scholarly journals Biological integrity enhances the qualitative effectiveness of conditional mice-oak mutualisms

2021 ◽  
Author(s):  
Mario Díaz ◽  
Teresa Morán-López ◽  
Jesús Sánchez-Dávila ◽  
Ignasi Torre ◽  
Alvaro Navarro-Castilla ◽  
...  
Keyword(s):  
Seed Dispersal ◽  
Predation Risk ◽  
Large Scale ◽  
Transition Probability ◽  
Joint Effect ◽  
Tree Regeneration ◽  
Probability Models ◽  
Scatter Hoarding ◽  
Extrinsic Factors ◽  
Dispersal Effectiveness

Scatter-hoarding decisions by rodents are key for the long-term maintenance of scattered tree populations. Decisions are determined by seed value, competition and predation risk, so that they can be influenced by the integrity of the biological system composed by trees, rodents, ungulate competitors, and rodent predators. We manipulate and model the oak-mice interaction in a Spanish dehesa, an anthropogenic savanna system suffering chronic tree regeneration failure, and quantify the joint effect of intrinsic and extrinsic factors on acorn dispersal effectiveness. First, we conducted a large-scale cafeteria field experiment, where we modified ungulate presence and predation risk, and followed mouse scatter-hoarding decisions under contrasting levels of moonlight and acorn availability. Then, we estimated the net effects of competition and risk by means of transition probability models that simulated mouse scatter-hoarding decisions according to the environmental context.  Our results show that suboptimal conditions for mice balance the interaction towards the mutualism as they force mice to forage less efficiently. Under stressful conditions (predation risks and presence of ungulates), lack of antipredatory cover around dehesa trees limited transportation of acorns, but also precluded mice activities outside tree canopies. As a result, post-dispersal predation rates were reduced and large acorns had a higher probability to survive. Our work shows that inter-specific interactions preventing efficient foraging by scatter-hoarders benefitted seed dispersal. Therefore, the maintenance of the full set of producers, consumers, dispersers and predators in ecosystems is key for promoting seed dispersal effectiveness in conditional mutualisms.

scholarly journals Large Scale Shell Model Calculations of the Negative-Parity States Structure in 24Mg Nucleus

2021 ◽  
Vol 66 (4) ◽  
pp. 293
Author(s):  
A.A. Al-Sammarraie ◽  
F.A. Ahmed ◽  
A.A. Okhunov
Keyword(s):  
Shell Model ◽  
Large Scale ◽  
Transition Probabilities ◽  
Transition Probability ◽  
Energy Levels ◽  
Form Factors ◽  
Model Space ◽  
Negative Parity ◽  
Matrix Elements ◽  
Model Calculations

The negative-parity states of 24Mg nucleus are investigated within the shell model. We are based on the calculations of energy levels, total squared form factors, and transition probability using the p-sd-pf (PSDPF) Hamiltonian in a large model space (0 + 1) hW. The comparison between the experimental and theoretical states showed a good agreement within a truncated model space. The PSDPF-based calculations successfully reproduced the data on the total squared form factors and transition probabilities of the negative-parity states in 24Mg nucleus. These quantities depend on the one-body density matrix elements that are obtained from the PSDPF Hamiltonian. The wave functions of radial one-particle matrix elements calculated with the harmonic-oscillator potential are suitable to predict experimental data by changing the center-of-mass corrections.

scholarly journals The timing of frugivore‐mediated seed dispersal effectiveness

2018 ◽  
Vol 28 (2) ◽  
pp. 219-231 ◽  
Author(s):  
Juan P. González‐Varo ◽  
Juan M. Arroyo ◽  
Pedro Jordano
Keyword(s):  
Seed Dispersal ◽  
Seed Dispersal Effectiveness ◽  
Dispersal Effectiveness

Canopy openness of individual tree promotes seed dispersal by scatter-hoarding rodents

2022 ◽  
Vol 507 ◽  
pp. 120016
Author(s):  
Jie Chen ◽  
Wenwen Chen ◽  
Zhiyun Lu ◽  
Bo Wang
Keyword(s):  
Seed Dispersal ◽  
Canopy Openness ◽  
Scatter Hoarding ◽  
Individual Tree

Seed dispersal effectiveness by frugivorous birds: Identifying functional equivalent species in bird assemblages

2019 ◽  
Vol 12 (3) ◽  
pp. 103-108
Author(s):  
Facundo Xavier Palacio
Keyword(s):  
Seed Dispersal ◽  
Statistical Significance ◽  
Bird Species ◽  
Kernel Functions ◽  
Bird Conservation ◽  
Frugivorous Birds ◽  
Seed Dispersal Effectiveness ◽  
Bird Assemblages ◽  
Functional Equivalent ◽  
Dispersal Effectiveness

Seed dispersal by birds is a pivotal ecosystem function worldwide; yet, the rapid and ongoing global biodiversity loss poses a major threat to this essential ecosystem service. Seed dispersal effectiveness (SDE) is a key outcome of the interaction, represented by the product of seed dispersal quantity (number of seed dispersed) and quality (probability of recruitment of dispersed seeds). Therefore, identifying functional equivalent species in terms of SDE should become a key issue for bird conservation, since the effects of local extinctions on seed dispersal services may be weakened by remaining equivalent species. However, a method to quantitatively identify functional equivalent species in frugivorous bird assemblages is still lacking. To estimate SDE overlap between seed dispersers and assess whether two species may be functionally equivalent, I apply a novel nonparametric niche overlap index based on kernel functions and null models to test its statistical significance. For each bird species, I account for intraspecific variation in seed dispersal effectiveness to obtain a distribution of seed dispersal effectiveness values, an often neglected source of variation in seed dispersal assemblages. Non-significant differences in seed dispersal effectiveness overlap support the hypothesis that two species are functional equivalent, thus playing similar functional roles. The model proposed is applicable to any other quantity or quality component and is independent from the method or sampling design used to quantify SDE. The identification of functional equivalent species in seed dispersal assemblages adds to the theoretical framework of seed dispersal effectiveness and offers new insights into the ecology of the seed dispersal service provided by birds.

scholarly journals ON-CHART SUCCESS DYNAMICS OF POPULAR SONGS

2018 ◽  
Vol 21 (03n04) ◽  
pp. 1850008
Author(s):  
SEUNGKYU SHIN ◽  
JUYONG PARK
Keyword(s):  
Large Scale ◽  
Information Source ◽  
Interdisciplinary Approach ◽  
Extrinsic Factors ◽  
Data Set ◽  
Cultural Products ◽  
Life Trajectories ◽  
Scientific Goal ◽  
Performance Patterns ◽  
Life Trajectory

In the modern era where highly-commodified cultural products compete heavily for mass consumption, finding the principles behind the complex process of how successful, “hit” products emerge remains a vital scientific goal that requires an interdisciplinary approach. Here, we present a framework for tracing the cycle of prosperity-and-decline of a product to find insights into influential and potent factors that determine its success. As a rapid, high-throughput indicator of the preference of the public, popularity charts have emerged as a useful information source for finding the market performance patterns of products over time, which we call the on-chart life trajectories that show how the products enter the chart, fare inside it, and eventually exit from it. We propose quantitative parameters to characterize a life trajectory, and analyze a large-scale data set of nearly 7,000 songs from Gaon Chart, a major weekly Korean Pop (K-Pop) chart that covers a span of six years. We find that a significant role is played by nonmusical extrinsic factors such as the established fan base of the artist and the might of production companies in the on-chart success of songs, strongly indicative of the commodified nature of modern cultural products. We also review a possible mathematical model of this phenomenon, and discuss several nontrivial yet intriguing trajectories that we call the “Late Bloomers” and the “Re-entrants” that appear to be strongly driven by serendipitous exposure on mass media and the changes of seasons.

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