Complete Mitochondrial Genome of the Spanish toothcarp, Aphanius iberus (Valenciennes, 1846) (Actinopterygii, Aphaniidae) and its phylogenetic position within the Cyprinodontiformes order

Abstract The Spanish toothcarp (Aphanius iberusValenciennes, 1846) is a small fish species endemic to the eastern coastline of the Iberian Peninsula. Along its area of distribution, it mainly inhabits brackish waters which can exhibit large fluctuations in temperature and salinity throughout the year. Aphanius iberus belongs to the family Aphaniidae within the order Cyprinodontiformes and is currently listed as “Endangered” (category IUCN: EN), facing a very high risk of extinction in the wild. The genetics of A. iberus are not well-known since most studies have only evaluated the genetic structure of the species under a conservation framework in order to identify its potential conservation units. In the present study, the entire mitochondrial genome of A. iberus was obtained for the first time in the context of an A. iberus reference genome. The mitogenome was reconstructed and aligned against 83 cyprinodontiformes and two outgroup taxa to create the phylogenetic reconstruction of A. iberus. PartitionFinder was first used to test for the best evolutionary model for both coding and non-coding genes and the phylogenetic analysis was performed using two methods: Maximun-Likelihood approximation (IQ-Tree) and Bayesian inference (MrBayes). Our results show that A. iberus forms a sister group with Orestias ascotanensis, a cyprinodontiform species native to South America. We believe the information gained from this study is valuable for improving our understanding of the historical evolution of A. iberus and that it can be useful for future genomic studies.