New Stonefly Synonymy Changes Conservation Outlook: 100-Year-Old Specimens and Integrated Taxonomy Clarify Species Concepts and Distributions of Several Eastern Nearctic Stripetails (Perlodidae: Isoperla Banks, 1905)

Isoperla powhatan Szczytko & Kondratieff, 2015 is newly proposed as a junior synonym of I. myersi Szczytko & Kondratieff, 2015 based on an integrative analysis of morphological and molecular phylogenetic data. Revised descriptions of the adult male, adult female, and mature egg of I. myersi are presented, together with the first description of the final instar larva. Comparative morphological observations of I. arcana Beaty, Holland & Lenat, 2017 and I. holochlora Klapálek, 1923 improve the taxonomic concepts of each species and provides support for a new species group containing the three taxa. The new synonymy adds 868 unique locations from nine USA states to the distribution of I. myersi, including 826 from North Carolina Department of Environmental Quality samples. This new synonymy has dramatically changed our understanding of the overall range and frequency of occurrence of I. myersi populations, which will impact any impending conservation status assessment of this species. This study includes color light microscopy images, scanning electron micrographs, a substantial amount of new occurrence data, and distribution maps for each species.