Abstract
High morphological plasticity in populations of brine shrimp subjected to different environmental conditions, mainly salinity, hindered for centuries the identification of the taxonomic entities encompassed within Artemia. In addition, the mismatch between molecular and morphological evolution rates complicates the characterization of evolutionary lineages, generating taxonomic problems. Here, we propose a phylogenetic hypothesis for Artemia based on two new complete mitogenomes, and determine levels of congruence in the definition of evolutionary units using nuclear and mtDNA data. We used a fossil of Artemia to calibrate the molecular clock and discuss divergence times within the genus. The hypothesis proposed herein suggests a more recent time frame for lineage splitting than previously considered. Phylogeographic analyses were performed using GenBank available mitochondrial and nuclear markers. Evidence of gen e flow, identified through discordances between nuclear and mtDNA markers, was used to reconsider the specific status of some taxa. As a result, we consider Artemia to be represented by five evolutionary units: Southern Cone, Mediterranean—South African, New World, Western Asian, and Eastern Asian Lineages. After an exhaustive bibliographical revision, unavailable names for nomenclatural purposes were discarded. The remaining available names have been assigned to their respective evolutionary lineage. The proper names for the evolutionary units in which brine shrimps are structured remain as follows: Artemia persimilis Piccinelli & Prosdocimi, 1968 for the Southern Cone Lineage, Artemia salina (Linnaeus, 1758) for the Mediterranean-SouthAfrican Lineage, Artemia urmiana Günther, 1899 for the Western Asian Lineage, and Artemia sinica Cai, 1989 for the Eastern Asian Lineage. The name Artemia monica Verrill, 1869 has nomenclatural priority over A. franciscana Kellogg, 1906 for naming the New World Lineage. New synonymies are proposed for A. salina (= C. dybowskii Grochowski, 1896 n. syn., and A. tunisiana Bowen & Sterling, 1978 n. syn.), A. monica (= A. franciscana Kellogg, 1906 n. syn., and A. salina var. pacifica Sars, 1904 n. syn.); A. urmiana (= B. milhausenii Fischer de Waldheim, 1834 n. syn., A. koeppeniana Fischer, 1851 n. syn., A. proxima King, 1855 n. syn., A. s. var. biloba Entz, 1886 n. syn., A. s. var. furcata Entz, 1886 n. syn., A. asiatica Walter, 1887 n. syn., A. parthenogenetica Bowen & Sterling, 1978 n. syn., A. ebinurica Qian & Wang, 1992 n. syn., A. murae Naganawa, 2017 n. syn., and A. frameshifta Naganawa & Mura, 2017 n. syn.). Internal deep nuclear structuring within the A. monica and A. salina clades, might suggest the existence of additional evolutionary units within these taxa.
Highlights
Taxonomic practice includes two separated but closely linked activities: the recognition and definition of the biological units resulting from speciation processes and the provision of a universal name for each of those biological units (Wiley, 1981; Minelli, 2003; De Carvalho et al, 2005; Padial et al, 2010)
Genome assembly of the Mexican specimen was carried out using as reference a sequence of the complete cox1 gene of a record named as A. franciscana available in Genbank, whereas for the sample of A. salina a partial sequence of cox1 was used as seed, and to avoid possible bias, checked against EU543451.1 (Muñoz et al, 2008)
Like many other mitochondrial genomes of arthropods, the major strand (J strand) carried most of the genes (9 PCGs and 13 tRNAs), while the remaining genes were on the minor strand (N strand)
Summary
Taxonomic practice includes two separated but closely linked activities: the recognition and definition of the biological units resulting from speciation processes and the provision of a universal name for each of those biological units (Wiley, 1981; Minelli, 2003; De Carvalho et al, 2005; Padial et al, 2010). Provision of a universal name for each animal is done by strictly applying the rules and recommendations of a code of practice, the International Code of Zoological Nomenclature (International Commission on Zoological Nomenclature, 1999), provided by the International Commission on Zoological Nomenclature Historical confusion between these two activities, identification of biological units and naming them, has rendered taxonomy a sort of obscure, almost mystical, discipline, difficult to accommodate to society or even to be understood by nontaxonomist scientists (Rosen, 1986; Dubois, 2003; Lipscomb, Platnick & Wheeler, 2003; Mace, 2004; Wheeler & Valdecasas, 2005; Garnett & Christidis, 2007; Ebach, Valdecasas & Wheeler, 2011). Some of those names were not accompanied by adequate descriptions or were applied to populations no longer existing or hard to locate, making
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