L ittoraria flava (Gastropoda: Littorinidae) mitogenome: phylogenetic considerations within the Caenogastropoda and evidence of microscale local adaptation

Littorinids, such as Littoraria flava, are attractive models for local adaptation studies in the rocky shore intertidal zone. The wide heterogeneity of the rocky shore might play a role shaping the evolution of communities distributed in its many micro environments. We extracted the L. flava mitogenome using RNA-seq reads, followed by selection tests at coding gene level using 69 Caenogastropoda species. Here, we present L. flava partial mitogenome with 15,807 bp and 13 PCGs, 21 tRNAs and two rRNAs. Using this new matrix, we produced the most comprehensive mitogenome phylogeny of Caenogastropoda, where we were able to recover the monophyly of Architaenioglossa, Cerithimorpha and Latrogastropoda. The phylogenetic reconstruction shows Littorinimorpha as paraphyletic, supporting that the Vermetidae classification should be re-evaluated. Littoraria flava presents a fragment of nd1 gene duplicated and three tRNAs not presenting the expected cloverleaf structure. We detected positive selection in a phosphoserine codon in nd2 gene from individuals living closer to the ocean, suggesting a hypoxia stress response. Conversely, cytb, cox1, nd1, nd4 and nd6 were under purifying selection and no correlation with the distance to ocean was observed. Our findings corroborate previous studies on evidence of local adaptation at a microscale distribution where few meters may require precise adjustments in energy metabolism, due to the determinant tide influence.