Completing the information gap in Gammarus anodon (Crustacea: Amphipoda) using molecular and ecological approaches

Gammarus anodon, an endemic amphipod species first described from the Hashilan Wetland in Iran, has faced significant challenges due to the periodic drying of its type locality. Consequently, no specimens were found during multiple sampling efforts in 20232024. In this paper, we report G. anodon at Sarab-e-Youan, a new locality 25 Km from the original site. Morphological analyses confirmed this population as G. anodon based on diagnostic characteristics. This paper also provides the first molecular and ecological insights into the species. Genetic analyses, including mitochondrial COI and nuclear 28S rDNA sequences, confirmed that G. anodon is genetically distinct from other Iranian Gammarus species. Maximum-likelihood phylogenetic trees revealed a close genetic relationship between G. anodon and G. ilamensis, with the Qaladez and Pahn populations forming a distinct clade. Furthermore, G. anodon is identified as part of the G. komareki species complex. Genetic distances between G. anodon and other Iranian species ranged from 0.68% to 16.22% for 28S rDNA and 2.19% to 32.73% for COI genes. Ecological assessments of Sarab-e-Youan highlighted environmental parameters that support G. anodon, including alkaline pH (8.6), high dissolved oxygen levels (10 mg/L), and moderate water conductivity (448 S/cm) with a water temperature of 17C. Comparative morphological studies revealed population-level variations, particularly in the antenna and gnathopods, between the Sarab-e-Youan and Hashilan populations. This research provides new insights into the taxonomy, phylogeny, and ecological preferences of G. anodon, emphasizing the need for further studies on the biogeography and conservation of this species in Iran.