# Environmental Factors and Co‐Occurrence Patterns Influence Dorsal Brightness in Two Jumping Mice Species in the Western United States

## TL;DR

This study shows that the coloration of two jumping mouse species is influenced by environmental and co-occurrence factors, with implications for conservation.

## Contribution

The study reveals how environmental and interspecific factors jointly influence dorsal coloration in endangered and sympatric jumping mice.

## Key findings

- Dorsal brightness of Z. luteus varies significantly among genetically distinct populations.
- Dorsal coloration differences between Z. luteus and Z. princeps are influenced by geographic, climatic, and interspecific factors.
- Accurate species identification is crucial for conservation due to subtle visual differences in sympatric populations.

## Abstract

The phenotype is the result of interactions between an organism's genotype and its environment. One phenotypic trait of interest is dorsal coloration, which animals use to communicate, avoid detection from predators, thermoregulate, and more. Here we used standardized photography of museum specimens to explore the variation in dorsal brightness of the endangered New Mexico jumping mouse (
Zapus luteus
) in areas of allopatry and sympatry with the western jumping mouse (
Z. princeps
) in the southwestern United States. For
Z. luteus
we found statistically significant differences in brightness among isolated, genetically differentiated populations in Arizona and New Mexico. We additionally found significant, predictable interspecific differences in color between
Z. luteus
and
Z. princeps
where they co‐occur; however, these differences would be difficult to distinguish visually. We also found evidence that the dorsal brightness of both species is associated with geographic (elevation, latitude) and bioclimatic (precipitation, temperature) features, as well as interspecific interactions (syntopy patterns). Our findings emphasize that both biotic and abiotic factors influence dorsal coloration in free‐living organisms, and highlight the importance of using multiple lines of evidence to identify co‐occurring congeners in the field. For endangered species like
Z. luteus
, correct identification can have important management implications.

We examined how dorsal coloration varies in the endangered New Mexico jumping mouse (
Zapus luteus
) and its close relative, the western jumping mouse (Z. princeps) in relation to environmental variables and co‐occurence patterns using standardized photographs of museum specimens. We found that dorsal brightness varied significantly among genetically distinct populations and was influenced by geographic, climatic, and interspecific factors. These results highlight that both environmental and biological interactions drive coloration differences and stress the need for accurate species identification to guide conservation efforts.