scholarly journals Abundance And Active Patch Selection Modulate Reproductive Connectivity And Fitness of Pea Crabs Living On Sand Dollars

2021 ◽  
Author(s):  
Juliana A. Souza ◽  
Augusto A. V. Flores
Keyword(s):  
Reproductive Potential ◽  
Population Level ◽  
Allee Effects ◽  
Sand Dollar ◽  
Patch Selection ◽  
Biological Organization ◽  
Individual Fitness ◽  
Offspring Production ◽  
Crab Abundance ◽  
Sand Dollars

Abstract Connectivity is paramount for population stability, but the mechanisms underlying the distribution of populated patches and how they affect reproductive connectivity and individual fitness remain elusive. Here, we mapped the distribution of sand dollars – as habitat patches for obligate-commensal pea crabs – at several sites. At occupied patches, we assessed whole-crab population structure and the fitness of ovigerous females. While sand-dollar supply did not limit the size of crab populations, overall crab abundance limited reproductive connectivity and the potential for offspring production. However, except for sites of extremely low and high connectivity, crab aggregations at sand-dollar clusters countervailed the overall random distribution of sand-dollar populations, greatly enhancing the reproductive potential of whole-crab populations. Crab interactions, likely controlled by larger females, added to reproductive connectivity by increasing the frequency of mating pairs in hosts. Differently from the population-level case, effects of crab abundance on individual fitness were dual and only detectable when abundance was lowest (positive) or highest (negative), so that fitness remained high at intermediate crab abundance, decreasing when it became either too low (e.g. Allee effects) or too high (e.g. energetic costs of intraspecific competition). This study indicates that connectivity may affect different levels of biological organization in specific ways.

Eels at the Edge: Science, Status, and Conservation Concerns

2009 ◽  
Keyword(s):  
Gonadosomatic Index ◽  
Reproductive Potential ◽  
Anguilla Rostrata ◽  
Spawning Ground ◽  
Silver Eel ◽  
Migration Distance ◽  
American Eel ◽  
Individual Fitness ◽  
Silver Eels ◽  
Somatic Tissues

<em>Abstract.—</em>The American eel <em>Anguilla rostrata </em>is declining in the St. Lawrence River watershed, where sex ratio is highly unbalanced in favor of females. Since the American eel is a panmictic species, this demographic dominance is implicated in reproductive potential of the species. The major objective of this study was to evaluate the reproductive strategies of five subpopulations of female eels. It was assumed that fecundity varies among subpopulations according to their migration distance because of the tradeoff between energy allocated to gonads and to somatic tissues. Thirty female silver eels were collected from each of five locations in the St. Lawrence watershed 2,850–4,300 km from the spawning area. Among subpopulations, mean length ranged from 67.9 to 104.3 cm, weight from 595 to 2,366 g, fecundity from 6.5 to 14.5 million oocytes, age from 20 to 23 years, gonadosomatic index from 2.9 to 4.1%, and somatic lipid content from 17.5 to 21.7%. Because of panmixia, no genetic influence on intersite variability is expected. Environmental differences in growth habitats and individual fitness might determine acquisition and allocation of resources, as well as subsequent variability in traits that would affect reproduction. In contrast to previous hypotheses, variations in such traits were attributed to eel size rather than migration distance. The number of oocytes per silver eel was positively correlated with length rather than negatively correlated with migration distance. In the St. Lawrence watershed, large eels are highly fecund regardless of their distance from the spawning ground.

The biogeography of origin and radiation: dendrasterid sand dollars in the northeastern Pacific

Paleobiology ◽  
1991 ◽  
Vol 17 (4) ◽  
pp. 325-339 ◽  
Author(s):  
Steven C. Beadle
Keyword(s):  
Coastal Waters ◽  
Pacific Coast ◽  
Sand Dollar ◽  
Central California ◽  
The Pacific ◽  
Northeastern Pacific ◽  
Place Of Origin ◽  
Transitional Forms ◽  
Sand Dollars ◽  
And Behavior

Under favorable circumstances, biogeographic and biostratigraphic data can be combined to identify accurately the time and place of origin of a given taxon, and to reconstruct the pattern of its subsequent radiation. This study considers the dendrasterid sand dollars, which are abundant today along the Pacific Coast of North America. The Neogene sand dollar record in this region is particularly good; in fact, sand dollars have traditionally been used as provincial index fossils.The dendrasterids originated in central California at the end of the Miocene; the oldest forms are dated at about 6.0–6.5 Ma. They spread south to Baja California during the Pliocene, and then north to Alaska during the Quaternary. This historical pattern is not an artifact of the record; it is consistent with independent paleogeographic evidence. The dendrasterids supplanted an older Mio-Pliocene sand dollar fauna; they are now completely dominant in the temperate coastal waters of the northeastern Pacific. They have reached this position in less than 7 m.y. since their first local appearance. The rapid rise of dendrasterids could be related to their aberrant morphology and behavior; these adaptations allow dendrasterids to suspension-feed, in a manner unique among living echinoids.Dendrasterids are characterized by “eccentric” test morphologies. Even the oldest species are highly eccentric; transitional forms are unknown. The first dendrasterids appear suddenly in the provincial “Jacalitos Stage,” above an unconformity which represents no more than about 1 m.y. They do not occur in the underlying units, although other fossil sand dollars are abundant. The dendrasterids may have arisen rapidly, through a heterochronic change in the development of older, noneccentric forms. Recent ontogenetic studies have documented the feasibility of this process.

The importance of superior-quality wildlife habitats

2004 ◽  
Vol 80 (1) ◽  
pp. 75-81 ◽  
Author(s):  
Ian D Thompson
Keyword(s):  
Habitat Selection ◽  
Habitat Quality ◽  
Population Level ◽  
Individual Fitness ◽  
Animal Populations ◽  
Cumulative Change ◽  
Few Data ◽  
Managed Landscapes ◽  
The Relationship

While animals may use many habitat types, relatively few are preferred and fewer yet are superior in quality (referring to individual fitness as the measure of quality). Historical reduction in habitat quality for some wildlife species has occurred such that we may now have limited reference to original superior-quality habitats. As time passes, managers may be unaware that superior habitats are slowly disappearing and that the slow but cumulative change is significant to a species at the population level. The perception of superior-quality habitat also changes with each successive generation of managers based on their experiences. This paper raises the concern that retrospective work may often be required to determine past forest habitats and associated animal populations to avoid the risk of falling into a trap of not recognizing ever-declining habitat quality through time and relegating animals to what is in fact much poorer quality habitat than those to which they are actually best adapted. Further, the relationship between relative abundance and habitat quality may often be uncertain owing to maladaptive habitat selection by animals, inappropriate survey timing or interannual population differences. While we have begun to appreciate aspects of habitat selection for many forest species, few data are yet available that relate selected habitats to fitness of individual animals. Hence, while we may have models to predict habitat use, considerable research remains to be done to be able to predict long-term sustainability of species in managed landscapes. Key words: habitat quality, forest management, sustainability, biodiversity

scholarly journals New insights into the evolutionary rate of HIV-1 at the within-host and epidemiological levels

2012 ◽  
Vol 279 (1741) ◽  
pp. 3367-3375 ◽  
Author(s):  
Katrina A. Lythgoe ◽  
Christophe Fraser
Keyword(s):  
Immune Escape ◽  
Population Level ◽  
The Body ◽  
Biological Organization ◽  
Calendar Time ◽  
Adaptive Mutations ◽  
Preferential Transmission ◽  
Ancestral Virus ◽  
Hiv 1 ◽  
Major Target

Over calendar time, HIV-1 evolves considerably faster within individuals than it does at the epidemic level. This is a surprising observation since, from basic population genetic theory, we would expect the genetic substitution rate to be similar across different levels of biological organization. Three different mechanisms could potentially cause the observed mismatch in phylogenetic rates of divergence: temporal changes in selection pressure during the course of infection; frequent reversion of adaptive mutations after transmission; and the storage of the virus in the body followed by the preferential transmission of stored ancestral virus. We evaluate each of these mechanisms to determine whether they are likely to make a major contribution to the mismatch in phylogenetic rates. We conclude that the cycling of the virus through very long-lived memory CD4 + T cells, a process that we call ‘store and retrieve’, is probably the major contributing factor to the rate mismatch. The preferential transmission of ancestral virus needs to be integrated into evolutionary models if we are to accurately predict the evolution of immune escape, drug resistance and virulence in HIV-1 at the population level. Moreover, early infection viruses should be the major target for vaccine design, because these are the viral strains primarily involved in transmission.

scholarly journals Hybridization can facilitate species invasions, even without enhancing local adaptation

2016 ◽  
Vol 113 (36) ◽  
pp. 10210-10214 ◽  
Author(s):  
Mohsen B. Mesgaran ◽  
Mark A. Lewis ◽  
Peter K. Ades ◽  
Kathleen Donohue ◽  
Sara Ohadi ◽  
...  
Keyword(s):  
Leading Edge ◽  
Allee Effects ◽  
Plant Populations ◽  
Individual Fitness ◽  
Founding Population ◽  
Species Invasions ◽  
Cakile Maritima ◽  
Model Predictions ◽  
Cakile Edentula

The founding population in most new species introductions, or at the leading edge of an ongoing invasion, is likely to be small. Severe Allee effects—reductions in individual fitness at low population density—may then result in a failure of the species to colonize, even if the habitat could support a much larger population. Using a simulation model for plant populations that incorporates demography, mating systems, quantitative genetics, and pollinators, we show that Allee effects can potentially be overcome by transient hybridization with a resident species or an earlier colonizer. This mechanism does not require the invocation of adaptive changes usually attributed to invasions following hybridization. We verify our result in a case study of sequential invasions by two plant species where the outcrosser Cakile maritima has replaced an earlier, inbreeding, colonizer Cakile edentula (Brassicaceae). Observed historical rates of replacement are consistent with model predictions from hybrid-alleviated Allee effects in outcrossers, although other causes cannot be ruled out.

scholarly journals Characterisation and practical importance of exerciseinduced cardiovascular response in a 6 - to 18-year-old population

2020 ◽  
Author(s):  
Katalin Havasi
Keyword(s):  
Screening Test ◽  
School Health ◽  
Cardiovascular Response ◽  
Practical Importance ◽  
Haemodynamic Effect ◽  
Population Level ◽  
Health Impact ◽  
Normal Weight ◽  
Cardiovascular Fitness ◽  
Individual Fitness

- Haemodynamic effect also has individual (fitness and health specifics) and population-level (public health impact) relevance to exercise. - Confirmed evidence about the pupils: differences exist between recovery HR and recovery BP trends: recovery HR remained at a high level, in contrast, the recovery BP decreased to starting level or below. - Established a pilot, exercise-related screening test, called “Fit-test”. It provides an opportunity to gain new insight into the relationship between later manifestations of illness and juvenile burden response.  Fit-test is a low-budget, whole-population screening test, which easily fits into an existing school and school health system.  We have found that is also suitable for screening for MHT, preHT, and sustained HT students, and for monitoring the effects of treatment. - We established a database, the first large dataset of haemodynamic changes of normal-weight pupils during a field exercise test.  We defined the population-specific dynamics and experienced individual dissimilarities.  It provided an opportunity to evaluate the physical and cardiovascular fitness together.  Established a possibility for subsequent monitoring of the health status of the affected generation, and risk group. This dataset is useful for physical education teachers, coaches, physicians and exercise physiologists to evaluate actual cardiovascular fitness and haemodynamic responses to exercise in children or adolescents and follow its change.

scholarly journals Fitness trade-offs of group formation and movement by Thomson's gazelles in the Serengeti ecosystem

2018 ◽  
Vol 373 (1746) ◽  
pp. 20170013 ◽  
Author(s):  
John M. Fryxell ◽  
Andrew M. Berdahl
Keyword(s):  
Group Formation ◽  
Movement Ecology ◽  
Population Level ◽  
Collective Behaviour ◽  
Illustrative Case ◽  
Environmental Fluctuation ◽  
Serengeti Ecosystem ◽  
Individual Fitness ◽  
Trade Offs ◽  
Risk Of Predation

Collective behaviours contributing to patterns of group formation and coordinated movement are common across many ecosystems and taxa. Their ubiquity is presumably due to altering interactions between individuals and their predators, resources and physical environment in ways that enhance individual fitness. On the other hand, fitness costs are also often associated with group formation. Modifications to these interactions have the potential to dramatically impact population-level processes, such as trophic interactions or patterns of space use in relation to abiotic environmental variation. In a wide variety of empirical systems and models, collective behaviour has been shown to enhance access to ephemeral patches of resources, reduce the risk of predation and reduce vulnerability to environmental fluctuation. Evolution of collective behaviour should accordingly depend on the advantages of collective behaviour weighed against the costs experienced at the individual level. As an illustrative case study, we consider the potential trade-offs on Malthusian fitness associated with patterns of group formation and movement by migratory Thomson's gazelles in the Serengeti ecosystem. This article is part of the theme issue ‘Collective movement ecology’.

Population structure of the sand dollar Echinarachnius parma in the subtidal zone of the northern Gulf of St. Lawrence, eastern Canada

1996 ◽  
Vol 74 (4) ◽  
pp. 698-709 ◽  
Author(s):  
A. Cabanac ◽  
J. H. Himmelman
Keyword(s):  
Growth Rate ◽  
Size Structure ◽  
Subtidal Zone ◽  
Size Distributions ◽  
Sand Dollar ◽  
Eastern Canada ◽  
Different Depths ◽  
Accelerated Growth ◽  
Sand Dollars ◽  
Water Turbulence

We examined changes in populations of Echinarachnius parma with depth on subtidal sediment slopes in the Mingan Islands. Size distributions showed the presence of two major groups measuring 1–21 and 37–62 mm in length, respectively. Intermediate-sized sand dollars were rare. Juveniles (< 28 mm in length) were extremely abundant at 16 and 20 m depth (460–660/m2) and decreased in number with decreasing depth, whereas the density of adults was relatively stable at different depths. Juveniles were more frequently buried (95%) than adults (30%). Analysis of growth lines and of shifts in juvenile cohorts indicated that growth rate increased with size up to a maximum between 20 and 40 mm and then decreased sharply. The bimodal size structure is possibly due to the accelerated growth rate at intermediate sizes. We hypothesize that sand dollars move to shallower water with increasing size to take advantage of food resources, possibly benthic diatoms, which are more abundant there. Large individuals are probably better adapted than juveniles to exploiting shallower water because they are less likely to be transported by water turbulence.

Host selection and distribution of Hypermastus placentae (Eulimidae), and ectoparasitic gastropod on the sand dollar Arachnoides placenta (Echinoidea)

1993 ◽  
Vol 44 (6) ◽  
pp. 835 ◽  
Author(s):  
MR Crossland ◽  
JD Collins ◽  
RA Alford
Keyword(s):  
Body Size ◽  
Host Selection ◽  
Littoral Zone ◽  
Host Density ◽  
Infestation Rate ◽  
Sand Dollar ◽  
Intertidal Sand ◽  
Parasite Infestation ◽  
Sand Dollars ◽  
Host Body Size

The intertidal sand dollar Arachnoides placenta is parasitized by the eulimid Hypermastus placentae at Pallarenda Beach, Townsville, Queensland. A. placenta is the only echinoderm species in the region with which H. placentae associates. Sand dollars are distributed in an aggregated pattern within the littoral zone at Pallarenda Beach, and the distribution of parasites within the adult sand dollar population conforms closely to Poisson expectations. A. placenta adults in all size classes are equally susceptible to parasitization by H. placentae, whereas juveniles are not parasitized; host selection may be determined by a requirement for host gonadal tissue in the diet of the parasite. Infestation rate and number of parasites per host decrease as host density increases. Parasite body size is not related to host body size.

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