of the middle Pleistocene, would render the early Pleistocene a key period for understanding its origin and phylogeny (Lopez-Martınez 1989; De Marfa 2009; Pelletier 2018)

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Conclusion