Search

Larval genetic information influences populations’ genetic pools, causing genetic homogenization or structuration. So, knowing about adult and larval genetic information is essential to understand processes such as connectivity. The aims are to evaluate Twospot flounder (Bothus robinsi, a fish with a high dispersal potential) larval pools’ genetic diversity, test if the larvae tend to mix or display collective dispersal, compare genetic information between larvae and adults and evaluate its connectivity. We used ddRADSEQ to genotype 1,034 single nucleotide polymorphic sites from B. robinsi larvae sampled in waters from the Bay of Campeche and the eastern Gulf of Mexico (GOM) and adults sampled on Florida’s continental shelf. Larvae were identified morphologically and by DNA barcoding. We estimated Fst-paired comparations, Principal Components Analysis (PCA), Discriminant Analyses of Principal Components (DAPC), and a Structure analysis to understand genetic trends. With the software COLONY, we made a sibship evaluation. We observed no significant heterogeneity among regions (Fst p-values>0.05). PCA, DAPC, and the Structure Analysis showed one genetic cluster, indicating genetic homogeneity. We did not detect full-sibs or half-sibs. We linked the results with the high dispersal potential of B. robinsi due to a long pelagic larval duration and the potential of ocean dynamics to transport and mix larvae from all GOM shelf areas. These findings suggest that the dispersal potential of B. robinsi is large enough to produce genetic connectivity in all GOM subpopulations and that time spent by its larvae in dispersal pathways is enough to mix larvae from different GOM subpopulations, indicating a panmictic population.

Loricifera is a group of marine, meiobenthic invertebrates of microscopic size that are found worldwide. The Loriciferan fauna of the Southern Gulf of Mexico (SGM) remains unknown. In the present study we report on the first exploration of the Loriciferans from the SGM, which is a strategic area for oil exploitation. The Loriciferan specimens were collected during deep-sea cruises XIXIMI-4 (August-September 2015) and XIXIMI-6 (August 2017), in which six out of 22 stations yielded specimens of Loricifera. A total of six specimens were found (although one of them was lost), namely two adults and four larval stages. Preliminary analyses based on the peculiarity of their morphological features indicate that the specimens include representatives of new species of Pliciloricus and Rugiloricus, an undescribed genus of Pliciloricidae and, possibly, an undescribed genus of Nanaloricidae. None of the specimens found could be assigned to previously described species. Since all specimens are either intermediate life cycle stages or poorly preserved, only a short description based on their morphological traits is provided here. Our findings are discussed from a comparative perspective with known Loriciferan species.

Deep-water sampling in the Perdido Fold Belt, Gulf of Mexico, Mexican Economic Exclusive Zone yielded five specimens of tardigrades belonging to the genus Coronarctus Renaud-Mornant, 1974. The specimens represent the first records of the genus for Mexico. Two two-clawed larvae and two four-clawed larvae of Coronarctus mexicus Romano, Gallo, D’Addabbo, Accogli, Baguley & Montagna, 2011 and a single four-clawed larval specimen of an undescribed Coronarctus species were identified. Taxonomic analysis of the specimens contributed to the knowledge of deep-sea and Mexican marine tardigrades, two data-poor areas of study.

The complete mitogenome of Thoosa mismalolli Carballo, Cruz-Barraza & Gómez, 2004 (Tetractinellida, Thoosidae) was sequenced. This is the first complete mitogenome of the suborden Thoosina and the third Tetractinellid so far. The mitochondrial genome of T. mismalolli was assembled based on reads obtained with the Illumina HiSeq platform. The length of complete mitogenome is 19,019 bp long and contained 14 protein-coding genes and 23 tRNA, with two tRNA genes. Phylogenetic reconstruction (maximum-likelihood) based on mitogenome of Tetractinellids, supports T. mismalolli as a sister group. This result is congruent with those obtained with molecular markers (CO1, 18S, and 28S), supporting the monophyletic status of Thoosa and providing additional molecular data in favor of the suborder Thoosina.

The GI microbiota of abalone contains a highly complex bacterial assemblage playing an essential role in the overall health of these gastropods. The gut bacterial communities of abalone species characterized so far reveal considerable interspecific variability, likely resulting from bacterial interactions and constrained by the ecology of their abalone host species; however, they remain poorly investigated. Additionally, the extent to which structural changes in the microbiota entail functional shifts in metabolic pathways of bacterial communities remains unexplored. In order to address these questions, we characterized the gut microbiota of the northeast Pacific blue (Haliotis fulgens or HF) and yellow (Haliotis corrugata or HC) abalone by 16S rRNA gene pyrosequencing to shed light on: (i) their gut microbiota structure; (ii) how bacteria may interact among them; and (iii) predicted shifts in bacterial metabolic functions associated with the observed structural changes. Our findings revealed that Mycoplasma dominated the GI microbiome in both species. However, the structure of the bacterial communities differed significantly in spite of considerable intraspecific variation. This resulted from changes in predominant species composition in each GI microbiota, suggesting host-specific adaptation of bacterial lineages to these sympatric abalone. We hypothesize that the presence of exclusive OTUs in each microbiota may relate to host-specific differences in competitive pressure. Significant differences in bacterial diversity were found between species for the explored metabolic pathways despite their functional overlap. A more diverse array of bacteria contributed to each function in HC, whereas a single or much fewer OTUs were generally observed in HF. The structural and functional analyses allowed us to describe a significant taxonomic split and functional overlap between the microbiota of HF and HC abalone.

The coral Porites sverdrupi is the only scleractinian endemic to the Gulf of California. Over the last 2 decades its populations have been restricted to 3 areas, La Paz Bay, Loreto Bay, and Concepción Bay. As this species faces a high risk of extinction, there is an urgent need for biological, ecological, and genetic information for the guidance of conservation efforts. This is the first study on genetic diversity and connectivity in the species. For this, we analyzed coral colonies from Loreto Bay and Concepción Bay. Our results show that there is high genetic diversity in P. sverdrupi at both sites, with significant genetic structure between them. This condition is caused by a combination of short pelagic larval duration, low dispersal potential between the populations, and local adaptation. Our results emphasize the need for more research in order to establish adequate conservation strategies.

We report the first mitochondrial genome of a Verongid sponge, Aplysina gerardogreeni from the Pacific Ocean. This has 19,620 bp and includes 14 protein-coding genes, 2 rRNAs genes, and 25 tRNAs genes. The gene arrangement was similar to the one found in two Caribbean Aplysina mitogenomes previously reported. Comparative analyses revealed a few substitutions among congeneric mitogenomes. The mitogenome of A. gerardogreeni could be useful to study the evolution of Verongimorpha group and also to identify adequate genes for its molecular systematics.

Background: Mycale cecilia is an abundant Eastern Tropical Pacific sponge living in a wide variety of habitats, including coral reefs where it may directly interact with corals. It is also known to possess secondary metabolites of pharmacological value. These aspects highlight the importance of having a better understanding of its biology, and genetic and population diversity. Methods and results: In the present study, we isolated and characterized twelve novel microsatellite loci by Illumina MiSeq sequencing. The loci were tested in 30 specimens collected from two coral reef localities (La Paz, Baja California Sur and Isabel Island, Nayarit) from the Mexican Pacific using M13(-21) labeling. All loci were polymorphic, with two to nine alleles per locus. Expected heterozygosities varied from 0.616 to 0.901. Eleven loci were tested and successfully amplified in M. microsigmatosa from the Gulf of Mexico. Conclusion: Here we report the first microsatellite loci developed for a sponge species from the Eastern Pacific coast. These molecular markers will be used for population genetic studies of M. cecilia, and potentially in other congeneric species; particularly in vulnerable marine areas that require protection, such as coral reefs. [ABSTRACT FROM AUTHOR]

Geographic variation in external morphology is thought to reflect an interplay between genotype and the environment. Morphological variation has been well-described for a number of cetacean species, including the bottlenose dolphin (Tursiops truncatus). In this study we analyzed dorsal fin morphometric variation in coastal bottlenose dolphins to search for geographic patterns at different spatial scales. A total of 533 dorsal fin images from 19 available photo-identification catalogs across the three Mexican oceanic regions (Pacific Ocean n = 6, Gulf of California n = 6 and, Gulf of Mexico n = 7) were used in the analysis. Eleven fin shape measurements were analyzed to evaluate fin polymorphism through multivariate tests. Principal Component Analysis on log-transformed standardized ratios explained 94% of the variance. Canonical Discriminant Function Analysis on factor scores showed separation among most study areas (p

Mark-recapture techniques are fundamental for assessing marine mammal population dynamics and individual temporal patterns. Since biases imposed by field conditions are generally unknown, we simulated variations in sampling effort (m) and maximum individual catchability (r max) to analyze their effects on residency levels measured through the number of recaptures (occurrence, O), duration of stay (permanence, P), and average recurrence (periodicity, I) relative to a reference level of exhaustive daily sampling frequency. The number or recorded individuals (Dr) was also used to determine the performance of the simulations. Results for standardized (s) parameters showed that occurrences (Os) were proportional to m and were not influenced by r max. Individual permanence (Ps) and individual periodicity (Is) were 8-49% and 3-11.74 times lower than expected, respectively, depending on m and r max. Also, Os, Ps, and Is were not influenced by study duration, thus inter-study comparisons are feasible if m and r max are similar. Dr was 68-92% (r max= 0.01) and 1-8% (r max= 1.0) lower than expected depending on m. Longer studies were more accurate but greater effort did not significantly increase Dr estimates. The use of bimonthly sampling frequencies (m= 0.07) was barely accurate and predictions for incomplete datasets were poor. Survey field data were also analyzed from 14 published studies on 4 dolphin species and compared to daily sampling frequencies; resulting values for Os, Ps, and Dr were 62.4-93.3%, 11.6-66.4%, and 2.4-33.8% lower than expected, respectively; also Is was 2.3-7.3 times lower than expected. The model produced Dr values that were similar to population estimates from empirical data, and bias was smaller than 15% in 87.5% of the cases, thus simulation accuracy was deemed acceptable.Las técnicas de marcado-recaptura son fundamentales para evaluar la dinámica poblacional de mamíferos marinos y sus patrones temporales individuales. Se simularon variaciones en el esfuerzo (m) y la máxima capturabilidad individual (r max) para analizar los sesgos en la residencia individual, medida como el número de recapturas (presencia, O), la duración de la estancia (permanencia, P) y la recurrencia promedio (asiduidad, I), en relación con un muestreo exhaustivo de frecuencia diaria. También se analizó el número de individuos registrados (Dr) para determinar el desempeño de las simulaciones. Los resultados de los parámetros estandarizados (s) mostraron que la presencia (Os) fue proporcional a m sin ser influida por r max. La permanencia (Ps) y la asiduidad (Is) fueron 8-49% y 3-11.74 veces más bajas que lo esperado, respectivamente, dependiendo de m y r max. Los valores de Os, Ps e Is no cambiaron con la duración del muestreo y las comparaciones entre estudios son posibles siempre que m y r max sean similares. El valor de Dr fue entre 68-92% (r max= 0.01) y 1-8% (r max= 1.0) menor de lo esperado dependiendo de m. Aunque los estudios más largos fueron más precisos, un mayor esfuerzo no incrementó significativamente el valor de Dr. Los muestreos quincenales fueron poco precisos y las predicciones para datos incompletos fueron poco confiables. También se analizaron los datos de campo de 14 estudios publicados de cuatro especies de delfines y se compararon contra muestreos diarios; los resultados de Os, Ps y Dr fueron 62.4-93.3%, 11.6-66.4% y 2.4-33.8% más bajos de lo esperado, respectivamente; además, Is fue 2.3-7.3 veces más baja que lo esperado. El modelo produjo valores para Dr que fueron similares a las estimaciones poblacionales de los estudios empíricos, con un sesgo menor al 15% en 87% de los casos, por lo que se considera que la precisión del modelo es aceptable.

The Mexican rockfish Sebastes macdonaldi is the Northeast Pacific rockfish with the southernmost distribution, featuring isolated populations in the Gulf of California. We analysed seven microsatellite loci in 111 organisms collected throughout most of its geographical range to test long-standing hypotheses regarding its disjunct distribution. One locus was fixed and the number of alleles in polymorphic loci ranged from 2 to 24 (average 13.5). We found very high levels of polymorphism (overall He = 0.75) comparable to other congeneric species but no significant differences in genetic diversity among localities or between Pacific and Gulf of California populations (p > 0.1). Significant shifts in allelic and genotypic frequencies were detected at three loci, which resulted in a small but significant partitioning of genetic variance among California, Baja California and Gulf of California populations (FST = 0.007, p = 0.03) and between Gulf and Pacific populations (FST = 0.01, p = 0.004). The latter but not the former result was corroborated by analyses of molecular variance (AMOVA) using the number of distinct alleles (FST) and the sum of square differences of allele sizes (RST) as Euclidean distances. The evidence argues against contemporary gene flow between the gulf and the Pacific ocean and against an ancient invasion of the gulf with a founder effect. The small level of divergence favours a recent dispersal but a larger data set including DNA sequences amenable to phylogenetic analyses will help to test alternative hypotheses of dispersal versus vicariance.

Water depth can affect the size spectra (SS) and biomass of free‐living nematodes, but these relationships are largely unknown for the Gulf of Mexico (GoM). Here, we examined the SS and biomass of meiofaunal nematode assemblages at 27 sites along a water‐depth gradient from 44 to 3466 m in the Perdido belt, northwestern GoM. Nematodes were identified to species level, measured (length and width), and assigned to shape morphotypes and trophic groups. Nematode SS were defined by a median length of 951 μm (range: 223–4289 μm) and a median width of 33 μm (range: 12–109 μm). SS revealed a dominant long/slender morphotype (e.g., Paramicrolaimus sp., Filoncholaimus sp., and Ledovitia sp.), better adapted to the very fine sediments of the deep sea, whereas stout/short nematodes (mostly Desmoscolex sp., Greeffiella sp., and Quadricoma sp.) were less abundant. Water‐depth gradient significantly influenced mean individual (IB) and total biomasses likely because reduced availability of organic carbon with depth. The two deepest sites had particularly high mean IB suggesting local sources of organic carbon in the abyssal region related to the Perdido belt oil field. The most abundant trophic group was microbial feeder sucker (56%), followed by microbial feeder scraper (23%), and predator ingester (20%). The mean IB of predator nematodes was significantly larger than that of nematode preys. However, the logarithm of ratio IBpredator/IBprey was rather low (0.34) and in agreement with the empiric consumer‐resource body‐size relationship calculated for marine invertebrates. Our study provides novel insights about the structure of benthic nematode assemblages in the western Gulf of Mexico across a wide depth gradient. [ABSTRACT FROM AUTHOR]

ABSTRACT Geoduck clams have become the most profitable emerging fishery resource in Northwest Mexico, with profits of more than USS30 million during the last few years. The fishery targets two [...]

Biodiversity has diminished over the past decades with climate change being among the main responsible factors. One consequence of climate change is the increase in sea surface temperature, which, together with long exposure periods in intertidal areas, may exceed the tolerance level of benthic organisms. Benthic communities may suffer structural changes due to the loss of species or functional groups, putting ecological services at risk. In sandy beaches, free-living marine nematodes usually are the most abundant and diverse group of intertidal meiofauna, playing an important role in the benthic food web. While apparently many functionally similar nematode species co-exist temporally and spatially, experimental results on selected bacterivore species suggest no functional overlap, but rather an idiosyncratic contribution to ecosystem functioning. However, we hypothesize that functional redundancy is more likely to observe when taking into account the entire diversity of natural assemblages. We conducted a microcosm experiment with two natural communities to assess their stress response to elevated temperature. The two communities differed in diversity (high [HD] vs. low [LD]) and environmental origin (harsh vs. moderate conditions). We assessed their stress resistance to the experimental treatment in terms of species and diversity changes, and their function in terms of abundance, biomass, and trophic diversity. According to the Insurance Hypothesis, we hypothesized that the HD community would cope better with the stressful treatment due to species functional overlap, whereas the LD community functioning would benefit from species better adapted to harsh conditions. Our results indicate no evidence of functional redundancy in the studied nematofaunal communities. The species loss was more prominent and size specific in the HD; large predators and omnivores were lost, which may have important consequences for the benthic food web. Yet, we found evidence for alternative diversity-ecosystem functioning relationships, such as the Rivets and the Idiosyncrasy Model.

Integrative taxonomy provides a major approximation to species delimitation based on integration of different perspectives (e.g. morphology, biochemistry and DNA sequences). The aim of this study was to assess the relationships and boundaries among Eastern Pacific Aplysina species using morphological, biochemical and molecular data. For this, a collection of sponges of the genus Aplysina from the Mexican Pacific was studied on the basis of their morphological, chemical (chitin composition), and molecular markers (mitochondrial COI and nuclear ribosomal rDNA: ITS1-5.8-ITS2). Three morphological species were identified, two of which are new to science. A. clathrata sp. nov. is a yellow to yellow-reddish or -brownish sponge, characterized by external clathrate-like morphology; A. revillagigedi sp. nov. is a lemon yellow to green, cushion-shaped sometimes lobate sponge, characterized by conspicuous oscules, which are slightly elevated and usually linearly distributed on rims; and A. gerardogreeni a known species distributed along the Mexican Pacific coast. Chitin was identified as the main structural component within skeletons of the three species using FTIR, confirming that it is shared among Verongida sponges. Morphological differences were confirmed by DNA sequences from nuclear ITS1-5.8-ITS2. Mitochondrial COI sequences showed extremely low but diagnostic variability for Aplysina revillagigedi sp. nov., thus our results corroborate that COI has limited power for DNA-barcoding of sponges and should be complemented with other markers (e.g. rDNA). Phylogenetic analyses of Aplysina sequences from the Eastern Pacific and Caribbean, resolved two allopatric and reciprocally monophyletic groups for each region. Eastern Pacific species were grouped in general accordance with the taxonomic hypothesis based on morphological characters. An identification key of Eastern Pacific Aplysina species is presented. Our results constitute one of the first approximations to integrative taxonomy, phylogeny and evolutionary biogeography of Eastern Pacific marine sponges; an approach that will significantly contribute to our better understanding of their diversity and evolutionary history.

Patterns of genetic structure among marine populations involve a variety of dispersal mechanisms and spatial scales. Pelagic species, such as the dolphinfish Coryphaena hippurus, epitomize the open and continuous nature of the marine environment due to their extensive migrations. Many studies have revealed that oceanic pelagic species tend to be genetically homogeneous over local and often extended geographic scales and only show levels of differentiation among extreme localities or ocean basins. Here we present genetic data suggesting genetic heterogeneity in the dolphinfish at geographic scales much smaller than those predicted by those generalizations. Mitochondrial NADH1 gene RFLPs revealed a highly significant (ΦST = 0.029, P = 0.004, AMOVA) molecular genetic structure among fish from Baja California Sur (BCS), Sinaloa and Hawaii, consistent with heterogeneous haplotype frequencies (P = 0.014, exact test of genetic differentiation) and a depressed molecular diversity in fish sampled off BCS.

Among diverse marine invertebrate taxa, the evolution of a non-planktotrophic larva is often associated with increased rates of cladogenesis, compared to related taxa that retain the ancestral planktotrophic larval form. Molecular phylogenetic analyses of non-planktotrophic (and, presumably species-rich) clades of marine invertebrates are rare. Here we analyze 1542 base pairs of mitochondrial DNA sequence comprising two gene regions, the cytochrome oxidase I gene and the putative control region and flanking sequences, for 23 molecular lineages in the obligately brood-protecting asteroid genus Leptasterias. Using maximum likelihood, minimum evolution, and maximum parsimony methods, five major clades were identified that corresponded to five taxa (species or species complexes) in the subgenus Hexasterias, section camtschatica (following the taxonomy of Walter K. Fisher). Two clades (L. aequalis complex and L. aleutica/L, camtschatica complex) were composed of numerous molecular lineages (7-8 lineages/clade), and several clades had multiple shallow nodes, suggestive of recent radiations. Two of the clades (L. aleutica/L, camtschatica complex and L. hexactis complex), with geographic ranges restricted to latitudes higher than 48 degrees N, were lacking deep phylogenetic nodes. This pattern is consistent with the hypothesis that high-latitude taxa have high rates of extinction due to repeated climatic crises. A log-likelihood ratio test performed on the camtschatica section, including a member (Leptasterias polar/s) of the polaris section and using a representative (L. mulleri) of Leptasterias subgenus Leptasterias as an outgroup, demonstrated that the camtschatica section is monophyletic.

Mitochondrial DNA sequence variation of Sebastes was used to address systematic and evolutionary issues, relating to several species in the Southern Hemisphere. Results showed high levels of genetic differentiation amongst sampled populations, indicating limited gene flow. The existence of two differing lineages of austral Sebastes was also corroborated, and the existence of a third evolutionary lineage with high rates of genetic divergence, was abundant in the south-western Atlantic.

We analyzed the genetic diversity and structure of three allopatric populations of the Pacific red snapper Lutjanus peru (Nichols and Murphy, 1922) by means of restriction fragment length polymorphisms of the entire mitochondrial control region (1350 bp). We found high levels of haplotype (h = 0.966) and nucleotide (π = 3.23%) diversities among the 100 organisms analyzed from Baja California Sur, Sinaloa and Jalisco (Mexico). Most of the molecular variability was detected with only one of the five restriction enzymes used (MseI). Heterogeneity analysis of haplotype frequencies was not significant (χ2 = 125.1, P > 0.25); neither were Wright's fixation index (FST = 0.0062, P = 0.140) nor its molecular analogue (ΦST = 0.0194, P = 0.056). An analysis of molecular variance (AMOVA) confirmed the absence of differentiation between peninsular and continental populations, even though it produced a marginally significant ΦST (ΦST = 0.0116, P = 0.048). No phylogeographic pattern was detected in a Neighbor-Joining gene tree. We argue that high molecular diversity levels are consistent with a large population size and that the absence of an apparent genetic structure, in the extreme north of the species distribution, suggests the action of mechanisms favoring passive larval transport among allopatric populations; although active adult migration cannot be ruled out.

Marine biodiversity can be surveyed using underwater visual censuses and recently with eDNA metabarcoding. Although a promising tool, eDNA studies have shown contrasting results related to its detection scale and the number of species identified compared to other survey methods. Also, its accuracy relies on complete reference databases used for taxonomic assignment and, as other survey methods, species detection may show false‐negative and false‐positive errors. Here, we compared results from underwater visual censuses and simultaneous eDNA metabarcoding fish surveys in terms of observed species and community composition. We also assess the effect of a custom reference database in the taxonomic assignment, and evaluate occupancy, capture and detection probabilities, as well as error rates of eDNA survey data. We amplified a 12S rRNA fish barcode from 24 sampling sites in the gulf of California. More species were detected with eDNA metabarcoding than with UVC. Because each survey method largely detected different sets of species, the combined approach doubled the number of species registered. Both survey methods recovered a known biodiversity gradient and a biogeographic break, but eDNA captured diversity over a broader geographic and bathymetric scale. Furthermore, the use of a modest‐sized custom reference database significantly increased taxonomic assignment. In a subset of species, occupancy models revealed eDNA surveys provided similar or higher detection probabilities compared to UVC. The occupancy value of each species had a large influence on eDNA detectability, and in the false positive and negative error. Overall, these results highlight the potential of eDNA metabarcoding in complementing other established ecological methods for studies of marine fishes. [ABSTRACT FROM AUTHOR]

Otoliths were found for be useful for determining the age of the Pacific red snapper Lutjanus peru. This was concluded from the inspection of otoliths from 717 Pacific red snapper collected from March 1989 to March 1991. Otolith and fish growth were correlated using a power model. The monthly percentage of otoliths with translucent margin showed that growth marks are formed once a year (mainIy from May to September) during the period of reproductive activity, as indicated by the gonadosomatic index. Both the index and the percentage of translucent margins peaked in July. Measurement of annuli radii showed that the otolith marking pattern was consistent in fishes of different ages and reflected the variation of the fish growth rate.

The complete mitogenome of Thoosa mismalolli Carballo, Cruz-Barraza & Gómez, 2004 (Tetractinellida, Thoosidae) was sequenced. This is the first complete mitogenome of the suborden Thoosina and the third Tetractinellid so far. The mitochondrial genome of T. mismalolli was assembled based on reads obtained with the Illumina HiSeq platform. The length of complete mitogenome is 19,019 bp long and contained 14 protein-coding genes and 23 tRNA, with two tRNA genes. Phylogenetic reconstruction (maximum-likelihood) based on mitogenome of Tetractinellids, supports T. mismalolli as a sister group. This result is congruent with those obtained with molecular markers (CO1, 18S, and 28S), supporting the monophyletic status of Thoosa and providing additional molecular data in favor of the suborder Thoosina. [ABSTRACT FROM AUTHOR]

The GI microbiota of abalone contains a highly complex bacterial assemblage playing an essential role in the overall health of these gastropods. The gut bacterial communities of abalone species characterized so far reveal considerable interspecific variability, likely resulting from bacterial interactions and constrained by the ecology of their abalone host species; however, they remain poorly investigated. Additionally, the extent to which structural changes in the microbiota entail functional shifts in metabolic pathways of bacterial communities remains unexplored. In order to address these questions, we characterized the gut microbiota of the northeast Pacific blue (Haliotis fulgens or HF) and yellow (Haliotis corrugata or HC) abalone by 16S rRNA gene pyrosequencing to shed light on: (i) their gut microbiota structure; (ii) how bacteria may interact among them; and (iii) predicted shifts in bacterial metabolic functions associated with the observed structural changes. Our findings revealed that Mycoplasma dominated the GI microbiome in both species. However, the structure of the bacterial communities differed significantly in spite of considerable intraspecific variation. This resulted from changes in predominant species composition in each GI microbiota, suggesting hostspecific adaptation of bacterial lineages to these sympatric abalone. We hypothesize that the presence of exclusive OTUs in each microbiota may relate to host-specific differences in competitive pressure. Significant differences in bacterial diversity were found between species for the explored metabolic pathways despite their functional overlap. A more diverse array of bacteria contributed to each function in HC, whereas a single or much fewer OTUs were generally observed in HF. The structural and functional analyses allowed us to describe a significant taxonomic split and functional overlap between the microbiota of HF and HC abalone. [ABSTRACT FROM AUTHOR]

Copyright of Revista Mexicana de Biodiversidad is the property of Universidad Nacional Autonoma de Mexico, Instituto de Biologia and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

For highly mobile species that nevertheless show fine-scale patterns of population genetic structure, the relevant evolutionary mechanisms determining structure remain poorly understood. The bottlenose dolphin (Tursiops truncatus) is one such species, exhibiting complex patterns of genetic structure associated with local habitat dependence in various geographic regions. Here we studied bottlenose dolphin populations in the Gulf of California and Pacific Ocean off Baja California where habitat is highly structured to test associations between ecology, habitat dependence and genetic differentiation. We investigated population structure at a fine geographic scale using both stable isotope analysis (to assess feeding ecology) and molecular genetic markers (to assess population structure). Our results show that there are at least two factors affecting population structure for both genetics and feeding ecology (as indicated by stable isotope profiles). On the one hand there is a signal for the differentiation of individuals by ecotype, one foraging more offshore than the other. At the same time, there is differentiation between the Gulf of California and the west coast of Baja California, meaning that for example, nearshore ecotypes were both genetically and isotopically differentiated either side of the peninsula. We discuss these data in the context of similar studies showing fine-scale population structure for delphinid species in coastal waters, and consider possible evolutionary mechanisms. [ABSTRACT FROM AUTHOR]

Movements of many cetacean species are commonly related to temporal and spatial variations in food resources and human activities. Worldwide evidence shows that anthropogenic pressures faced by coastal dolphin populations are increasing; however, the lack of reliable baseline information generally prevents the assessment of such interactions. We studied the temporal dynamics in abundance, site fidelity, and residency of bottlenose dolphins (Tursiops truncatus) off the productive Alvarado lagoon in the Gulf of Mexico, and we assessed the potential hazards posed by human activities and natural predators. This 2-y study (2006 to 2008) was based on the photographic identification of 174 individuals from 871 high-quality dorsal fin photographs obtained during 41 surveys totaling 225.4 h of observation. Overall monthly abundance averaged 125 (SD = 52) dolphins, whereas naturally marked individuals averaged 106 (SD = 25); abundance values were somewhat consistent within and between years, but the community was composed of different dolphins at any given time. Seasonal site fidelity and residency were higher during the dry (March to June) and rainy (July to October) seasons. Previous studies from Alvarado and elsewhere suggest long-term residency (up to 7 y) but also widespread movements (100 to 300 km) for some individuals. Physical evidence of attacks by large predators was exclusively found in nonresident adult dolphins (3.5%), suggesting a seasonal incursion to the area by individuals from deeper waters. Also, dolphins bearing marks of interactions with fisheries were more common in adult residents (11.5%). Despite these threats, dolphins are recurrent in the area, possibly due to high prey abundance and availability, which may constitute the main factors driving their distribution and abundance. [ABSTRACT FROM AUTHOR]

Defining species boundaries is important not only for the appropriate attribution of life history and ecological traits but also for sustainable fishery management and for the conservation of biodiversity. Problems arise from taxonomic uncertainty and incorrect species delineation leading to historical misidentification. This is the case of Pacific guitarfishes in the genus Zapteryx. We use a molecular phylogenetic approach combining mitochondrial and nuclear loci to investigate genetic variation in fish along the Mexican Pacific coast. Our analyses reveal a lack of nuclear and mitochondrial distinction between rays identified morphologically as banded guitarfish Z. exasperata and as southern banded guitarfish Z. xyster, casting doubts on the validity of their current systematics. However, we detected two mitochondrial lineages in accordance with the number of species described for the Pacific: a "northern" lineage corresponding to Z. exasperata and a "southern" lineage possibly attributable to Z. xyster. The poorly understood phenotypic plasticity in coloration and size of the evolutionary lineage of Z. exasperata and its apparently wider than currently thought geographic distribution (at least to Oaxaca) are the major sources of confusion regarding the taxonomic and geographic delineation of these nominal species. In light of our findings, eastern Pacific guitarfishes in the genus Zapteryx require a thorough taxonomic revision using morphological and genetic data to unveil what appears to be a complex pattern of diversification. [ABSTRACT FROM AUTHOR]