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- Further evidence for diversification within the diogenes pugilator complex (Anomura, Diogenidae) in the mediterranean and black seasPublication . Erk, Cornelia Pia; Uzunova, Sonya; Chartosia, Niki P.; Kevrekidis, Kosmas; Almón, Bruno; Schubart, Christoph D.We document an unrecognised genetic lineage within the European hermit crab Diogenes pugilator species complex. Specifically, we propose the revalidation of the previously synonymised species D. ponticus, , for specimens previously identified as D. pugilator from the Adriatic, Ionian, Aegean, and Black Seas. Analyses of the mitochondrial genes COI and 16S rRNA resulted in a clear genetic separation to East Atlantic and Western Mediterranean populations of Diogenes. . Morphological analyses confirmed differences in the individuals assigned to D. ponticus compared to the congeners D. curvimanus and D. pugilator and thereby a concordance between molecular and morphological characters. Despite the relatively high morphological resemblance to D. armatus, , the molecular differentiation and the remarkable geographic segregation within the species complex suggest at least one speciation or radiation event in the past, underlining the growing importance of molecular methods in the identification of species and evolutionarily significant units. Major oceanographic processes that are known to shape genetic variability and population genetic structure in the marine environment are pointed out as possible structuring factors for the observed intrageneric divergence. The evidence of long evolutionary independence is therefore considered sufficient to re-establish the validity of D. ponticus as a valid species in the northern-central and north-eastern Mediterranean Sea and the Black Sea and is redescribed accordingly.
- Genetic diversity in the American elephantfish (Chimaeriformes: Callorhinchus callorynchus) and among its congenersPublication . Erk, Cornelia Pia; Concha, Francisco J.; Awruch, Cynthia; Finucci, Brittany; Cristiani, Franco; Guzmán‐Castellanos, Ana B.; Silva, Charlene da; Veríssimo, AnaUnderstanding genetic population structure and connectivity is essential for effective species-specific management and conservation strategies. The American elephantfish Callorhinchus callorynchus is targeted and retained as incidental catch in commercial and recreational fisheries in Chile and Argentina. Its wide-ranging distribution across southern South America may require transnational co-operation to ensure sustainable use, but its current population structure is not known. In this work, we analysed the levels of genetic diversity and differentiation within C. callorynchus in South America using two mitochondrial markers, the control region (CR) and the cytochrome oxidase subunit I gene (CO1). Moreover, we assessed levels of genetic diversity within, and divergence among, the three extant callorhinchids (genus Callorhinchus), a group that exhibits allopatric geographical distributions in the southern hemisphere. Overall, sequence analyses of the mitochondrial CR and the CO1 revealed extremely low levels of sequence variation both within and among Callorhinchus species. Genetic homogeneity was found throughout the range of C. callorynchus coupled to low-frequency haplotype sharing across spatially distant locations in Chile and Argentina, suggesting gene flow along the South American coast. Moreover, our analyses supported a scenario of recent population expansion of the species in South America. Given the absence of dispersive eggs or juvenile stages in chondrichthyans, gene flow is mainly mediated by actively swimming adults. Based on the available data, gene flow in callorhinchids appears to occur along continuous coastal regions, with deep oceanic waters serving as strong barriers. Findings here provide an important baseline for future research on dispersal and gene flow in holocephalans.