Heterocypris exodonta sp. nov. (Ostracoda, Cyprididae), morphological and molecular description of a high altitude asexual microcrustacean from the Nam Co region, Southern Tibetan Plateau

A new ostracod species, <i>Heterocypris exodonta</i> Bonilla-Flores & Karanovic, <b>sp. nov.</b> is described from a high-altitude temporary pond near Nam Co, Southern Tibetan Plateau. Detailed morphological analyses of valves, soft body, and the partial mitochondrial COI (cytochrome c oxidase subunit I) sequence distinguish this species from its close congeners, <i>Heterocypris incongruens</i> and <i>Heterocypris salina</i>. Key taxonomic features include the morphology of the female genital lobe and the structure of the internal opening of normal pores, particularly variations in the female genital aperture at the intersection of the seminal duct and the oviduct. Pore openings in <i>H. exodonta</i> Bonilla-Flores & Karanovic, <b>sp. nov.</b> and <i>H. incongruens</i> exhibit a turbine shape, while in <i>H. salina</i> they display a simple aperture. Phylogenetic analysis based on the COI dataset supports the new species description and suggests potential synonymy and cryptic species within the <i>H. salina</i> and <i>H. incongruens</i> complexes. Ecologically, these species mainly inhabit temporary water bodies with high oxygen levels and likely follow an r-type ecological strategy, being opportunistic in colonizing new habitats, reproducing via parthenogenesis, and undergoing rapid population growth. This study enhances the understanding of Southern Tibetan Plateau ostracod biodiversity, providing crucial morphological and molecular data for species identification, particularly for parthenogenetic species lacking standard male morphological characters. Additionally, this research offers methods to prevent misidentifications and misinterpretations in (paleo-)ecological studies, contributing significantly to the broader knowledge of taxonomy and ecology of ostracods from the Southern Tibetan Plateau. Due to the high morphological plasticity of <i>Heterocypris incongruens</i>, our findings highlight the need for caution when identifying similar species, as external resemblance may conceal genetic divergence.