Diversity of free-living marine nematodes (Enoplida) from Baja California assessed by integrative taxonomy |
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Authors: | Tiago José Pereira Gustavo Fonseca Manuel Mundo-Ocampo Betânia Cristina Guilherme Axayácatl Rocha-Olivares |
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Institution: | 1. 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 2. Department of Nematology, University of California, Riverside, CA, 92521, USA 3. Centro de Biologia Marinha da Universidade de S?o Paulo, Rod. Manoel Hipolito do Rego km 131.5, S?o Sebasti?o, 11600-000, Brazil 4. Centro de Educa??o e Saúde, CES, Universidade Federal de Campina Grande, Av. Olho D’água da Bica s/n, Cuité, PB, Brazil
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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
genus Mesacanthion (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 and M. sp2) and three in the Pacific coast (M. sp3, M. sp4 and M. 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 involving Rhabdodemania and Bathylaimus. On the other hand, the close relationship of Pareurystomina (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. |
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