Environmental Stochasticity and Extinction Risk in a Population of a Small Songbird, the Great Tit

1998 ◽  
Vol 151 (5) ◽  
pp. 441-450 ◽  
Author(s):  
Bernt‐Erik Sæther ◽  
Steinar Engen ◽  
Aminul Islam ◽  
Robin McCleery ◽  
Christopher Perrins
Keyword(s):  
Extinction Risk ◽  
Great Tit ◽  
Environmental Stochasticity

Environmental Stochasticity and Extinction Risk in a Population of a Small Songbird, the Great Tit

1998 ◽  
Vol 151 (5) ◽  
pp. 441
Author(s):  
Saether ◽  
Engen ◽  
Islam ◽  
McCleery ◽  
Perrins
Keyword(s):  
Extinction Risk ◽  
Great Tit ◽  
Environmental Stochasticity

scholarly journals Harvesting can stabilize population fluctuations and buffer the impacts of climate change

2021 ◽  
Author(s):  
Bart Peeters ◽  
Vidar GrØtan ◽  
Marlène Gamelon ◽  
Vebjørn Veiberg ◽  
Aline Magdalena Lee ◽  
...  
Keyword(s):  
Life Histories ◽  
Resource Competition ◽  
Extinction Risk ◽  
Population Models ◽  
Environmental Stochasticity ◽  
Environmental Drivers ◽  
Population Fluctuations ◽  
Vital Rates ◽  
Density Dependent ◽  
Environmental Perturbations

Harvesting can magnify the destabilizing effects of environmental perturbations on population dynamics and, thereby, increase extinction risk. However, population-dynamic theory predicts that impacts of harvesting depend on the type and strength of density-dependent regulation. Here, we used population models for a range of life histories and an empirical reindeer case study to show that harvesting can actually buffer populations against environmental perturbations. This occurs because of density-dependent environmental stochasticity, where negative environmental impacts on vital rates are amplified at high population density due to intra-specific resource competition. Simulations from our population models show that even low levels of proportional harvesting may prevent overabundance, thereby dampening population fluctuations and reducing the risk of population collapse and quasi-extinction induced by environmental perturbations. Thus, depending on the species’ life history and the strength of density-dependent environmental drivers, harvesting can improve population resistance to increased climate variability and extreme weather expected under global warming.

scholarly journals The Last Two Remaining Populations of the Critically Endangered Estuarine Pipefish Are Inbred and Not Genetically Distinct

2022 ◽  
Vol 8 ◽  
Author(s):  
Sven-Erick Weiss ◽  
Arsalan Emami-Khoyi ◽  
Horst Kaiser ◽  
Paul D. Cowley ◽  
Nicola C. James ◽  
...  
Keyword(s):  
Genetic Diversity ◽  
Extinction Risk ◽  
Significant Risk ◽  
Small Population ◽  
Environmental Stochasticity ◽  
Critically Endangered ◽  
Conservation Strategy ◽  
Genome Wide Data ◽  
Significant Genetic Structure ◽  
Population Sizes

The critically endangered estuarine pipefish, Syngnathus watermeyeri, is one of Africa’s rarest fish species and currently faces a significant risk of extinction. A combination of anthropogenic and natural factors threaten submerged macrophyte beds in the two South African estuaries (Bushmans and Kariega) in which the species’ only two known remaining populations reside. Here, we genotyped 34 pipefish from both populations using genome-wide data to determine whether the two estuaries harbour distinct genetic diversity, such that translocating individuals between them might improve the genetic health of both. Our results show that both populations are highly inbred, and no statistically significant genetic structure was found between them. Moreover, individuals both within and between estuaries were very closely related to each other. These results indicate that the remaining populations of the estuarine pipefish suffer from the adverse genetic effects of small population sizes. Even though recent surveys have estimated population sizes in the order of thousands of individuals, these may fluctuate considerably. Although the translocation of genetically similar individuals between habitats will not increase local genetic diversity, the creation of additional populations across the species’ historical range may be a suitable conservation strategy to prevent further loss of genetic diversity, and to minimise the overall extinction risk posed by environmental stochasticity.

scholarly journals Interactions between demography, genetics, and landscape connectivity increase extinction probability for a small population of large carnivores in a major metropolitan area

2016 ◽  
Vol 283 (1837) ◽  
pp. 20160957 ◽  
Author(s):  
John F. Benson ◽  
Peter J. Mahoney ◽  
Jeff A. Sikich ◽  
Laurel E. K. Serieys ◽  
John P. Pollinger ◽  
...  
Keyword(s):  
Los Angeles ◽  
Inbreeding Depression ◽  
Landscape Connectivity ◽  
Extinction Risk ◽  
Empirical Support ◽  
Small Population ◽  
Environmental Stochasticity ◽  
Extinction Probability ◽  
Isolated Populations ◽  
Extinction Vortex

The extinction vortex is a theoretical model describing the process by which extinction risk is elevated in small, isolated populations owing to interactions between environmental, demographic, and genetic factors. However, empirical demonstrations of these interactions have been elusive. We modelled the dynamics of a small mountain lion population isolated by anthropogenic barriers in greater Los Angeles, California, to evaluate the influence of demographic, genetic, and landscape factors on extinction probability. The population exhibited strong survival and reproduction, and the model predicted stable median population growth and a 15% probability of extinction over 50 years in the absence of inbreeding depression. However, our model also predicted the population will lose 40–57% of its heterozygosity in 50 years. When we reduced demographic parameters proportional to reductions documented in another wild population of mountain lions that experienced inbreeding depression, extinction probability rose to 99.7%. Simulating greater landscape connectivity by increasing immigration to greater than or equal to one migrant per generation appears sufficient to largely maintain genetic diversity and reduce extinction probability. We provide empirical support for the central tenet of the extinction vortex as interactions between genetics and demography greatly increased extinction probability relative to the risk from demographic and environmental stochasticity alone. Our modelling approach realistically integrates demographic and genetic data to provide a comprehensive assessment of factors threatening small populations.

scholarly journals Evidence and implications of higher-order scaling in the environmental variation of animal population growth

2015 ◽  
Vol 112 (9) ◽  
pp. 2782-2787 ◽  
Author(s):  
Jake M. Ferguson ◽  
José M. Ponciano
Keyword(s):  
Population Dynamics ◽  
Density Dependence ◽  
Extinction Risk ◽  
Environmental Variation ◽  
Higher Order ◽  
Environmental Stochasticity ◽  
Population Variance ◽  
Environmental Variance ◽  
Animal Populations ◽  
Environmental Fluctuations

Environmental stochasticity is an important concept in population dynamics, providing a quantitative model of the extrinsic fluctuations driving population abundances. It is typically formulated as a stochastic perturbation to the maximum reproductive rate, leading to a population variance that scales quadratically with abundance. However, environmental fluctuations may also drive changes in the strength of density dependence. Very few studies have examined the consequences of this alternative model formulation while even fewer have tested which model better describes fluctuations in animal populations. Here we use data from the Global Population Dynamics Database to determine the statistical support for this alternative environmental variance model in 165 animal populations and test whether these models can capture known population–environment interactions in two well-studied ungulates. Our results suggest that variation in the density dependence is common and leads to a higher-order scaling of the population variance. This scaling will often stabilize populations although dynamics may also be destabilized under certain conditions. We conclude that higher-order environmental variation is a potentially ubiquitous and consequential property of animal populations. Our results suggest that extinction risk estimates may often be overestimated when not properly taking into account how environmental fluctuations affect population parameters.

scholarly journals Floaters may buffer the extinction risk of small populations: an empirical assessment

2017 ◽  
Vol 284 (1853) ◽  
pp. 20170074 ◽  
Author(s):  
Hugo Robles ◽  
Carlos Ciudad
Keyword(s):  
Patch Size ◽  
Extinction Risk ◽  
Empirical Support ◽  
Poor Quality ◽  
Environmental Stochasticity ◽  
Small Populations ◽  
Stochastic Effects ◽  
Fragmented Habitats ◽  
Intrinsic Quality

The high extinction risk of small populations is commonly explained by reductions in fecundity and breeder survival associated with demographic and environmental stochasticity. However, ecological theory suggests that population extinctions may also arise from reductions in the number of floaters able to replace the lost breeders. This can be particularly plausible under harsh fragmentation scenarios, where species must survive as small populations subjected to severe effects of stochasticity. Using a woodpecker study in fragmented habitats (2004–2016), we provide here empirical support for the largely neglected hypothesis that floaters buffer population extirpation risks. After controlling for population size, patch size and the intrinsic quality of habitat, populations in patches with floaters had a lower extinction probability than populations in patches without floaters (0.013 versus 0.131). Floaters, which often replace the lost breeders, were less likely to occur in small and low-quality patches, showing that population extirpations may arise from unnoticed reductions in floater numbers in poor-quality habitats. We argue that adequate pools of the typically overlooked floaters may buffer extirpation risks by reducing the detrimental impacts of demographic and environmental stochasticity. However, unravelling the influence of floaters in buffering stochastic effects and promoting population stability require additional studies in an ample array of species and stochastic scenarios.

scholarly journals When rarity has costs: coexistence under positive frequency-dependence and environmental stochasticity

2017 ◽  
Author(s):  
Sebastian J. Schreiber ◽  
Masato Yamamichi ◽  
Sharon Y. Strauss
Keyword(s):  
Reproductive Success ◽  
Frequency Dependence ◽  
Resource Competition ◽  
Extinction Risk ◽  
Niche Overlap ◽  
Environmental Stochasticity ◽  
Environmental Fluctuations ◽  
Positive Frequency Dependence ◽  
Demographic Responses ◽  
Positive Frequency

AbstractStable coexistence relies on negative frequency-dependence, in which rarer species invading a patch benefit from a lack of conspecific competition experienced by residents. In nature, however, rarity can have costs, resulting in positive frequency-dependence (PFD) particularly when species are rare. Many processes can cause positive frequency-dependence, including a lack of mates, mutualist interactions, and reproductive interference from heterospecifics. When species become rare in the community, positive frequency-dependence creates vulnerability to extinction, if frequencies drop below certain thresholds. For example, environmental fluctuations can drive species to low frequencies where they are then vulnerable to PFD. Here, we analyze deterministic and stochastic mathematical models of two species interacting through both PFD and resource competition in a Chessonian framework. Reproductive success of individuals in these models is reduced by a product of two terms: the reduction in fecundity due to PFD, and the reduction in fecundity due to competition. Consistent with classical coexistence theory, the effect of competition on individual reproductive success exhibits negative frequency-dependence when individuals experience greater intraspecific competition than interspecific competition i.e., niche overlap is less than one. In the absence of environmental fluctuations, our analysis reveals that (1) a synergistic effect of PFD and niche overlap that hastens exclusion, (2) trade-offs between susceptibility to PFD and maximal fecundity can mediate coexistence, and (3) coexistence, when it occurs, requires that neither species is initially rare. Analysis of the stochastic model highlights that environmental fluctuations, unless perfectly correlated, coupled with PFD ultimately drive one species extinct. Over any given time frame, this extinction risk decreases with the correlation of the demographic responses of the two species to the environmental fluctuations, and increases with the temporal autocorrelation of these fluctuations. For species with overlapping generations, these trends in extinction risk persist despite the strength of the storage effect decreasing with correlated demographic responses and increasing with temporal autocorrelations. These results highlight how the presence of PFD may alter the outcomes predicted by modern coexistence mechanisms.

scholarly journals Predicting evolutionary rescue via evolving plasticity in stochastic environments

2016 ◽  
Vol 283 (1839) ◽  
pp. 20161690 ◽  
Author(s):  
Jaime Ashander ◽  
Luis-Miguel Chevin ◽  
Marissa L. Baskett
Keyword(s):  
Genetic Variation ◽  
Phenotypic Plasticity ◽  
Extinction Risk ◽  
Environmental Stochasticity ◽  
High Plasticity ◽  
Cryptic Genetic Variation ◽  
Stochastic Environments ◽  
Evolutionary Rescue ◽  
Stochastic Demography

Phenotypic plasticity and its evolution may help evolutionary rescue in a novel and stressful environment, especially if environmental novelty reveals cryptic genetic variation that enables the evolution of increased plasticity. However, the environmental stochasticity ubiquitous in natural systems may alter these predictions, because high plasticity may amplify phenotype–environment mismatches. Although previous studies have highlighted this potential detrimental effect of plasticity in stochastic environments, they have not investigated how it affects extinction risk in the context of evolutionary rescue and with evolving plasticity. We investigate this question here by integrating stochastic demography with quantitative genetic theory in a model with simultaneous change in the mean and predictability (temporal autocorrelation) of the environment. We develop an approximate prediction of long-term persistence under the new pattern of environmental fluctuations, and compare it with numerical simulations for short- and long-term extinction risk. We find that reduced predictability increases extinction risk and reduces persistence because it increases stochastic load during rescue. This understanding of how stochastic demography, phenotypic plasticity, and evolution interact when evolution acts on cryptic genetic variation revealed in a novel environment can inform expectations for invasions, extinctions, or the emergence of chemical resistance in pests.

scholarly journals Metapopulation extinction risk is increased by environmental stochasticity and assemblage complexity

2006 ◽  
Vol 274 (1606) ◽  
pp. 87-96 ◽  
Author(s):  
James C Bull ◽  
Nicola J Pickup ◽  
Brian Pickett ◽  
Michael P Hassell ◽  
Michael B Bonsall
Keyword(s):  
Extinction Risk ◽  
Spatial Scales ◽  
Single Species ◽  
Apparent Competition ◽  
Environmental Stochasticity ◽  
Recent Theory ◽  
Ecological Processes ◽  
Extrinsic Factors ◽  
Persistence Time ◽  
The Individual

Extinction risk is a key area of investigation for contemporary ecologists and conservation biologists. Practical conservation efforts for vulnerable species can be considerably enhanced by thoroughly understanding the ecological processes that interact to determine species persistence or extinction. Theory has highlighted the importance of both extrinsic environmental factors and intrinsic demographic processes. In laboratory microcosms, single-species single-habitat patch experimental designs have been widely used to validate the theoretical prediction that environmental heterogeneity can increase extinction risk. Here, we develop on this theme by testing the effects of fluctuating resource levels in experimental multispecies metapopulations. We compare a three-species host–parasitoid assemblage that exhibits apparent competition to the individual pairwise, host–parasitoid interactions. Existing theory is broadly supported for two-species assemblages: environmental stochasticity reduces trophic interaction persistence time, while metapopulation structure increases persistence time. However, with increasing assemblage complexity, the effects of trophic interactions mask environmental impacts and persistence time is further reduced, regardless of resource renewal regime. We relate our findings to recent theory, highlighting the importance of taking into account both intrinsic and extrinsic factors, over a range of spatial scales, in order to understand resource–consumer dynamics.

scholarly journals Harvesting can stabilize population fluctuations and buffer the impacts of extreme climatic events

2021 ◽  
Author(s):  
Bart Peeters ◽  
Vidar Grøtan ◽  
Marlène Gamelon ◽  
Vebjørn Veiberg ◽  
Aline Magdalena Lee ◽  
...  
Keyword(s):  
Resource Competition ◽  
Growth Models ◽  
Extinction Risk ◽  
Environmental Stochasticity ◽  
Environmental Drivers ◽  
Population Fluctuations ◽  
Vital Rates ◽  
Density Dependent ◽  
Environmental Perturbations

Harvesting can magnify the destabilizing effects of environmental perturbations on population dynamics and, thereby, increase extinction risk. However, population-dynamic theory predicts that impacts of harvesting depend on the type and strength of density-dependent regulation. Here, we used logistic population growth models and an empirical reindeer case study to show that low to moderate harvesting can actually buffer populations against environmental perturbations. This occurs because of density-dependent environmental stochasticity, where negative environmental impacts on vital rates are amplified at high population density due to intraspecific resource competition. Simulations from our population models show that even low levels of harvesting may prevent overabundance, thereby dampening population fluctuations and reducing the risk of population collapse and quasi-extinction following environmental perturbations. Thus, depending on the species’ life history and the strength of density-dependent environmental drivers, low to moderate harvesting can improve population resistance to increased climate variability and extreme weather expected under global warming.

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