scholarly journals Effects of evolution on niche displacement and emergent population properties, a discussion on optimality

2020 ◽  
Author(s):  
Rudolf P. Rohr ◽  
Nicolas Loeuille
Keyword(s):  
Species Abundance ◽  
Niche Differentiation ◽  
Invasion Ecology ◽  
Biological Traits ◽  
Practical Applications ◽  
Fitness Functions ◽  
Invasion Fitness ◽  
Niche Displacement ◽  
Theoretical Question ◽  
Empirical Implications

AbstractUnderstanding the effects of evolution on emergent population properties such as intrinsic growth rate, species abundance, or dynamical resilience is not only a key theoretical question, but has major empirical implications for conservation, agroecology, invasion ecology among others. In particular, could we classify evolutionary scenarios leading to optimisation of those properties, from the ones who do not. First, we uncover two classes of invasion fitness functions, only the first one allowing optimization of some (but typically not all) population properties. Second, we showed that our two classes are also strongly linked to niche displacement and emergence of polymorphism. Our results indicate that optimization is, in general, incompatible with niche differentiation and, therefore, with emergence of polymorphism through evolutionary branching. Actually, niche displacement between resident and mutant morphs, and potentially polymorphism, only arise when we do not expect optimality to hold. We extensively discuss which biological traits can fall into which class of invasion fitness. Although, it is possible to find traits for which optimality is expected, we argue that for the majority of the cases it does not hold. Finally, we provide practical applications of our results in conservation, agroecology, harvesting and invasion ecology.

A historical perspective of niche differentiation between two top predators in the Uruguayan coastal area

2019 ◽  
Vol 46 (2) ◽  
pp. 136 ◽  
Author(s):  
Florencia Artecona ◽  
Maite De María ◽  
Leandro Bergamino ◽  
Diana Szteren
Keyword(s):  
Marine Mammals ◽  
Species Abundance ◽  
Niche Differentiation ◽  
Trophic Niche ◽  
Trophic Levels ◽  
Isotopic Niche ◽  
Recent Period ◽  
The South ◽  
Coastal Habitat ◽  
Top Predators

Context As top predators, marine mammals play a key role consuming in different trophic levels and the trophic niche characterization may help to understand how species utilize and share resources . On the coast of the Río de la Plata and the South-west Atlantic, the South American sea lion (Otaria flavescens) and the franciscana dolphin (Pontoporia blainvillei) are two important predators. Aims The present study investigated potential trophic overlap of both species by measuring stable carbon (δ13C) and nitrogen (δ15N) isotopes over two periods: historical (1959–79) and recent (2002–15) on the Uruguayan coast. Methods Bone samples of P. blainvillei and O. flavescens were used to determine the isotopic niche using the Stable Isotope Bayesian Ellipses in R (SIBER) analysis. Key results The isotopic niche did not overlap between species in any period. δ15N was higher in O. flavescens in both periods (20.29‰±0.73 in the historical and 19.95‰±1.0 in the recent period), indicating that it feeds at a higher trophic level than P. blainvillei. The δ13C was also significantly higher in O. flavescens than in P. blainvillei during the two periods (O. flavescens: –11.43±0.6‰ historic, –12.72±0.4‰ recent, and P. blainvillei: –12.69±1.1‰ historic, –13.84±1.3‰ recent). The isotopic niche areas of P. blainvillei in recent and historic periods confirmed they forage in 2 distinct environments, marine and estuarine, with low isotopic overlap. This overlap was higher in the recent period. Conclusions and Implications O. flavescens and both P. blainvillei groups were segregated in both periods, with a higher overlap in the recent. These species appear to reduce competition by using different resources in the same coastal habitat. O. flavescens preferentially feeds on benthic fish and showed wider trophic amplitude in both periods, whereas P. blainvillei has a more coastal–pelagic diet and included a greater variability of resources in its diet. The differences between species trophic niches can still be detected after both marine mammals species abundance has declined and after the development of fisheries.

scholarly journals Unveiling below-ground species abundance in a biodiversity experiment: a test of vertical niche differentiation among grassland species

2010 ◽  
Vol 98 (5) ◽  
pp. 1117-1127 ◽  
Author(s):  
Liesje Mommer ◽  
Jasper Van Ruijven ◽  
Hannie De Caluwe ◽  
Annemiek E. Smit-Tiekstra ◽  
Cornelis A.M. Wagemaker ◽  
...  
Keyword(s):  
Species Abundance ◽  
Niche Differentiation ◽  
Grassland Species ◽  
Below Ground

Natural Selection in Relation to Complexity

2008 ◽  
Vol 14 (3) ◽  
pp. 363-374 ◽  
Author(s):  
Stanley N. Salthe
Keyword(s):  
Natural Selection ◽  
Life Histories ◽  
Structural Complexity ◽  
Dissipative Structures ◽  
Biological Traits ◽  
Natural Systems ◽  
Fitness Functions ◽  
Soft Selection ◽  
The Face ◽  
Natural Selection Theory

Structural complexity characterizes our representations of dissipative structures. As a mechanistic concept, when referred to natural systems it generates perplexity in the face of logically sound models. Natural selection is a simple mechanistic concept, whose logic is well exemplified in genetic algorithms. While biological traits and functions do appear to have been subjected to selective culling, current neo-Darwinian theory is unable to account for the evolution of traits or functions when many of these are taken as the separate objects of independent fitness functions. Soft selection, acting in a phenotypically holistic manner, does model selection acting upon structurally complex systems with many traits and functions, but does not account for the evolution of specific traits or functions. It is further suggested that selection cannot be other than a weak force in the early, generative stages of complex life histories, and that this is a good thing, preserving their generativity. I conclude that natural selection theory by itself cannot account for increases in structural complexity.

scholarly journals Insights into Bioindicator Redundancy for Monitoring Water Quality based on Functional Units of Periphytic Protozoan Communities in Marine Ecosystems

2021 ◽  
Author(s):  
Syed Shabi Ul Hassan Kazmi ◽  
Uroosa Uroosa ◽  
Alan Warren ◽  
Guangjian Xu ◽  
Henglong Xu
Keyword(s):  
Water Quality ◽  
Relative Abundance ◽  
Species Abundance ◽  
Oxygen Demand ◽  
Functional Redundancy ◽  
Baseline Survey ◽  
High Signal ◽  
Biological Traits ◽  
Signal To Noise ◽  
Functional Units

Abstract Although periphytic protozoan communities have long been used for the bioassessment of water quality, their utility is hampered by functional redundancy leading to high “signal to noise” ratios. In this study, a 1-year baseline survey of periphytic protozoan communities was carried out in coastal waters of Yellow sea, northern China, in order to determine redundancy levels in conditions of differing water quality. Samples were collected at four sampling sites along a pollution gradient. Environmental variables such as salinity, chemical oxygen demand (COD), and concentrations of dissolved oxygen (DO), soluble reactive phosphates (SRP), ammonium nitrogen (NH4-N) and nitrate nitrogen (NO3-N) were measured to compare with biotic factors. A total of 53 functional units (FUs) were identified from 144 observed protozoan species based on four biological traits, i.e., feeding type, body size, movement type and source of food supply. For reducing the “signal to noise” ratios of species-abundance/biomass data, the peeling procedure was used to identify the bioindicator redundancy levels based on these FUs. Three consecutive subsets of response units (RU1–RU3) with correlation coefficients >0.75 of the full FU dataset were identified, comprising 12, 21 and 9 FUs, respectively. Algivores and bacterivores were dominant in RU1 and RU2 among the polluted sites, whereas raptors were dominant in RU3 at the unpolluted site. In terms of relative abundance, RU1 was the primary contributor to the protozoan communities during the 1-year cycle and its relative abundance increased with increasing pollution, whereas RU2 and RU3, with complementary temporal distributions, generally decreased with increasing pollution. Ordinations based on boot-strapped average analyses revealed a significant variation in functional pattern of all three RUs among the four sampling sites. Biological-environmental match analysis demonstrated that the variability was driven by the increasing concentrations of nutrients (e.g., NH4-N, NO3-N and PO4-P) and decreasing concentrations of DO (P<0.05). Based on these findings, it is suggested that there were high levels of functional redundancy among periphytic protozoan communities used as bioindicators of marine water quality.

scholarly journals Decomposing the causes for niche differentiation between species using hypervolumes

2018 ◽  
Author(s):  
Jose Carlos Carvalho ◽  
Pedro Cardoso
Keyword(s):  
Community Assembly ◽  
Niche Partitioning ◽  
Niche Differentiation ◽  
Niche Shift ◽  
Niche Space ◽  
Niche Dynamics ◽  
Niche Shifts ◽  
Coexisting Species ◽  
Reduced Space ◽  
Niche Displacement

Hutchinson's n-dimensional hypervolume concept holds a central role across different fields of ecology and evolution. The question of the amount of hypervolume overlap and differentiation between species is of great interest to understand the processes that drive niche dynamics, competitive interactions and, ultimately, community assembly. A novel framework is proposed to decompose overall differentiation among hypervolumes into two distinct components: niche shifts and niche contraction / expansion processes. Niche shift corresponds to the replacement of space between the hypervolumes occupied by two species, whereas niche contraction / expansion processes correspond to net differences between the amount of space enclosed by each hypervolume. Hypervolumes were constructed for two Darwin' finches, Geospiza conirostris and Geospiza magnirostris, using intraspecific trait data from Genovesa Island, where they live in sympatry. Results showed that significant niche shifts, not niche contraction, occurred between these species. This means that Geospiza conirostris occupied a different niche space and not a reduced space on Genovesa. The proposed framework allows disentangling different processes and understand the drivers of niche partitioning between coexisting species. Niche displacement due to competition can this way be separated from niche contraction due to specialization or expansion due to lower pressure on newly occupied ecological settings.

Testing dominance-diversity hypotheses using data from abandoned plantations and pastures in Puerto Rico and Ecuador

2010 ◽  
Vol 26 (2) ◽  
pp. 247-250 ◽  
Author(s):  
Randall W. Myster
Keyword(s):  
Puerto Rico ◽  
Plant Communities ◽  
Structural Parameters ◽  
Species Abundance ◽  
Niche Differentiation ◽  
Relative Importance ◽  
Abundance Patterns ◽  
Competitive Success ◽  
Using Data ◽  
Sampling Plot

Ecosystems have long been categorized by their function and structure (Odum 1953) and dominance and diversity are among the most common structural parameters measured in plant communities. The dominance of a plant species over another has been defined by having (1) more individual plants in a given sampling plot, (2) more collective biomass, or (3) greater cover (i.e. leaf area), but implicit in all definitions is a better ability to capture resources, grow and compete. Alternatively, diversity is a community-wide parameter encompassing both the raw number of species and the distribution of individual plants among them. Combining dominance and diversity together gives curves that show the distribution of abundances within a community (Whittaker 1965, Wilson 1991) and explore how these two aspects of structure relate to each other, change over time, and compare between communities separated in time or space. These curves are also effective in displaying contrasting patterns of species richness, highlighting differences in evenness among assemblages, and comparing species abundance patterns across communities (Magurran 2004). Indeed combining the dominance of particular species and the relative importance of that species within a community can suggest a ranking in competitive success and niche differentiation.

scholarly journals Evaluation of the estimate bias magnitude of the Rao’s quadratic diversity index

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e5211
Author(s):  
Youhua Chen ◽  
Yongbin Wu ◽  
Tsung-Jen Shen
Keyword(s):  
Diversity Index ◽  
Species Abundance ◽  
Diversity Indices ◽  
Ecological Community ◽  
Practical Applications ◽  
True Value ◽  
Standard Calculation ◽  
Number Of Individuals ◽  
Phylogenetic Ecology ◽  
Species Abundance Data

Rao’s quadratic diversity index is one of the most widely applied diversity indices in functional and phylogenetic ecology. The standard way of computing Rao’s quadratic diversity index for an ecological assemblage with a group of species with varying abundances is to sum the functional or phylogenetic distances between a pair of species in the assemblage, weighted by their relative abundances. Here, using both theoretically derived and observed empirical datasets, we show that this standard calculation routine in practical applications will statistically underestimate the true value, and the bias magnitude is derived accordingly. The underestimation will become worse when the studied ecological community contains more species or the pairwise species distance is large. For species abundance data measured using the number of individuals, we suggest calculating the unbiased Rao’s quadratic diversity index.

Ion Beam Induced Interfacial Reactions in Molybdenum Thin Films on Silicon

1981 ◽  
Vol 39 ◽  
pp. 162-163
Author(s):  
L. J. Chen ◽  
L. S. Hung ◽  
J. W. Mayer
Keyword(s):  
Ion Beam ◽  
Chemical Vapor ◽  
Interfacial Reactions ◽  
Practical Applications ◽  
Microelectronic Devices ◽  
Recent Emergence ◽  
Chemical Vapor Deposited ◽  
Atomic Mixing ◽  
Silicon Interface ◽  
Kinetics Of

When an energetic ion penetrates through an interface between a thin film (of species A) and a substrate (of species B), ion induced atomic mixing may result in an intermixed region (which contains A and B) near the interface. Most ion beam mixing experiments have been directed toward metal-silicon systems, silicide phases are generally obtained, and they are the same as those formed by thermal treatment.Recent emergence of silicide compound as contact material in silicon microelectronic devices is mainly due to the superiority of the silicide-silicon interface in terms of uniformity and thermal stability. It is of great interest to understand the kinetics of the interfacial reactions to provide insights into the nature of ion beam-solid interactions as well as to explore its practical applications in device technology.About 500 Å thick molybdenum was chemical vapor deposited in hydrogen ambient on (001) n-type silicon wafer with substrate temperature maintained at 650-700°C. Samples were supplied by D. M. Brown of General Electric Research & Development Laboratory, Schenectady, NY.

1250-kilovolt scanning transmission electron microscope

1984 ◽  
Vol 42 ◽  
pp. 624-625
Author(s):  
T. Imura ◽  
S. Maruse ◽  
K. Mihama ◽  
M. Iseki ◽  
M. Hibino ◽  
...  
Keyword(s):  
High Voltage ◽  
Electron Probe ◽  
Scanning Transmission Electron Microscope ◽  
Pressure Vessels ◽  
Practical Applications ◽  
Voltage Generator ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
New Applications ◽  
High Voltage Generator

Ultra high voltage STEM has many inherent technical advantages over CTEM. These advantages include better signal detectability and signal processing capability. It is hoped that it will explore some new applications which were previously not possible. Conventional STEM (including CTEM with STEM attachment), however, has been unable to provide these inherent advantages due to insufficient performance and engineering problems. Recently we have developed a new 1250 kV STEM and completed installation at Nagoya University in Japan. It has been designed to break through conventional engineering limitations and bring about theoretical advantage in practical applications.In the design of this instrument, we exercised maximum care in providing a stable electron probe. A high voltage generator and an accelerator are housed in two separate pressure vessels and they are connected with a high voltage resistor cable.(Fig. 1) This design minimized induction generated from the high voltage generator, which is a high frequency Cockcroft-Walton type, being transmitted to the electron probe.

Characterization of intergranular cuprous oxide in polycrystalline YBa2Cu3O7-x

1988 ◽  
Vol 46 ◽  
pp. 880-881
Author(s):  
Bradley L. Thiel ◽  
Chan Han R. P. ◽  
Kurosky L. C. Hutter ◽  
I. A. Aksay ◽  
Mehmet Sarikaya
Keyword(s):  
Grain Boundary ◽  
Cuprous Oxide ◽  
Room Temperature ◽  
Boundary Phase ◽  
Spectroscopic Techniques ◽  
Transition Width ◽  
Practical Applications ◽  
Thin Foils ◽  
Superconducting Oxides

The identification of extraneous phases is important in understanding of high Tc superconducting oxides. The spectroscopic techniques commonly used in determining the origin of superconductivity (such as RAMAN, XPS, AES, and EXAFS) are surface-sensitive. Hence a grain boundary phase several nanometers thick could produce irrelevant spectroscopic results and cause erroneous conclusions. The intergranular phases present a major technological consideration for practical applications. In this communication we report the identification of a Cu2O grain boundary phase which forms during the sintering of YBa2Cu3O7-x (1:2:3 compound).Samples are prepared using a mixture of Y2O3. CuO, and BaO2 powders dispersed in ethanol for complete mixing. The pellets pressed at 20,000 psi are heated to 950°C at a rate of 5°C per min, held for 1 hr, and cooled at 1°C per min to room temperature. The samples show a Tc of 91K with a transition width of 2K. In order to prevent damage, a low temperature stage is used in milling to prepare thin foils which are then observed, using a liquid nitrogen holder, in a Philips 430T at 300 kV.

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