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Results for “Habitat characterization”

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At least 19 recordsLinked to original sources

PubMed1995

Simulium metallicum cytospecies E larval habitat characterization in the Altamira focus of onchocerciasis, northern Venezuela.

Simulium metallicum sibling species E was identified cytotaxonomically from an onchocerciasis focus at Altamira in northern Venezuela. S. metallicum E larvae were sampled monthly from two small mountain streams over a 15-month period (July 1990 to September 1991) and eleven habitat variables were measured at two altitudes. One stream consistently harboured much higher densities of S. metallicum E larvae than the other, with three annual peaks of abundance: during the dry season and at the beginning and end of the rainy season. These peak densities were correlated with high rainfall 4 months previously. Larvae were most abundant on submerged rocks and fallen leaves, in small shallow areas characterized by slow water current, high conductivity and sparse terrestrial vegetation cover. Stream variables which best explained the temporal changes in abundance were water discharge and conductivity. The population dynamics of S. metallicum E appeared to be influenced primarily by interactions between stream discharge and substrate stability. Relevance of these results to vector control with larvicides is discussed.

Animals↗

PubMed1988

Interaction of temperature and other environmental variables influencing plant distribution.

Statistical analyses of the relationships between the patterns of distribution of plants with C4 photosynthesis and Crassulacean acid metabolism (CAM) have revealed a variety of correlations with environmental variables. The worldwide abundance of C4 grasses, relative to C3 grasses, is highly positively correlated with growing season temperature. However, microscale analyses have revealed that C4 grasses are more abundant than C3 grasses in habitats with high levels of solar irradiance and low moisture availability. There are numerous exceptions to these generalizations. C4 dicots generally are more abundant in habitats characterized by high rates of evaporation. Species possessing CAM occur in habitats having low levels of soil moisture store. In the Cactaceae such habitats also have very high potential rates of evaporation and the CAM pathway is the primary mechanism of the uptake of atmospheric CO2. In contrast many species of the Crassulaceae grow in habitats with lower potential rates of evaporation and the CAM pathway is less important or not used at all in the uptake of atmospheric CO2.

Environment↗

PubMed1995

Geographic variation of native people along the Pacific Coast.

Data gathered by Boas in the 1890s from 1749 adult males and 1056 adult females were subjected to anthropometric analyses to investigate possible effects of climatic adaptation. The subjects were native people from California, Oregon, Washington, the panhandle of Alaska, and British Columbia. They were categorized by their tribe's latitude and longitude (the center point of tribal distribution) and by habitat (characterized as coastal, western lowlands, and interior). Multiple R regressions were used to determine complex relationships between age, habitat, latitude, rainfall, mean January temperature, mean July temperature, and blood quantum, all of which affected some anthropometric variables to statistically significant degrees in both the male and the female samples. Body size and proportional differences support other studies of Bergmann's and Allen's rules, and variation in the nasal index supports prior studies of selection of longer, narrower noses in cold and dry climates and broader noses in warmer, moister ones. Recent disruption in the central portion of the study area was detectable in reduced size of subjects in these regions. Other complicating factors, such as ethnicity and the possibility of prior migrations and intermarriage between populations, are discussed.

Adaptation, Physiological↗

PubMed2026

Comparative analysis of olfactory receptor repertoires reveals evolutionary dynamics and high-altitude adaptation in Schizopygopsis younghusbandi based on the chromosome-level genomes.

The olfactory receptor (OR) gene represent a significant multigene family in vertebrates, forming the core molecular basis of olfactory perception and playing a crucial role in the environmental adaptation of species. High-altitude ecosystems represent extreme habitats characterized by specific abiotic stresses, including low oxygen levels, low temperatures, and intense ultraviolet radiation. These environments also exhibit low aquatic biodiversity and a limited variety of odor molecules, factors that have influenced the adaptive evolution of the sensory systems in endemic species. However, the genetic mechanisms underlying olfactory adaptation in high-altitude freshwater fish remained inadequately understood. In this study, we performed comparative genomics analyses to reveal the evolutionary processes underlying the adaptive and functional evolution of OR genes in S. younghusbandi, a cyprinid fish endemic to the Qinghai-Xizang Plateau. The results indicated that, compared to their low-altitude relatives, S. younghusbandi possessed a significantly smaller number of OR genes, with only 98 genes, which revealed the contraction of the gene family. Phylogenetic analysis revealed that the OR genes of cyprinid fish could be categorized into two major lineages: type I and type II. The η and δ families, which perceive water-soluble odors, in S. younghusbandi underwent significant and specific expansion, while the ε family was completely absent. This pattern reflected adaptive changes in olfactory recognition to accommodate the simplified odor spectrum of high-altitude water bodies. Chromosomal localization analysis demonstrated that OR genes were clustered, and collinearity analysis confirmed the presence of conserved genomic fragments among species. Selection pressure analysis revealed that the Ka/Ks values of all homologous gene pairs were less than 1, indicating that the OR genes of S. younghusbandi underwent strong purifying selection as a group to preserve core olfactory function. A few genes exhibited relaxed selection characteristics, which may have facilitated the fine-tuning of adaptability to high-altitude environments. In conclusion, this study elucidated the evolutionary dynamics and adaptive characteristics of the OR gene in S. younghusbandi, offering a new perspective on the molecular mechanisms underlying olfactory adaptation at high altitudes and enriching the research on sensory evolution in vertebrates.

Schizopygopsis younghusbandi↗

PubMed1995

Locomotion of black howlers in a habitat with discontinuous canopy.

The locomotor behaviour of howler monkeys (genus Alouatta) has been the subject of several detailed field studies [1-6]. This paper describes the locomotor behaviour of black howler monkeys (Alouatta caraya) living in a small area of forested habitat characterized by a discontinuous canopy.

Alouatta↗

PubMed1990

Limnological and botanical characterization of larval habitats for two primary malarial vectors, Anopheles albimanus and Anopheles pseudopunctipennis, in coastal areas of Chiapas State, Mexico.

Field surveys of mosquito breeding sites on the Pacific coastal plain and foothill regions of southern Chiapas, Mexico, were carried out in the dry and wet seasons of 1988. At each site, selected environmental variables were measured or estimated, presence and percent cover of aquatic plants recorded, a water sample collected for subsequent analyses, and 10-30 dips made for mosquito larvae. Logistic regression and discriminant analyses revealed that the occurrence of Anopheles albimanus larvae in both the wet and dry seasons was positively associated with planktonic algae and negatively associated with altitude. In the dry season, An. albimanus larvae were largely restricted to the margins of permanent water bodies and were associated with the presence of floating plants, particularly Eichhornia crassipes. During the wet season An. albimanus larvae were positively associated with emergent plants, particularly seasonally flooded Cyperaceae, and phosphorus (PO4) concentrations, and were negatively associated with abundant filamentous algae, high levels of total suspended solids (TSS) and Salvinia. In the dry season, An. pseudopunctipennis larvae were positively associated with filamentous algae, altitude and the presence of Heteranthera if encountered in a riverine setting, and were negatively associated with water depth. During the wet season, flooding eliminated typical flood plain An. pseudopunctipennis habitats, and larvae were rarely encountered.

Altitude↗

PubMedDate not supplied

Pulsed-field gel electrophoresis analysis of a Pseudomonas aeruginosa pathovar.

This paper presents the genome organization and mobility of Pseudomonas aeruginosa strains that had been isolated in half-year intervals from 30 patients with cystic fibrosis since the onset of colonization over a 2- to 8-year period. The chromosomes were digested with DraI or SpeI, separated by pulsed-field gel electrophoresis, blotted and hybridized with probes encoding housekeeping or virulence genes. Strains were differentiated by relatedness of macrorestriction fingerprints. After some turnover of strains during the first two years of colonization, each patient had acquired a set of strains that diversified during the course of the disease. In the majority of patients, two clonal lineages were found to account for colonization in the air passages but each lung habitat was characterized by some specific signature of bands in the macrorestriction fragment pattern.

Cystic Fibrosis↗

PubMed2025

Migration strategies, connectivity and corridor features of the partial migrant little bustard (Tetrax tetrax) across the Iberian Peninsula.

The study of migration ecology is crucial for understanding the factors and pressures affecting migratory species. Here, we studied the migratory ecology of the little bustard (Tetrax tetrax), a steppe bird that has suffered a sharp decline over recent decades, mainly due to agricultural intensification. Using 105 adult birds tagged across the main Iberian regions where the species is present (Alentejo, Extremadura, Ebro Valley, Northern Plateau, Southern Plateau and Guadalquivir Valley), we analysed the ratio of migratory and resident birds in each population and assessed their connectivity during the three main migratory periods (summer, winter and pre-breeding). Additionally, we describe the features of the migrations recorded in terms of length, duration and day period. Our results corroborate that little bustards can be considered partial migrants across Iberia, although the proportion of residents versus migrants varied between populations: the Alentejo (94.74%) and Northern Plateau (93.75%) had the highest proportion of migrants, followed by Guadalquivir Valley (81.82%), Extremadura (65.38%), Southern Plateau (55.56%) and Ebro Valley (25.93%). Migratory connectivity varied between periods: the pre-breeding and summering migrations showed a trend to move northwards, while birds moved southwards for winter. Regarding the migratory corridors obtained from the 253 migrations identified, we found three main routes: one corridor that connects the Northern Plateau with the western part of the Southern Plateau and Extremadura, another one that connects the Southern Plateau, Extremadura, Alentejo and Guadalquivir Valley, and one corridor that concentrates migrations within the Ebro Valley, and between the Ebro Valley and the Southern Plateau. Finally, analyses showed that little bustards migrate at night through areas dominated by herbaceous cover (avoiding tree-covered land and water bodies) and of low elevation and terrain roughness. Our results highlight the importance of developing an international and inter-regional conservation strategy to protect not only the breeding and wintering quarters, but also this endangered species' migratory corridors, thus supporting the viability of the metapopulation.

Brownian bridge kernel↗

PubMed1991

Lyme disease: a proposed ecological index to assess areas of risk in the northeastern United States.

BACKGROUND: Recent public awareness has resulted in a demand for information about ways to reduce the risk of acquiring Lyme disease. METHODS: Twenty-two school properties and recreational areas within a Lyme disease endemic area of central Monmouth County, New Jersey were evaluated for risk of transmission using an ecological index on the suitability, amount, and access to Ixodes dammini habitat by target human populations and the abundance of infected adult ticks. RESULTS: The characterization of tick habitat accurately predicted the elimination of 11 sites from concern. Of the remaining 11 sites, six were classified high risk and five as moderate risk. On-site tick surveys identified infected I. dammini adults at only four sites (three risk; one moderate risk). CONCLUSIONS: These results indicate that the use of selected ecological parameters provides a cost-effective method to rapidly identify areas at risk for Lyme disease transmission.

Animals↗

PubMed1994

Characterization of Arxula adeninivorans strains from different habitats.

Some Arxula adeninivorans strains selected from wood hydrolysates in Siberia, from soil in South Africa and from maize silage and soil in The Netherlands were compared. DNA-fingerprinting, pulse field gel electrophoresis as well as analysis of secretory proteins have been chosen to describe the similarities among the strains. Combination of the three methods allowed identification of each strain. Strains from the same origin show extensive similarities. The results of the DNA-fingerprints indicate that the strain isolated in Siberia belongs to the group of strains originated from South Africa. However, it differed in the molecular weight of the third chromosome and in the pattern of secretory proteins from the South African isolates.

Ascomycota↗

PubMed1986

Enzymatic characterization of Staphylococcus aureus strains: a possible role of habitat and methicillin-resistance in the determination of the differences observed.

Twenty five strains of Staphylococcus aureus of human and environmental origin were tested for their enzymatic patterns. All human strains possessed acid phosphatase, while only 25% of the environmental staphylococci demonstrated acid phosphatase activity. In addition, the enzyme alpha-glucosidase was present only in the methicillin resistant-multiresistant strains, in spite of their origin. This work suggests a possible role of the enzyme on penicillin-binding protein mediated methicillin-resistance and stresses the importance of external habitat in the expression of enzymatic activity of bacteria. The enzymatic pattern may confirm or exclude cross-infection, when a single species, with uniformly antibiotic responses, is involved.

Acid Phosphatase↗

PubMed1985

Isolation and characterization of moderately halophilic nonmotile rods from different saline habitats.

A total of 736 strains were isolated from samples taken from three different saline habitats: solar saltern, saline soils and the sea, near Alicante (Spain). For a further study 60 moderately halophilic nonmotile rods were selected and studied for 57 phenotypic characteristics. The highest proportion of moderately halophilic nonmotile rods were isolated from saline soils and in media with 10 or 20% salts, being very scarce in sea water samples. All were Gram-negative rods and were included in two groups: 33 oxidase positive strains could be assigned to the genus Flavobacterium and 24 oxidase negative strains to the genus Acinetobacter.

Acinetobacter↗

PubMed1991

Hominoid dietary evolution.

During the later Palaeocene and early Miocene, catarrhine primates and the evolving hominoids had adaptations for frugivorous diets, with the emphasis on soft foods. Early in the middle Miocene the hominoids underwent a major shift, both in morphology and in habitat, with the morphology characterized by thickened enamel on the molars, enlarged incisors and massive jaws. The diet indicated by this morphology is interpreted as still mainly frugivorous but with changed emphasis, possibly towards harder objects. The thick-enamelled hominoids are found associated with more open forest habitats, and the distribution of food resources in equivalent habitats today is discontinuous both in time and in space, leading to evolutionary pressures particularly affecting locomotion, brain size and social behaviour. The earliest known hominid fossils differed little in dental and mandibular morphology from the middle Miocene apes, and the implied dietary similarity, together with ape-like patterns of dental development and retained arboreal adaptations of the postcrania, suggests little change in the foraging strategies of the earliest hominids compared with their ape ancestors and further suggests similarity in evolutionary grade. This similarity may have extended to other aspects of behaviour, for example to patterns of tool making and use, which may have been similar in the common ancestor of apes and humans to the pattern shared by the earliest australopithecines and chimpanzees.

Animals↗

PubMedDate not supplied

[Tick-borne relapsing fever morbidity in Namangan].

The authors discuss the incidence of tick-borne relapsing fever in the town of Namangan (Uzbekistan) in 1976-1991 and the possible sites of human infection; the agent, Ornithodoros papillipes, has never been detected over this period. Analysis of many-year and seasonal time course of the disease incidence, of the age of the patients and their residence, characterization of the possible habitats of the agents, and comparison of the situation in the town with that in the adjacent rural territories permit a suggestion that the majority of the patients were infected at home.

Adolescent↗

PubMed1993

Morphological and physiological consequences of parasites encysted in the bulbus arteriosus of an estuarine fish, the sheepshead minnow, Cyprinodon variegatus.

The contribution of parasites to host population regulation is undefinable without knowledge of parasite effects on individual host performance and survival. Effects are best determined by examining performance of differentially parasitized hosts under the varying environmental conditions that characterize the host's habitat. The sheepshead minnow, Cyprinodon variegatus, an estuarine fish, is heavily parasitized in the bulbus arteriosus by the heterophyid trematode Ascocotyle pachycystis in semi-enclosed shallow bodies of water in northwestern Florida. Laboratory experiments were conducted to examine the morphological and physiological effects of parasitization of these fish. Differentially parasitized fish were compared for differences in ventricle weight and swimming performance. Parasitized fish ventricles were hypertrophied due to mechanical blockage of normal blood flow by metacercariae in the bulbus. Swimming performance generally was reduced by the presence of parasites, which had their most significant negative effect at cold temperatures and low dissolved oxygen levels.

Analysis of Variance↗

PubMed1994

Isolation, characterization, and distribution of denitrifying toluene degraders from a variety of habitats.

Enrichments capable of toluene degradation under O2-free denitrifying conditions were established with diverse inocula including agricultural soils, compost, aquifer material, and contaminated soil samples from different geographic regions of the world. Successful enrichment was strongly dependent on the initial use of relatively low toluene concentrations, typically 5 ppm. From the enrichments showing positive activity for toluene degradation, 10 bacterial isolates were obtained. Fingerprints generated by PCR-amplified DNA, with repetitive extragenic palindromic sequence primers, showed that eight of these isolates were different. Under aerobic conditions, all eight isolates degraded toluene, five degraded ethylbenzene, three consumed benzene, and one degraded chlorobenzene, meta-Xylene was the only other substrate used anaerobically and was used by only one isolate. All isolates were motile gram-negative rods, produced N2 from denitrification, and did not hydrolyze starch. All strains but one fixed nitrogen as judged by ethylene production from acetylene, but only four strains hybridized to the nifHDK genes. All strains appeared to have heme nitrite reductase since their DNA hybridized to the heme (nirS) but not to the Cu (nirU) genes. Five strains hybridized to a toluene ortho-hydroxylase catabolic probe, and two of those also hybridized to a toluene meta-hydroxylase probe. Partial sequences of the 16S rRNA genes of all isolates showed substantial similarity to 16S rRNA sequences of Azoarcus sp. Physiological, morphological, fatty acid, and 16S rRNA analyses indicated that these strains were closely related to each other and that they belong to the genus Azoarcus.(ABSTRACT TRUNCATED AT 250 WORDS)

Aerobiosis↗

PubMed1990

Characterization & larvicidal activity of indigenous isolates of Bacillus sphaericus from natural breeding habitats.

Soil, water and moribund/or dead mosquito larval samples collected from various mosquito breeding habitats of Pondicherry and Tamil Nadu were screened for the presence of mosquito pathogenic B. sphaericus isolates. From 1892 samples 21 isolates were obtained. All these isolates fell under 3 serogroups viz., H5a5b, H6 and H45, the latter two serotypes not reported hitherto as toxic to mosquito larvae and three phage-groups namely, phage group 2, phage group 3 and an unknown one. Twelve of the isolates were highly toxic and superior to the standard strains 1593, 2297 and 2362 supplied by Pasteur Institute, Paris when tested against Culex quinquefasciatus larvae. Out of these 12 strains 11 belonged to the serotype H5a5b and the phage-group 3 and 1 belonged to the serotype H45 and an unknown phage group.

Animals↗

PubMed2026

Vibrio limimangrovi sp. nov., Vibrio phycocola sp. nov. and Vibrio sediminis sp. nov., isolated from coastal habitats.

Four marine bacterial strains of the genus Vibrio, designated WJH972T, RC27, FJH11T, and HA2012T, were isolated from coastal habitats in China. Phenotypic and physiological characterization showed that all four strains are Gram-stain-negative, facultatively anaerobic, short rod-shaped cells, and motile. The 16S rRNA gene sequence similarities between the isolates and their closest relatives were 96.5% - 98.2%, above the genus-level threshold but below the species delineation cutoff. Genomic analysis revealed that strains WJH972T and RC27 shared an average nucleotide identity (ANI) of 98.7% and a digital DNA-DNA hybridization (dDDH) value of 89.9%, confirming their conspecificity. In contrast, the ANI and dDDH values between the four strains and known Vibrio species ranged from 78.6% to 85.8% and from 13.7% to 59.3%, respectively, both falling below the thresholds for species delineation. The biosynthetic gene clusters support bacterial potentials for stress tolerance and antibiotic synthesis, consistent with strain FJH11T's resistance to all 20 antibiotics and other strains' sensitivity to chloramphenicol and penicillin. Based on these polyphasic taxonomic evidence above, three novel species are thus proposed: Vibrio limimangrovi sp. nov. (type strain FJH11T), Vibrio phycocola sp. nov. (type strain WJH972T), and Vibrio sediminis sp. nov. (type strain HA2012T). This study provides novel insights into the systematics, metabolic diversity, antibiotic resistance, and ecological distribution of the genus Vibrio.

Vibrio↗