Search

Many gaps in our theoretical understanding of the variations in the diversity and structure of intertidal communities exist for the Eastern Pacific. In order to fill some of these gaps, we censused intertidal communities and compared patterns of diversity on multiple spatial scales using several measures in alpha (α) and beta (β) diversities at twenty-one sites in a cold temperate, a warm temperate and a tropical Eastern Pacific ecoregion that were unique in terms of research effort and each with distinct geographic features. Diversity and richness on all spatial scales were compared using area curves, Hill numbers, ordination and cluster analyses, and the Hutcheson's t-test with post hoc PERMANOVA, which revealed significant differences in diversity within and among ecoregions. Functional group and species richness and abundance were found to be highest in the cold and warm temperate ecoregions, and the functional group richness was second highest in the tropical Guayaquil ecoregion. The Bray–Curtis similarity method proved useful for determining patterns of small-scale intertidal zonation, while the Sorensen–Dice method suggested high indices of similarity in the functional group and subclass structures among all ecoregions. [ABSTRACT FROM AUTHOR]

Large areas of the Pacific coast of the Americas remain unstudied regarding their intertidal ecosystems. Given the increasing disturbance related to human impacts on intertidal ecosystems, it is essential to gather census data on the biological composition of poorly studied regions so that a framework for future monitoring and management can be developed. Here, we synthesize the available research on intertidal communities along the Pacific rim to support the goal to fill bioregional gaps in knowledge in three less-studied areas in Southeast Alaska and Peru. A census of taxonomic and functional group hierarchies in these communities should include the use of various measures of alpha and beta diversity to provide a metric of temporal and spatial comparisons. A narrower-scale approach focusing on foundation species that harbor algal and invertebrate communities and serve as buffers against environmental stresses should also be conducted. Conducting a comprehensive census in poorly studied or unstudied areas will contribute to a better understanding of the response to disturbances caused by oil spills, El Niño and marine heatwaves and provide a latitudinal continuum of scientific knowledge about the biodiversity and ecosystem functioning in rocky intertidal systems on a trans-regional scale. [ABSTRACT FROM AUTHOR]

Seaweeds are important components of marine ecosystems with emerging potential in aquaculture and as sources of biofuel, food products and pharmacological compounds. However, an increasingly recognised threat to natural and industrial seaweed populations is infection with parasitic single‐celled eukaryotes from the relatively understudied oomycete lineage. Here we examine the eukaryomes of diverse brown, red and green marine macroalgae collected from polar (Baffin Island), cold‐temperate (Falkland Islands) and tropical (Ascension Island) locations, with a focus on oomycete and closely related diatom taxa. Using 18S rRNA gene amplicon sequencing, we show unexpected genetic and taxonomic diversity of the eukaryomes, a strong broad‐brush association between eukaryome composition and geographic location, and some evidence of association between eukaryome structure and macroalgal phylogenetic relationships (phylosymbiosis). However, the oomycete fraction of the eukaryome showed disparate patterns of diversity and structure, highlighting much weaker association with geography and no evidence of phylosymbiosis. We present several novel haplotypes of the most common oomycete Eurychasma dicksonii and report for the first time a cosmopolitan distribution and absence of host specificity of this important pathogen. This indicates rich diversity in macroalgal oomycete pathogens and highlights that these pathogens may be generalist and highly adaptable to diverse environmental conditions. [ABSTRACT FROM AUTHOR]

BackgroundDNA barcoding offers an efficient way to determine species identification and to measure biodiversity. For dinoflagellates, an ancient alveolate group of about 2000 described extant species, DNA barcoding studies have revealed large amounts of unrecognized species diversity, most of which is not represented in culture collections. To date, two mitochondrial gene markers, Cytochrome Oxidase I (COI) and Cytochrome b oxidase (COB), have been used to assess DNA barcoding in dinoflagellates, and both failed to amplify all taxa and suffered from low resolution. Nevertheless, both genes yielded many examples of morphospecies showing cryptic speciation and morphologically distinct named species being genetically similar, highlighting the need for a common marker. For example, a large number of cultured Symbiodinium strains have neither taxonomic identification, nor a common measure of diversity that can be used to compare this genus to other dinoflagellates.Methodology/principal findingsThe purpose of this study was to evaluate the Internal Transcribed Spacer units 1 and 2 (ITS) of the rDNA operon, as a high resolution marker for distinguishing species dinoflagellates in culture. In our study, from 78 different species, the ITS barcode clearly differentiated species from genera and could identify 96% of strains to a known species or sub-genus grouping. 8.3% showed evidence of being cryptic species. A quarter of strains identified had no previous species identification. The greatest levels of hidden biodiversity came from Scrippsiella and the Pfiesteriaceae family, whilst Heterocapsa strains showed a high level of mismatch to their given species name.Conclusions/significanceThe ITS marker was successful in confirming species, revealing hidden diversity in culture collections. This marker, however, may have limited use for environmental barcoding due to paralogues, the potential for unidentifiable chimaeras and priming across taxa. In these cases ITS would serve well in combination with other markers or for specific taxon studies.

BackgroundDinoflagellates are an ecologically important group of protists with important functions as primary producers, coral symbionts and in toxic red tides. Although widely studied, the natural diversity of dinoflagellates is not well known. DNA barcoding has been utilized successfully for many protist groups. We used this approach to systematically sample known "species", as a reference to measure the natural diversity in three marine environments.Methodology/principal findingsIn this study, we assembled a large cytochrome c oxidase 1 (COI) barcode database from 8 public algal culture collections plus 3 private collections worldwide resulting in 336 individual barcodes linked to specific cultures. We demonstrate that COI can identify to the species level in 15 dinoflagellate genera, generally in agreement with existing species names. Exceptions were found in species belonging to genera that were generally already known to be taxonomically challenging, such as Alexandrium or Symbiodinium. Using this barcode database as a baseline for cultured dinoflagellate diversity, we investigated the natural diversity in three diverse marine environments (Northeast Pacific, Northwest Atlantic, and Caribbean), including an evaluation of single-cell barcoding to identify uncultivated groups. From all three environments, the great majority of barcodes were not represented by any known cultured dinoflagellate, and we also observed an explosion in the diversity of genera that previously contained a modest number of known species, belonging to Kareniaceae. In total, 91.5% of non-identical environmental barcodes represent distinct species, but only 51 out of 603 unique environmental barcodes could be linked to cultured species using a conservative cut-off based on distances between cultured species.Conclusions/significanceCOI barcoding was successful in identifying species from 70% of cultured genera. When applied to environmental samples, it revealed a massive amount of natural diversity in dinoflagellates. This highlights the extent to which we underestimate microbial diversity in the environment.

Research on intertidal mussel assemblages and associated communities has revealed that complexity and structure are influenced by environmental heterogeneity and local‐scale factors affecting recruitment. Research in situ in eastern and western Pacific intertidal ecosystems has suggested drivers of species diversity and community structure encompassing large geographic scales, however, there are major gaps in geographic coverage. Our aim is to fill some of these gaps by analyzing macrofaunal functional group diversity and effects of environmental factors on intertidal mussel communities from three distinct marine ecoregions in the southern and northern hemispheres. We identified the effects of algal cover and environmental heterogeneity on species richness and evenness, and we modeled factors effecting mussel layer complexity from assemblages in three marine ecoregions. We analyzed macrofaunal species diversity within one of the austral ecoregions based on the width of the coastal shelf. Species richness was highest in samples from the northern hemisphere while evenness was highest in samples from the southern hemisphere. Similarity in functional group structure for all communities sampled was ≤55% (Bray–Curtis dissimilarity) and ≤35% (Chao–Jaccard dissimilarity). Wave exposure had a significant effect on shell length and complexity of mussel matrices on rocky bench platforms. The presence of algal cover had a strong effect on species richness in mussel matrices regardless of complexity, while algal canopies had no effect on species evenness. Overall, this study provides significant new insight on the community complexity of mussel beds in parts of the world which have been poorly studied in this regard. [ABSTRACT FROM AUTHOR]

Aquatic invasive species are among the greatest threats to freshwater biodiversity. The aim of this study was to understand the effects of two invasive watermilfoil species (Myriophyllum heterophyllum Michx. and Myriophyllum spicatum L.) on native macrophyte communities and to assess community response to a range of invasion intensities as well as examine the influence of canopy types. We hypothesized that some communities would be more sensitive to invasion, and that some canopy species would facilitate watermilfoil presence. We used a novel approach to give better representation of the 3D aspect of the community which involved employing a modified quadrat approach to sample at two Connecticut lakes. Results show that watermilfoil invasion has a significant negative effect on native species richness. Floating canopy does not vary with invasion intensity, but submerged canopy does. One species, (Utricularia purpurea Walter), was associated with high native species richness and rarely occurred with invasive species. The results identify potential species that are disproportionally threatened by invasive species, as well as identifying invasion indicator species. The examination of canopy effects is uncommon in aquatic invasion ecology, and this study suggests that this aspect may have significant effects on resilience to invasion and overall community dynamics.