scholarly journals Inter-specific Variability in Demographic Processes Affects Abundance-Occupancy Relationships

2020 ◽  
Author(s):  
Bilgecan Şen ◽  
H. Reşit Akçakaya
Keyword(s):  
Density Dependence ◽  
Bird Species ◽  
Population Level ◽  
Mathematical Structure ◽  
Demographic Parameters ◽  
Vital Rates ◽  
Analysis Method ◽  
Demographic Processes ◽  
Dependence Assumption ◽  
Population Demographic

AbstractSpecies with large local abundances tend to occupy more sites. One of the mechanisms proposed to explain this widely reported inter-specific relationship is a cross-scale hypothesis based on dynamics at the population level. Called the vital rates mechanism, it uses within-population demographic processes of population growth and density dependence to explain how positive inter-specific abundance-occupancy relationships can arise. Even though the vital rates mechanism is mathematically simple, it has never been tested directly because of the difficulty in estimating the demographic parameters involved. Here, using a recently introduced mark-recapture analysis method on 17 bird species, we show that inter-specific variability in density dependence strength can weaken both abundance-occupancy relationships and the expected corollaries of the vital rates mechanism. We demonstrate that one of the key assumptions of vital rates mechanism, that density dependence strength should be similar among species, is not met for these 17 species. Additionally, the mathematical structure of vital rates mechanism that relate population-level abundance and intrinsic growth rate is only weakly observed in our data. We argue that this mismatch of mathematical structure and data together with the violation of density dependence assumption weakens the expected positive abundance-occupancy association. Vital rates mechanism also predicts conditions under which positive abundance-occupancy association is weakened or even reversed; our results are consistent with these predictions. More generally, our findings support a cross-scale mechanism of macroecological abundance-occupancy relationship emerging from density-dependent dynamics at the population level.

scholarly journals Density dependence can obscure nonlethal effects of disturbance on life history of medium-sized cetaceans

PLoS ONE ◽  
2021 ◽  
Vol 16 (6) ◽  
pp. e0252677
Author(s):  
Vincent Hin ◽  
John Harwood ◽  
André M. de Roos
Keyword(s):  
Density Dependence ◽  
Prey Availability ◽  
Population Level ◽  
Vital Rates ◽  
Negative Effects ◽  
Pilot Whale ◽  
Individual Health ◽  
Individual Health Status ◽  
History Of ◽  
Nonlethal Effects

Nonlethal disturbance of animals can cause behavioral and physiological changes that affect individual health status and vital rates, with potential consequences at the population level. Predicting these population effects remains a major challenge in ecology and conservation. Monitoring fitness-related traits may improve detection of upcoming population changes, but the extent to which individual traits are reliable indicators of disturbance exposure is not well understood, especially for populations regulated by density dependence. Here we study how density dependence affects a population’s response to disturbance and modifies the disturbance effects on individual health and vital rates. We extend an energy budget model for a medium-sized cetacean (the long-finned pilot whale Globicephala melas) to an individual-based population model in which whales feed on a self-replenishing prey base and disturbance leads to cessation of feeding. In this coupled predator-prey system, the whale population is regulated through prey depletion and the onset of yearly repeating disturbances on the whale population at carrying capacity decreased population density and increased prey availability due to reduced top-down control. In populations faced with multiple days of continuous disturbance each year, female whales that were lactating their first calf experienced increased mortality due to depletion of energy stores. However, increased prey availability led to compensatory effects and resulted in a subsequent improvement of mean female body condition, mean age at first reproduction and higher age-specific reproductive output. These results indicate that prey-mediated density dependence can mask negative effects of disturbance on fitness-related traits and vital rates, a result with implications for the monitoring and management of marine mammal populations.

scholarly journals Perturbation Analysis of Population Growth Rates in Taiwan

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Shun-Chieh Hsieh
Keyword(s):  
Perturbation Analysis ◽  
Census Data ◽  
Population Management ◽  
Management Policy ◽  
Demographic Parameters ◽  
Relative Importance ◽  
Vital Rates ◽  
Management Effectiveness ◽  
Substantial Impact ◽  
Population Growth Rates

The total fertility rate in Taiwan has fallen below 1.3 since 2003. The objective of the study is to use perturbation analysis with census data from 1992 to 2017 to identify which demographic parameters are most important to target for population management. The research shows that the fertility of older ages plays an important role for declining population in Taiwan. From a practical viewpoint, population management policy having a substantial impact on the survival of prereproductive females and the fertility of order females is likely to produce the most dramatic change in population trends. Therefore, the perturbation analysis is useful in understanding the relative importance of vital rates to increase management effectiveness.

scholarly journals Nine Years After the Exxon Valdez Oil Spill: Effects on Marine Bird Populations in Prince William Sound, Alaska

The Condor ◽  
2000 ◽  
Vol 102 (4) ◽  
pp. 723-737 ◽  
Author(s):  
David B. Irons ◽  
Steven J. Kendall ◽  
Wallace P. Erickson ◽  
Lyman L. McDonald ◽  
Brian K. Lance
Keyword(s):  
Oil Spill ◽  
Bird Species ◽  
Population Level ◽  
Prince William Sound ◽  
Negative Effects ◽  
Exxon Valdez ◽  
Marine Bird ◽  
Marine Birds ◽  
Exxon Valdez Oil Spill ◽  
Positive Effects

Abstract We compared post Exxon Valdez oil-spill densities of marine birds in Prince William Sound from 1989–1991, 1993, 1996, and 1998 to pre-spill densities from 1984–1985. Post-spill densities of several species of marine birds were lower than expected in the oiled area of Prince William Sound when compared to densities in the unoiled area. These negative effects continued through 1998 for five taxa: cormorants, goldeneyes, mergansers, Pigeon Guillemot (Cepphus columba), and murres. Black Oystercatchers (Haematopus bachmani) and Harlequin Ducks (Histrionicus histrionicus) exhibited negative effects in 1990 and 1991. Loons showed a weak negative effect in 1993. Black-legged Kittiwakes (Rissa tridactyla) showed relative decreases in 1989, 1996, and 1998 which may have been caused by shifts in foraging distribution rather than declines in populations. Glaucous-winged Gulls (Larus glaucescens) showed positive effects in most post-spill years. Murrelets and terns showed relative increases in 1993, 1996, and 1998. Generally, taxa that dive for their food were negatively affected, whereas taxa that feed at the surface were not. Effects for some taxa were dependent upon the spatial scale at which they were analyzed. Movements of birds and the mosaic pattern of oiling reduced our ability to detect oil-spill effects, therefore our results may be conservative. Several marine bird species were negatively affected at the population level and have not recovered to pre-spill levels nine years after the oil spill. The reason for lack of recovery may be related to persistent oil remaining in the environment and reduced forage fish abundance.

scholarly journals From global to local scale: where is the best for conservation purpose?

2020 ◽  
Vol 30 (1) ◽  
pp. 183-200
Author(s):  
Elena Sulis ◽  
Gianluigi Bacchetta ◽  
Donatella Cogoni ◽  
Giuseppe Fenu
Keyword(s):  
Population Dynamics ◽  
Local Level ◽  
Demographic Data ◽  
Conservation Status ◽  
Population Level ◽  
Local Scale ◽  
Local Analysis ◽  
Vital Rates ◽  
Spanish Populations ◽  
Local Trend

AbstractDemographic analysis of plant populations represents an essential conservation tool allowing to identify the population trends both at global and at the local level. In this study, the population dynamics of Helianthemum caput-felis (Cistaceae) was investigated at the local level by monitoring six populations distributed in Sardinia, Balearic Islands and Ibero-Levantine coast (Alicante). Demographic data for each population were analysed by performing Integral Projection Models (IPMs). Our results showed that, although the local trend of the main basic demographic functions was similar, vital rates and demographic dynamics varied among populations indicating high variability. In fact, asymptotic growth rate in Spanish populations widely varied both between years and populations (some populations growth, decline or strongly decline), while Sardinian populations showed greater equilibrium or a slight increase. Also, the typical pattern of a long-lived species was not supported by the results at the local scale. These results indicated that different populations of the same species can present extremely different population dynamics and support the belief that, for conservation needs, local studies are more informative than global ones: the conservation status of H. caput-felis could notably vary at a small spatial scale and, accordingly, the conservation efforts must be planned at the population level and supported by local analysis.

A Bird's-Eye View of Pollination: Biotic Interactions as Drivers of Adaptation and Community Change

2019 ◽  
Vol 50 (1) ◽  
pp. 477-502 ◽  
Author(s):  
Anton Pauw
Keyword(s):  
Community Composition ◽  
Bird Species ◽  
Biotic Interactions ◽  
Population Level ◽  
Community Change ◽  
Plant Evolution ◽  
Relative Fitness ◽  
Fitness Advantage ◽  
Bird Evolution ◽  
Composition I

Nectarivorous birds and bird-pollinated plants are linked by a network of interactions. Here I ask how these interactions influence evolution and community composition. I find near complete evidence for the effect of birds on plant evolution. Experiments show the process in action—birds select among floral phenotypes in a population—and comparative studies find the resulting pattern—bird-pollinated species have long-tubed, red flowers with large nectar volumes. Speciation is accomplished in one “magical” step when adaptation for bird pollination brings about divergent morphology and reproductive isolation. In contrast, evidence that plants drive bird evolution is fragmentary. Studies of selection on population-level variation are lacking, but the resulting pattern is clear—nectarivorous birds have evolved a remarkable number of times and often have long bills and brush-tipped or tubular tongues. At the level of the ecological guild, birds select among plant species via an effect on seed set and thus determine plant community composition. Plants simultaneously influence the relative fitness of bird species and thus determine the composition of the bird guild. Interaction partners may give one guild member a constant fitness advantage, resulting in competitive exclusion and community change, or may act as limiting resources that depress the fitness of frequent species, thus stabilizing community composition and allowing the coexistence of diversity within bird and plant guilds.

INCREASING THE EFFICIENCY OF REGULATING DEMOGRAPHIC PROCESSES IN THE REPUBLIC OF UZBEKISTAN

2020 ◽  
pp. 19-22
Keyword(s):  
Health Care ◽  
Population Growth ◽  
Economic Efficiency ◽  
Healthcare Costs ◽  
State Regulation ◽  
The State ◽  
Demographic Processes ◽  
The Republic ◽  
Population Demographic ◽  
Health Care Efficiency

The article considers economic and health care efficiency of population growth in the Republic of Uzbekistan and develops scientific proposals and recommendations for improving the state regulation of demographic processes. Keywords: population, demographic processes, economic efficiency, healthcare costs.

Density dependence in a recovering osprey population: demographic and behavioural processes

2008 ◽  
Vol 77 (5) ◽  
pp. 998-1007 ◽  
Author(s):  
V. Bretagnolle ◽  
F. Mougeot ◽  
J.-C. Thibault
Keyword(s):  
Density Dependence ◽  
Population Demographic

scholarly journals Effects of weather variation on waterfowl migration: lessons from a continental-scale generalizable avian movement and energetics model

2021 ◽  
Author(s):  
Kevin Aagaard ◽  
Eric Lonsdorf ◽  
Wayne Thogmartin
Keyword(s):  
Bird Species ◽  
Model Performance ◽  
Population Level ◽  
Weather Data ◽  
Breeding Period ◽  
Land Use Land Cover ◽  
Continental Scale ◽  
Weather Variation ◽  
Daily Weather Data ◽  
Average Proportion

We developed a nonbreeding period continental-scale energetics-based model of daily waterfowl movement to predict year-specific migration and overwinter occurrence. The model approximates energy-expensive movements and energy-gaining stopovers as functions of metabolism and weather, in terms of temperature and frozen precipitation (i.e., snow). The model is a Markov process operating at the population level and is parameterized through a review of literature. We examined model performance against 62 years of non-breeding period daily weather data. The average proportion of available habitat decreased as weather severity increased, with mortality decreasing as the proportion of available habitat increased. The most commonly used nodes during the course of the nonbreeding period were generally consistent across years, with the most inter-annual variation present in the overwintering area. Our model revealed that the distribution of birds on the landscape changed more dramatically when the variation in daily available habitat was greater. The main routes for avian migration in North America were predicted by our simulations: the Eastern, Central, and Western flyways. Our model predicted an average of 77.4% survivorship for the nonbreeding period across all years (range = 76.4 – 78.4%), with lowest survivorship during the fall, intermediate survivorship in the winter, and greatest survivorship in the spring. We provide the parameters necessary for exploration within and among other taxa to leverage the generalizability of this migration model to a broader expanse of bird species, and across a range of climate change and land use/land cover change scenarios.

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