Life-History Variation Predicts the Effects of Demographic Stochasticity on Avian Population Dynamics

Sæther,; Engen, John R.; Möller, Sören; Weimerskirch,; Visser, Joost; Fiedler,; Matthysen, Erik; Lambrechts,; Badyaev,; Becker, Ulrik; Brommer,; Bukacinski,; Bukacinska,; Christensen, Henrik I.; Dickinson,; Feu, du; Gehlbach,; Heg,; Hötker,; Merilä,; Nielsen,; Rendell,; Robertson, Daniel; Thomson, M. A.; Torok,; Hecke, Van

doi:10.2307/3473237

Cited by 49 publications

(107 citation statements)

References 30 publications

(46 reference statements)

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“…This might hold particularly for oystercatchers, which seem to have a low environmental variance of population growth compared with other avian species [57]. More generally, the relative importance of environmental and demographic stochasticity on dynamics is expected to vary between species as a function of general life-history properties [57]. Demographic noise is not necessarily completely white, as individual heterogeneity can cause demographic rates to be correlated in time [58].…”

Section: Discussionmentioning

confidence: 99%

“…At low population size, demographic noise owing to chance effects becomes increasingly important and can even outweigh the effects of environmental noise on population fluctuations [12]. This might hold particularly for oystercatchers, which seem to have a low environmental variance of population growth compared with other avian species [57]. More generally, the relative importance of environmental and demographic stochasticity on dynamics is expected to vary between species as a function of general life-history properties [57].…”

Section: Discussionmentioning

confidence: 99%

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Poor environmental tracking can make extinction risk insensitive to the colour of environmental noise

et al. 2011

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The relative importance of environmental colour for extinction risk compared with other aspects of environmental noise (mean and interannual variability) is poorly understood. Such knowledge is currently relevant, as climate change can cause the mean, variability and temporal autocorrelation of environmental variables to change. Here, we predict that the extinction risk of a shorebird population increases with the colour of a key environmental variable: winter temperature. However, the effect is weak compared with the impact of changes in the mean and interannual variability of temperature. Extinction risk was largely insensitive to noise colour, because demographic rates are poor in tracking the colour of the environment. We show that three mechanisms-which probably act in many species-can cause poor environmental tracking: (i) demographic rates that depend nonlinearly on environmental variables filter the noise colour, (ii) demographic rates typically depend on several environmental signals that do not change colour synchronously, and (iii) demographic stochasticity whitens the colour of demographic rates at low population size. We argue that the common practice of assuming perfect environmental tracking may result in overemphasizing the importance of noise colour for extinction risk. Consequently, ignoring environmental autocorrelation in population viability analysis could be less problematic than generally thought.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Poor environmental tracking can make extinction risk insensitive to the colour of environmental noise

et al. 2011

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“…Populations undergoing recovery often display wide fluctuations in abundance and population growth rates. These fluctuations could be the result of demographic stochasticity, particularly early on in the recovery process, inter-and intra-specific interactions, or environmental variation (Saether et al 2004, Shelton & Mangel 2011. Regardless of the cause, interannual variability in abundance makes it difficult to determine population trends to quantify the rate of recovery and to make predictions.…”

Section: Introductionmentioning

confidence: 99%

Trends and variability in demographic indicators of a recovering population of green sea turtles Chelonia mydas

Piacenza¹,

Balazs²,

Hargrove³

et al. 2016

Endang. Species. Res.

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Multiple populations of green sea turtles Chelonia mydas show signs of population recovery. In Hawaii (USA), green turtles have increased 5.4% yr −1 since 1973, but fluctuations in census counts of nesting females make recovery diagnosis difficult. Evaluating demographic rates for temporal change and in relation to population density, and indicators of recruitment to sea turtle nesting populations, will ultimately improve population assessments. Using linear mixed and multistate open robust design models, we estimated the demographic indicators (DIs) of size at maturity, nester carapace length, breeding probability, and adult female survival using 3677 tagged nesting green turtles from 1973 to 2010 in Hawaii. To evaluate changes with density, we correlated the DIs with nesting female counts. We estimated size at maturity, assuming that newly tagged nesters are new recruits and that first-time nesters have statistically significant smaller carapace length than recaptures, but the difference in size was only ~0.5 cm. Mean nester carapace length (range: 89.21−91.69 cm) and breeding probability (range: 0.0766−0.444 yr −1 ) showed directional changes over time, suggesting shifts in age structure that could be due to recruitment. The top-ranked model predicted constant female survival over time (S = 0.929 yr −1 , 95% CI: 0.924−0.933, model likelihood = 1.00). Counter to our hypothesis based on density-dependence, breeding probability increases with increasing nester abundance. This work contributes to a growing set of studies evaluating sea turtle demography for temporal variability and is the first for Hawaiian green turtles. Our study demonstrates that some easily monitored demographic variables may serve as indicators of population change.

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“…In birds-arguably the taxonomic group with the most information on the topic-the amount of demographic stochasticity resulting from individual differences in reproductive success appears to depend on a species' position in the slow-fast continuum of life-histories (Saether et al 2004): Species on the slow end of the spectrum have large generation times and small clutch sizes, and they exhibit relatively little demographic variability. Species on the fast end of the spectrum have short generation times and large clutch sizes, and they exhibit larger variability.…”

Section: Discussionmentioning

confidence: 99%

“…By contrast, if whole clutches can be destroyed by a predator or encounter unfavorable environmental conditions, survival is positively correlated within families and variation increases with increasing average clutch size and decreasing survival probability (see File S3). Some marine organisms like oysters and cod, for example, have extremely high variance in reproductive success, apparently because parents that by chance match their reproductive activity with favorable oceanic conditions leave a large number of surviving offspring, whereas others might not leave any (Hedgecock 1994;Hedgecock and Pudovkin 2011).In birds-arguably the taxonomic group with the most information on the topic-the amount of demographic stochasticity resulting from individual differences in reproductive success appears to depend on a species' position in the slow-fast continuum of life-histories (Saether et al 2004): Species on the slow end of the spectrum have large generation times and small clutch sizes, and they exhibit relatively little demographic variability. Species on the fast end of the spectrum have short generation times and large clutch sizes, and they exhibit larger variability.…”

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confidence: 99%

Population Genetic Consequences of the Allee Effect and the Role of Offspring-Number Variation

2014

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A strong demographic Allee effect in which the expected population growth rate is negative below a certain critical population size can cause high extinction probabilities in small introduced populations. But many species are repeatedly introduced to the same location and eventually one population may overcome the Allee effect by chance. With the help of stochastic models, we investigate how much genetic diversity such successful populations harbor on average and how this depends on offspring-number variation, an important source of stochastic variability in population size. We find that with increasing variability, the Allee effect increasingly promotes genetic diversity in successful populations. Successful Allee-effect populations with highly variable population dynamics escape rapidly from the region of small population sizes and do not linger around the critical population size. Therefore, they are exposed to relatively little genetic drift. It is also conceivable, however, that an Allee effect itself leads to an increase in offspringnumber variation. In this case, successful populations with an Allee effect can exhibit less genetic diversity despite growing faster at small population sizes. Unlike in many classical population genetics models, the role of offspring-number variation for the population genetic consequences of the Allee effect cannot be accounted for by an effective-population-size correction. Thus, our results highlight the importance of detailed biological knowledge, in this case on the probability distribution of family sizes, when predicting the evolutionary potential of newly founded populations or when using genetic data to reconstruct their demographic history.T HE demographic Allee effect, a reduction in per-capita population growth rate at small population sizes (Stephens et al. 1999), is of key importance for the fate of both endangered and newly introduced populations and has inspired an immense amount of empirical and theoretical research in ecology (Courchamp et al. 2008). By shaping the population dynamics of small populations, the Allee effect should also strongly influence the strength of genetic drift they are exposed to and hence their levels of genetic diversity and evolutionary potential. In contrast to the well-established ecological research on the Allee effect, however, research on its population genetic and evolutionary consequences is only just beginning (Kramer and Sarnelle 2008;Hallatschek and Nelson 2008;Roques et al. 2012). In this study, we focus on the case in which the average population growth rate is negative below a certain critical population size. This phenomenon is called a strong demographic Allee effect (Taylor and Hastings 2005). Our goal is to quantify levels of genetic diversity in introduced populations that have successfully overcome such a strong demographic Allee effect. Of course, the population genetic consequences of the Allee effect could depend on a variety of factors, some of which we investigated in a companion article ). Here we f...

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Life-History Variation Predicts the Effects of Demographic Stochasticity on Avian Population Dynamics

Cited by 49 publications

References 30 publications

Poor environmental tracking can make extinction risk insensitive to the colour of environmental noise

Poor environmental tracking can make extinction risk insensitive to the colour of environmental noise

Trends and variability in demographic indicators of a recovering population of green sea turtles Chelonia mydas

Population Genetic Consequences of the Allee Effect and the Role of Offspring-Number Variation

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