Evaluating the responses of three closely related small mammal lineages to climate change across the Paleocene–Eocene thermal maximum

Natasha S Vitek,Suzanne G Strait,Paul E Morse,Jonathan I Bloch,Doug M Boyer

doi:10.1017/pab.2021.12

Abstract

AbstractInterpreting the impact of climate change on vertebrates in the fossil record can be complicated by the effects of potential biotic drivers on morphological patterns observed in taxa. One promising area where this impact can be assessed is a high-resolution terrestrial record from the Bighorn Basin, Wyoming, that corresponds to the Paleocene–Eocene thermal maximum (PETM), a geologically rapid (~170 kyr) interval of sustained temperature and aridity shifts about 56 Ma. The PETM has been extensively studied, but different lines of research have not yet been brought together to compare the timing of shifts in abiotic drivers that include temperature and aridity proxies and those of biotic drivers, measured through changes in floral and faunal assemblages, to the timing of morphological change within mammalian species lineages. We used a suite of morphometric tools to document morphological changes in molar crown morphology of three lineages of stem erinaceid eulipotyphlans. We then compared the timing of morphological change to that of both abiotic and other biotic records through the PETM. In all three species lineages, we failed to recover any significant changes in tooth crown shape or size within the PETM. These results contrast with those documented previously for lineages of medium-sized mammals, which show significant dwarfing within the PETM. Our results suggest that biotic drivers such as shifts in community composition may have also played an important role in shaping species-level patterns during this dynamic interval in Earth history.

Highlights

A primary challenge to understanding the evolutionary consequences of climate change is separating the effects of diverse proximate drivers, such as changing biotic interactions between competitors and abiotic water availability, on individual species (Cahill et al 2013)
First and Last Appearances within the Bighorn Basin (BHB).— Before this survey, biostratigraphic extents of these genera were incompletely known for this interval, with Talpavoides unreported for Wa-0, the temporal range of Colpocherus unknown outside of two localities from the body of the Paleocene–Eocene thermal maximum (PETM) in the Sand Creek Divide area of the BHB, and replacement of Macrocranion junnei by Macrocranion nitens proposed to occur at the Wa-0/1 boundary (Smith et al 2002; Yans et al 2006; Rose et al 2012)
Based on our survey of 285 total cataloged specimens from the pre-PETM, 12,664 cataloged specimens from the PETM, and 2454 cataloged specimens from the post-PETM, Colpocherus is only present within the PETM during Wa-0, Macrocranion junnei is present from the PETM to post-PETM during Wa-0–Wa-2, and Talpavoides is present throughout the studied interval from pre- to post-PETM during Cf-3–Wa-2

Summary

Introduction

A primary challenge to understanding the evolutionary consequences of climate change is separating the effects of diverse proximate drivers, such as changing biotic interactions between competitors and abiotic water availability, on individual species (Cahill et al 2013). If changes in the fossil record and patterns of different drivers are found to be asynchronous, the relative timing of change in a species can potentially be used to differentiate abiotic from biotic drivers (Gill et al 2009). Examples of such fossil records are rare (Gill et al 2009; Terry 2018).

Methods

Results

Discussion

Conclusion