Taxonomic Revision of Endemic Rodents

Abstract

Rodents are the most species-rich mammalian order, with approximately 2,500 described species constituting 40% of all mammals, yet island and archipelago endemic rodent faunas remain poorly characterised taxonomically, with unresolved species boundaries, incorrect synonymies, and undescribed species -- all with direct consequences for IUCN Red List assessments and conservation prioritisation. This study conducted a comprehensive taxonomic revision of endemic rodents from 28 island and mountain archipelago systems across Europe, Asia, and Africa, applying integrative taxonomy combining COI and cytochrome b DNA barcoding (2,840 sequences from 284 museum specimens and 240 fresh-collected individuals), geometric morphometrics of 18 cranial landmarks (1,284 museum specimens), and external morphometric measurements to 84 nominal species representing 12 genera. The integrative approach confirmed 64 of the 84 nominal species as valid, synonymised 12 nominal species (reducing to 6 valid species in 4 revised species groups), resurrected 4 synonymised names as valid species, and formally described 8 species new to science. Net result: 72 valid species from the 84 nominal -- a 14.3% reduction through synonymy offset by 19.0% increase from resurrections and new species. Geographic range reassessments based on revised taxonomy changed the IUCN Red List category of 18 species: 8 species moved from Least Concern to Vulnerable or Endangered (their ranges are smaller than previously recognised), 6 from Endangered to Least Concern (their ranges are larger through synonymy dissolution), and 4 new species require immediate Endangered or Critically Endangered assessment given their restricted island endemism. These revisions demonstrate the direct conservation impact of taxonomic research and the urgent need for taxonomy-conservation integration in island rodent management.