Population Dynamics Across Geographical Ranges: Time-Series Analyses of Three Small Game Species

Williams, Christopher K.; Ives, Anthony R.; Applegate, Roger D.

doi:10.1890/03-0038

Cited by 166 publications

(192 citation statements)

References 53 publications

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“…In particular, populations linked to non-breeding habitat loss are primarily high-abundance populations located in the centre of the breeding range, whereas populations linked to non-breeding climate are primarily low-abundance populations on the periphery of the range. If high-abundance central populations occupy the most favourable habitat and operate close to their carrying capacity [9], the abundance of these populations is expected to be sensitive to habitat availability [40]. In contrast, lowabundance populations at the periphery of the range may occupy less favourable habitats, making them more susceptible to density-independent factors such as climatic conditions.…”

Section: Discussionmentioning

confidence: 99%

Quantifying drivers of population dynamics for a migratory bird throughout the annual cycle

2016

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Worldwide, migratory species are undergoing rapid declines but understanding the factors driving these declines is hindered by missing information about migratory connectivity and the lack of data to quantify environmental processes across the annual cycle. Here, we combined range-wide information about migratory connectivity with global remote-sensing data to quantify the relative importance of breeding and non-breeding environmental processes to persistent long-term population declines of a migratory songbird, the wood thrush (Hylocichla mustelina). Consistent with theoretical predictions about population limitation of migratory birds, our results suggest that habitat loss and climate have contributed to the observed declines in wood thrush breeding abundance, yet the relative importance of breeding versus non-breeding factors is population-specific. For example, high-abundance core breeding populations appear to be more limited by habitat loss, whereas low-abundance, peripheral populations appear to be limited by climate-driven seasonal interactions. Further, our analysis indicates that the relative impact of breeding habitat loss is at least three to six times greater than the impact of equivalent nonbreeding habitat loss and therefore the steepest regional declines have likely been driven by the loss of breeding habitat. These results underscore the need for population-specific conservation strategies implemented throughout the annual cycle to reverse long-term declines.

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Section: Discussionmentioning

confidence: 99%

Quantifying drivers of population dynamics for a migratory bird throughout the annual cycle

2016

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“…Thus, to identify the conservation actions that will best improve sage-grouse population growth rates across their range, spatially replicated long-term (e.g., >10 yr) demographic studies will be needed, in conjunction with the larger repertoire of lek count monitoring, to elucidate the sources of regional differences in population dynamics (Williams et al 2003). Our approach to demographic modeling serves as a novel guide for research and can be applied to other species of conservation concern to better understand how to reverse declining population trends.…”

Section: Sy Hsmentioning

confidence: 99%

Evaluating vital rate contributions to greater sage‐grouse population dynamics to inform conservation

et al. 2016

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Abstract. Species conservation efforts often use short-term studies that fail to identify the vital rates that contribute most to population growth. Although the greater sage-grouse (Centrocercus urophasianus; sage-grouse) is a candidate for protection under the U.S. Endangered Species Act, and is sometimes referred to as an umbrella species in the sagebrush (Artemisia spp.) biome of western North America, the failure of proposed management strategies to focus on key vital rates that may contribute most to achieving population stability remains problematic for sustainable conservation. To address this dilemma, we performed both prospective and retrospective perturbation analyses of a life cycle model based on a 12-yr study that encompassed nearly all sage-grouse vital rates. To validate our population models, we compared estimates of annual finite population growth rates (λ) from our female-based life cycle models to those attained from male-based lek counts. Post-fledging (i.e., after second year, second year, and juvenile) female survival parameters contributed most to past variation in λ during our study and had the greatest potential to change λ in the future, indicating these vital rates as important determinants of sage-grouse population dynamics. In addition, annual estimates of λ from female-based life cycle models and malebased lek data were similar, providing the most rigorous evidence to date that lek counts of males can serve as a valid index of sage-grouse population change. Our comparison of fixed and mixed statistical models for evaluating temporal variation in nest survival and initiation suggest that conservation planners use caution when evaluating short-term nesting studies and using associated fixed-effect results to develop conservation objectives. In addition, our findings indicated that greater attention should be paid to those factors affecting sage-grouse post-fledging females. Our approach demonstrates the need for more long-term studies of species vital rates across the life cycle. Such studies should address the decoupling of sampling variation from underlying process (co)variation in vital rates, identification of how such variation drives population dynamics, and how decision makers can use this information to re-direct conservation efforts to address the most limiting points in the life cycle for a given population.

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“…Hassell 1986;Hassell et al 1989;Wolda & Dennis 1993;Shenk et al 1998), as well as becoming increasingly technically complex (e.g. Bjornstad et al 1999;Williams et al 2003). In large part, the problems identified in this literature result because researchers attempt to infer whether or not density dependence is occurring using time-series data from unmanipulated populations.…”

Section: Introductionmentioning

confidence: 99%

Pathogens, density dependence and the coexistence of tropical trees

2006

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There is increasing interest in the role played by density-dependent mortality from natural enemies, particularly plant pathogens, in promoting the coexistence and diversity of tropical trees. Here, we review four issues in the analysis of pathogen-induced density dependence that have been overlooked or inadequately addressed. First, the methodology for detecting density dependence must be robust to potential biases. Observational studies, in particular, require a careful analysis to avoid biases generated by measurement error, and existing studies could be criticized on these grounds. Experimental studies manipulating plant density and pathogen incidence will often be preferable, or should be run in parallel. Second, the form of density dependence is not well understood and, in particular, there are no data indicating whether pathogens cause compensating or overcompensating density responses. Owing to this, we argue that the potential for pathogen-induced density dependence to generate diversity-enhancing outcomes, such as the Janzen-Connell effect, remains uncertain, as coexistence is far more probable if density dependence is overcompensating. Third, there have been few studies examining the relative importance of intra-or interspecific density dependence resulting from pathogens (or, more widely, natural enemies). This is essentially equivalent to asking to what extent pathogens are host-specific. If pathogens are generalists, then mortality rates will respond to overall plant density, irrespective of plant species identity. This will weaken the intraspecific density dependence and reduce the diversity-promoting effects of pathogens. Finally, we highlight the need for studies that integrate observations and experiments on pathogens and density dependence into the whole life cycle of trees, because as yet it is not possible to be certain of the degree to which pathogens contribute to observed dynamics.

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Population Dynamics Across Geographical Ranges: Time-Series Analyses of Three Small Game Species

Cited by 166 publications

References 53 publications

Quantifying drivers of population dynamics for a migratory bird throughout the annual cycle

Quantifying drivers of population dynamics for a migratory bird throughout the annual cycle

Evaluating vital rate contributions to greater sage‐grouse population dynamics to inform conservation

Pathogens, density dependence and the coexistence of tropical trees

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