The role of environmental, geographical, morphometric and spatial variables on plankton communities in lakes of the arid Patagonian plateaus

2020 ◽  
Vol 42 (2) ◽  
pp. 173-187
Author(s):  
Sol Porcel ◽  
Griselda Chaparro ◽  
M Cristina Marinone ◽  
Juan F Saad ◽  
Julio Lancelotti ◽  
...  
Keyword(s):  
Variation Partitioning ◽  
Null Model ◽  
Taxonomic Diversity ◽  
Conservation Strategies ◽  
High Dispersion ◽  
Spatial Effects ◽  
Spatial Factors ◽  
Zooplankton Communities ◽  
Planktonic Communities

Abstract Species diversity is one of the most informative community metrics and is influenced by regional and local factors. We studied the spatial patterns of taxonomic and functional phyto- and zooplankton diversity in 33 lakes from two basaltic plateaus of the arid Patagonia. The aims of our study were to evaluate α, β and γ taxonomic diversity of phyto- and zooplankton; to assess the influence of environmental, spatial, geographical and morphometric factors on phyto- and zooplankton communities and to compare the influence of these variables on the taxonomic and functional composition. β1-diversity (within plateaus) was the major component for phytoplankton, rotifers and microcrustaceans taxonomic regional diversities. Planktonic communities were mainly constrained by macrophytes, fish, conductivity, dissolved organic carbon, altitude and spatial factors. The high dispersion of small individuals within plateaus tends to homogenize these communities, as indicated by null model results and the high explanation of fine-scale spatial factors in variation partitioning. This knowledge contributes to explaining the diversity patterns of planktonic communities of these valuable environments and to develop conservation strategies, considering both environmental heterogeneity and spatial effects.

scholarly journals Ecotones and gradient as determinants of herpetofaunal community structure in the primary forest of Mount Kupe, Cameroon

2000 ◽  
Vol 16 (4) ◽  
pp. 517-533 ◽  
Author(s):  
Ulrich Hofer ◽  
Louis-Félix Bersier ◽  
Daniel Borcard
Keyword(s):  
Forest Type ◽  
Variation Partitioning ◽  
Null Model ◽  
Elevational Gradient ◽  
Community Response ◽  
Primary Forest ◽  
Minor Importance ◽  
Breeding Sites ◽  
Physiological Tolerance ◽  
The Individual

The relative effects of the elevational gradient and of environmental discontinuities (ecotones) on the structure of a herpetofaunal assemblage in a tropical upland forest were contrasted by means of canonical correspondence analysis. Qualitative descriptors were used to define the elevational positions of the ecotones of interest, namely transitions in forest type and presence/absence of water bodies. The elevational gradient was coded in a form that accommodated different types of community response. Analyses were run for four subsets of the entire assemblage: (1) reptiles, (2) amphibians, (3) amphibians dependent on streams for reproduction, and (4) amphibians that do not use streams for reproduction. All subsets showed a significant relationship with the gradient, which suggested that most species respond to the physical continuum associated with the change in elevation. A response to ecotones was revealed for the amphibian subset only and associated with the presence or absence of watercourses. However, this response disappeared within subsets 3 and 4. A variation partitioning analysis was used to assess the individual and common contributions of gradient and ecotone descriptors to the elevational variation in the structure of subsets 1 and 2. The gradient descriptors explained more variation in the reptile subset than did ecotones, while the reverse was found in the amphibian subset. The dependence of most amphibians on aquatic breeding sites that were not available at all elevations reduced the relative importance of the gradient on the species distributions in subset 2 and accounted for the difference to the reptiles. In all, these findings add to the results of previous null model tests on the same four subsets, where competitive interactions were assigned a minor importance in limiting elevational distributions. The response patterns revealed by the present approach, with ecotones and gradient contrasted in a single analysis, emphasised the role of individual responses to the gradient according to the species' physiological tolerance limits.

Spatial Effects on Temporal Categorisation

Perception ◽  
10.1068/p6165 ◽  
2009 ◽  
Vol 38 (5) ◽  
pp. 748-762 ◽  
Author(s):  
Marie-Ève Roussel ◽  
Simon Grondin ◽  
Peter Killeen
Keyword(s):  
Temporal Processing ◽  
Critical Role ◽  
Vertical Plane ◽  
Spatial Effects ◽  
Time Intervals ◽  
Spatial Factors ◽  
Upper Visual Field ◽  
Sensitivity Level ◽  
Marking Time ◽  
Perceived Duration

We examined the influence of spatial factors in temporal processing. Participants categorised as short or long empty intervals marked by two brief flashes delivered from locations differing in height and depth (experiment 1), or from two of three locations on a vertical plane (experiment 2). The perceived duration of intervals, as determined by the point of subjective equality, was affected by the height and depth of the signals (experiment 1). Experiment 2 showed that the point of fixation plays a critical role in perceived duration. The duration of an interval located in the upper visual field is perceived as longer when participants fixate the higher visual source and shorter when the fixation point is set in the middle; this latter result also generally applies when the fixation point is in the lower source. Finally, for the sensitivity level, there was a significant segment (upper versus lower) × direction (descending versus ascending) interaction in experiment 1; a similar interaction effect varied according to the fixation point in experiment 2. In experiment 2, the Weber fractions were around 0.22. Most results can be explained in terms of the need to shift attention from one visual source—for marking time intervals—to another.

The role of aerobic metabolism and intragel oxygen in hypoxia tolerance of three ctenophores: Pleurobrachia bachei, Bolinopsis infundibulum and Mnemiopsis leidyi

2005 ◽  
Vol 85 (3) ◽  
pp. 627-633 ◽  
Author(s):  
Erik V. Thuesen ◽  
Ladd D. Rutherford ◽  
Patricia L. Brommer
Keyword(s):  
Aerobic Metabolism ◽  
Hypoxia Tolerance ◽  
Mnemiopsis Leidyi ◽  
Survival Times ◽  
Partial Pressures ◽  
Pleurobrachia Bachei ◽  
Oxygen Measurements ◽  
Surrounding Seawater ◽  
Planktonic Communities

Ctenophores are important members of planktonic communities that are often abundant in dysaerobic environments. Previous studies have shown that ctenophores are not adversely affected by extended periods of hypoxia. The three species used in this study, Pleurobrachia bachei, Bolinopsis infundibulum, and Mnemiopsis leidyi, were all able to oxyregulate to very low partial pressures of oxygen (PO2s). These species were found to have mean critical oxygen tensions of 7.7, 10.6, and 7.2 hPa respectively. In general, ctenophores are better oxyregulators than medusae and many species of shrimps, fish and squid. Intragel oxygen was measured using a fibre optic oxygen optode. All these ctenophores have intragel subsurface [O2]s of 5–10% below that of the surrounding seawater. Intragel oxygen measurements of P. bachei showed a gradient of decreasing PO2 from surface tissues to the gut. Specimens of P. bachei over 14 mm in diameter had anaerobic guts. Survival times in anoxia ranged from 0 h for M. leidyi to up to 6 h for P. bachei. Ctenophores rely on aerobic metabolism to tolerate hypoxia.

scholarly journals Metabarcoding reveals different zooplankton communities in northern and southern areas of the North Sea

2020 ◽  
Author(s):  
Jan Niklas Macher ◽  
Berry B. van der Hoorn ◽  
Katja T. C. A. Peijnenburg ◽  
Lodewijk van Walraven ◽  
Willem Renema
Keyword(s):  
North Sea ◽  
Zooplankton Community ◽  
Taxonomic Diversity ◽  
Molecular Techniques ◽  
Trophic Levels ◽  
List Type ◽  
The North ◽  
Shelf Sea ◽  
The North Sea ◽  
Zooplankton Communities

AbstractZooplankton are key players in marine ecosystems, linking primary production to higher trophic levels. The high abundance and high taxonomic diversity renders zooplankton ideal for biodiversity monitoring. However, taxonomic identification of the zooplankton assemblage is challenging due to its high diversity, subtle morphological differences and the presence of many meroplanktonic species, especially in coastal seas. Molecular techniques such as metabarcoding can help with rapid processing and identification of taxa in complex samples, and are therefore promising tools for identifying zooplankton communities. In this study, we applied metabarcoding of the mitochondrial cytochrome c oxidase I gene to zooplankton samples collected along a latitudinal transect in the North Sea, a shelf sea of the Atlantic Ocean. Northern regions of the North Sea are influenced by inflow of oceanic Atlantic waters, whereas the southern parts are characterised by more coastal waters. Our metabarcoding results indicated strong differences in zooplankton community composition between northern and southern areas of the North Sea, particularly in the classes Copepoda, Actinopterygii (ray-finned fishes) and Polychaeta. We compared these results to the known distributions of species reported in previous studies, and by comparing the abundance of copepods to data obtained from the Continuous Plankton Recorder (CPR). We found that our metabarcoding results are mostly congruent with the reported distribution and abundance patterns of zooplankton species in the North Sea. Our results highlight the power of metabarcoding to rapidly assess complex zooplankton samples, and we suggest that the technique could be used in future monitoring campaigns and biodiversity assessments.HighlightsZooplankton communities are different in northern and southern areas of the North SeaMetabarcoding results are consistent with known species distributions and abundanceMetabarcoding allows for fast identification of meroplanktonic species

The Maoist people's war and conservation in Nepal

2005 ◽  
Vol 24 (1-2) ◽  
pp. 2-11 ◽  
Author(s):  
Nabin Baral ◽  
Joel T. Heinen
Keyword(s):  
Civil Wars ◽  
Wildlife Trade ◽  
Conservation Strategies ◽  
Military Force ◽  
Community Based ◽  
Governmental Organizations ◽  
Non Governmental Organizations ◽  
Maoist Insurgency ◽  
Developed Nations

Civil wars are frequent in lesser-developed nations, wherein is harbored a disproportionate share of the world's biodiversity. These wars have had serious detrimental effects, direct and indirect, on conservation programs. From 2001 to 2005, we conducted site visits, personal interviews, and document searches bearing upon this problem as exemplified by Nepal's ongoing Maoist insurgency. Cases of insurgents usurping full control of several protected areas have come to light, as has a rapid increase in poaching and illicit wildlife trade nation-wide. Staff and infrastructure of conservation agencies and non-governmental organizations have been attacked. The Nepalese situation invites reassessment of traditional “fortresses-and-fines” conservation strategies as well as more modern “community-based” approaches that require local governmental offices to remain functional. Also called into question is the role of military force in the protection of parks and reserves. In times of civil strife, we conclude, robust conservation may most likely be achieved by nongovernmental organizations that are politically neutral and financially independent.

scholarly journals Deagrarianisation of the Economic Structure and the Evolution of Rural Settlement Patterns in Poland

Land ◽  
2020 ◽  
Vol 9 (12) ◽  
pp. 523
Author(s):  
Andrzej Rosner ◽  
Monika Wesołowska
Keyword(s):  
Rural Areas ◽  
Settlement Patterns ◽  
Economic Structure ◽  
Rural Settlement ◽  
Spatial Effects ◽  
Central Statistical ◽  
Central Statistical Office ◽  
Second World

Since the Second World War, Poland has been undergoing an intensive process of transformation of the economic structure of rural areas, manifested, among other things, in the change in the occupational make-up of its inhabitants. The development of non-agricultural methods of management in rural areas has led to the emergence of multifunctional rural areas, where the role of agriculture as a source of income for the inhabitants is decreasing. There is a process of deagrarianisation of the economic structure, which has been indicated by many researchers as an unavoidable process, connected with the changes taking place in rural areas. One of the effects of this process are changes in rural settlement patterns. The aim of this article is to present the spatial effects of the deagrarianisation process in the Polish countryside, expressed in the changes in the rural settlement network. The authors used the statistical database of the Central Statistical Office (over 41 thousand records) to draw up the classification of rural areas by the nature of changes in population numbers in the period 1950–2011, which was compared with the research carried out as part of the Monitoring of Rural Development in Poland. The study confirmed that the factor behind the evolution of the rural settlement network is the process of decreasing agricultural demand for labour. As a consequence, there is a polarisation of localities into multifunctional rural localities, mainly headquarter villages and local government offices, and those with a predominantly agricultural function. On a supra-local scale, a process of polarisation of rural areas between a growing suburban population and a reducing peripheral location around large and medium-sized towns has been observed.

Spatial Effects and Ecological Inference

2002 ◽  
Vol 10 (3) ◽  
pp. 276-297 ◽  
Author(s):  
Luc Anselin ◽  
Wendy K. Tam Cho
Keyword(s):  
Data Analysis ◽  
Spatial Autocorrelation ◽  
Random Coefficient ◽  
Parameter Estimates ◽  
Spatial Effects ◽  
Ecological Inference ◽  
Simulation Experiments ◽  
Coefficient Variation ◽  
Inference Methods

This paper examines the role of spatial effects in ecological inference. Both formally and through simulation experiments, we consider the problems associated with ecological inference and cross-level inference methods in the presence of increasing degrees of spatial autocorrelation. Past assessments of spatial autocorrelation in aggregate data analysis focused on unidimensional, one-directional processes that are not representative of the full complexities caused by spatial autocorrelation. Our analysis is more complete and representative of true forms of spatial autocorrelation and pays particular attention to the specification of spatial autocorrelation in models with random coefficient variation. Our assessment focuses on the effects of this specification on the bias and precision of parameter estimates.

Sign in / Sign up

Export Citation Format

Share Document