Taxonomic identity of Distaplia stylifera (Tunicata, Ascidiacea), a new arrival to the eastern Pacific displaying invasive behavior in the Gulf of California, Mexico

A colonial ascidian of the genus Distaplia caused a mass mortality of the pen shell Atrina maura (Sowerby, 1835) during June 2016 in the southwest of the Gulf of California (Mexico), with a significant socio-economic cost. Tentatively identified in previous works as Distaplia cf. stylifera, a precise taxonomic determination was still lacking. In the present work, based on a detailed morphological study, it is confirmed that this aggressive species is Distaplia stylifera (Kowalevsky, 1874). Originally described from the Red Sea, the species currently has a wide circumtropical distribution (with the exception of the Eastern Pacific to date) and is reported as introduced in parts of its range. The present account thus represents an important range extension of this species. However, when revising the original description and later observations, the reported variability of several characters makes it likely that the binomen is in fact a complex of species, as is common in other ascidians with wide distributions. A complete morphological and genetic study including populations from the entire range of distribution would be necessary to settle the status of D. stylifera. Taxonomic uncertainties hinder a correct interpretation of biogeographical patterns and inference on the origin of the studied population. Nevertheless, the known introduction potential of the species, coupled with an explosive growth in an anthropized environment, and the lack of any previous reports in the Eastern Pacific, strongly suggest that the investigated population represents yet another instance of ascidian introduction. From the point of view of management, its invasive behavior is cause for great concern and warrants mitigation measures

Three new species of the sea fan genus Muricea (Cnidaria, Octocorallia, Plexauridae) from the northwest region of Mexico

Twenty-one nominal species of Muricea have been reported in the Eastern Pacific with nine of them reported in the Mexican Pacific. We describe three new species of Muricea: Muricea ambarae sp. nov. and Muricea cacao sp. nov., from rocky reefs on the central and the northern Gulf of California and the Pacific coast of Baja California Sur, and Muricea molinai sp. nov., from the Pacific coast of Baja California Sur. Muricea ambarae sp. nov. and M. cacao sp. nov. are taxonomically allied to the nominal species Muricea fruticosa Verrill, 1869 due to the morphological similarity of colony growth patterns and the phylogenetic closeness based on the mitochondrial MutS gene (mtMutS); but differ mainly in the calyx form and composition of sclerites. The main morphological differences between the new Muricea species are in their sclerite forms and color; M. ambarae sp. nov. has orange-colored colonies, thin leaf spindles and tuberculated blunt spindles, while M. cacao sp. nov. has dark brown colored colonies, strong spinous spindles and an absence of tuberculated blunt spindles. Muricea molinai sp. nov. is phylogenetically close and morphologically similar to Muricea squarrosa Verrill, 1869 in the growth form of the colony and tubular calyces; but has dark brown colored colonies and has calyces from the base to the branch tips. With these three new species, the total number of Muricea species reported in the Mexican northwest region increases to twelve and a total of 24 nominal species in the Eastern Pacific

The complete mitogenome of the live-bearing fish Xenotoca variata (Bean, 1887) (Actinopterygii: Goodeidae)

The live-bearing fish Xenotoca variata is representative of the viviparous Goodeinae subfamily (Goodeidae) from central Mexico. The mitogenome of the X. variata consist of 37 genes in 16,462 bp. Comparing with X. eiseni, the most related of the mitogenomes included, an identity of 91.1% was found and trna-met duplication in X. eiseni is absent in X. variata. The mitogenome provide important information for future studies in evolution of the live-bearing subfamily.This work was supported by the SAGARPA-FIRCO 2012 under Grant RGA- BCS-12-000003.Peer Reviewe

Genetic diversity and structure of circumtropical almaco jack Seriola rivoliana : tool for conservation and management.

The almaco jack Seriola rivoliana is a circumtropical pelagic fish of importance both in commercial fisheries and aquaculture. To understand levels of genetic diversity within and among populations in the wild, population genetic structure and the relative magnitude of migration were assessed with mtDNA sequence data and SNPs from individuals sampled from locations in the Pacific and Atlantic Oceans. A total of 25 variable sites of COI and 3,678 neutral SNPs were recovered. Three genetic groups were identified with both marker types distributed in different oceanic regions: Pacific‐1 in central Pacific, Pacific‐2 in eastern Pacific and Atlantic in western Atlantic. However, analysis of SNP identified a fourth population in Pacific coast of Baja California Sur, Mexico (Pacific‐3), while mtDNA did not. This mito‐nuclear discordance is likely explained by a recently diverged Pacific‐3 population. In addition, two mtDNA haplogroups were found within the western Atlantic, likely indicating that the species came into the Atlantic from the Indian with historical gene flow from the eastern Pacific. Relative gene flow among ocean basins was low with r m  0.79). The results reflect the importance of assessing genetic structure and gene flow of natural populations for the purposes of sustainable management

Role of oceanography in shaping the genetic structure in the North Pacific hake <i>Merluccius productus</i>

<div><p>Determining the relative influence of biotic and abiotic factors on genetic connectivity among populations remains a major challenge in evolutionary biology and in the management and conservation of species. North Pacific hake (<i>Merluccius productus</i>) inhabits upwelling regions in the California Current ecosystem from the Gulf of California to the Gulf of Alaska. In this study, we examined mitochondrial DNA (mtDNA) and microsatellite variation to estimate levels of genetic differentiation of <i>M</i>. <i>productus</i> in relation to the role of oceanographic features as potential barriers to gene flow. Samples were obtained from nine sites spanning a large part of the geographic range of the species, from Puget Sound, Washington to Costa Rica. The microsatellite results revealed three genetically discrete populations: one spanning the eastern Pacific coast, and two apparently resident populations circumscribed to the Puget Sound and the northern Gulf of California (F_ST = 0.032, p = 0.036). Cytochrome b sequence data indicated that isolation between the Puget Sound and northern Gulf of California populations from the coastal Pacific were recent phenomena (18.5 kyr for Puget Sound and 40 kyr for the northern Gulf of California). Oceanographic data obtained from the Gulf of California support the hypothesis that permanent fronts within the region, and strong gradients at the entrance to the Gulf of California act as barriers to gene flow. A seascape genetics approach found significant genetic–environment associations, where the daytime sea surface temperature and chlorophyll concentrations were the best predictive variables for the observed genetic differentiation. Considering the potential causes of genetic isolation among the three populations, e.g. spawning areas in different latitudes associated with upwelling processes, oceanographic barriers, asymmetric migration and specialized diet, oceanographic barriers appear to be a likely mechanism restricting gene flow.</p></div

Relaxed Bayesian topology with the estimated divergence times based on CYTB sequences for populations of <i>Merluccius productus</i> obtained with BEAST [65].

<p>Numbers at nodes indicate divergence time in millions of years. Blue bars correspond to the 95% highest posterior density (HPD) intervals. For clarity, samples from the NGC, PC and PS were collapsed into triangles.</p

Pairwise F_<i>ST</i> values (below diagonal) and ϕ_<i>ST</i> (above diagonal) for <i>Merluccius productus</i>.

<p>Location abbreviations as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0194646#pone.0194646.t001" target="_blank">Table 1</a>.</p

Role of oceanography in shaping the genetic structure in the North Pacific hake <i>Merluccius productus</i> - Fig 4

<p><b>Genetic barriers detected using pairwise population differentiation indices for <i>Merluccius productus</i>: a) mtDNA and b) microsatellite data.</b> Red lines indicate genetic barriers. Voronoï tessellation shown in blue and the corresponding Delaunay triangulation of samples in green. Numbers in parentheses indicate bootstrap percentages. Abbreviations are as in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0194646#pone.0194646.t001" target="_blank">Table 1</a>.</p

Redundancy analysis (RDA) for the association of oceanographic variables obtained from Ocean Color Web, and the ancestry coefficients of the three populations.

<p>Puget Sound (PS), Pacific Coast (PC) and Northern Gulf of California (NGC) generated in STRUCTURE. Chlorophyll <i>a</i> concentration (CHL) and sea day time surface temperature (SSTd).</p

Hierarchical analysis of molecular variance (AMOVA) of genetic variation of <i>Merluccius productus</i> for mitochondrial DNA (mtDNA) and microsatellite loci (M).

<p>Hierarchical analysis of molecular variance (AMOVA) of genetic variation of <i>Merluccius productus</i> for mitochondrial DNA (mtDNA) and microsatellite loci (M).</p