# Phylogenomic Analysis of Wide‐Ranging Least Shrews Refines Conservation Priorities and Supports a Paradigm for Evolution of Biota Spanning Eastern North America and Mesoamerica

## TL;DR

This study uses genomic data to refine the classification and conservation priorities of least shrews, revealing distinct evolutionary units and a shared diversification pattern across North America and Mesoamerica.

## Contribution

The study provides a phylogenomic framework for least shrews, identifying distinct species and conservation units, and proposes a paradigm for regional biotic diversification.

## Key findings

- Least shrews warrant recognition as multiple distinct species and discrete infraspecific lineages.
- Western populations are evolutionarily distinct based on nuclear data, possibly due to mitochondrial capture.
- Hindcast and forecast niche modeling supports shared diversification processes and future niche loss in peripheral regions.

## Abstract

Anthropogenic global change is impacting the evolutionary potential of biodiversity in ways that have been difficult to predict. Distinct evolutionary units within species may respond differently to the same environmental trends, reflecting unique geography, ecology, adaptation, or drift. Least shrews (Cryptotis parvus group) have a widespread distribution across North America, yet systematic relationships and ongoing evolutionary processes remain unresolved. Westernmost peripheral populations have been prioritized for conservation, but little is known of their evolutionary histories or population trajectories. The broad range of this group of species is coincident with many other temperate taxa, presenting a hypothesis that diversification of least shrews follows a repeated process through the Pleistocene, leading to regionally diagnosable conservation units. We use genomic data and niche modeling to delimit species and conservation units of least shrews. Our results show that least shrews warrant recognition as multiple distinct species, along with geographically discrete infraspecific lineages of
C. parvus
(sensu stricto). Western peripheral populations are evolutionarily distinct based on nuclear, but not mitochondrial data, possibly reflecting mitochondrial capture during the last glacial phase. This population represents a relict conservation unit, consistent with both an “adaptive unit” and “management unit” based on non‐neutral and neutral divergence, respectively. Hindcast niche modeling supports growing evidence for a shared process of diversification among co‐distributed biota, and forecast modeling suggests continued future loss of suitable environmental niche in peripheral regions. Given mito‐nuclear discordance among samples of parapatric lineages, future environmental perturbation may continue to impact the genomic integrity of important conservation units, making ecological and genomic monitoring a critical need.

Least shrews, distributed widely across North America and Mesoamerica, remain an enigmatic group in terms of their evolutionary history, biogeography, and ongoing responses to environmental change. Under a phylogenomic framework using reduced representation genome data, we investigated these dynamics across multiple scales of analysis. We found that the current taxonomy is in need of revision and provide updated nomenclature, systematic relationships, and conservation implications. This group provides a clear demonstration of diagnosable diversification across this vast study area.