Body size trends in response to climate and urbanization in the widespread North American deer mouse, Peromyscus maniculatus

Maggie M. Hantak,Bryan S. McLean,Robert Guralnick,Daijiang Li

doi:10.1038/s41598-020-65755-x

Maggie M. Hantak, Bryan S. McLean + Show 2 more

Open Access

https://doi.org/10.1038/s41598-020-65755-x

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Abstract

Body size decline is hypothesized to be a key response to climate warming, including warming driven by urban heat islands. However, urbanization may also generate selective gradients for body size increases in smaller endotherms via habitat fragmentation. Here we utilize a densely sampled, multi-source dataset to examine how climate and urbanization affect body size of Peromyscus maniculatus (PEMA), an abundant rodent found across North America. We predicted PEMA would conform to Bergmann’s Rule, e.g. larger individuals in colder climates, spatially and temporally. Hypotheses regarding body size in relation to urbanization are less clear; however, with increased food resources due to greater anthropogenic activity, we expected an increase in PEMA size. Spatial mixed-models showed that PEMA conform to Bergmann’s Rule and that PEMA were shorter in more urbanized areas. With the inclusion of decade in mixed-models, we found PEMA mass, but not length, is decreasing over time irrespective of climate or population density. We also unexpectedly found that, over time, smaller-bodied populations of PEMA are getting larger, while larger-bodied populations are getting smaller. Our work highlights the importance of using dense spatiotemporal datasets, and modeling frameworks that account for bias, to better disentangle broad-scale climatic and urbanization effects on body size.

Highlights

Body size decline is hypothesized to be a key response to climate warming, including warming driven by urban heat islands
When examining body mass as a body size metric, we found spatial variation correlated with mean annual temperature (MAT), mean annual precipitation (MAP), season, and sex (Tables 1A, S2a, S3a,c)
Much has been made about the potential for global change to impact key functional traits of organisms, in particular body size change in the face of changing climates[1]

Summary

Introduction

Body size decline is hypothesized to be a key response to climate warming, including warming driven by urban heat islands. Body size change has been hypothesized to be a third universal response to climate warming[1] The rationale for this hypothesis is based on a space-for-time substitution of the well-studied but still-controversial relationship between body size and latitude or temperature in endotherms, e.g. Bergmann’s Rule or cline. The challenge is vexing because long-term and systematic monitoring are often incomplete in places where humans are most impacting the environment, and incidental data (e.g., museum specimens) and other geographically targeted census/survey efforts often have inherent spatiotemporal bias that limit broadest use[10] Assembly of these disparate data streams is an essential remit for effective monitoring of many different types of species traits in global change contexts[11]. Excellent representation across biodiversity data streams makes PEMA an ideal case study for examining spatiotemporal body size trends in the context of global change drivers, while parsing the biases associated with opportunistic sampling and a diversity of data sources

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