title: Cryptic diversity in the Western Balkan endemic copepod: Four species in one?
abstract: We use mitochondrial (mtCOI) and nuclear (nH3) sequence data to investigate differentiation of Eudiaptomus hadzici, a freshwater copepod endemic to the Western Balkans. E. hadzici has a disjunct distribution and morphological differences were observed at regional scale. In the current study 6 out of 7 known populations are included. We applied several species delimiting approaches, distance based methods (K2P p-distance and Automatic Barcode Gap Discovery, ABGD) using the mtCOI, Bayesian phylogeny and the Bayesian method implemented in bPTP and BPP programs using the concatenated sequences of both genes. Phylogenetic and species delimitation analyses all suggest that the nominal species E. hadzici consists of four isolated, cryptic evolutionary lineages in the Western Balkans. Each of the four lineages inhabits a single lake or a group of lakes in close proximity. They exhibit major differences in secondary sexual characters, e.g. right antennule in males. Denticulation of spine on 13th segment is substantially distinct among the four lineages, having different number and shape of tooth-like protrusions. Gene flow and dispersal are restricted to very small spatial scale, but with local differences, implying that diverse historical and contemporary processes are operating at small spatial scales in E. hadzici. In order to further examine spatial and temporal diversification patterns, we constructed a dated species tree analysis using (*)BEAST. Due to lack of reliable calibration points and taxa specific evolutionary rates, two evolutionary rates were applied and the faster one (2.6% myr) seems more plausible considering the geological history of the region. The divergence of E. hadzici lineages is dated from Early Miocene onwards with geographically close lineages diverging more recently, Late Miocene to Pleistocene and Pleistocene, respectively. Overall, our findings shed light on cryptic genetic complexity of endemics in one of European biodiversity hotspots. Moreover, this study represents one further example of integrative taxonomy, linking DNA methodology and classical taxonomy based on morphology. Therefore, it lays groundwork for future taxonomy and biogeography of freshwater microcrustaceans in the region.
authors.affiliation: Department of Biology, Faculty of Science, University of Zagreb, Rooseveltov trg 6, 10000 Zagreb, Croatia. Electronic address: ana.previsic@biol.pmf.hr.
authors.forename: Ana
authors.initials: A
authors.lastname: Previšić
authors.affiliation: School of Medicine, University of Split, Šoltanska 2, 21000 Split, Croatia.
authors.forename: Andrea
authors.initials: A
authors.lastname: Gelemanović
authors.affiliation: Institute for Water of the Republic of Slovenia, Hajdrihova 28 c, 1000 Ljubljana, Slovenia.
authors.forename: Gorazd
authors.initials: G
authors.lastname: Urbanič
authors.affiliation: Department of Biology, Faculty of Science, University of Zagreb, Rooseveltov trg 6, 10000 Zagreb, Croatia.
authors.forename: Ivančica
authors.initials: I
authors.lastname: Ternjej
mesh_terms: D000818:Animals; D063368:Balkan Peninsula; D001499:Bayes Theorem; D044822:Biodiversity; D005075:Biological Evolution; D033342:Copepoda / Q000145:classification* / Q000235:genetics; D004247:DNA / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D004272:DNA, Mitochondrial / Q000737:chemistry / Q000378:metabolism; D051456:Gene Flow; D014644:Genetic Variation; D006657:Histones / Q000235:genetics; D008297:Male; D010802:Phylogeny; D017422:Sequence Analysis, DNA
chemical_list: D004272:DNA, Mitochondrial; D006657:Histones; D004247:DNA
keywords: Allopatric fragmentation; Freshwater Calanoida; Integrative taxonomy; Phylogeography; Speciation; Species delimitation