scholarly journals Teamwork in the viscous oceanic microscale

2021 ◽  
Vol 118 (29) ◽  
pp. e2018193118
Author(s):  
Eva A. Kanso ◽  
Rubens M. Lopes ◽  
J. Rudi Strickler ◽  
John O. Dabiri ◽  
John H. Costello
Keyword(s):  
Natural Populations ◽  
Fluid Flows ◽  
Nutrient Flux ◽  
Nutrient Acquisition ◽  
Centric Diatom ◽  
Diatom Cell ◽  
Ciliary Beating ◽  
Solitary Solutions ◽  
Marine Aggregates ◽  
The Relationship

Nutrient acquisition is crucial for oceanic microbes, and competitive solutions to solve this challenge have evolved among a range of unicellular protists. However, solitary solutions are not the only approach found in natural populations. A diverse array of oceanic protists form temporary or even long-lasting attachments to other protists and marine aggregates. Do these planktonic consortia provide benefits to their members? Here, we use empirical and modeling approaches to evaluate whether the relationship between a large centric diatom, Coscinodiscus wailesii, and a ciliate epibiont, Pseudovorticella coscinodisci, provides nutrient flux benefits to the host diatom. We find that fluid flows generated by ciliary beating can increase nutrient flux to a diatom cell surface four to 10 times that of a still cell without ciliate epibionts. This cosmopolitan species of diatom does not form consortia in all environments but frequently joins such consortia in nutrient-depleted waters. Our results demonstrate that symbiotic consortia provide a cooperative alternative of comparable or greater magnitude to sinking for enhancement of nutrient acquisition in challenging environments.

Interpretation of shadowgraph patterns in Rayleigh-Bénard convection

1988 ◽  
Vol 190 ◽  
pp. 451-469 ◽  
Author(s):  
D. R. Jenkins
Keyword(s):  
Rayleigh Number ◽  
Linear Theory ◽  
Vertical Component ◽  
Fluid Flows ◽  
Bénard Convection ◽  
Benard Convection ◽  
Higher Order Terms ◽  
The Relationship ◽  
Rayleigh Benard Convection ◽  
Rayleigh Benard

The relationship between observations of cellular Rayleigh-Bénard convection using shadowgraphs and theoretical expressions for convection planforms is considered. We determine the shadowgraphs that ought to be observed if the convection is as given by theoretical expressions for roll, square or hexagonal planforms and compare them with actual experiments. Expressions for the planforms derived from linear theory, valid for low supercritical Rayleigh number, produce unambiguous shadowgraphs consisting of cells bounded by bright lines, which correspond to surfaces through which no fluid flows and on which the vertical component of velocity is directed downwards. Dark spots at the centre of cells, indicating regions of hot, rising fluid, are not accounted for by linear theory, but can be produced by adding higher-order terms, predominantly due to the temperature dependence of a material property of the fluid, such as its viscosity.

An ecological explanation for hyperallometric scaling of reproduction

2021 ◽  
Author(s):  
Tomos Potter ◽  
Anja Felmy
Keyword(s):  
Body Size ◽  
Reproductive Output ◽  
Resource Competition ◽  
Natural Populations ◽  
Scaling Exponent ◽  
Wild Populations ◽  
Wet Season ◽  
Size Dependent ◽  
In The Wild ◽  
The Relationship

AbstractIn wild populations, large individuals have disproportionately higher reproductive output than smaller individuals. We suggest an ecological explanation for this observation: asymmetry within populations in rates of resource assimilation, where greater assimilation causes both increased reproduction and body size. We assessed how the relationship between size and reproduction differs between wild and lab-reared Trinidadian guppies. We show that (i) reproduction increased disproportionately with body size in the wild but not in the lab, where effects of resource competition were eliminated; (ii) in the wild, the scaling exponent was greatest during the wet season, when resource competition is strongest; and (iii) detection of hyperallometric scaling of reproduction is inevitable if individual differences in assimilation are ignored. We propose that variation among individuals in assimilation – caused by size-dependent resource competition, niche expansion, and chance – can explain patterns of hyperallometric scaling of reproduction in natural populations.

scholarly journals RNA-Seq and differential gene expression analysis in Temora stylifera copepod females with contrasting non-feeding nauplii survival rates: an environmental transcriptomics study

BMC Genomics ◽  
2020 ◽  
Vol 21 (1) ◽  
Author(s):  
Ennio Russo ◽  
Chiara Lauritano ◽  
Giuliana d’Ippolito ◽  
Angelo Fontana ◽  
Diana Sarno ◽  
...  
Keyword(s):  
Differential Expression ◽  
De Novo ◽  
Transcriptome Assembly ◽  
Survival Rates ◽  
Natural Populations ◽  
Zooplankton Community ◽  
Differentially Expressed ◽  
Diatom Cell ◽  
Functional Interpretation ◽  
Protein Ubiquitination

Abstract Background Copepods are fundamental components of pelagic food webs, but reports on how molecular responses link to reproductive success in natural populations are still scarce. We present a de novo transcriptome assembly and differential expression (DE) analysis in Temora stylifera females collected in the Gulf of Naples, Mediterranean Sea, where this copepod dominates the zooplankton community. High-Throughput RNA-Sequencing and DE analysis were performed from adult females collected on consecutive weeks (May 23rd and 30th 2017), because opposite naupliar survival rates were observed. We aimed at detecting key genes that may have influenced copepod reproductive potential in natural populations and whose expression was potentially affected by phytoplankton-derived oxylipins, lipoxygenase-derived products strongly impacting copepod naupliar survival. Results On the two sampling dates, temperature, salinity, pH and oxygen remained stable, while variations in phytoplankton cell concentration, oxylipin concentration and oxylipin-per-diatom-cell production were observed. T. stylifera naupliar survival was 25% on May 23rd and 93% on May 30th. De novo assembly generated 268,665 transcripts (isoforms) and 120,749 unique ‘Trinity predicted genes’ (unigenes), of which 50% were functionally annotated. Out of the 331 transcript isoforms differentially expressed between the two sampling dates, 119 sequences were functionally annotated (58 up- and 61 down-regulated). Among predicted genes (unigenes), 144 sequences were differentially expressed and 31 (6 up-regulated and 25 down-regulated) were functionally annotated. Most of the significantly down-regulated unigenes and isoforms were A5 Putative Odorant Binding Protein (Obp). Other differentially expressed sequences (isoforms and unigenes) related to developmental metabolic processes, protein ubiquitination, response to stress, oxidation-reduction reactions and hydrolase activities. DE analysis was validated through Real Time-quantitative PCR of 9 unigenes and 3 isoforms. Conclusions Differential expression of sequences involved in signal detection and transduction, cell differentiation and development offered a functional interpretation to the maternally-mediated low naupliar survival rates observed in samples collected on May 23rd. Down-regulation of A5 Obp along with higher quantities of oxylipins-per-litre and oxylipins-per-diatom-cell observed on May 23rd could suggest oxylipin-mediated impairment of naupliar survival in natural populations of T. stylifera. Our results may help identify biomarker genes explaining variations in copepod reproductive responses at a molecular level.

Modelling patterns of parasite aggregation in natural populations: trichostrongylid nematode–ruminant interactions as a case study

Parasitology ◽  
1995 ◽  
Vol 111 (S1) ◽  
pp. S135-S151 ◽  
Author(s):  
B. T. Grenfell ◽  
K. Wilson ◽  
V. S. Isham ◽  
H. E. G. Boyd ◽  
K. Dietz
Keyword(s):  
Population Biology ◽  
Negative Binomial ◽  
Natural Populations ◽  
Parasite Load ◽  
Host Immunity ◽  
Moment Closure ◽  
The Mean ◽  
Parasite Aggregation ◽  
The Impact ◽  
The Relationship

SUMMARYThe characteristically aggregated frequency distribution of macroparasites in their hosts is a key feature of host–parasite population biology. We begin with a brief review of the theoretical literature concerning parasite aggregation. Though this work has illustrated much about both the sources and impact of parasite aggregation, there is still no definitive analysis of both these aspects. We then go on to illustrate the use of one approach to this problem – the construction of Moment Closure Equations (MCEs), which can be used to represent both the mean and second moments (variances and covariances) of the distribution of different parasite stages and phenomenological measures of host immunity. We apply these models to one of the best documented interactions involving free-living animal hosts – the interaction between trichostrongylid nematodes and ruminants. The analysis compares patterns of variability in experimental infections of Teladorsagia circumcincta in sheep with the equivalent wildlife situation – the epidemiology of T. circumcincta in a feral population of Soay sheep on St Kilda, Outer Hebrides. We focus on the relationship between mean parasite load and aggregation (inversely measured by the negative binomial parameter, k) for cohorts of hosts. The analysis and empirical data indicate that k tracks the increase and subsequent decline in the mean burden with host age. We discuss this result in terms of the degree of heterogeneity in the impact of host immunity or parasite-induced mortality required to shorten the tail of the parasite distribution (and therefore increase k) in older animals. The model is also used to analyse the relationship between estimated worm and egg counts (since only the latter are often available for wildlife hosts). Finally, we use these results to review directions for future work on the nature and impact of parasite aggregation.

scholarly journals The relationship of telomere length to baseline corticosterone levels in nestlings of an altricial passerine bird in natural populations

2016 ◽  
Vol 13 (1) ◽  
Author(s):  
Verónica Quirici ◽  
Claudia Jimena Guerrero ◽  
Jesse S. Krause ◽  
John C. Wingfield ◽  
Rodrigo A. Vásquez
Keyword(s):  
Telomere Length ◽  
Natural Populations ◽  
Passerine Bird ◽  
Baseline Corticosterone ◽  
Relationship Of ◽  
The Relationship

The relationship between animal foraging and nutrient patchiness in south-west Australian woodland soils

Soil Research ◽  
2003 ◽  
Vol 41 (4) ◽  
pp. 665 ◽  
Author(s):  
Mark J. Garkaklis ◽  
J. S. Bradley ◽  
R. D. Wooller
Keyword(s):  
Soil Nutrients ◽  
Surface Soil ◽  
Natural Populations ◽  
Water Infiltration ◽  
European Settlement ◽  
South West ◽  
Bettongia Penicillata ◽  
Australian Continent ◽  
The Relationship ◽  
Preferential Water

The woylie (Bettongia penicillata) was once common and abundant over the southern third of the Australian continent. Since European settlement the range of this rat-kangaroo has become reduced by more than 97%, and until the early 1990s, only 3 small natural populations remained, all in south-western Australia. These medium-sized (c. 1 kg) marsupials create a large number of diggings as they forage for the hypogeous fruiting bodies of ectomycorrhizal fungi upon which they feed. The effect of such foraging activity on the availability of plant nutrients in the vicinity of such diggings was evaluated in simulated digging experiments. Available nitrate, ammonium, and sulfur decreased significantly 3 years after diggings were constructed and had filled in, whereas phosphorus, potassium, iron, and organic carbon remained unchanged. The results suggest that preferential water infiltration via woylie diggings leads to a decrease in those soil nutrients that are susceptible to leaching and indicates that digging vertebrates may influence the distribution of surface soil nutrients.

A Paedomorphocline in Eucalyptus. II. Variation in Seedling Morphology in the E. risdonii/E. tenuiramis Complex

1992 ◽  
Vol 40 (6) ◽  
pp. 789 ◽  
Author(s):  
RJE Wiltshire ◽  
BM Potts ◽  
JB Reid
Keyword(s):  
East Coast ◽  
Natural Populations ◽  
The Other ◽  
Ontogenetic Variation ◽  
Seedling Morphology ◽  
Transitional Area ◽  
Juvenile Leaf ◽  
Phenetic Relationships ◽  
The Difference ◽  
The Relationship

Previous studies of phenotypic variation among natural populations in the Eucalyptus risdonii/E. tenuiramis cindicated that the two taxa are linked by a cline in the retention of the juvenile leaf form (paedomorphocline) and that division into the two taxa, E. risdonii and E. tenuiramis, on the basis of these ontogenetic differences obscures the phenetic relationships within and between the taxa. This study attempts to remove the environmental and ontogenetic variation to reveal the genetically based variation by examining seedling morphology. The results suggest that genetic variation between geographically contiguous populations of E. risdonii and E. tenuiramis is relatively small and continuous, and classification into either taxon on the basis of seedling phenotype is not possible for populations in this transitional area. The major dichotomy between phenetic clusters is not between forms that can be assigned to E. risdonii and E. tenuiramis on the basis of ontogenetic differences, but between geographically isolated forms of E. tenuiramis. The ambiguous variation in the adult phenotype is clarified by the marked difference in seedling morphology between the two East Coast populations and the other E. tenuiramis populations which, on present data, appear to be separated by a geographical disjunction. When viewed in terms of the phenetic distance between populations of the two closest species (E. coccifera and E. nitida), the magnitude of the difference between the East Coast E. tenuiramis and the other phenetic groups in the E. risdonii/E. tenuiramis complex is emphasised. The relationship and origin of populations intermediate between E. tenuiramis and E. coccifera are also discussed.

scholarly journals Pervasive Phenotypic Impact of a Large Nonrecombining Introgressed Region in Yeast

2020 ◽  
Vol 37 (9) ◽  
pp. 2520-2530 ◽  
Author(s):  
Christian Brion ◽  
Claudia Caradec ◽  
David Pflieger ◽  
Anne Friedrich ◽  
Joseph Schacherer
Keyword(s):  
Mating Type ◽  
Budding Yeast ◽  
Natural Populations ◽  
Phenotypic Effect ◽  
Genetic Characteristics ◽  
Type Locus ◽  
First Time ◽  
The Relationship ◽  
Insight Into ◽  
Introgressed Region

Abstract To explore the origin of the diversity observed in natural populations, many studies have investigated the relationship between genotype and phenotype. In yeast species, especially in Saccharomyces cerevisiae, these studies are mainly conducted using recombinant offspring derived from two genetically diverse isolates, allowing to define the phenotypic effect of genetic variants. However, large genomic variants such as interspecies introgressions are usually overlooked even if they are known to modify the genotype–phenotype relationship. To have a better insight into the overall phenotypic impact of introgressions, we took advantage of the presence of a 1-Mb introgressed region, which lacks recombination and contains the mating-type determinant in the Lachancea kluyveri budding yeast. By performing linkage mapping analyses in this species, we identified a total of 89 loci affecting growth fitness in a large number of conditions and 2,187 loci affecting gene expression mostly grouped into two major hotspots, one being the introgressed region carrying the mating-type locus. Because of the absence of recombination, our results highlight the presence of a sexual dimorphism in a budding yeast for the first time. Overall, by describing the phenotype–genotype relationship in the Lachancea kluyveri species, we expanded our knowledge on how genetic characteristics of large introgression events can affect the phenotypic landscape.

scholarly journals LIMITS TO THE RELATIONSHIP AMONG RECOMBINATION, DISEQUILIBRIUM AND EPISTASIS IN TWO-LOCUS MODELS

Genetics ◽  
1986 ◽  
Vol 113 (1) ◽  
pp. 177-185
Author(s):  
Alan Hastings
Keyword(s):  
Linear Programming ◽  
Natural Populations ◽  
Allele Frequencies ◽  
Symmetric Model ◽  
Strongly Interacting ◽  
Equilibrium Relationship ◽  
Programming Techniques ◽  
The Relationship

ABSTRACT I determine limits to the equilibrium relationship among epistasis, recombination and disequilibrium in two-locus, two-allele models using linear programming techniques. I show that when allele frequencies are one-half at each locus, the symmetric model is the fitness pattern that generates the most disequilibrium for the smallest level of epistasis. When allele frequencies deviate from one-half, much larger levels of epistasis are required to generate similar levels of disequilibrium. I determine the level of epistasis required to generate observed significant levels of disequilibrium in natural populations. The overall implication is that disequilibrium will be large at equilibrium only between strongly interacting, closely linked loci.

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