scholarly journals Disentangling diatom species complexes: does morphometry suffice?

PeerJ ◽  
2017 ◽  
Vol 5 ◽  
pp. e4159 ◽  
Author(s):  
Saúl Blanco ◽  
María Borrego-Ramos ◽  
Adriana Olenici
Keyword(s):  
Taxonomic Resolution ◽  
Correct Identification ◽  
Large Sample Size ◽  
Diatom Species ◽  
Diatom Assemblages ◽  
Species Complexes ◽  
Size Number ◽  
Length Width ◽  
Number Of Individuals ◽  
Diatom Taxonomy

Accurate taxonomic resolution in light microscopy analyses of microalgae is essential to achieve high quality, comparable results in both floristic analyses and biomonitoring studies. A number of closely related diatom taxa have been detected to date co-occurring within benthic diatom assemblages, sharing many morphological, morphometrical and ecological characteristics. In this contribution, we analysed the hypothesis that, where a large sample size (number of individuals) is available, common morphometrical parameters (valve length, width and stria density) are sufficient to achieve a correct identification to the species level. We focused on some common diatom taxa belonging to the genusGomphonema. More than 400 valves and frustules were photographed in valve view and measured using Fiji software. Several statistical tools (mixture and discriminant analysis, k-means clustering, classification trees, etc.) were explored to test whether mere morphometry, independently of other valve features, leads to correct identifications, when compared to identifications made by experts. In view of the results obtained, morphometry-based determination in diatom taxonomy is discouraged.

Taxonomic Synopsis of Eriosema (Leguminosae: Papilionoideae, Phaseoleae) in Brazil

Phytotaxa ◽  
2019 ◽  
Vol 416 (2) ◽  
pp. 91-137 ◽  
Author(s):  
ELISA SILVA CÂNDIDO ◽  
WANDERLEIA DE VARGAS ◽  
LUÍSA MARIA DE PAULA ALVES BEZERRA ◽  
VIDAL DE FREITAS MANSANO ◽  
MOHAMMAD VATANPARAST ◽  
...  
Keyword(s):  
Field Work ◽  
Morphological Characters ◽  
Second Step ◽  
Correct Identification ◽  
Type Specimens ◽  
Distribution Maps ◽  
Savanna Vegetation ◽  
Tropical Environments ◽  
Species Complexes ◽  
Representative Species

Eriosema is a pantropical genus occurring mostly in savanna vegetation and grasslands of tropical environments, with approximately 150 species and two centers of diversity, one in Africa with about 110 species, and the other in the Neotropics with about 40 species. Considering the large number of Eriosema taxa in Brazil, including five recently described, and the lack of recent study that encompasses all species that occur in the country, a taxonomic synopsis of the Brazilian species of Eriosema was needed and is presented here. Herbaria collections, including type specimens, were consulted and field work was carried out in Brazil. Our study records 35 Eriosema species in Brazil, which concentrates most of the diversity of the genus in the Americas (85%; 35 out of 41 species). Most of this diversity occurs in the Central Brazilian savannas, particularly in the states of Goiás (29 taxa, eight endemic), and Minas Gerais (26 taxa, four endemic). Among all American species in the genus, Eriosema simplicifolium and E. crinitum have the broadest geographical distributions, and occur throughout Brazil and most part of the American continent. They form species complexes and future detailed studies will be necessary in order to understand taxon boundaries and delimitations. An identification key, taxon descriptions, information about type specimens as well as information on the habitat, phenological and geographical records, together with distribution maps, images of representative species in the field and the main morphological characters are provided to assist in the correct identification of this group of savanna plants. We also present 15 lectotypifications, out of which three are second-step.

scholarly journals The use of epilithic diatom assemblages in assessing land use in Silago, Southern Leyte, Philippines

2019 ◽  
Vol 12 (2) ◽  
Keyword(s):  
Water Quality ◽  
Land Use ◽  
Tolerance Index ◽  
Diatom Species ◽  
Diatom Assemblages ◽  
Pollution Tolerance ◽  
Land Use Types ◽  
Freshwater Bodies ◽  
Forested Areas ◽  
Epilithic Diatom

Silago is a municipality in Southern Leyte in which logging for high-quality timber and land clearing for agricultural purposes threaten stream ecosystems. The objective of this study was to assess the response of diatom assemblages in relation to land use. Diatoms and water quality sampling was done at 27 sites on two sampling occasions (June and July 2014). Multiple diatom metrics were calculated to measure the response of diatoms to changes in land use. In all, 135 diatom species distributed to 48 genera were recorded. The results showed that diatom species and their attributes gave similar responses to those obtained in environmental variables. Pollution tolerance index classified all sampling sites as oligo-b-mesosaprobic. Meanwhile, Cymbella richness, percent motile taxa, and percent Achnanthidium minutissimum indicated good water quality in forested areas, distinguishing them from other land use types. Contrary to other studies, species richness was found to increase with greater degrees of disturbance, thus giving unreliable evaluation of water quality. Overall, the study suggests that epilithic diatoms can be applied in biomonitoring of freshwater bodies in the country.

scholarly journals Three New Diatom Species from Spring Habitats in the Northern Apennines (Emilia-Romagna, Italy)

Diversity ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 549
Author(s):  
Marco Cantonati ◽  
Olena Bilous ◽  
Nicola Angeli ◽  
Liesbeth van Wensen ◽  
Horst Lange-Bertalot
Keyword(s):  
Human Impacts ◽  
Hard Water ◽  
Northern Apennines ◽  
Similar Species ◽  
Diatom Species ◽  
Wetland Type ◽  
Species Complexes ◽  
The Face ◽  
Three New Species ◽  
Typical Habitat

Using light (LM, including plastid characterization on fresh material) and scanning electron microscopy (SEM), as well as a thorough morphological, physical, chemical, and biological characterization of the habitats, the present study aims at describing three species new to science. They belong to the genera Eunotia Ehrenb., Planothidium Round and L. Bukht., and Delicatophycus M.J. Wynne, and were found in two contrasting spring types in the northern Apennines. The three new species described differ morphologically from the most similar species by: less dense striae and areolae, and the absence of a ridge at the valve face-mantle transition (SEM feature) [Eunotia crassiminor Lange-Bert. et Cantonati sp. nov.; closest established species: Eunotia minor (Kütz.) Grunow]; narrower and shorter cells [Planothidium angustilanceolatum Lange-Bert. et Cantonati sp. nov.; most similar species: Planothidium lanceolatum (Bréb. ex Kütz.) Lange-Bert.]; barely-dorsiventral symmetry, set off ends, and lower density of the central dorsal striae [Delicatophycus crassiminutus Lange-Bert. et Cantonati sp. nov.; most similar species: Delicatophycus minutus M.J.Wynne]. Two of the three species we described are separated from the closest species by dimensions. Their description improved knowledge on two taxa (Eunotia minor s.l. and Planothidium lanceolatum s.l.) likely to be only partially resolved species complexes. We could also refine knowledge on the ecological profiles of the three newly-described species. Eunotia crassiminor sp. nov., as compared to Eunotia minor, appears to occur in colder inland waters with a circumneutral pH and a strict oligotrophy as well with respect to nitrogen. The typical habitat of Planothidium angustilanceolatum sp. nov. appears to be oligotrophic mountain flowing springs with low conductivity. Delicatophycus crassiminutus sp. nov. was observed only in limestone-precipitating springs, and is therefore likely to be restricted to hard water springs and comparable habitats where CO2 degassing leads to carbonate precipitation. Springs are a unique but severely threatened wetland type. Therefore, the in-depth knowledge of the taxonomy and ecology of characteristic diatom species is important, because diatoms are excellent indicators of the quality and integrity of these peculiar ecosystems in the face of direct and indirect human impacts.

Studying the Number of Lineages Through Monte Carlo Simulations of Biological Ageing

1998 ◽  
Vol 09 (06) ◽  
pp. 809-813 ◽  
Author(s):  
S. Moss de Oliveira ◽  
G. A. de Medeiros ◽  
P. M. C. de Oliveira ◽  
D. Stauffer
Keyword(s):  
Power Law ◽  
Biological Diversity ◽  
String Model ◽  
Biological Ageing ◽  
Power Law Decay ◽  
Family Names ◽  
Size Number ◽  
The Family ◽  
The Mean ◽  
Number Of Individuals

We studied different versions of the Penna bit-string model for biological ageing and found that, after many generations, the number of lineages N (maternal family names) always decays to one as a power-law N∝t-z with an exponent z roughly equal to one. Measuring the mean correlation between the ancestor genome and those of the actual population we obtained the result that it goes to zero much earlier before the number of families goes to one, the population keeping thus its biological diversity. Considering maternal and paternal family names (doubled names) we also finished with only one pair of common ancestors. Computing the number of families of a given size as a function of the size (number of individuals the family has had during its whole existence) again a power-law decay is obtained.

The influence of water-table depth and pH on the spatial distribution of diatom species in peatlands of the Boreal Shield and Hudson Plains, Canada

Botany ◽  
2015 ◽  
Vol 93 (2) ◽  
pp. 57-74 ◽  
Author(s):  
Kathryn E. Hargan ◽  
Kathleen M. Rühland ◽  
Andrew M. Paterson ◽  
Sarah A. Finkelstein ◽  
James R. Holmquist ◽  
...  
Keyword(s):  
Environmental Change ◽  
Water Table ◽  
Vegetation Type ◽  
Diatom Assemblage ◽  
Diatom Species ◽  
Diatom Assemblages ◽  
Poor Fen ◽  
Influence Of Water ◽  
Boreal Shield ◽  
Northern Peatlands

Diatoms collected from 113 surface peat samples from the Boreal Shield and Hudson Plains show taxonomic distributions that are associated with macro-vegetation type, pH, and position relative to the water table, the main environmental variables measured in this study. The overall goal of our research was to determine the ecological distribution and response of diatoms to microhabitat conditions, and to assess the potential for diatoms to be applied as indicators of long-term environmental change in northern peatlands. Our results indicate that diatom assemblage composition was determined by both the broader peatland type (i.e., bog, rich and poor fens) and microhabitats within peatland formations (e.g., hummock, hollow). The diatom assemblages were primarily influenced by pH with the sites divided at a critical pH of 5.5, and secondarily by the depth to the water table. Acidic bog hollow and hummock microhabitats were species-poor and dominated almost exclusively by Eunotia paludosa A.Grunow and (or) Eunotia mucophila (H.Lange-Bertalot, M.Nörpel-Schempp & E.Alles) H.Lange-Bertalot. These acidophilic and aerophilic diatom species were associated with the narrow pH optima of the dominant Sphagnum L. species (e.g., Sphagnum fuscum (Schimp.) Klinggr., Sphagnum angustifolium (C.E.O.Jensen ex Russow) C.E.O.Jensen) found in these bog habitats. Rich and poor fen samples, which were less acidic, supported a more diverse diatom assemblage (>30 species) with greater variability in both diatom and bryophyte pH tolerances. The diatom assemblages recorded in the bogs and fens of our study are similar to those found in peatlands around the world, demonstrating that diatom species are very specialized to exist in these often harsh semi-aquatic environments. Diatoms from peatlands have great potential as biomonitors of environmental change in these important ecosystems.

scholarly journals Diatom Species That Characterize Saline Ponds (South of Spain) With The Description of A New Navicula Species

2021 ◽  
Author(s):  
David Fernandez Moreno ◽  
Pedro M. Sánchez-Castillo ◽  
Cristina Delgado ◽  
Salomé F.P. Almeida
Keyword(s):  
Electric Conductivity ◽  
Aquatic Organisms ◽  
Early Summer ◽  
Scaling Analysis ◽  
Diatom Species ◽  
Diatom Assemblages ◽  
The South ◽  
Multidimensional Scaling Analysis ◽  
Diatom Community Composition ◽  
High Electric Conductivity

Abstract The south of the Iberian Peninsula has a high number of saline ponds where electric conductivity (EC) is an important factor that affects directly aquatic organisms, influencing their distribution and abundance. Environmental factors (such as pH, EC and temperature) were measured and diatom assemblages were sampled in 15 saline shallow ponds in the south of Spain along a range of electric conductivity (1.4 mS to 51.6 mS cm-1) between spring of 2004 to early summer of 2006. Three groups of ponds were defined based on conductivity (oligosaline 1.4 to 5.3 mScm-1, mesosaline 10.9 to 17.3 mScm-1 and euhaline 32.3 to 51.6 mScm-1) and diatom assemblages were studied. PERMANOVA analysis showed significant differences in diatom community composition between the three groups of ponds. Multidimensional scaling analysis (nMDS) showed distinct clusters of diatom assemblages in oligosaline and mesosaline ponds. Dominant diatom species in the eusaline ponds were Tryblionella pararostrata, Halamphora cf. petrusa, Halamphora sp.1 and Cocconeis euglypta; in the mesosaline ponds Navicula veneta, Nitzschia elegantula and Planothidium delicatulum were dominant taxa and the oligosaline ponds were dominated by Navicula veneta, Pseudostaurosira brevistriata and Nitzschia inconspicua. A new diatom species was described in ponds with high electric conductivity (32-56 mS cm-1) and named N. maiorpargemina.A detailed description of N. maiorpargemina sp. nov. is presented in this study based on light and scanning electron microscopy after comparison with morphologically and ecologically related taxa.

scholarly journals An assessment of diatom assemblages in the Sea of Okhotsk as a proxy for sea-ice cover

2020 ◽  
Vol 39 (1) ◽  
pp. 77-92
Author(s):  
Hiroki Nakamura ◽  
Yusuke Okazaki ◽  
Susumu Konno ◽  
Takeshi Nakatsuka
Keyword(s):  
Sea Ice ◽  
Surface Sediment ◽  
Sea Of Okhotsk ◽  
Spring Bloom ◽  
Diatom Species ◽  
Diatom Assemblages ◽  
Sea Ice Extent ◽  
Sinking Particles ◽  
Resting Spores ◽  
Fragilariopsis Cylindrus

Abstract. Knowledge of past variations in sea-ice extent is crucial for understanding the relationship between climate change and changes in sea ice. Diatom assemblages could be applied as a proxy for paleo-sea-ice extent; this requires accurate information on the modern species that are indicative of sea ice. Scanning electron microscope observations were performed on modern diatom assemblages in sea ice, sinking particles, and surface sediments in the Sea of Okhotsk. A sea-ice sample was collected in the southwestern Sea of Okhotsk near Hokkaido island in February 2013. Fragilariopsis cylindrus was the dominant diatom species in the sea-ice sample, accounting for 87 % of the total diatom assemblage. Time-series sediment traps were deployed during 1998–2000 at two stations, M4 and M6, off Sakhalin island. Total diatom fluxes ranged from 105 to 108 valves m−2 d−1 with noticeable seasonality. During the sea-ice covering period, the total diatom flux decreased by 1 or 2 orders of magnitude. The highest diatom fluxes were observed in spring and summer. The diatom species composition in sinking particles also showed pronounced seasonal changes. During summer and fall, the Shionodiscus trifultus group and Neodenticula seminae were the major diatom taxa. During the sea-ice covering period, Fragilariopsis cylindrus and Bacterosira bathyomphala resting spores were abundant. Both the sea-ice-related species showed similar flux patterns except for the spring bloom after sea-ice retreat: F. cylindrus fluxes exhibited pronounced spring bloom peaks of 108 valves m−2 d−1; in contrast, the fluxes of Bacterosira bathyomphala resting spores during the spring bloom were 1 order of magnitude lower than those of F. cylindrus. Surface-sediment core XP98-MC4 was obtained near station M6 sediment-trap site off Sakhalin island. The relative abundance of Fragilariopsis cylindrus in the surface-sediment diatom assemblage was only 6.4 %, markedly lower than that in the sediment-trap samples (43.4 %). In the surface sediment, the relative abundances of diatom taxa with heavily silicified valves such as B. bathyomphala resting spores, Shionodiscus variantius, and Thalassionema nitzschioides were greater than their relative abundances in sinking particles.

scholarly journals Evaluating the estimation of genetic correlation and heritability using summary statistics

2021 ◽  
Author(s):  
Ju Zhang ◽  
Fredrick R. Schumacher
Keyword(s):  
Sample Size ◽  
Genetic Correlation ◽  
Reference Panel ◽  
Summary Statistics ◽  
External Reference ◽  
Size Number ◽  
Admixed Population ◽  
Statistical Approaches ◽  
Panel Summary ◽  
Number Of Individuals

AbstractWhile novel statistical methods quantifying the shared heritability of traits and diseases between ancestral distinct populations have been recently proposed, a thorough evaluation of these approaches under differing circumstances remain elusive. Brown et al.2016 proposed the method Popcorn to estimate the shared heritability, i.e. genetic correlation, using only summary statistics. Here, we evaluate Popcorn under several parameters and circumstances: sample size, number of SNPs, sample size of external reference panel, various population pairs, inappropriate external reference panel, and admixed population involved. Our results determined the minimum sample size of the external reference panel, summary statistics, and number of SNPs required to accurately estimate both the genetic correlation and heritability. Moreover, the number of individuals and SNPs required to produce accurate and stable estimates was directly proportional with heritability in Popcorn. Misrepresentation of the reference panel overestimated the genetic correlation by 20% and heritability by 60%. Lastly, applying Popcorn to homogeneous (EUR) and admixed (ASW) populations underestimated the genetic correlation by 15%. Although statistical approaches estimating the shared heritability between ancestral populations will provide novel etiologic insight, caution is required ensuring results are based on the appropriate sample size, number of SNPs, and the generalizability of the reference panel to the discovery populations.

Postglacial Diatom Stratigraphy of Kirchner Marsh, Minnesota

1980 ◽  
Vol 13 (1) ◽  
pp. 133-146 ◽  
Author(s):  
Richard B. Brugam
Keyword(s):  
Cluster Analysis ◽  
Aquatic Macrophytes ◽  
Diatom Species ◽  
Diatom Assemblages ◽  
Geological Society ◽  
Lake Water Level ◽  
The Core ◽  
Pollen Zone ◽  
Pine Pollen ◽  
Diatom Stratigraphy

AbstractFossil diatom assemblages from a 12-m core from Kirchner Marsh were compared with modern surface assemblages from 159 Minnesota and Labrador lakes using cluster analysis. The deepest levels of the core (spruce pollen zone 13,000 to 10,200 yr B.P.) resemble modern diatom assemblages from deep oligotrophic lakes of northeastern Minnesota. Diatom assemblages of the pine pollen zone (about 10,200 to 9500 yr B.P.) have few modern analogs. In the oak zone (9500 yr B.P. to present) after a brief pulse of diatom species indicative of eutrophication, the assemblages are dominated by species characteristic of shallow lakes, suggesting a drop in the lake water level during the prairie period (5500 to 7500 yr B.P.). Macrofossil data of W. A. Watts and T. C. Winter (1966, Geological Society of America Bulletin 77, 1339–1360) show that this shift to shallow-water diatoms occurred when aquatic macrophytes appeared at the site in abundance.

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