scholarly journals Benthic macroinvertebrate communities in sites with native forest presence and absence in north Patagonia

2020 ◽  
Vol 110 ◽  
Author(s):  
Patricio De los Ríos-Escalante ◽  
Carlos Esse ◽  
Rodrigo Santander-Massa ◽  
Pablo Saavedra ◽  
Francisco Encina-Montoya
Keyword(s):  
Species Composition ◽  
Neutral Theory ◽  
Null Model ◽  
Niche Overlap ◽  
Null Models ◽  
Species Number ◽  
Group Method ◽  
Native Forest ◽  
Macroinvertebrate Communities ◽  
Nothofagus Forests

ABSTRACT The benthic fauna in northern Patagonian streams is characterized by presence of water quality indicator species. The aim of the present study was characterized the benthic communities in streams associated to sites with presence of Nothofagus forests and with human intervention without Nothofagus forests using null models in ecology, unified neutral theory of biodiversity (UNTB) and unweighted pair group method with arithmetic mean (UPGMA). The results of species co-occurrence null model revealed that species associations are random, whereas the results of niche overlap null models revealed the presence of niche overlap. The UNTB results revealed low species number. The results of UPGMA revealed that species composition is specific for each site existing marked differences. The exposed results agree with results observed for central and northern Patagonian Chilean rivers, where the species composition is variable in according to surrounding basin properties and seasonal conditions.

scholarly journals Use of Null Models to Explain Crustacean Zooplankton Assemblages in Northern Patagonian Lakes (Chile) with and Without Mixotrophic Ciliates

Crustaceana ◽  
2011 ◽  
Vol 84 (9) ◽  
pp. 1061-1068 ◽  
Author(s):  
Patricio De Los Ríos-Escalante ◽  
Stefan Woelfl
Keyword(s):  
Null Model ◽  
Field Work ◽  
Study Data ◽  
Null Models ◽  
Crustacean Zooplankton ◽  
Species Number ◽  
Calanoid Copepods ◽  
Patagonian Lakes ◽  
Study Sites ◽  
Mixotrophic Ciliates

AbstractThe zooplankton assemblages in deep, mostly oligotrophic northern Patagonian lakes are characterized by a low species number and a marked dominance of calanoid copepods, as well as often by the presence of large mixotrophic ciliates (Stentor). In the present study, data collected in field work on four northern Patagonian lakes were analysed using co-occurrence of null models, with the aim to determine potential regulating factors for the observed crustacean and mixotrophic ciliate assemblages, using a presence-absence matrix. The null model uses species co-occurrence, and the basis of this model is that the species associations observed are random. The results revealed the absence of regulating factors and indicate that the sites are relatively homogeneous, with low species numbers, and similar plankton assemblages at all study sites. This finding coincides with similar descriptions for zooplankton assemblages in other Chilean Patagonian lakes.

scholarly journals First Descriptions of Aquatic Arthropods in an Unpolluted Native Forest Relict (Rucamanque, 38° S, Araucaria Region, Chile)

Zoodiversity ◽  
2021 ◽  
Vol 55 (3) ◽  
pp. 195-200
Author(s):  
P. De los Rios-Escalante ◽  
A. Alejandro Espinosa ◽  
P. Nunez
Keyword(s):  
Protected Area ◽  
Null Model ◽  
Niche Overlap ◽  
Ecological Niches ◽  
Native Forest ◽  
Aquatic Fauna ◽  
Native Forests ◽  
Chilean Patagonia ◽  
Water Ecosystems ◽  
First Descriptions

The Araucania region (38° S, Chile) originally had native perennial forest in middle valleys regions, that was gradually replaced by towns and agricultural zones during the last century, nevertheless there is some relicts of these native forests that are preserved, one of these relicts is Rucamanque, a protected area in the surrounding of Temuco town. The aim of the present study was a first aquatic Arthropoda description in a stream of this protected area using species co-occurrence and niche overlap null models. The results of species co-occurrence null model revealed that species associations are random, whereas the results of niche sharing revealed that species reported have different ecological niches, and in consequence there is not interspecifi c competence. The exposed results revealed the presence of aquatic fauna representative for unpolluted streams; similar descriptions were found for other similar inland water ecosystems in Argentinean and Chilean Patagonia.

scholarly journals Non-random seasonal variation in the structure of a Mediterranean snake community

Web Ecology ◽  
2007 ◽  
Vol 7 (1) ◽  
pp. 40-46
Author(s):  
E. Filippi ◽  
L. Luiselli
Keyword(s):  
Monte Carlo ◽  
Community Structure ◽  
Seasonal Variation ◽  
Central Italy ◽  
Habitat Type ◽  
Null Model ◽  
Niche Overlap ◽  
Null Models ◽  
Habitat Niche ◽  
Mediterranean Community

Abstract. The community structure in relation to habitat type was studied in a Mediterranean community of snakes from Canale Monterano, central Italy. Habitat data for snakes were analysed both overall and divided by season, i.e. spring (April–June) and summer (July–September). Community analyses were performed using null models (RA2 and RA3 algorithms) and Monte Carlo simulations on habitat niche overlap estimates. Null models suggested that the community was assembled non-randomly (according to RA2 but not RA3), indicating that the generalist-specialist nature (the number of resource states, but not necessarily the types) used by each species in the assemblage reduced ecological similarity. Similar results were reached also performing the same null model procedures on the spring datasets, whereas no structure emerged during summer either by RA2 or RA3 algorithms. In general, this study suggests that the community structure of snakes during spring may be shaped by the different eco-physiological needs of the various species (probably, the differential tolerance to cold and the consequent needs of finding suitable hibernacula), whereas the lack of structure during summer may be caused by the between-species similar foraging needs.

scholarly journals Regional and Seasonal Differences in Species Composition and Trophic Groups for Tidepool Fishes of a Western Pacific Island – Taiwan

2018 ◽  
Vol 23 (1) ◽  
pp. 1 ◽  
Author(s):  
Colin K. C. Wen ◽  
Li-Shu Chen ◽  
Kwang-Tsao Shao
Keyword(s):  
Species Composition ◽  
Fish Species ◽  
Fish Assemblages ◽  
Coastal Development ◽  
Species Number ◽  
Pacific Region ◽  
Trophic Groups ◽  
Species Numbers ◽  
Intertidal Fish ◽  
Intertidal Fishes

Spatial and temporal variations in the species composition of assemblages are common in many marine organisms, including fishes. Variations in the fish species composition of subtidal coral reefs have been well documented, however much less is known about such differences for intertidal fish assemblages. This is surprising, given that intertidal fishes are more vulnerable to terrestrial human disturbances. It is critical to evaluate the ecology and biology of intertidal fishes before they are severely impacted by coastal development, especially in developing countries such as those in the tropical western Pacific region where coastal development is rapidly increasing. In this study, we investigated the species composition, abundance, biomass and species number (richness) for intertidal fish assemblages in subtropical (northern) and tropical (southern) Taiwan across four seasons by collecting fishes from tidepools using clove oil. We also examined the gut contents of collected fishes to identify their trophic functional groups in order to investigate regional and seasonal variations for different trophic groups. We found significant differences in the species composition of tidepool fish assemblages between subtropical and tropical Taiwan. Bathygobius fuscus, Abudefduf vaigiensis and Istiblennius dussumieri were dominant species in subtropical Taiwan, whereas Bathygobius coalitus, Abudefduf septemfasciatus and Istiblennius lineatus were dominant in tropical Taiwan. Other species such as Bathygobius cocosensis, Abudefduf sordidus and Istiblennius edentulus were common in both regions. For trophic groups, omnivores and detritivores had or showed trends towards higher species numbers and abundances in the subtropical region, whereas herbivores, planktivores and general carnivores had or showed trends towards higher species numbers and biomass in the tropical region. Overall, many intertidal fish species and trophic groups showed differences in abundance, biomass and species number between subtropical and tropical Taiwan. Further studies on large scale geographical gradients in trophic groups and species compositions in the Indo-west Pacific region are encouraged to assist with ecosystem monitoring and assessment. Keywords: Intertidal fishes, spatio-temporal pattern, feeding guild, diet

scholarly journals Inland water microcrustacean assemblages in an altitudinal gradient in Aysen region (46° S, Patagonia Chile)

2014 ◽  
Vol 74 (1) ◽  
pp. 8-15 ◽  
Author(s):  
Patricio De los Ríos-Escalante ◽  
Esteban Quinán ◽  
Patricio Acevedo
Keyword(s):  
National Park ◽  
Altitudinal Gradient ◽  
Null Model ◽  
Tierra Del Fuego ◽  
Species Number ◽  
Regional Studies ◽  
Inland Water ◽  
Chilean Patagonia ◽  
Water Ecosystems ◽  
Torres Del Paine

The Chilean Patagonia has numerous kinds of inland water ecosystems such as lakes, ponds, wetlands and rivers that have been poorly studied due to access difficulties. This study was carried out in Aysen region, in southern Chile, and it included different kinds of water bodies such as rivers, streams, ponds, lagoons and lakes distributed along an altitudinal gradient at 46° S. It was found a low species number, essentially cladocerans, copepods and amphipods. A null model was applied in order to determine the existence of regulator factors of species associations, and the results revealed that they are not random. The patterns would be influenced by geographical and limnological characteristics of the studied sites. Our results would agree with regional studies on habitat heterogeneity such as in Torres del Paine National Park and other zones in Tierra del Fuego island.

scholarly journals Null Models for Formal Contexts

Information ◽  
2020 ◽  
Vol 11 (3) ◽  
pp. 135
Author(s):  
Maximilian Felde ◽  
Tom Hanika ◽  
Gerd Stumme
Keyword(s):  
Formal Concept Analysis ◽  
Null Model ◽  
Null Models ◽  
Formal Concept ◽  
Model Generation ◽  
Coin Toss ◽  
Novel Approach ◽  
Random Models ◽  
Real World Datasets ◽  
Stochastic Properties

Null model generation for formal contexts is an important task in the realm of formal concept analysis. These random models are in particular useful for, but not limited to, comparing the performance of algorithms. Nonetheless, a thorough investigation of how to generate null models for formal contexts is absent. Thus we suggest a novel approach using Dirichlet distributions. We recollect and analyze the classical coin-toss model, recapitulate some of its shortcomings and examine its stochastic properties. Building upon this we propose a model which is capable of generating random formal contexts as well as null models for a given input context. Through an experimental evaluation we show that our approach is a significant improvement with respect to the variety of contexts generated. Furthermore, we demonstrate the applicability of our null models with respect to real world datasets.

Seasonal distribution of abundance, biomass and secondary production of free-living nematodes and their community composition in different stream micro-habitats

Nematology ◽  
2020 ◽  
Vol 22 (4) ◽  
pp. 401-422 ◽  
Author(s):  
Henrike Brüchner-Hüttemann ◽  
Walter Traunspurger
Keyword(s):  
Species Composition ◽  
Leaf Litter ◽  
Secondary Production ◽  
Dead Wood ◽  
Nematode Species ◽  
Species Number ◽  
Order Stream ◽  
Nematode Communities ◽  
Feeding Types ◽  
Nematode Abundance

Summary The nematode communities of four different micro-habitats in an unpolluted first-order stream were investigated over a 13-month period in a study of the sediment and the biofilms on dead wood, macrophytes and leaf litter. Nematode abundances, biomass and secondary production were analysed, together with the species composition, proportion of feeding types and diversity of the nematode communities of the micro-habitats. Differences between the investigated micro-habitats in terms of seasonal variations, species composition, proportion of feeding types and diversity were expected. The annual mean values of nematode abundance, biomass and secondary production differed significantly between the micro-habitats. Abundances were highest on dead wood, whereas biomass and secondary production were highest in sediment. In the sediment and on leaf litter, nematode abundance and biomass showed pronounced seasonal patterns. The largest contribution to the total secondary production of the stream was from sediment nematodes. In total, 108 nematode species were detected in the micro-habitats during the 13-month study. Comparisons between them revealed differences in nematode species composition. The annual mean species number was significantly higher in sediment and on leaf litter than on dead wood and macrophytes, whereas the annual mean Shannon-Wiener index was significantly higher in sediment than at all other micro-habitats. All micro-habitats in the studied stream, as well as the stream as a whole, were dominated by nematode species belonging to the deposit feeders. Our study clearly showed that the composition of nematode communities from different micro-habitats within a single stream reach can differ markedly.

scholarly journals Cladocera of the Lençóis Maranhenses (NE - Brazil): faunal composition and a reappraisal of Sars' Method

2010 ◽  
Vol 70 (3 suppl) ◽  
pp. 755-779 ◽  
Author(s):  
K. Van Damme ◽  
HJ. Dumont
Keyword(s):  
Invasive Species ◽  
Species Composition ◽  
Rare Species ◽  
Simple Technique ◽  
Species Number ◽  
Acid System ◽  
Faunal Composition ◽  
Hit And Run ◽  
Total Species

We studied the Cladocera of a group of ephemeral interdunal pools in the Lençóis Maranhenses, Maranhão State (NE - Brazil) and recorded 34 species. The fauna was overwhelmingly neotropical, with no evidence of invasive species. Species composition differed in Lagoa da Colher, an acid system. We provide notes on behaviour, morphology and taxonomy of some lesser-known anomopods, with emphasis on the Chydoridae. We figure male Oxyurella longicaudis, Chydorus eurynotus, Disparalona leptorhyncha, Alonella dadayi and A. clathratula. We provide notes on the "Sars' Method", hatching of freshwater crustaceans from dry mud, a simple technique that complements the information of hit-and-run surveys. About half of the total species number (44%) was revived through this method; 18% of species were additional to field-collected samples. The Sars' method also yielded abundant specimens of rare species, useful for identification and studies on behaviour.

scholarly journals Native forests but not agroforestry systems preserve arbuscular mycorrhizal fungal species richness in southern Ethiopia

Mycorrhiza ◽  
2020 ◽  
Vol 30 (6) ◽  
pp. 749-759
Author(s):  
Zerihun Belay ◽  
Mesele Negash ◽  
Janne Kaseva ◽  
Mauritz Vestberg ◽  
Helena Kahiluoto
Keyword(s):  
Land Use ◽  
Species Richness ◽  
Species Composition ◽  
Arbuscular Mycorrhizal ◽  
Soil Samples ◽  
Southern Ethiopia ◽  
Native Forest ◽  
Native Forests ◽  
Land Use Types ◽  
The Impact

Abstract The rapid conversion of native forests to farmland in Ethiopia, the cradle of biodiversity, threatens the diversity of the arbuscular mycorrhizal fungi (AMF) pivotal to plant nutrition and carbon sequestration. This study aimed to investigate the impact of this land-use change on the AMF species composition and diversity in southern Ethiopia. Soil samples were collected from nine plots in each of three land-use types: native forest, agroforestry, and khat monocropping. The plots of the three land-use types were located adjacent to each other for each of the nine replicates. Three 10 × 10m subplots per plot were sampled. AMF spores were extracted from the soil samples, spore densities were determined, and species composition and diversity were evaluated through morphological analysis. Both spore density and species richness were statistically significantly higher in the native forest than in the agroforestry plots with no clear difference to khat, whereas the true diversity (exponential of Shannon–Wiener diversity index) did not differ among the three land-use types due to high evenness among the species in agroforestry. In total, 37 AMF morphotypes belonging to 12 genera in Glomeromycota were found, dominated by members of the genera Acaulospora and Glomus. The highest isolation frequency index (78%) was recorded for Acaulospora koskei from native forest. Consequently, the agroforestry system did not appear to aid in preserving the AMF species richness of native forests relative to perennial monocropping, such as khat cultivation. In contrast, the native forest areas can serve as in situ genetic reserves of mycorrhizal symbionts adapted to the local vegetative, edaphic, and microbial conditions.

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