Dispersal-based versus niche-based processes as drivers of flea species composition on small mammalian hosts: inferences from species occurrences at large and small scales

Oecologia ◽  
2021 ◽  
Author(s):  
Corentin Gibert ◽  
Georgy I. Shenbrot ◽  
Michal Stanko ◽  
Irina S. Khokhlova ◽  
Boris R. Krasnov
2016 ◽  
Vol 22 (1) ◽  
pp. 9-18
Author(s):  
James Skelton ◽  
Robert P. Creed ◽  
Lukas Landler ◽  
Kevin M. Geyer ◽  
Bryan L. Brown

Abstract We analyzed historical data from 1961-1965 for species occurrences of branchiobdellidans and their crayfish hosts throughout the Mountain Lake Region of southwestern Virginia, USA to quantify geographic variability in species composition and identify patterns in host and symbiont diversity. We collected contemporary census data of branchiobdellidan assemblages from the same region in 2011-2014 for intra-annual variation in symbiont abundance and species composition. We compared historical and contemporary records to assess the stability of geographic patterns in symbiont diversity over decadal timescales. Branchiobdellidan assemblages followed a hump-shaped relationship with Strahler stream order. Much of the geographic variation in symbiont species composition was explained by host species composition, despite low host fidelity in branchiobdellidans. There were strong seasonal cycles in branchiobdellidan abundance and species composition. A comparison of historical and contemporary records revealed little change in species distributions over 50 years. Thus, branchiobdellidan species composition changes predictably along habitat gradients, tracks variation in host composition, is repeatable across decadal timescales, and follow strong cyclic seasonal changes in total and relative abundances. These results suggest that complex but deterministic ecological processes drive symbiont population dynamics at multiple spatial and temporal scales.


PeerJ ◽  
2019 ◽  
Vol 7 ◽  
pp. e7013
Author(s):  
Daniela N. López ◽  
Patricio A. Camus ◽  
Nelson Valdivia ◽  
Sergio A. Estay

Community similarity is often assessed through similarities in species occurrences and abundances (i.e., compositional similarity) or through the distribution of species interactions (i.e., interaction similarity). Unfortunately, the joint empirical evaluation of both is still a challenge. Here, we analyze community similarity in ecological systems in order to evaluate the extent to which indices based exclusively on species composition differ from those that incorporate species interactions. Borrowing tools from graph theory, we compared the classic Jaccard index with the graph edit distance (GED), a metric that allowed us to combine species composition and interactions. We found that similarity measures computed using only taxonomic composition could differ strongly from those that include composition and interactions. We conclude that new indices that incorporate community features beyond composition will be more robust for assessing similitude between natural systems than those purely based on species occurrences. Our results have therefore important conceptual and practical consequences for the analysis of ecological communities.


2018 ◽  
Vol 10 (1) ◽  
Author(s):  
Ruben Danielyan

Objective: The objective of this study was to determine the species composition of mammals and parasites involved in the epizootic process of plague in Armenia and their geographic distribution.Introduction: Plague was first identified in Armenia in 1958 when Y. pestiswas isolated and cultured from the flea species Ct. teres collected from the burrows of common voles in the northwestern part of the country. In the process of digitalizing archived data, a statistical and spatial analysis of the species composition of mammals and parasites involved in the epizootic process of plague between 1958 and 2016 was performed.Methods: The plague archives of the NCDCP were exploited. The geographic addresses from which strains of Y. pestis were isolated from mammals and their parasite species were analyzed and grouped into 38 administrative regions (Fig.1). For geostatistical analysis, databases were created using Microsoft Excel and converted into a ESRI Geodatabase (Fig.2).Results: Data from the especially dangerous pathogen laboratories indicate that 9329 Y. pestis strains were isolated in 27 of the 38 regions of the country with 7022 (75%) of the strains found in just four regions: Abovyan 2597 (28%), Sisian 1953 (21%), Martuni 1416 (15%) and Ashotsk 1056 (11%) (Fig.3). During this period, plague bacteria were isolated from 17 mammal species including 15 rodents, Mustela nivalis (weasel), and Neomys fodiens (shrew) (Fig.4). Y. pestis was isolated from 22 species of fleas belonging to 11 genera along with two families of ticks. Of the 9329 bacterial isolates, 6540 (70.2%) came from fleas, 2646 (28.3%) came from mammals and 143 (1.5%) were from ticks (Fig.5).Conclusions: In Armenia, the primary mammalian host for Y. pestis is the common vole Microtus arvalis from which 2600 isolates (27.9%) were taken. Flea species from which large numbers of plague bacteria have been isolated include Ct. teres-3758 (40.3%), Ct. wladimiri-1262 (13.5%) and C. caspia-667 (7.1%).


2017 ◽  
Vol 52 (6) ◽  
pp. 1279-1286
Author(s):  
G.P. Kononenko ◽  
◽  
E.A. Piryazeva ◽  
E.V. Zotova ◽  
A.A. Burkin ◽  
...  
Keyword(s):  

2014 ◽  
Vol 25 (3-4) ◽  
pp. 53-68
Author(s):  
I. V. Goncharenko ◽  
H. M. Holyk

Cenotic diversity and leading ecological factors of its floristic differentiation were studied on an example of two areas – Kyiv parks "Nivki" and "Teremki". It is shown that in megalopolis the Galeobdoloni-Carpinetum impatientosum parviflorae subassociation is formed under anthropogenic pressure on the typical ecotope of near-Dnieper hornbeam oak forests on fresh gray-forest soils. The degree of anthropogenic transformation of cenofloras can be estimated by the number of species of Robinietea and Galio-Urticetea classes, as well as neophytes and cultivars. Phytoindication for hemeroby index may be also used in calculation. We propose the modified index of biotic dispersion (normalized by alpha-diversity) for the estimation of ecophytocenotic range (beta-diversity) of releves series. We found that alpha-diversity initially increases (due to the invasion of antropophytes) at low level of antropogenic pressure, then it decreases (due to the loss of aboriginal species) secondarily with increasing of human impact. Also we found that beta-diversity (differential diversity) decreases, increasing homogeneity of plant cover, under the influence of anthropogenic factor. Vegetation classification was completed by a new original method of cluster analysis, designated as DRSA («distance-ranked sorting assembling»). The classification quality is suggested to be validated on the "seriation" diagram, which is а distance matrix between objects with gradient filling. Dark diagonal blocks confirm clusters’ density (intracluster compactness), uncolored off-diagonal blocks are evidence in favor of clusters’ isolation (intercluster distinctness). In addition, distinction of clusters (syntaxa) in ordination area suggests their independence. For phytoindication we propose to include only species with more than 10% constancy. Furthermore, for the description of syntaxonomic amplitude we suggest to use 25%-75% interquartile scope instead of mean and standard deviation. It is shown that comparative analysis of syntaxa for each ecofactor is convenient to carry out by using violin (bulb) plots. A new approach to the phytoindication of syntaxa, designated as R-phytoindication, was proposed for our study. In this case, the ecofactor values, calculated for individual releves, are not taken into account, however, the composition of cenoflora with species constancies is used that helps us to minimize for phytoindication the influence of non-typical species. We suggested a syntaxon’s amplitude to be described by more robust statistics: for the optimum of amplitude (central tendency) – by a median (instead of arithmetic mean), and for the range of tolerance – by an interquartile scope (instead of standard deviation). We assesses amplitudes of syntaxa by phytoindication method for moisture (Hd), acidity (Rc), soil nitrogen content (Nt), wetting variability (vHd), light regime (Lc), salt regime (Sl). We revealed no significant differences on these ecofactors among ecotopes of our syntaxa, that proved the variant syntaxonomic rank for all syntaxa. We found that the core of species composition of our phytocenoses consists of plants with moderate requirements for moisture, soil nitrogen, light and salt regime. We prove that the leading factor of syntaxonomic differentiation is hidden anthropogenic, which is not subject to direct measurement. But we detect that hidden factor of "human pressure" was correlated with phytoindication parameters (variables) that can be measured "directly" by species composition of plant communities. The most correlated factors were ecofactors of soil nitrogen, wetting variability, light regime and hemeroby. The last one is the most indicative empirically for the assessment of "human impact". We establish that there is a concept of «hemeroby of phytocenosis» (tolerance to human impact), which can be calculated approximately as the mean or the median of hemeroby scores of individual species which are present in it.


2013 ◽  
Vol 25 (1-2) ◽  
pp. 136-148
Author(s):  
I. V. Gryb

The concept of an explosion in freshwater ecosystems as a result of the release of accumulated energy, accompanied by the destruction of the steady climax successions of hydrocenoses is presented. The typification of local explosions as well as methods for assessing their risk during the development of river basins are shown. The change in atmospheric circulation, impaired phases of the hydrological regime of rivers, increasing the average temperature of the planet, including in Polesie to 0,6 ºC, deforestation leads to concentration and release of huge amounts of unmanaged terrestrial energy, which manifests itself in the form of disasters and emergencies. Hydroecological explosion is formed as a result of multifactorial external influence (natural and anthropogenic) on the water body in a certain period of time. Moreover, its level at wastewater discharge depends on the mass of recycled impurities and behaved processing capacity of the reservoir, and the mass of dumped on biocides and the possibility of the water flow to their dilution and to the utilization of non-toxic concentrations. In all these cases the preservation of "centers of life" in the tributaries of the first order – local fish reproduction areas contributed to ecosystem recovery, and the entire ecosystem has evolved from equilibrium to non-equilibrium with further restructuring after the explosion and environmental transition to a new trophic level. It means that hydroecological explosion can be researched as the logical course of development of living matter in abiotic environmental conditions, ending abruptly with the formation of new species composition cenoses and new bio-productivity. The buffer capacity of the water environment is reduced due to re-development and anthropic transformation of geobiocenoses of river basins, which leads to a weakening of life resistance. This applies particularly to the southern industrial regions of Ukraine, located in the arid zone that is even more relevant in the context of increased average temperature due to the greenhouse effect, as well as to Polesie (Western, Central and Chernihiv), had been exposed to large-scale drainage of 60-80th years, which contributed to the degradation of peatlands and fitostroma. Imposing the western trace of emissions from the Chernobyl accident to these areas had created the conditions of prolonged hydroecological explosion in an intense process of aging water bodies, especially lakes, change in species composition of fish fauna and the occurrence of neoplasms at the organismal level. Under these conditions, for the existence of man and the environment the vitaukta should be strengthened, i.e. buffer resistance and capacitance the aquatic environment, bioefficiency on the one hand and balanced using the energy deposited - on the other. This will restore the functioning of ecosystems "channel-floodplain", "riverbed-lake", reducing the energy load on the aquatic environment. Hydroecological explosions of natural origin can not be considered a pathology – it is a jump process of natural selection of species of biota. Another thing, if they are of anthropogenic origin and if the magnitude of such an impact is on the power of geological factors. Hydroecological explosions can be regarded as a manifestation of environmental wars that consciously or unconsciously, human society is waging against themselves and their kind in the river basins, so prevention of entropy increase in the aquatic environment and the prevention of hydroecological explosions is a matter of human survival. While the man - is not the final link in the development of living matter, it can develop without him, as matter is eternal, and the forms of its existence are different.


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