The lady of the rings: integrative systematics of Nanuca Er. Marcus, 1957 (Mollusca: Nudibranchia: Myrrhinidae) reveals a hidden diversity

AbstractMyrrhinidae are one of the most species-rich families of aeolid nudibranchs. The genus Nanuca comprises a single species, N. sebastiani, which has a wide geographical distribution along the tropical Western Atlantic. The taxonomy of Nanuca has not been thoroughly studied, and its relationship with the genus Dondice is unclear. Using newly generated sequences, we created the most comprehensive dataset to date for studying evolution of Myrrhinidae. We employed an integrative approach combining phylogenetic analyses and species’ delimitation methods (ABGD, ASAP, GMYC, PTP) with mitochondrial (COI, 16S) and nuclear (28S LSU D1-D2) genes, as well as morphological and biogeographical evidence. Our analysis recovered the six genera of Myrrhinidae as monophyletic, reinforcing Dondice and Nanuca as distinct taxa. Molecular phylogenetics, species’ delimitation, and morphological data support the existence of six species of Nanuca: the polymorphic N. sebastiani and five new pseudocryptic species, N. smaugi sp. nov., N. perolata sp. nov., N. cahuitaensis sp. nov., N. alboviridis sp. nov., and N. leali sp. nov. Our work sheds light on biogeographic barriers, like the Amazon River plume, and ecological transitions along Florida, the Caribbean Sea, and Brazil as drivers to Nanuca diversification. Our findings highlight the importance of considering nudibranch species’ diversity within an evolutionary context.Description of the data and file structureThe current data were used in our phylogenetic, species´ delimitation, molecular distances, haplotype network, and molecular diagnostic character analyses of integrative taxonomy for the nudibranch genus Nanuca in the tropical Western Atlantic.FilesSupp_File_01_COI_alignment_larger_dataset.fasFASTA alignment of 98 sequences from COI. Alignment length: 657 bp.Supp_File_02_16S_alignment_larger_dataset.fasFASTA alignment of 75 sequences from 16S rRNA. Alignment length: 381 bp.Supp_File_03_COI_alignment_shorter_dataset.fasFASTA alignment of 25 sequences from COI, with one Dondice species included as outgroup. Alignment length: 657 bp.Supp_File_04_28S_LSU_D1-D2_alignment_shorter_dataset.fasFASTA alignment of 16 sequences from 28S LSU D1–D2 and one Dondice outgroup. Alignment length: 940 bp.Supp_File_05_COI_ABGD_and_ASAP.fasFASTA alignment of 17 unique haplotype sequences from COI used in ABGD and ASAP species delimitation analyses. Alignment length: 657 bp.Supp_File_06_COI_GMYC_and_PTP.fasFASTA alignment of 17 unique haplotype sequences from COI, including one Dondice outgroup, used for tree-based species delimitation (GMYC and PTP). Alignment length: 680 bp.Supp_File_07_28S_LSU_D1-D2_ABGD_and_ASAP.fasFASTA alignment of four unique haplotype sequences from 28S LSU D1–D2 used in ABGD and ASAP analyses. The alignment also includes duplicates of unique haplotypes to enable species delimitation methods. Alignment length: 951 bp.Supp_File_08_28S_LSU_D1-D2_GMYC_and_PTP.fasFASTA alignment of four unique haplotype sequences from 28S LSU D1–D2 and a Dondice outgroup, used for tree-based species delimitation (GMYC and PTP). The alignment also includes duplicates of unique haplotypes to enable species delimitation methods. Alignment length: 956 bp.Supp_File_09_COI_network.nexNEXUS file with 24 sequences from COI and associated trait data, formatted for haplotype network analysis in PopArt.