Evidence of cryptic and pseudocryptic speciation in the Paracalanus parvus species complex (Crustacea, Copepoda, Calanoida)

Abstract

IntroductionMany marine planktonic crustaceans such as copepods have been considered as widespread organisms. However, the growing evidence for cryptic and pseudo-cryptic speciation has emphasized the need of re-evaluating the status of copepod species complexes in molecular and morphological studies to get a clearer picture about pelagic marine species as evolutionary units and their distributions. This study analyses the molecular diversity of the ecologically important Paracalanus parvus species complex. Its seven currently recognized species are abundant and also often dominant in marine coastal regions worldwide from temperate to tropical oceans.ResultsCOI and Cytochrome b sequences of 160 specimens of the Paracalanus parvus complex from all oceans were obtained. Furthermore, 42 COI sequences from GenBank were added for the genetic analyses. Thirteen distinct molecular operational taxonomic units (MOTU) and two single sequences were revealed with cladistic analyses (Maximum Likelihood, Bayesian Inference), of which seven were identical with results from species delimitation methods (barcode gaps, ABDG, GMYC, Rosenberg’s P(AB)). In total, 10 to 12 putative species were detected and could be placed in three categories: (1) temperate geographically isolated, (2) warm-temperate to tropical wider spread and (3) circumglobal warm-water species.ConclusionsThe present study provides evidence of cryptic or pseudocryptic speciation in the Paracalanus parvus complex. One major insight is that the species Paracalanus parvus s.s. is not panmictic, but may be restricted in its distribution to the northeastern Atlantic.

Occurrence of the <i>Paracalanus parvus</i> species complex in offshore waters south of Japan and their genetic and morphological identification to species

“…The morphological information obtained was used to compare the present specimens to those described in previous reports (e.g. Ibe et al 2005, Cornils & Held 2014, which included discussions regarding the morphology of the forehead, morphological features of the genital double-somite, and numerical characteristics related to the swimming legs.…”

“…These authors examined only mitochondrial genes and indicated that differences in nuclear genetic material should be examined to confirm reproductive isolation among strains. Additionally, some morphological examinations in the study by Cornils & Held (2014) were not completed due to the physical condition of the samples, and the spatial resolution was low in terms of covering such broad distributional ranges. It was therefore insufficient to adequately describe the distributional patterns of each species with respect to major oceanographic structures.…”

“…Species of the Paracalanus parvus (Claus, 1863) complex (Cornils & Held 2014) are distributed in many temperate and tropical regions (e.g. Bowman 1971, BradfordGrieve 1994, Liang & Uye 1996, Kesarkar & Anil 2010.…”

“…To this end, molecular approaches can provide valuable insights on taxonomic delineations and have been widely used in detecting cryptic species of marine zooplankton (Bucklin et al 2011). Cornils & Held (2014) introduced an integrative approach of genetic and morphological analyses for evaluating the taxonomic status of the P. parvus complex. They collected material belonging to the P. parvus complex on a global scale and recognized 10-12 putative species out of their material.…”

Population genetic structure of Calanoides natalis (Copepoda, Calanoida) in the eastern Atlantic Ocean and Benguela upwelling system

“…However, recent discoveries of cryptic and pseudo-cryptic species complexes in copepods (Goetze, 2003;Goetze and Ohman, 2010;Laakmann et al, 2012;Andrews et al, 2014;Cornils and Held, 2014) clearly demonstrate that genetic diversity does not necessarily lead to distinguishable morphological features. Additionally, DNA barcoding solely relying on the mitochondrial marker genes such as cytochrome c oxidase subunit I (COI) may lead to the misinterpretation of species diversity (Song et al, 2008).…”