title: Diversity of free-living marine nematodes (Enoplida) from Baja California assessed by integrative taxonomy.
abstract: We used morphological and molecular approaches to evaluate the diversity of free-living marine nematodes (order Enoplida) at four coastal sites in the Gulf of California and three on the Pacific coast of Baja California, Mexico. We identified 22 morphological species belonging to six families, of which Thoracostomopsidae and Oncholaimidae were the most diverse. The genusMesacanthion(Thoracostomopsidae) was the most widespread and diverse. Five allopatric species, genetically and morphologically differentiated, were found in two localities in the Gulf of California (M. sp1 andM. sp2) and three in the Pacific coast (M. sp3,M. sp4 andM. sp5). Overall, we produced 19 and 20 sequences for the 18S and 28S genes, respectively. Neither gene displayed intraspecific polymorphisms, which allowed us to establish that some morphological variation was likely either ontogenetic or due to phenotypic plasticity. Although 18S and 28S phylogenies were topologically congruent (incongruence length difference test,P> 0.05), divergences between species were much higher in the 28S gene. Moreover, this gene possessed a stronger phylogenetic signal to resolve relationships involvingRhabdodemaniaandBathylaimus. On the other hand, the close relationship ofPareurystomina(Enchilidiidae) with oncholaimids warrants further study. The 28S sequences (D2D3 domain) may be better suited for DNA barcoding of marine nematodes than those from the 18S rDNA, particularly for differentiating closely related or cryptic species. Finally, our results underline the relevance of adopting an integrative approach encompassing morphological and molecular analyses to improve the assessment of marine nematode diversity and advance their taxonomy.
authors.affiliation: Department of Biological Oceanography, Centro de Investigación Científica y de Educación Superior de Ensenada, Carretera Ensenada-Tijuana 3918, Apdo. Postal 2732, CP 22860 Ensenada, Baja California Mexico ; Department of Nematology, University of California, Riverside, CA 92521 USA.
authors.forename: Tiago José
authors.initials: TJ
authors.lastname: Pereira
authors.affiliation: Centro de Biologia Marinha da Universidade de São Paulo, Rod. Manoel Hipolito do Rego km 131.5, São Sebastião, 11600-000 Brazil.
authors.forename: Gustavo
authors.initials: G
authors.lastname: Fonseca
authors.affiliation: Department of Nematology, University of California, Riverside, CA 92521 USA.
authors.forename: Manuel
authors.initials: M
authors.lastname: Mundo-Ocampo
authors.affiliation: Centro de Educação e Saúde, CES, Universidade Federal de Campina Grande, Av. Olho D'Água da Bica s/n, Cuité, PB Brazil.
authors.forename: Betânia Cristina
authors.initials: BC
authors.lastname: Guilherme
authors.affiliation: Department of Biological Oceanography, Centro de Investigación Científica y de Educación Superior de Ensenada, Carretera Ensenada-Tijuana 3918, Apdo. Postal 2732, CP 22860 Ensenada, Baja California Mexico.
authors.forename: Axayácatl
authors.initials: A
authors.lastname: Rocha-Olivares