Indirect Effects in Communities and Ecosystems

Ecology ◽  
2012 ◽  
Author(s):  
Thomas E. Miller ◽  
Casey P. terHorst
Keyword(s):  
Population Growth ◽  
Indirect Effects ◽  
Species Interactions ◽  
Individual Species ◽  
Relative Importance ◽  
Abiotic Conditions ◽  
Pairwise Interactions ◽  
General Importance ◽  
Keystone Predation ◽  
Different Types

The goal of ecology is to understand the distribution and abundance of organisms, generally by quantifying how abiotic conditions and species interactions contribute to population growth. Much ecology focuses on simple pairwise interactions, such as competition and predation; yet, species naturally exist in much more complex systems in which their abundances are determined by webs of species interactions. An important step for ecologists has been to understand how interactions may occur through loops and webs of connected species: it is these interactions that are now loosely collected together into what we call “indirect effects.” Some types of indirect effects are thought not only to widely occur but also to be particularly important for determining both the abundances of individual species and community properties such as diversity and stability. These include trophic cascades, where predators enhance producer growth by feeding on consumer species, and keystone predation, where predators consume dominant competitors, thus allowing inferior competitors to persist. Identifying and quantifying indirect effects has become a major issue in ecology. Although their general importance is well understood, we have little understanding of the relative importance of different types of indirect effects.

scholarly journals The relative importance of direct and indirect effects of hunting mortality on the population dynamics of brown bears

2015 ◽  
Vol 282 (1798) ◽  
pp. 20141840 ◽  
Author(s):  
Jacinthe Gosselin ◽  
Andreas Zedrosser ◽  
Jon E. Swenson ◽  
Fanie Pelletier
Keyword(s):  
Population Dynamics ◽  
Population Growth ◽  
Indirect Effects ◽  
Ursus Arctos ◽  
Brown Bear ◽  
Relative Importance ◽  
Direct And Indirect Effects ◽  
Negative Effects ◽  
Hunting Pressure ◽  
Demographic Rates

There is increasing evidence of indirect effects of hunting on populations. In species with sexually selected infanticide (SSI), hunting may decrease juvenile survival by increasing male turnover. We aimed to evaluate the relative importance of direct and indirect effects of hunting via SSI on the population dynamics of the Scandinavian brown bear ( Ursus arctos ). We performed prospective and retrospective demographic perturbation analyses for periods with low and high hunting pressures. All demographic rates, except yearling survival, were lower under high hunting pressure, which led to a decline in population growth under high hunting pressure ( λ = 0.975; 95% CI = 0.914–1.011). Hunting had negative indirect effects on the population through an increase in SSI, which lowered cub survival and possibly also fecundity rates. Our study suggests that SSI could explain 13.6% of the variation in population growth. Hunting also affected the relative importance of survival and fecundity of adult females for population growth, with fecundity being more important under low hunting pressure and survival more important under high hunting pressure. Our study sheds light on the importance of direct and indirect effects of hunting on population dynamics, and supports the contention that hunting can have indirect negative effects on populations through SSI.

scholarly journals Branching processes with interactions: subcritical cooperative regime

2021 ◽  
Vol 53 (1) ◽  
pp. 251-278
Author(s):  
Adrián González Casanova ◽  
Juan Carlos Pardo ◽  
José Luis Pérez
Keyword(s):  
Population Genetics ◽  
Branching Processes ◽  
Jump Diffusion ◽  
Pairwise Interaction ◽  
Pairwise Interactions ◽  
Different Types ◽  
Interesting Object ◽  
The Moment ◽  
Dynamics Of Populations

AbstractIn this paper, we introduce a family of processes with values on the nonnegative integers that describes the dynamics of populations where individuals are allowed to have different types of interactions. The types of interactions that we consider include pairwise interactions, such as competition, annihilation, and cooperation; and interactions among several individuals that can be viewed as catastrophes. We call such families of processes branching processes with interactions. Our aim is to study their long-term behaviour under a specific regime of the pairwise interaction parameters that we introduce as the subcritical cooperative regime. Under such a regime, we prove that a process in this class comes down from infinity and has a moment dual which turns out to be a jump-diffusion that can be thought as the evolution of the frequency of a trait or phenotype, and whose parameters have a classical interpretation in terms of population genetics. The moment dual is an important tool for characterizing the stationary distribution of branching processes with interactions whenever such a distribution exists; it is also an interesting object in its own right.

Demography of Xenosaurus platyceps (Squamata: Xenosauridae): a comparison between tropical and temperate populations

2008 ◽  
Vol 29 (2) ◽  
pp. 245-256 ◽  
Author(s):  
Carissa Jones ◽  
Isaac Rojas-González ◽  
Julio Lemos-Espinal ◽  
Jaime Zúñiga-Vega
Keyword(s):  
Life History ◽  
Population Growth ◽  
Adult Mortality ◽  
Life History Strategies ◽  
Relative Importance ◽  
Theoretical Frameworks ◽  
Population Growth Rates ◽  
Relative Contribution ◽  
Two Populations ◽  
Average Fitness

Abstract There appears to be variation in life-history strategies even between populations of the same species. For ectothermic organisms such as lizards, it has been predicted that demographic and life-history traits should differ consistently between temperate and tropical populations. This study compares the demographic strategies of a temperate and a tropical population of the lizard Xenosaurus platyceps. Population growth rates in both types of environments indicated populations in numerical equilibrium. Of the two populations, we found that the temperate population experiences lower adult mortality. The relative importance (estimated as the relative contribution to population growth rate) of permanence and of the adult/reproductive size classes is higher in the temperate population. In contrast, the relative importance for average fitness of fecundity and growth is higher in the tropical population. These results are consistent with the theoretical frameworks about life-historical differences among tropical and temperate lizard populations.

Subdimensions of total rewards satisfaction and creativity among R&D employees: a moderated mediation model

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Zhenyuan Wang ◽  
Jianghong Du ◽  
Herman H.M. Tse ◽  
Jun Gu ◽  
Hui Meng ◽  
...  
Keyword(s):  
Work Stress ◽  
Work Engagement ◽  
Indirect Effects ◽  
Moderated Mediation ◽  
Relative Importance ◽  
Mediation Model ◽  
Content Type ◽  
Moderated Mediation Model ◽  
Total Rewards

PurposeThis study aims to explore the relative importance of the subdimensions of total rewards satisfaction in predicting research and development (R&D) employee creativity. In addition, the study examines the indirect effects of the subdimensions of total rewards satisfaction on creativity via work engagement and the moderating role of challenge-related work stress in the first stage.Design/methodology/approachA two-wave design was used, in which total rewards satisfaction and challenge-related work stress were measured in the first wave. Work engagement and creativity were measured in the second wave. Dominance analysis and the latent moderated mediation model were used for the data analyses.FindingsThe analyses show that nonfinancial rewards satisfaction completely dominates indirect and direct financial rewards satisfaction when predicting creativity. Indirect financial rewards satisfaction completely dominates direct financial rewards satisfaction when predicting creativity. Work engagement mediates the relationships between the subdimensions of total rewards satisfaction and creativity. Challenge-related work stress moderates the relationships between the subdimensions of total rewards satisfaction and work engagement and the indirect effects of the subdimensions of total rewards satisfaction on creativity via work engagement.Practical implicationsThe results imply that managers should set challenge demands for R&D employees and try to improve their total rewards satisfaction, especially their nonfinancial and indirect financial rewards satisfaction, for them to be more creative.Originality/valueThis empirical study contributes to the literature by comparing the relative importance of the different dimensions of total rewards satisfaction in predicting creativity. The study also clarifies how (through work engagement) and when (based on challenge-related work stress) the subdimensions of total rewards satisfaction are positively related to R&D employees' creativity.

The relative importance of abiotic conditions and subsequent land use on the boreal primary succession of acidogenic mine tailings

2019 ◽  
Vol 127 ◽  
pp. 66-74 ◽  
Author(s):  
Antoine Tardif ◽  
Michaël Rodrigue-Morin ◽  
Vanessa Gagnon ◽  
Bill Shipley ◽  
Sébastien Roy ◽  
...  
Keyword(s):  
Land Use ◽  
Mine Tailings ◽  
Primary Succession ◽  
Relative Importance ◽  
Abiotic Conditions

scholarly journals Species interactions in three Lemnaceae species growing along a gradient of zinc pollution

2021 ◽  
Author(s):  
Lorena Lanthemann ◽  
Sofia van Moorsel
Keyword(s):  
Growth Rates ◽  
Species Interactions ◽  
Metal Removal ◽  
Lemna Minor ◽  
Polluted Water ◽  
Future Research ◽  
Individual Species ◽  
High Tolerance ◽  
Species Mixture ◽  
The Individual

Duckweeds (Lemnaceae) are increasingly studied for their potential for phytoremediation of heavy-metal polluted water bodies. A prerequisite for metal removal, however, is the tolerance of the organism to the pollutant, e.g., the metal zinc (Zn). Duckweeds have been shown to differ in their tolerances to Zn, however, despite them most commonly co-occurring with other species, there is a lack of research concerning the effect of species interactions on Zn tolerance. Here we tested whether the presence of a second species influenced the growth rate of the three duckweed species Lemna minor, Lemna gibba, and Lemna turionifera. We used four different Zn concentrations in a replicated microcosm experiment under sterile conditions, either growing the species in isolation or in a 2-species mixture. The response to Zn differed between species, but all three species showed a high tolerance to Zn, with low levels of Zn even increasing the growth rates. The growth rates of the individual species were influenced by the identity of the competing species, but this was independent of the Zn concentration. Our results suggest that species interactions should be considered in future research with duckweeds and that several duckweed species have high tolerance to metal pollution, making them candidates for phytoremediation efforts.

Differences in Perceptions of Managerial Roles by Gender among Southern Business Students

1991 ◽  
Vol 69 (3) ◽  
pp. 839-843
Author(s):  
James O. Smith ◽  
Robert E. Schellenberger
Keyword(s):  
Rank Order ◽  
Business Students ◽  
Relative Importance ◽  
Spearman Rank Order Correlation ◽  
Men And Women ◽  
Spearman Rank ◽  
Managerial Success ◽  
Managerial Roles ◽  
Different Types ◽  
Chi Squared

Perception of the roles necessary for managerial success based on the 10 verbal descriptors of the Mintzberg roles were gathered from 128 business students at a southern U.S. university. The objective was to assess whether these 72 men and 56 women viewed the importance of the roles differently. Ratings were collected on the 10 roles for each of four different types of managers. The data were analyzed by one-way analysis of variance, chi-squared analysis, and Spearman rank-order correlation. No differences were observed in the perception of men and women in these roles or of their relative importance.

Disturbance impacts on large rain-forest vertebrates differ with edge type and regional context in Sulawesi, Indonesia

2015 ◽  
Vol 31 (6) ◽  
pp. 509-517 ◽  
Author(s):  
Graden Z.L. Froese ◽  
Adrienne L. Contasti ◽  
Abdul Haris Mustari ◽  
Jedediah F. Brodie
Keyword(s):  
Camera Trap ◽  
Individual Species ◽  
Relative Importance ◽  
Vertebrate Species ◽  
Edge Type ◽  
Regional Context ◽  
Red Jungle Fowl ◽  
Local Abundance ◽  
Viverra Tangalunga ◽  
Landscape Level

Abstract:Anthropogenic edge effects, whereby disturbance strength increases in proximity to ecotone boundaries, are known to strongly affect individual species but we lack a general understanding of how they vary by species, disturbance type and regional context. We deployed 46 camera-trap stations for a total of 3545 trap-days at two sites in Sulawesi, Indonesia, obtaining 937 detections of five vertebrate species. Anoa (Bubalus spp.) were more abundant near edges, booted macaque (Macaca ochreata) and red jungle fowl (Gallus gallus) were less abundant near edges, and edges did not impact Sulawesi warty pig (Sus celebensis) or Malay civet (Viverra tangalunga). But the relative importance of habitat disturbance from agriculture, roads and villages differed for each species, and edge-induced disturbances varied not only in magnitude but also in direction between the study areas. In the strongest instance, macaque local abundance was 3.5 times higher near villages than it was 3 km into the forest in one reserve, but 2.8 times higher 3 km into the forest than near villages in the other reserve. Our results suggest that responses to habitat edges among species and edge types are idiosyncratic, and that landscape-level context can strongly alter the influence of local disturbance on biodiversity.

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