Alpha and beta diversity of freshwater meiofauna at different spatial scales in a Neotropical lotic system

2017 ◽  
Vol 68 (3) ◽  
pp. 538 ◽  
Author(s):  
T. Q. Araújo ◽  
H. H. Checon ◽  
A. R. S. Garraffoni
Keyword(s):  
Community Composition ◽  
Environmental Variability ◽  
Spatial Scales ◽  
Benthic Communities ◽  
Temporal Distribution ◽  
Distribution Patterns ◽  
Sampling Location ◽  
Alpha And Beta Diversity ◽  
Lotic System ◽  
Freshwater Habitats

Meiofaunal assemblages are important components of benthic communities in freshwater habitats, but studies about their ecology are scarce. In the present study we investigated the spatial and temporal distribution patterns of freshwater meiofaunal taxa, in a lotic system in south-eastern Brazil, assessing α and β diversities through additive partitioning of diversity. At each of six sampling sites, a 50-m transect was divided into five equal sections. Two random samples were collected in each section. Local spatial scales (α and β1) and among areas (β3) made the highest contribution to overall richness, but seasonal variation could be seen. Non-randomness patterns were observed, especially at the lowest and highest spatial scales, showing the effects of local intraspecific aggregation and environmental variability among areas. Temporal scale analysis showed that diversity was highly aggregated at the monthly scale, but sampling location affected these results. Community composition results highlighted the contrasting conditions found at the sampling sites, highlighting β3 as an important component of γ diversity across spatial scales. The effects of different levels of environmental degradation and precipitation on community composition and meiofaunal abundance affected the ability of the community to recover and recolonise the meiobenthos.

Does proximity to freshwater refuge affect the size structure of an estuarine predator (Carcharhinus leucas) in the north-western Gulf of Mexico?

2020 ◽  
Vol 71 (11) ◽  
pp. 1501 ◽  
Author(s):  
Philip Matich ◽  
Robert J. Nowicki ◽  
Jonathan Davis ◽  
John A. Mohan ◽  
Jeffrey D. Plumlee ◽  
...  
Keyword(s):  
Life Histories ◽  
Environmental Variability ◽  
Size Structure ◽  
Distribution Patterns ◽  
Freshwater Inflow ◽  
The North ◽  
Carcharhinus Leucas ◽  
Freshwater Habitats ◽  
Bull Shark ◽  
River Mouths

The life histories of estuarine species are often adapted to the environmental variability they experience. However, estuaries are increasingly vulnerable to natural and anthropogenic changes, necessitating an understanding of how shifting conditions affect the survival, behaviour and population structure of estuarine-dependent animals. In this study we used data from fisheries-independent surveys collected across six estuaries with variable salinity regimes in Texas, USA, from 1975 to 2016 to investigate the role sources of freshwater inflow play in shaping juvenile bull shark Carcharhinus leucas size structure. High frequencies of co-occurrence with similarly sized conspecifics (59% of capture events) suggest bull sharks segregated within Texan estuaries based on body size. Bull shark sizes increased with distance to the nearest source of freshwater inflow, although effect sizes were small and access to freshwater habitats may be more important in shaping size-dependent distribution patterns. River mouths were disproportionately used by smaller juveniles (<90-cm total length, TL) and avoided by larger juveniles (>135cm TL). However, the use of river mouths decreased in estuaries characterised by limited freshwater inflow and greater variability in salinities at river mouths, highlighting geographic differences in the functions these habitats provide as potential environmental and predator refugia. Young-of-the-year (i.e. age-0) sharks also increased their use of river mouths throughout the 40-year study period, revealing the growing importance of river mouths as potential nursery habitats.

scholarly journals Alpha and beta diversity patterns of macro-moths reveal a breakpoint along a latitudinal gradient in Mongolia

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Khishigdelger Enkhtur ◽  
Gunnar Brehm ◽  
Bazartseren Boldgiv ◽  
Martin Pfeiffer
Keyword(s):  
Community Composition ◽  
Beta Diversity ◽  
Distribution Patterns ◽  
Latitudinal Gradients ◽  
Conservation Strategies ◽  
Species Loss ◽  
Generalist Species ◽  
Alpha And Beta Diversity ◽  
The North ◽  
Baseline Information

AbstractLittle is known about the diversity and distribution patterns of moths along latitudinal gradients. We studied macro-moths in Mongolia along an 860 km latitudinal climatic gradient to gain knowledge on community composition, alpha, beta, and gamma diversity as well as underlying factors, which can be used as baseline information for further studies related to climate change. We identified 236 species of moths of ten families. Our study shows that the diversity of moths increased with the latitude, i.e., low species richness in the south and higher richness in the north. Moth community composition changed along the gradient, and we revealed a breakpoint of beta diversity that divided grassland and desert communities. In the desert, beta diversity was driven by species loss (i.e., nestedness), and few tolerant species existed with high abundance. In contrast, in the grassland, beta diversity was driven by species replacement with more unique species, (i.e., species which occurred only in one site). We found the lowest species diversity in the transitional zones dominated by few generalist species such as Agrotis ripae and Anarta trifolii. Low precipitation and an increasing number of grazing goats are drivers of species loss. We suggest different conservation strategies regarding the contrasting patterns of beta diversity in desert and grassland.

scholarly journals A null-model analysis of the spatio-temporal distribution of earthworm species assemblages in Colombian grasslands

2009 ◽  
Vol 25 (4) ◽  
pp. 415-427 ◽  
Author(s):  
Thibaud Decaëns ◽  
Juan José Jiménez ◽  
Jean-Pierre Rossi
Keyword(s):  
Spatial Scales ◽  
Null Model ◽  
Temporal Distribution ◽  
Niche Overlap ◽  
Past Research ◽  
Distribution Patterns ◽  
Species Assemblages ◽  
Spatially Explicit ◽  
Similar Species ◽  
Spatio Temporal

Abstract:Earthworm assemblages are usually spatio-temporally structured in mosaics of patches with different species composition. We re-analysed results of past research carried out in Eastern Colombia to explore how interspecific competition accounts for this pattern. In three sown pastures and three native savannas, density data matrices were obtained from spatially explicit samplings at several successive dates, and spatio-temporal patterns of species assemblages were described through partial triadic analyses and geostatistics. This first analysis detected assemblage patchiness in the six plots at spatial scales ranging from 6 to 33 m. Species richness ranged from 5 to 6 species per plot. Null models were further used to analyse niche overlap and morphometric distribution patterns at two different scales, i.e. at the ‘plot level’ and the ‘patch level’. Seasonal and vertical niche overlaps were higher than expected by chance at both scales, indicating high environmental constraints on assemblage membership. Within-patch overlaps were lower than plot-scale overlaps. Biometric niche overlap was random at the plot level and was weakly lower than that expected by chance in patches. Body weight was significantly overdispersed and constant whatever the scale, while body length and diameter showed a similar trend within patches. These results suggest that earthworms form distinct assemblages within patches, mainly driven by deterministic responses to competition: ecologically similar species avoid competition through spatial segregation, whereas a minimal level of ecological segregation is required to allow co-existence in a given patch.

scholarly journals Selection imposed by local environmental conditions drives differences in microbial community composition across geographically distinct groundwater aquifers

2019 ◽  
Vol 95 (11) ◽  
Author(s):  
Lucas Fillinger ◽  
Katrin Hug ◽  
Christian Griebler
Keyword(s):  
Microbial Community ◽  
Community Composition ◽  
Environmental Conditions ◽  
Spatial Scales ◽  
Variation Partitioning ◽  
Microbial Community Composition ◽  
Dispersal Limitation ◽  
Distribution Patterns ◽  
Groundwater Aquifers ◽  
Specific Factors

ABSTRACT Several studies have analyzed biogeographic distribution patterns of microbial communities across broad spatial scales. However, it is often unclear to what extent differences in community composition across different regions are caused by dispersal limitation or selection, and if selection is caused by local environmental conditions alone or additional broad-scale region-specific factors. This is especially true for groundwater environments, which have been understudied in this context relative to other non-subsurface habitats. Here, we analyzed microbial community composition based on exact 16S rRNA amplicon sequence variants (ASVs) from four geographically separated aquifers located in different regions along a latitudinal transect of ∼700 km across Germany. Using a combination of variation partitioning and ecological null models revealed that differences in microbial community composition were mainly the product of selection imposed by local environmental conditions and to a smaller but still significant extent dispersal limitation and drift across regions. Only ∼23% of the total variation in microbial community composition remained unexplained, possibly due to underestimated effects of dispersal limitation among local communities within regions and temporal drift. No evidence was found for selection due to region-specific factors independent of local environmental conditions.

scholarly journals Intra-Storm Pattern Recognition through Fuzzy Clustering

Hydrology ◽  
2021 ◽  
Vol 8 (2) ◽  
pp. 57
Author(s):  
Konstantinos Vantas ◽  
Epaminondas Sidiropoulos
Keyword(s):  
Fuzzy Clustering ◽  
A Priori ◽  
Temporal Distribution ◽  
Distribution Patterns ◽  
Rainfall Data ◽  
Rainfall Runoff ◽  
Domain Specific ◽  
Runoff Modeling ◽  
National Bank ◽  
Rainfall Patterns

The identification and recognition of temporal rainfall patterns is important and useful not only for climatological studies, but mainly for supporting rainfall–runoff modeling and water resources management. Clustering techniques applied to rainfall data provide meaningful ways for producing concise and inclusive pattern classifications. In this paper, a timeseries of rainfall data coming from the Greek National Bank of Hydrological and Meteorological Information are delineated to independent rainstorms and subjected to cluster analysis, in order to identify and extract representative patterns. The computational process is a custom-developed, domain-specific algorithm that produces temporal rainfall patterns using common characteristics from the data via fuzzy clustering in which (a) every storm may belong to more than one cluster, allowing for some equivocation in the data, (b) the number of the clusters is not assumed known a priori but is determined solely from the data and, finally, (c) intra-storm and seasonal temporal distribution patterns are produced. Traditional classification methods include prior empirical knowledge, while the proposed method is fully unsupervised, not presupposing any external elements and giving results superior to the former.

scholarly journals Detection of areas of endemism on two spatial scales using Parsimony Analysis of Endemicity (PAE): the Neotropical region and the Atlantic Forest

2008 ◽  
Vol 8 (4) ◽  
pp. 33-42 ◽  
Author(s):  
Mário Sérgio Sigrist ◽  
Claudio José Barros de Carvalho
Keyword(s):  
Atlantic Forest ◽  
Spatial Scales ◽  
Distribution Patterns ◽  
Neotropical Region ◽  
Conservation Priorities ◽  
Parsimony Analysis ◽  
Areas Of Endemism ◽  
Endemic Areas ◽  
Analysis Scale ◽  
Parsimony Analysis Of Endemicity

An important biological challenge today is the conservation of biodiversity. Biogeography, the study of the distribution patterns of organisms, is an important tool for this challenge. Endemism, the co-occurrence of several species unique to the same area, has important implications for the preservation of biodiversity, since many areas of endemism are also areas with large human impact. More rigorously defined, areas of endemism are historical units of distributional congruence of monophyletic taxa. These areas often assumed to be due to nonrandom historical events that favored conditions associated with high rates of speciation. Thus, understanding endemism and the delimitation of endemic areas has important implications for conservation. Today, most studies delimit areas of endemism by superimposing maps of distribution for various species. This approach suffers from arbitrary delimitations, however, when a great distributional data is used. In this paper we used the method of Parsimony Analysis of Endemicity (PAE) based on georeferenced quadrats in order to delimit areas of endemism. This modality of the method is important due to its testable nature and can also be used to infer area relationships. We applied the method to raw distributional data from 19 unrelated taxa to delimit general patterns of endemism in the Neotropical Region and in the Atlantic forest domain using different grid scales. Neotropical areas found are comprised over the Panama region, northern Andean region and the Atlantic forest. Atlantic forest showed a major division into two distinct components (northern x southern). Endemic areas delimited using smaller scale grids on the Atlantic forest should be considered for conservation priorities once they showed endemism at regional and local scales. The results were also compared to other studies using different taxa and methods. Finally, some considerations on the analysis scale and future perspectives of the method are presented.

scholarly journals Regional variation in otolith geochemistry of juvenile Atlantic cod (Gadus morhua) in coastal Newfoundland

2016 ◽  
Vol 73 (10) ◽  
pp. 1507-1519 ◽  
Author(s):  
Ryan R.E. Stanley ◽  
Claudio DiBacco ◽  
Simon R. Thorrold ◽  
Paul V.R. Snelgrove ◽  
Corey J. Morris ◽  
...  
Keyword(s):  
Gadus Morhua ◽  
Environmental Variability ◽  
Atlantic Cod ◽  
Environmental Influence ◽  
Spatial Scales ◽  
Early Life History ◽  
Otolith Chemistry ◽  
Geographic Patterns ◽  
Assignment Success ◽  
Scale Classification

We examined spatial variation in otolith geochemistry as a natural tag in juvenile Atlantic cod (Gadus morhua) to resolve geographic patterns during early life history. Individuals from 54 inshore sites spanned five embayments in eastern Newfoundland. Otolith composition differed at all spatial scales and related inversely to spatial scale. Classification analysis revealed increasing discrimination at coarser spatial scales: site (26%–58%), bay (49%), and coast (76%). Assignment success declined by ∼10% per added site with increasing sampling sites per bay, demonstrating fine-scale (<100 km) variation. When we partitioned environmental variability from observed otolith chemistry using predictive models, assignment success improved by 56%, 14%, and 5% for site, bay, and coast, respectively. Our results demonstrate environmental influence on spatial structure of otolith chemistry and illustrate the importance of resolving baseline variability in otolith chemistry when conducting assignment tests. Collectively, our results describe the potential utility of juvenile otolith composition in evaluating contributions of subpopulations to the Northwest Atlantic cod stock and highlight important limitations imposed by environmental variation at scales less than 100 km.

Free-living freshwater nematodes from Brazil: checklist of genera and regional patterns of diversity

Nematology ◽  
2021 ◽  
pp. 1-14
Author(s):  
Taciana Kramer de Oliveira Pinto ◽  
Sérgio A. Netto ◽  
André Morgado Esteves ◽  
Francisco José Victor de Castro ◽  
Patricia Fernandes Neres ◽  
...  
Keyword(s):  
Benthic Communities ◽  
Extreme Environments ◽  
Freshwater Ecosystems ◽  
Freshwater Biodiversity ◽  
High Turnover ◽  
Free Living ◽  
Regional Patterns ◽  
Freshwater Nematodes ◽  
Spatial Coverage ◽  
Freshwater Habitats

Summary Brazil has one of the largest varieties of aquatic ecosystems and rich freshwater biodiversity, but these components have constantly been damaged by the expansion of unsustainable activities. Free-living nematodes are an abundant and ubiquitous component of continental benthic communities, occurring in all freshwater habitats, including extreme environments. Despite this, hardly any studies have examined the generic composition of nematodes in different latitudes and the geographic overlap of assemblages. We provide data on nematode genera from six regions in Brazil, over a north-south gradient spanning about 4000 km, encompassing rivers, coastal lakes, and reservoirs with different levels of human impact. Interpolation/extrapolation curves were generated and the zeta diversity was used to assess the overlap of nematode assemblages. Freshwater nematode assemblages comprised 54 families and 132 genera. Mononchidae, Monhysteridae, Chromadoridae, Tobrilidae and Dorylaimidae were the most diverse families. Differences in diversity and high turnover of genera were found among regions, probably related to stochastic processes. Mononchus was the only widely distributed genus. Our results revealed a high biodiversity of free-living freshwater nematodes among the regions. The limited spatial coverage of the data reveals an enormous knowledge gap in a country with 12% of the world’s freshwater resources. The lack of spatial patterns, e.g., latitudinal variation, suggests that freshwater nematode assemblages are primarily structured by the intrinsic properties of habitats. This reinforces the uniqueness of freshwater ecosystems and suggests that the nematode assemblages may be sensitive to environmental disturbances, since the limited distributions of taxa may lead to lower resilience.

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