Cranial geometric morphometrics of jumping mice (Genera: Eozapus, Napaeozapus, and Zapus; Zapodinae, Rodentia): Implications for subspecies conservation

Jumping mice (subfamily Zapodinae) occur across most of North America ( Zapus and Napaeozapus ) and in confined regions in China ( Eozapus ). Recent molecular phylogenies have revised their taxonomy, raising some subspecies to full species and synonymizing others. This taxonomic revision has implications for subspecies conservation and management, since Z. hudsonius preblei and Z. h. luteus are legally protected by the United States federal Endangered Species Act (ESA), while Z. h. campestris and Z. trinotatus orarius are conserved in parts of their range. Several molecular studies have either synonymized Z. h. preblei with Z. h. campestris (and Z. h. intermedius ) or grouped it with Z. h. alascensis and Z. h. tenellus as a widely distributed “Northern” lineage, arguing against its continued legal protection. However, genetic differentiation is a proxy for historical but not always adaptive distinctiveness, and the ESA considers both for conservation (i.e., Evolutionarily Significant Units). This study uses geometric morphometrics to compare adaptive distinctiveness of jumping mice subspecies. This compares scaled cranial shape, leading to insights that differ from linear measurements. For broader insights, cranial morphology was compared within jumping mice and with the closely related birch mice. Subspecies pairs within the three traditionally accepted Zapus species were ranked in order morphometric distinctiveness. The most distinct pair was found to be Z. h. preblei vs. Z. h. alascensis , members of the same genetic lineage. Other morphometrically distinct subspecies pairs were parts of the same or different genetic lineages, some having been elevated to full species. Other members of especially distinct pairs include Z. princeps oregonus , Z. p. saltator , Z. p. cinereus , Z. p. minor , Z. p. pacificus , and Z. p. idahoensis . Other aspects of adaptive distinctiveness should be examined in these subspecies for validation and to prioritize conservation efforts.