scholarly journals Remembrance of things past: modelling the relationship between species' abundances in living communities and death assemblages

2011 ◽  
Vol 8 (1) ◽  
pp. 131-134 ◽  
Author(s):  
Thomas D. Olszewski
Keyword(s):  
Half Life ◽  
Species Differences ◽  
Species Abundance ◽  
Time Averaging ◽  
Ecological Communities ◽  
Post Mortem ◽  
Death Assemblages ◽  
Species Abundances ◽  
The Relationship ◽  
Range Of Variation

Accumulations of dead skeletal material are a valuable archive of past ecological conditions. However, such assemblages are not equivalent to living communities because they mix the remains of multiple generations and are altered by post-mortem processes. The abundance of a species in a death assemblage can be quantitatively modelled by successively integrating the product of an influx time series and a post-mortem loss function (a decay function with a constant half-life). In such a model, temporal mixing increases expected absolute dead abundance relative to average influx as a linear function of half-life and increases variation in absolute dead abundance values as a square-root function of half-life. Because typical abundance distributions of ecological communities are logarithmically distributed, species' differences in preservational half-life would have to be very large to substantially alter species' abundance ranks (i.e. make rare species common or vice-versa). In addition, expected dead abundances increase at a faster rate than their range of variation with increased time averaging, predicting greater consistency in the relative abundance structure of death assemblages than their parent living community.

Testing the effects of durability (shell thickness) on species over-representation in death assemblages, a taphonomic baseline for conservation paleobiology

2021 ◽  
Author(s):  
Adam Tomašových ◽  
Susan M. Kidwell
Keyword(s):  
Southern California ◽  
Anthropogenic Impacts ◽  
Spatial Scales ◽  
Organic Content ◽  
Time Averaging ◽  
Shell Size ◽  
Interspecific Differences ◽  
Conservation Paleobiology ◽  
Death Assemblages ◽  
Species Abundances

<p>Differences in the taxonomic or functional composition of living and death assemblages is a key means of identifying the magnitude and drivers of past ecological changes in conservation paleobiology, especially when assessing the effects of anthropogenic impacts. However, such live-dead differences in species abundances can arise not only from ecological (stochastic or deterministic) changes in abundance over the duration of time averaging but also from interspecific differences in the postmortem durability of skeletal remains or from the lifespan of the individuals. Here, we attempt to directly incorporate the effects of durability on species abundances in death assemblages by modeling dead abundance as a function of species’ durability traits and using abundances in living assemblages as a prior. Species inferred to be negatively affected by anthropogenic impacts should be over-represented in death assemblages relative to their abundance in death assemblages predicted by the durability model (rather than just relative to their abundance in living assemblages). Using species-level durability trait data for bivalves (shell size, thickness, mineralogy, shell organic content, and life habit) from the southern California shelf, we find that, among these traits, valve thickness correlates consistently positively and at multiple spatial scales with the log of the dead:live ratio of species abundances, and accounts for ~20-30% of live-dead mismatch. Using this benchmark for the discordance that might be taphonomic in origin, we confirm that the over-representation of epifaunal suspension-feeders and siphonate deposit-feeders in death assemblages of the southern California shelf owes in fact to their ecological decline in recent centuries, even when accounting for their greater durability.</p>

The preservational fidelity of evenness in molluscan death assemblages

Paleobiology ◽  
2007 ◽  
Vol 33 (1) ◽  
pp. 1-23 ◽  
Author(s):  
Thomas D. Olszewski ◽  
Susan M. Kidwell
Keyword(s):  
Environmental Gradient ◽  
Time Averaging ◽  
Data Sets ◽  
Sufficient Time ◽  
Soft Bottom ◽  
Rapid Loss ◽  
Fine Mesh ◽  
Death Assemblages ◽  
Species Abundances ◽  
Depositional Setting

The richness (number of species) and evenness (uniformity of species abundances) of death assemblages can differ from corresponding living communities due to processes such as between-habitat transport, environmental condensation, and differential taphonomic destruction. Analysis of 132 single-census live-dead comparisons of benthic molluscs from a variety of soft-bottom marine settings indicates that on average evenness does not differ greatly between live and dead assemblages, regardless of the particular depositional setting or grain size of associated sediment. However, individual death assemblages can deviate quite substantially from their corresponding living assemblages, especially if processed using a fine mesh. In addition, death assemblages collected using sieves with 2 mm mesh or coarser showed consistently and significantly greater evenness than corresponding living assemblages. These results are encouraging for broad-scale assessments of evenness in the fossil record based on the comparison of average values (rather than for individual assemblages) and where trends in evenness are the aim of the study.Our live-dead comparisons of richness sample-size corrected by rarefaction revealed that death assemblages were on average ~1.45 times richer than the corresponding living assemblages regardless of rarefied size. In 63.6% of death assemblages both dead richness and dead evenness were greater than live, suggesting sufficient time-averaging to catch significant random or directional changes in the living community and/or introduction of individuals from outside the sampled habitat. In 12.9% of collections both dead richness and dead evenness were less than live, suggesting either rapid loss of dead shells so that dead diversity is depressed below the local living community or selective loss of taphonomically vulnerable taxa. In 18.2% of data sets dead richness was elevated but dead evenness was depressed relative to live: these are interpreted to reflect the addition of low-evenness allochthonous material. The remaining 4.5% of data sets had elevated dead evenness but depressed dead richness, suggesting that live and dead in this case may not be closely related.In seven available time series, temporal volatility in living communities over 6–24 months was considerable but could not account for observed (mostly higher) evenness values in corresponding death assemblages, whose evenness and composition were quite stable in the few examined studies. A densely sampled spatial transect shows that changes in living-assemblage evenness along an environmental gradient were preserved in the corresponding death assemblages, although dead evenness at any location on the gradient was substantially higher than living evenness.

scholarly journals Effect of Localization on the Stability of Mutualistic Ecological Networks

2015 ◽  
Author(s):  
Samir Suweis ◽  
Jacopo Grilli ◽  
Jayanth Banavar ◽  
Stefano Allesina ◽  
Amos Maritan
Keyword(s):  
Species Abundance ◽  
Interaction Network ◽  
Species Interaction ◽  
Interaction Networks ◽  
Ecological Communities ◽  
Weighted Degree ◽  
Perturbation Propagation ◽  
The Stability ◽  
The Impact ◽  
The Relationship

The relationships between the core-periphery architecture of the species interaction network and the mechanisms ensuring the stability in mutualistic ecological communities are still unclear. In particular, most studies have focused their attention on asymptotic resilience or persistence, neglecting how perturbations propagate through the system. Here we develop a theoretical framework to evaluate the relationship between architecture of the interaction networks and the impact of perturbations by studying localization, a measure describing the ability of the perturbation to propagate through the network. We show that mutualistic ecological communities are localized, and localization reduces perturbation propagation and attenuates its impact on species abundance. Localization depends on the topology of the interaction networks, and it positively correlates with the variance of the weighted degree distribution, a signature of the network topological hetereogenity. Our results provide a different perspective on the interplay between the architecture of interaction networks in mutualistic communities and their stability.

The Abundant Niche-centroid Hypothesis: Key Points About Unfilled Niches and the Potential Use of Supraspecfic Modeling Units

2020 ◽  
Vol 15 (3) ◽  
pp. 92-102
Author(s):  
Carlos Yañez ◽  
Gerardo Martín ◽  
Luis Osorio-Olvera ◽  
Jazmín Escobar-Luján ◽  
Sandra Castaño-Quintero ◽  
...  
Keyword(s):  
Ecological Niche ◽  
Inverse Relationship ◽  
Species Abundance ◽  
Species Level ◽  
Key Points ◽  
Species Abundances ◽  
Abundance Variation ◽  
Species Occurrences ◽  
The Relationship ◽  
Potential Use

Correlative estimates of fundamental niches are gaining momentum as an alternative to predict species’ abundances, particularly via the abundant niche-centroid hypothesis (an expected inverse relationship between species’ abundance variation across its range and the distance to the geometric centroid of its multidimensional ecological niche). The main goal of this review is to recapitulate what has been done, where we are now, and where should we move towards in regards to this hypothesis. Despite evidence in support of the abundance-distance to niche centroid relationship, its usefulness has been highly debated, although with little consideration of the underlying theory regarding the circumstances that might break down the relationship. We address some key points about the conditions needed to test the hypothesis in correlative studies, specifically in relation to nichecharacterization and configurations of the Biotic-Abiotic-Mobility (BAM) framework to illustrate the problem of unfilled niches. Using a created supraspecific modeling unit, we show that species for which only a portion of their fundamental niche is represented in their area of historical accessibility (M)—i.e., when the environmental equilibrium condition is violated—it is impossible to characterize their true niche centroid. Therefore, we strongly recommend to analyze this assumption prior toassess the abundant niche-centroid hypothesis. Finally, we discuss the potential of using modeling units above the species level for cases in which environmental conditions associated with species’ occurrences may not be sufficient to fully characterize their fundamental niches.

scholarly journals Emergence of structural and dynamical properties of ecological mutualistic networks

2014 ◽  
Author(s):  
Samir Suweis ◽  
Filippo Simini ◽  
Jayanth Banavar ◽  
Amos Maritan
Keyword(s):  
Species Abundance ◽  
Interaction Matrix ◽  
Ecological Communities ◽  
Generalist Species ◽  
Mutualistic Interactions ◽  
Species Abundances ◽  
Dynamical Properties ◽  
Mutualistic Networks ◽  
Specialist Species ◽  
The Many

Mutualistic networks are formed when the interactions between two classes of species are mutually beneficial. They are important examples of cooperation shaped by evolution. Mutualism between animals and plants has a key role in the organization of ecological communities. Such networks in ecology have generally evolved a nested architecture independent of species composition and latitude; specialist species, with only few mutualistic links, tend to interact with a proper subset of the many mutualistic partners of any of the generalist species. Despite sustained efforts to explain observed network structure on the basis of community-level stability or persistence, such correlative studies have reached minimal consensus. Here we show that nested interaction networks could emerge as a consequence of an optimization principle aimed atmaximizing the species abundance in mutualistic communities. Using analytical and numerical approaches, we show that because of the mutualistic interactions, an increase in abundance of a given species results in a corresponding increase in the total number of individuals in the community, and also an increase in the nestedness of the interaction matrix. Indeed, the species abundances and the nestedness of the interaction matrix are correlated by a factor that depends on the strength of the mutualistic interactions. Nestedness and the observed spontaneous emergence of generalist and specialist species occur for several dynamical implementations of the variational principle under stationary conditions. Optimized networks, although remaining stable, tend to be less resilient than their counterparts with randomly assigned interactions. In particular, we show analytically that the abundance of the rarest species is linked directly to the resilience of the community. Our work provides a unifying framework for studying the emergent structural and dynamical properties of ecological mutualistic networks.

TAPHONOMY AND TIME AVERAGING OF MOLLUSCAN DEATH ASSEMBLAGES IN FLORIDA SPRINGS AND RIVERS

2018 ◽  
Author(s):  
Kristopher M. Kusnerik ◽  
◽  
Harley Means ◽  
Roger W. Portell ◽  
Michal Kowalewski
Keyword(s):  
Time Averaging ◽  
Death Assemblages ◽  
Florida Springs

Life span bias explains live–dead discordance in abundance of two common bivalves

Paleobiology ◽  
2018 ◽  
Vol 44 (4) ◽  
pp. 783-797 ◽  
Author(s):  
Kelly E. Cronin ◽  
Gregory P. Dietl ◽  
Patricia H. Kelley ◽  
Stewart M. Edie
Keyword(s):  
North Carolina ◽  
Life Span ◽  
Field Study ◽  
Species Abundance ◽  
Mercenaria Mercenaria ◽  
Mortality Rates ◽  
Global Maximum ◽  
Bivalve Species ◽  
Maximum Life Span ◽  
Death Assemblages

AbstractLife span bias potentially alters species abundance in death assemblages through the overrepresentation of short-lived organisms compared with their long-lived counterparts. Although previous work found that life span bias did not contribute significantly to live–dead discordance in bivalve assemblages, life span bias better explained discordance in two groups: longer-lived bivalve species and species with known life spans. More studies using local, rather than global, species-wide life spans and mortality rates would help to determine the prevalence of life span bias, especially for long-lived species with known life spans. Here, we conducted a field study at two sites in North Carolina to assess potential life span bias between Mercenaria mercenaria and Chione elevata, two long-lived bivalve species that can be aged directly. We compared the ability of directly measured local life spans with that of regional and global life spans to predict live–dead discordance between these two species. The shorter-lived species (C. elevata) was overrepresented in the death assemblage compared with its live abundance, and local life span data largely predicted the amount of live–dead discordance; local life spans predicted 43% to 88% of discordance. Furthermore, the global maximum life span for M. mercenaria resulted in substantial overpredictions of discordance (1.4 to 1.6 times the observed live–dead discordance). The results of this study suggest that life span bias should be considered as a factor affecting proportional abundances of species in death assemblages and that using life span estimates appropriate to the study locality improves predictions of discordance based on life span compared with using global life span estimates.

The relationship between early post-mortem pH and the tenderisation of beef muscles

Meat Science ◽  
1997 ◽  
Vol 45 (2) ◽  
pp. 239-251 ◽  
Author(s):  
G.R. O'Halloran ◽  
D.J. Troy ◽  
D.J. Buckley
Keyword(s):  
Post Mortem ◽  
The Relationship ◽  
Beef Muscles

scholarly journals Los Austrias y las ceremonias alrededor de la muerte del rey, ritual y simbología // The Habsburg’s kings in Spain and the ceremonies around the king’s death, rites and symbols

2016 ◽  
Vol 3 (4) ◽  
pp. 251
Author(s):  
María Gómez Requejo
Keyword(s):  
Catholic Church ◽  
Roman Catholic ◽  
Roman Catholic Church ◽  
Audience Participation ◽  
Symbolic Language ◽  
Post Mortem ◽  
The Dead ◽  
The One ◽  
The Relationship

Las ceremonias que se tenían lugar cuando se producía el fallecimiento de un monarca de la casa de Austria, tanto las pre como las post mortem, eran el  vehículo de un lenguaje simbólico cargado de representaciones y emblemas que le recordaban al súbdito tanto el poder del rey muerto como el que iba a tener su sucesor y asimismo ponían de manifiesto la unión de la dinastía con la Iglesia Católica. Enfermedad, muerte y exequias se convierten, con estos monarcas, en un espectáculo fastuoso que requiere escenografía, actores, vestuario, guion  y un público –los súbditos- del que se busca una participación ya sea consciente y activa o pasiva, como mero espectador, pero en todo caso necesario para que el espectáculo cumpla su objetivo: persuadir del poder real. Abstract The ceremonies around the death of a Habsburg king in Spain, where the vehicle to a symbolic language, full of representations and emblems, used to remind to his loyal subjects not only the power of the dead king and the one his heir and successor was going to hold, but also the relationship between the dynasty and the Roman Catholic Church. With the Habsburg’s, the illness, death and exequies of the monarch were converted into a sumptuous show that needed: a set, actors, lavish costumes, script and audience –the loyal subjects- to which audience participation, whether it be active or passive, was essential to fulfill its objective: to be persuaded of the king’s power.

scholarly journals A new method to analyze species abundances in space using generalized dimensions

2015 ◽  
Author(s):  
Leonardo A Saravia
Keyword(s):  
Species Abundance ◽  
Abundance Distribution ◽  
Community Patterns ◽  
Information Dimension ◽  
Generalized Dimension ◽  
Species Abundances ◽  
Species Abundance Distributions ◽  
Species Area ◽  
Generalized Dimensions ◽  
Relationship Of

Species-area relationships (SAR) and species abundance distributions (SAD) are among the most studied patterns in ecology, due to their application to both theoretical and conservation issues. One problem with these general patterns is that different theories can generate the same predictions, and for this reason they cannot be used to detect different mechanisms of community assembly. A solution is to search for more sensitive patterns, for example by extending the SAR to the whole species abundance distribution. A generalized dimension ($D_q$) approach has been proposed to study the scaling of SAD, but to date there has been no evaluation of the ability of this pattern to detect different mechanisms. An equivalent way to express SAD is the rank abundance distribution (RAD). Here I introduce a new way to study SAD scaling using a spatial version of RAD: the species-rank surface (SRS), which can be analyzed using $D_q$. Thus there is an old $D_q$ based on SAR ($D_q^{SAD}$), and a new one based on SRS ($D_q^{SRS}$). I perform spatial simulations to examine the relationship of $D_q$ with SAD, spatial patterns and number of species. Finally I compare the power of both $D_q$, SAD, SAR exponent, and the fractal information dimension to detect different community patterns using a continuum of hierarchical and neutral spatially explicit models. The SAD, $D_q^{SAD}$ and $D_q^{SRS}$ all had good performance in detecting models with contrasting mechanisms. $D_q^{SRS}$, however, had a better fit to data and allowed comparisons between hierarchical communities where the other methods failed. The SAR exponent and information dimension had low power and should not be used. SRS and $D_q^{SRS}$ could be interesting methods to study community or macroecological patterns.

Sign in / Sign up

Export Citation Format

Share Document