Exploitation of Marine Mammals: r-Selection of K-Strategists?

1979 ◽  
Vol 36 (8) ◽  
pp. 1009-1017 ◽  
Author(s):  
James A. Estes
Keyword(s):  
Marine Mammals ◽  
Resource Limitation ◽  
Population Increase ◽  
Structure Evolution ◽  
Physiological Constraints ◽  
Resource Limited ◽  
Selective Forces ◽  
Stable Populations ◽  
Selection Of ◽  
Key Words Community Structure

The importance of marine mammals as predators to the organization of marine communities is poorly known, although in several structurally analogous systems the ecological and evolutionary roles of predators are known to be of considerable importance. Occupation of the marine environment by mammals probably carried physiological constraints for single-young pregnancies thereby limiting all species to low intrinsic rates of population increase. As such, species subjected to high mortality rates from predation or other natural disturbances became extinct; those that survived probably were largely resource limited. In view of this scenario it is suggested that stable populations of marine mammals can be maintained at high levels without being manipulated in most communities. Exploitation probably constitutes a rather dramatic environmental change to marine mammals consequently subjecting them to selective forces fundamentally different from many of those under the influence of which they evolved. Key words: community structure, evolution, exploitation, fitness, life history, marine mammal, predation, resource limitation

scholarly journals Physiological constraints and energetic costs of diving behaviour in marine mammals: a review of studies using trained Steller sea lions diving in the open ocean

2016 ◽  
Vol 187 (1) ◽  
pp. 29-50 ◽  
Author(s):  
David A. S. Rosen ◽  
Allyson G. Hindle ◽  
Carling D. Gerlinsky ◽  
Elizabeth Goundie ◽  
Gordon D. Hastie ◽  
...  
Keyword(s):  
Marine Mammals ◽  
Open Ocean ◽  
Diving Behaviour ◽  
Steller Sea Lions ◽  
Energetic Costs ◽  
Sea Lions ◽  
Physiological Constraints

scholarly journals Cryptococcus neoformans Capsule Structure Evolution In Vitro and during Murine Infection

2004 ◽  
Vol 72 (6) ◽  
pp. 3359-3365 ◽  
Author(s):  
Dea Garcia-Hermoso ◽  
Françoise Dromer ◽  
Guilhem Janbon
Keyword(s):  
Cryptococcus Neoformans ◽  
Organ Specificity ◽  
Structure Evolution ◽  
Specific Monoclonal Antibody ◽  
Organ Specific ◽  
The Brain ◽  
Over Time ◽  
Selection Of

ABSTRACT Cryptococcus neoformans capsule structure modifications after prolonged in vitro growth or in vivo passaging have been reported previously. However, nothing is known about the dynamics of these modifications or about their environmental specificities. In this study, capsule structure modifications after mouse passaging and prolonged in vitro culturing were analyzed by flow cytometry using the glucuronoxylomannan-specific monoclonal antibody E1. The capsule structures of strains recovered after 0, 1, 8, and 35 days were compared by using the level of E1-specific epitope expression and its cell-to-cell heterogeneity within a given cell population. In vitro, according to these parameters, the diversity of the strains was higher on day 35 than it was initially, suggesting the absence of selection during in vitro culturing. In contrast, the diversity of the strains recovered from the brain tended to decrease over time, suggesting that selection of more adapted strains had occurred. The strains recovered on day 35 from the spleen and the lungs had different phenotypes than the strains isolated from the brain of the same mouse on the same day, thus strongly suggesting that there is organ specificity for C. neoformans strain selection. Fingerprinting of the strains recovered in vitro and in vivo over time confirmed that genotypes evolved very differently in vitro and in vivo, depending on the environment. Overall, our results suggest that organ-specific selection can occur during cryptococcosis.

scholarly journals PENAMPILAN REPRODUKSI TERNAK SAPI POTONG DI KECAMATAN BINTAUNA KABUPATEN BOLAANG MONGONDOW UTARA

ZOOTEC ◽  
2017 ◽  
Vol 38 (1) ◽  
pp. 102
Author(s):  
Aikal Pohontu ◽  
Agustinus Lomboan ◽  
Jantje F. Paath ◽  
Siane C. Rimbing
Keyword(s):  
Beef Cattle ◽  
Reproductive Performance ◽  
Random Sampling ◽  
Sampling Method ◽  
Descriptive Analysis ◽  
Population Increase ◽  
Calving Interval ◽  
Analysis Model ◽  
Reproduction Performance ◽  
Selection Of

REPRODUCTIVE PERFORMANCE OF BEEF CATTLE IN BINTAUNA DISTRICT OF NORTH BOLAANG MONGONDOW REGENCY. This study was conducted to evaluate the reproduction performance of beef cattle in Bintauna district of North Bolaang Mongondow regency. Reproductive performance was studied to determine the productivity of livestock especially in population increase and availability of meat. This research used samples of farmer as breeder of beef cattle. The selections of village samples were determined purposively by consideration of the villages with the largest population of livestock including the villages of Pimpi, Kopi, and Bintauna. Selection of respondents using random sampling method involved 10 farmers for each selected village, with the total of 30 farmers as respondents. Data of the variables were analyzed using descriptive analysis model. The results showed that the age of puberty animal was 12.03 ± 4.81 months, service per conception was 1.19, conception rate was 73%, pregnancy period was 276 ± 2.53 days, and calving interval was 366 ± 3.21 days. Based on these results, it can be concluded that the reproduction of beef cattle in Bintauna district of North Bolaang Mongondow regency was categorized into good performance. Keyword: Reproduction performance, beef cattle, Bintauna district

LEGAL PRINCIPLES OF DEVELOPMENT OF HYDROENERGETICS ARE IN CONTEXT OF STEADY DEVELOPMENT OF UKRAINE

2017 ◽  
Author(s):  
Karyna Karakhanian ◽  
Keyword(s):  
Energy Source ◽  
Natural Environment ◽  
Negative Influence ◽  
Population Increase ◽  
Negative Consequences ◽  
Hydro Power ◽  
Legal Principles ◽  
Alternative Sources ◽  
Industry Trends ◽  
Selection Of

Historical, socio-economic and legislative principles of development power to the sector of economy are considered in the article, in particular, question of production energies from alternative sources, among that one of leading places, next to energy of a sun and wind, occupies hydroenergetics. World experience is investigational. World experience, and also historical aspects of development of hydroenergetic direction, that comes forward as a maximally ecological refurbishable energy source and inflicts minimum negative influence on a natural environment, and also progress of this industry trends in Ukraine, is investigational. It is established, that for our state of the use of hydro power is one of strategic directions of development to the sector of refurbishable energy sources, taking into account high dependence of country on the imported power mediums, first of all, natural gas. It is marked that even at reputation ecologically safe energy source, a hydroenergetics can however carry ecological risks that is subject to the removal both practical and legislative initiatives are certain. The analysis of current legislation is carried out at industry of hydroenergetics, and also defence of environment with the aim of selection of basic directions of ecologization of the investigated industry and requirements that is pulled out to the indicated objects. It is set that the indicated question is regulated by both national and international legislation, in that norms are envisaged in relation to warning of negative consequences of work of hydro stations both for a natural environment and for a man. Among such events distinguish the estimation of influence on an environment, ecological control, monitoring and possibility to carry out influence on an environment. Іt is marked that for today as tasks of the state providing of passing ahead height of energygenerating powers comes forward for a reliable production and supply of electric power to the industrial consumers and population, increase of efficiency of work of the incorporated power system of Ukraine and her integration with a European grid, reduction to the import of energy resources, providing of power safety with the maximal use of hydroenergetic potential, and also observance of terms of steady development.

A correlation of phylogenetic diversity in the Proteobacteria with the influences of ecological forces

1991 ◽  
Vol 37 (1) ◽  
pp. 1-6 ◽  
Author(s):  
G. A. Zavarzin ◽  
E. Stackebrandt ◽  
R. G. E. Murray
Keyword(s):  
Phylogenetic Analysis ◽  
Key Words ◽  
Bacterial Diversity ◽  
Ribosomal Rna ◽  
Phylogenetic Diversity ◽  
Bacterial Evolution ◽  
Ecological Selection ◽  
Selective Forces ◽  
Selection Of

The Proteobacteria are physiologically and morphologically diverse, although they form a coherent set of four main lineages on phylogenetic analysis of ribosomal RNA. A rational and consistent taxonomic arrangement bringing today's phenotypic and phylogenetic conclusions about them into register is not yet possible. It is also difficult to understand the selective forces involved in their evolution that fostered such diversity. This latter problem is addressed in this essay and is based on the assumption that bacterial evolution could only have occurred in ecological consortia whose products of metabolism modified the environment, provided nutrition, and have a basis for selection of new capabilities. Key words: Proteobacteria, bacterial diversity, bacterial evolution, ecological selection.

scholarly journals RNA Structure Duplication in the Dengue Virus 3′ UTR: Redundancy or Host Specificity?

mBio ◽  
2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Luana de Borba ◽  
Sergio M. Villordo ◽  
Franco L. Marsico ◽  
Juan M. Carballeda ◽  
Claudia V. Filomatori ◽  
...  
Keyword(s):  
Viral Replication ◽  
Viral Genome ◽  
Untranslated Region ◽  
Rna Synthesis ◽  
Rna Structures ◽  
Functional Diversification ◽  
Selective Pressures ◽  
Selective Forces ◽  
Rna Elements ◽  
Selection Of

ABSTRACTFlaviviruses include a diverse group of medically important viruses that cycle between mosquitoes and humans. During this natural process of switching hosts, each species imposes different selective forces on the viral population. Using dengue virus (DENV) as model, we found that paralogous RNA structures originating from duplications in the viral 3′ untranslated region (UTR) are under different selective pressures in the two hosts. These RNA structures, known as dumbbells (DB1 and DB2), were originally proposed to be enhancers of viral replication. Analysis of viruses obtained from infected mosquitoes showed selection of mutations that mapped in DB2. Recombinant viruses carrying the identified variations confirmed that these mutations greatly increase viral replication in mosquito cells, with low or no impact in human cells. Use of viruses lacking each of the DB structures revealed opposite viral phenotypes. While deletion of DB1 reduced viral replication about 10-fold, viruses lacking DB2 displayed a great increase of fitness in mosquitoes, confirming a functional diversification of these similar RNA elements. Mechanistic analysis indicated that DB1 and DB2 differentially modulate viral genome cyclization and RNA replication. We found that a pseudoknot formed within DB2 competes with long-range RNA-RNA interactions that are necessary for minus-strand RNA synthesis. Our results support a model in which a functional diversification of duplicated RNA elements in the viral 3′ UTR is driven by host-specific requirements. This study provides new ideas for understanding molecular aspects of the evolution of RNA viruses that naturally jump between different species.IMPORTANCEFlaviviruses constitute the most relevant group of arthropod-transmitted viruses, including important human pathogens such as the dengue, Zika, yellow fever, and West Nile viruses. The natural alternation of these viruses between vertebrate and invertebrate hosts shapes the viral genome population, which leads to selection of different viral variants with potential implications for epidemiological fitness and pathogenesis. However, the selective forces and mechanisms acting on the viral RNA during host adaptation are still largely unknown. Here, we found that two almost identical tandem RNA structures present at the viral 3′ untranslated region are under different selective pressures in the two hosts. Mechanistic studies indicated that the two RNA elements, known as dumbbells, contain sequences that overlap essential RNA cyclization elements involved in viral RNA synthesis. The data support a model in which the duplicated RNA structures differentially evolved to accommodate distinct functions for viral replication in the two hosts.

scholarly journals Thresholds for impaired species recovery

2015 ◽  
Vol 282 (1809) ◽  
pp. 20150654 ◽  
Author(s):  
Jeffrey A. Hutchings
Keyword(s):  
Population Size ◽  
Marine Mammals ◽  
Small Population ◽  
Marine Fishes ◽  
Population Increase ◽  
Allee Effects ◽  
Individual Fitness ◽  
Resource Managers ◽  
Aquatic Vertebrates ◽  
Declining Populations

Studies on small and declining populations dominate research in conservation biology. This emphasis reflects two overarching frameworks: the small-population paradigm focuses on correlates of increased extinction probability; the declining-population paradigm directs attention to the causes and consequences of depletion. Neither, however, particularly informs research on the determinants, rate or uncertainty of population increase. By contrast, Allee effects (positive associations between population size and realized per capita population growth rate, r realized , a metric of average individual fitness) offer a theoretical and empirical basis for identifying numerical and temporal thresholds at which recovery is unlikely or uncertain. Following a critique of studies on Allee effects, I quantify population-size minima and subsequent trajectories of marine fishes that have and have not recovered following threat mitigation. The data suggest that threat amelioration, albeit necessary, can be insufficient to effect recovery for populations depleted to less than 10% of maximum abundance ( N max ), especially when they remain depleted for lengthy periods of time. Comparing terrestrial and aquatic vertebrates, life-history analyses suggest that population-size thresholds for impaired recovery are likely to be comparatively low for marine fishes but high for marine mammals. Articulation of a ‘recovering population paradigm’ would seem warranted. It might stimulate concerted efforts to identify generic impaired recovery thresholds across species. It might also serve to reduce the confusion of terminology, and the conflation of causes and consequences with patterns currently evident in the literature on Allee effects, thus strengthening communication among researchers and enhancing the practical utility of recovery-oriented research to conservation practitioners and resource managers.

Individual foraging behaviour indicates resource limitation: an experiment with mallard ducklings

2000 ◽  
Vol 78 (11) ◽  
pp. 1891-1895 ◽  
Author(s):  
Petri Nummi ◽  
Kjell Sjöberg ◽  
Hannu Pöysä ◽  
Johan Elmberg
Keyword(s):  
Foraging Behaviour ◽  
Time Budget ◽  
Resource Limitation ◽  
Boreal Lakes ◽  
High Concentration ◽  
Resource Limited ◽  
Foraging Performance ◽  
The Rich ◽  
Brood Stage ◽  
Do So

The linkage between individual behaviour and population processes has recently been emphasized. Within this framework we studied the effect of resource limitation on the behaviour of mallard (Anas platyrhynchos) ducklings in boreal lakes. One group of 12 human-imprinted ducklings (4-16 days old) were taken to 11 "rich" lakes, i.e., with a relatively high concentration of total phosphorus in the water, and the other group of 12 ducklings to 11 "poor" lakes to forage for a period of 6 h. During this, a time budget study lasting 5 min was done of each of the 12 ducklings. In the rich lakes, ducklings fed significantly more and moved less than in the poor ones. This difference was particularly striking in above-surface feeding. Variation in foraging performance was associated with change in body mass of the ducklings: the less distance the ducklings moved and the more they fed above water, the more they gained mass. Earlier results had suggested that at least some of the boreal wetlands that lack duck broods year after year (70% of the total in one study) do so because they do not harbour enough food. Hence, it is possible that mallard populations are resource-limited at the brood stage during the breeding season.

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