scholarly journals Diatoms in an extreme euxinic environment (Rogoznica Lake, eastern Adriatic coast)

2015 ◽  
Vol 74 (2) ◽  
pp. 333-343 ◽  
Author(s):  
Nikola Malešević ◽  
Irena Ciglenečki ◽  
Elvira Bura-Nakić ◽  
Marina Carić ◽  
Iris Dupčić ◽  
...  
Keyword(s):  
Environmental Conditions ◽  
Species Abundance ◽  
Temporal Distribution ◽  
Single Species ◽  
Diatom Species ◽  
Chaetoceros Curvisetus ◽  
Cyclotella Choctawhatcheeana ◽  
Marine System ◽  
Adriatic Coast ◽  
Sample Maximum

AbstractThe Rogoznica Lake marine system is a small, karstic, naturally eutrophic and euxinic marine environment. Abundance and temporal distribution of phytoplankton was investigated in relation to environmental conditions in the period from 1998 to 2013. The 36 determined diatoms contributed 90% of the total phytoplankton abundance. The diatom composition is characterized by low species diversity and high single species abundance (up to 107 cells L-1). There were, on average, 2.6 diatom species per sample (maximum 14 diatom species per sample) reflecting extreme environmental conditions. Dominant diatoms Thalassionema nitzschioides, Cyclotella choctawhatcheeana, Dactyliosolen fragilissimus and Chaetoceros curvisetus occurred repeatedly and were alternately dominant in the lake during the whole research period. Some diatoms were dominant only in limited period, like Cyclotella choctawhatcheeana (evident since 2001), and Pseudo-nitzschia spp. (evident in the period 2002 to 2009). It appears that the interplay of environmental conditions such as variability in thermohaline and redox conditions, nutrient and reduced sulphur concentration influence the phytoplankton development and abundance in the lake.

scholarly journals Late Cretaceous non-marine turtles of Asia: a review of taxonomic diversity and paleobiogeography

2015 ◽  
Author(s):  
Igor Danilov ◽  
Ekaterina Obraztsova ◽  
Vladimir Sukhanov
Keyword(s):  
Late Cretaceous ◽  
Environmental Conditions ◽  
Geographical Area ◽  
Temporal Distribution ◽  
Taxonomic Diversity ◽  
Coastal Areas ◽  
Marine Turtle ◽  
Marine Turtles ◽  
Middle Asia ◽  
Different Ages

Background. This report reviews data on taxonomic diversity and paleobiogeography of Late Cretaceous (K2) non-marine turtles of Asia accumulated since latest reviews in 2000s. K2 non-marine turtles of Asia are known from four main geographical areas: Middle Asia-Kazakhstan (MAK), Mongolia (MO), China (CH) and Japan (JA). Methods. We critically reviewed composition of non-marine turtle assemblages of the K2 for each of the mentioned geographical area to make estimates of taxonomic diversity for different ages of the K2. Based on these data we analyzed temporal distribution of taxa of non-marine turtles and change in taxonomic diversity of turtle assemblages. Results. K2 turtles of MAK are represented by eight suprageneric taxa – Adocidae (Ad), Carettochelyidae (Ca), Lindholmemydidae (Li), Macrobaenidae (Ma), Nanhsiungchelyidae (Na), Trionychidae (Tr), Eucryptodira indet. (Eu), and Testudines indet. (Te), of which Ad, Li, Ma and Tr are known from the Cenomanian(CE) – early Campanian(CA), whereas other taxa only from the CE-early Turonian(TU). Taxonomic diversity changes from 10–12 species and genera, 6–8 suprageneric taxa in the CE to 7 species and genera, 4 families in the late TU early CA. K2 turtles of MO are represented by seven suprageneric taxa – Ad, Ca, Li, Ma, Meiolaniformes (Me), Na, and Tr, of which Li, Na and Tr are known from the CE-Maastrichtian(MA), Ad, Ca, and Ma, from the CE-Santonian(SA), and Me, only from the MA. Taxonomic diversity changes from 12 species, 10 genera, 6 families in the CE – SA, 8–9 species, 7–9 genera, 3 families in the CA, and 9 species, 7–8 genera, and 4 suprageneric taxa in the MA. K2 turtles of CH are represented by three suprageneric taxa (Li, Na, and Tr), but their precise temporal distribution is poorly known. Taxonomic diversity in the K2 is 12 species, 11–12 genera, and 3 families. K2 turtles of JA are represented by six suprageneric taxa (Ad, Ca, Na, Tr, Eu, and Te), of which Na are known from the CE-SA, Tr from the Coniacian(CO)-CA, and other taxa from the CO-SA. Taxonomic diversity changes from 1 species, genus, and family in the CE-TU to 7 species and genera, and 5–6 suprageneric taxa in the CO-SA. Discussion. In MAK, most significant transformation of turtle assemblages occurred in the CE-TU, whereas transformation in the SA-CA was less significant. On the contrary, in MO, most significant transformation occurred in the SA-CA, and less significant in the CA-MA.The patterns of transformation of the K2 turtle assemblages of CH and JA are not clear. The differences in the patterns of diversity and transformations of the K2 turtle assemblages in different geographical areas of Asia may be explained by different environmental conditions in these areas at that time and influence of such factors as transgressions in coastal areas (MAK and JA) and cooling and aridizations in inland areas (MO and CH).

scholarly journals Geomorphological and Anthropic Control of the Development of Some Adriatic Historical Towns (Italy) Since the Roman Age

2017 ◽  
Vol 36 (3) ◽  
pp. 111-123 ◽  
Author(s):  
Pier Luigi Dall’Aglio ◽  
Mauro de Donatis ◽  
Carlotta Franceschelli ◽  
Cristiano Guerra ◽  
Veronica Guerra ◽  
...  
Keyword(s):  
Urban Development ◽  
Environmental Conditions ◽  
Boundary Elements ◽  
Adriatic Coast ◽  
Urbanized Areas ◽  
Historical Sites ◽  
Roman Age ◽  
River Mouths ◽  
Geomorphological Analysis ◽  
Basic Boundary

Abstract The geomorphological analysis of historically urbanized areas is the best scientific way to understand how the extant geomorphological factors conditioned urbanization. It also provides a baseline to enable comparisons to be made with the modern environment. This paper considers four urbanized historical sites on the Adriatic coast (Italy) that owe their urban development to particular geomorphological and environmental conditions that were modified over the centuries from the Roman age to the present day. The focus here is on the evolution of the shoreline and associated geomorphic variables (streambeds and river mouths migration). These factors are fundamental for determining the development of a city, both as basic boundary elements – therefore including defence and protection – and also for the development of harbours.

scholarly journals Estimation of the relative abundance of species in artificial mixtures of insects using low-coverage shotgun metagenomics

2020 ◽  
Vol 4 ◽  
Author(s):  
Lidia Garrido-Sanz ◽  
Miquel Àngel Senar ◽  
Josep Piñol
Keyword(s):  
Relative Abundance ◽  
Species Abundance ◽  
Single Species ◽  
Insect Species ◽  
Individual Species ◽  
Advanced Degree ◽  
Mixed Species ◽  
Species List ◽  
Shotgun Metagenomics ◽  
Low Coverage

Amplicon metabarcoding is an established technique to analyse the taxonomic composition of communities of organisms using high-throughput DNA sequencing, but there are doubts about its ability to quantify the relative proportions of the species, as opposed to the species list. Here, we bypass the enrichment step and avoid the PCR-bias, by directly sequencing the extracted DNA using shotgun metagenomics. This approach is common practice in prokaryotes, but not in eukaryotes, because of the low number of sequenced genomes of eukaryotic species. We tested the metagenomics approach using insect species whose genome is already sequenced and assembled to an advanced degree. We shotgun-sequenced, at low-coverage, 18 species of insects in 22 single-species and 6 mixed-species libraries and mapped the reads against 110 reference genomes of insects. We used the single-species libraries to calibrate the process of assignation of reads to species and the libraries created from species mixtures to evaluate the ability of the method to quantify the relative species abundance. Our results showed that the shotgun metagenomic method is easily able to set apart closely-related insect species, like four species of Drosophila included in the artificial libraries. However, to avoid the counting of rare misclassified reads in samples, it was necessary to use a rather stringent detection limit of 0.001, so species with a lower relative abundance are ignored. We also identified that approximately half the raw reads were informative for taxonomic purposes. Finally, using the mixed-species libraries, we showed that it was feasible to quantify with confidence the relative abundance of individual species in the mixtures.

scholarly journals Integrating dispersal proxies in ecological and environmental research in the freshwater realm

2017 ◽  
Vol 25 (3) ◽  
pp. 334-349 ◽  
Author(s):  
Jani Heino ◽  
Janne Alahuhta ◽  
Terhi Ala-Hulkko ◽  
Harri Antikainen ◽  
Luis Mauricio Bini ◽  
...  
Keyword(s):  
Environmental Conditions ◽  
Restoration Ecology ◽  
Spatial Dynamics ◽  
Single Species ◽  
Environmental Research ◽  
Freshwater Systems ◽  
Biological Communities ◽  
Research Fields ◽  
Basic And Applied Research ◽  
Applied Fields

Dispersal is one of the key mechanisms affecting the distribution of individuals, populations, and communities in nature. Despite advances in the study of single species, it has been notoriously difficult to account for dispersal in multispecies metacommunities, where it potentially has strong effects on community structure beyond those of local environmental conditions. Dispersal should thus be directly integrated in both basic and applied research by using proxies. Here, we review the use of proxies in the current metacommunity research, suggest new proxies, and discuss how proxies could be used in community modelling, particularly in freshwater systems. We suggest that while traditional proxies may still be useful, proxies formerly utilized in transport geography may provide useful novel insights into the structuring of biological communities in freshwater systems. We also suggest that understanding the utility of such proxies for dispersal in metacommunities is highly important for many applied fields such as freshwater bioassessment, conservation planning, and recolonization research in the context of restoration ecology. These research fields have often ignored spatial dynamics and focused mostly on local environmental conditions and changes therein. Yet, the conclusions of these applied studies may change considerably if dispersal is taken into account.

scholarly journals Emergent Rarity Properties in Carabid Communities From Chinese Steppes With Different Climatic Conditions

2021 ◽  
Vol 9 ◽  
Author(s):  
Noelline Tsafack ◽  
Paulo A. V. Borges ◽  
Yingzhong Xie ◽  
Xinpu Wang ◽  
Simone Fattorini
Keyword(s):  
Community Structure ◽  
Environmental Conditions ◽  
Large Scale ◽  
Species Abundance ◽  
Climatic Conditions ◽  
Carabid Beetles ◽  
Model Parameters ◽  
Desert Steppe ◽  
Best Fit ◽  
Scale Of Analysis

Species abundance distributions (SADs) are increasingly used to investigate how species community structure changes in response to environmental variations. SAD models depict the relative abundance of species recorded in a community and express fundamental aspects of the community structure, namely patterns of commonness and rarity. However, the influence of differences in environmental conditions on SAD characteristics is still poorly understood. In this study we used SAD models of carabid beetles (Coleoptera: Carabidae) in three grassland ecosystems (desert, typical, and meadow steppes) in China. These ecosystems are characterized by different aridity conditions, thus offering an opportunity to investigate how SADs are influenced by differences in environmental conditions (mainly aridity and vegetation cover, and hence productivity). We used various SAD models, including the meta-community zero sum multinomial (mZSM), the lognormal (PLN) and Fisher’s logseries (LS), and uni- and multimodal gambin models. Analyses were done at the level of steppe type (coarse scale) and for different sectors within the same steppe (fine scale). We found that the mZSM model provided, in general, the best fit at both analysis scales. Model parameters were influenced by the scale of analysis. Moreover, the LS was the best fit in desert steppe SAD. If abundances are rarefied to the smallest sample, results are similar to those without rarefaction, but differences in models estimates become more evident. Gambin unimodal provided the best fit with the lowest α-value observed in desert steppe and higher values in typical and meadow steppes, with results which were strongly affected by the scale of analysis and the use of rarefaction. Our results indicate that all investigated communities are adequately modeled by two similar distributions, the mZSM and the LS, at both scales of analyses. This indicates (1) that all communities are characterized by a relatively small number of species, most of which are rare, and (2) that the meta-communities at the large scale maintain the basic SAD shape of the local communities. The gambin multimodal models produced exaggerated α-values, which indicates that they overfit simple communities. Overall, Fisher’s α, mZSM θ, and gambin α-values were substantially lower in the desert steppe and higher in the typical and meadow steppes, which implies a decreasing influence of environmental harshness (aridity) from the desert steppe to the typical and meadow steppes.

scholarly journals Temporal variation in the phytoplankton community of Acapulco Bay, Mexico

2012 ◽  
Vol 3 (1) ◽  
pp. 4 ◽  
Author(s):  
Agustín A. Rojas-Herrera ◽  
Juan Violante Gonzalez ◽  
Sergio García-Ibáñez ◽  
Víctor M.G. Sevilla-Torres ◽  
Jaime S. Gil-Guerrero ◽  
...  
Keyword(s):  
Species Composition ◽  
Temporal Variation ◽  
Rainy Season ◽  
Phytoplankton Community ◽  
Species Abundance ◽  
Sampling Period ◽  
Dry Season ◽  
Nutrient Concentrations ◽  
Diatom Species ◽  
Oceanic Environments

<p>Species composition and abundance of the phytoplankton community in Acapulco Bay, Mexico, were studied from May to December 2009. Samples were collected at 5 stations (4 coastal and 1 oceanic) at 3 depths (1, 5 and 10 m). Eighty-seven species were identified: 54 dinoflagellates, 32 diatoms and 1 silicoflagellate. The community was structured mainly by adiaphoric species, that is, species adapted to both neritic and oceanic environments. Species abundance and composition varied significantly during the sampling period due to increased nutrient concentrations in the rainy season. Dinoflagellate species were more abundant during the dry season, and diatom species dominated numerically during the rainy season.</p>

Exploring cryptic diversity in publicly available strains of the model diatom Thalassiosira pseudonana (Bacillariophyceae)

2015 ◽  
Vol 95 (6) ◽  
pp. 1081-1090 ◽  
Author(s):  
Cecilia Rad-Menéndez ◽  
Michele Stanley ◽  
David H. Green ◽  
Eileen J. Cox ◽  
John G. Day
Keyword(s):  
Morphological Analysis ◽  
Fragment Length Polymorphism ◽  
Temporal Distribution ◽  
Single Species ◽  
Thalassiosira Pseudonana ◽  
Salinity Range ◽  
Culture Collections ◽  
Geographic Origins ◽  
Its1 And Its2 Rdna ◽  
Its1 And Its2

The model diatom Thalassiosira pseudonana is believed to be a single species with a global distribution, but it has not been confirmed previously whether isolates from different environmental and geographic origins are genotypically and phenotypically identical. In the present study, a polyphasic approach was employed to characterize nine clonal isolates, plus an additional replicate of one of the isolates, of the diatom T. pseudonana from culture collections to investigate whether there was any cryptic speciation in the publicly available strains of this species. Morphological analysis using scanning electron microscopy concluded that the strains were indistinguishable. Furthermore, conventional DNA barcoding genes (SSU rDNA, ITS1 and ITS2 rDNA and rbcL), revealed no nucleotide variation among the strains tested. On employing a whole genome fingerprinting technique, Amplified Fragment Length Polymorphism (AFLP), three clusters were revealed, although the level of variation between the clusters was surprisingly low. These findings indicate a low level of diversity among these cultured T. pseudonana strains, despite their wide spatial and temporal distribution and the salinity range of their original habitats. Based on the limited number of available strains, this suggests that T. pseudonana is a highly conserved diatom that nevertheless has an ability to tolerate wide ranges of salinity and populate varied geographic locations.

scholarly journals An efficient extension of N-mixture models for multi-species abundance estimation

2016 ◽  
Author(s):  
Juan Pablo Gomez ◽  
Scott K. Robinson ◽  
Jason K. Blackburn ◽  
José Miguel Ponciano
Keyword(s):  
Maximum Likelihood ◽  
Mixture Models ◽  
Mixture Model ◽  
Species Abundance ◽  
Single Species ◽  
Tropical Species ◽  
Complex Data ◽  
Sample Sizes ◽  
Data Generating Process ◽  
Community Parameter

Abstract1. In this study we propose an extension of the N-mixture family of models that targets an improvement of the statistical properties of rare species abundance estimators when sample sizes are low, yet typical size for tropical studies. The proposed method harnesses information from other species in an ecological community to correct each species’ estimator. We provide guidance to determine the sample size required to estimate accurately the abundance of rare tropical species when attempting to estimate the abundance of single species.2. We evaluate the proposed methods using an assumption of 50-m radius plots and perform simulations comprising a broad range of sample sizes, true abundances and detectability values and a complex data generating process. The extension of the N-mixture model is achieved by assuming that the detection probabilities of a set of species are all drawn at random from a beta distribution in a multi-species fashion. This hierarchical model avoids having to specify a single detection probability parameter per species in the targeted community. Parameter estimation is done via Maximum Likelihood.3. We compared our multi-species approach with previously proposed multi-species N-mixture models, which we show are biased when the true densities of species in the community are less than seven individuals per 100-ha. The beta N-mixture model proposed here outperforms the traditional Multi-species N-mixture model by allowing the estimation of organisms at lower densities and controlling the bias in the estimation.4. We illustrate how our methodology can be used to suggest sample sizes required to estimate the abundance of organisms, when these are either rare, common or abundant. When the interest is full communities, we show how the multi-species approaches, and in particular our beta model and estimation methodology, can be used as a practical solution to estimate organism densities from rapid inventory datasets. The statistical inferences done with our model via Maximum Likelihood can also be used to group species in a community according to their detectabilities.

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