Reproductive value, the stable stage distribution, and the sensitivity of the population growth rate to changes in vital rates

Temporal variation in vital rates (e.g., survival, reproduction) can decrease the long-term mean performance of a population. Species are therefore expected to evolve demographic strategies that counteract the negative effects of vital rate variation on the population growth rate. One key strategy, demographic buffering, is reflected in a low temporal variation in vital rates critical to population dynamics. However, comparative studies in plants have found little evidence for demographic buffering, and little is known about the prevalence of buffering in animal populations. Here, we used vital rate estimates from 31 natural populations of 29 animal species to assess the prevalence of demographic buffering. We modeled the degree of demographic buffering using a standard measure of correlation between the standard deviation of vital rates and the sensitivity of the population growth rate to changes in such vital rates across populations. We also accounted for the effects of life-history traits, i.e., age at first reproduction and spread of reproduction across the life cycle, on these correlation measures. We found no strong or consistent evidence of demographic buffering across the study populations. Instead, key vital rates could vary substantially depending on the specific environmental context populations experience. We suggest that it is time to look beyond concepts of demographic buffering when studying natural populations towards a stronger focus on the environmental context-dependence of vital-rate variation.

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Fire effects on the vital rates and stochastic population growth rate of the rare shrub Lindera subcoriacea Wofford

Plant Ecology ◽

10.1007/s11258-020-01092-3 ◽

2020 ◽

Author(s):

Wade A. Wall ◽

Andrew S. Walker ◽

Janet B. Gray ◽

Matthew G. Hohmann

Keyword(s):

Growth Rate ◽

Population Growth ◽

Population Growth Rate ◽

Fire Effects ◽

Vital Rates ◽

Stochastic Population Growth

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Fish predation and trapping for rusty crayfish (Orconectes rusticus) control: a whole-lake experiment

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/f05-229 ◽

2006 ◽

Vol 63 (2) ◽

pp. 383-393 ◽

Cited By ~ 65

Author(s):

Catherine L Hein ◽

Brian M Roth ◽

Anthony R Ives ◽

M Jake Vander Zanden

Keyword(s):

Growth Rate ◽

Population Growth ◽

Population Growth Rate ◽

Fish Predation ◽

Reproductive Value ◽

Orconectes Rusticus ◽

Long Term Effects ◽

Structured Population Model ◽

Rusty Crayfish ◽

Crayfish Population

Improved methods are needed for the prevention and control of invasive species. We investigated the potential to control a rusty crayfish (Orconectes rusticus) population in an isolated lake in northern Wisconsin by trapping adult crayfish and restricting fishing, thereby increasing fish populations and predation on small crayfish. Over a 3 year period, traps and predatory fishes removed substantial portions of the rusty crayfish population. We used an age-structured population model to determine which removal method had the largest effect on crayfish population growth rates. Because more crayfish were vulnerable to and removed by fish predation than by trapping, fish predation caused a larger decline in the population growth rate. However, trapping removed crayfish with the highest reproductive value and caused the largest decline in population growth rate per individual crayfish removed. Consideration of density-dependent responses to removal is necessary to predict long-term effects on rusty crayfish population dynamics. Nonetheless, our results suggest that the combination of trapping and fish predation can control established rusty crayfish populations and deserves further consideration for management.

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Warming, soil moisture, and loss of snow increase Bromus tectorum’s population growth rate

Elem Sci Anth ◽

10.12952/journal.elementa.000020 ◽

2014 ◽

Vol 2 ◽

Cited By ~ 11

Author(s):

Aldo Compagnoni ◽

Peter B. Adler

Keyword(s):

Growth Rate ◽

Population Growth ◽

Snow Cover ◽

Population Growth Rate ◽

Experimental Manipulation ◽

Direct Effects ◽

Vital Rates ◽

Positive Effects ◽

The North ◽

Increasing Temperature

Abstract Climate change threatens to exacerbate the impacts of invasive species. In temperate ecosystems, direct effects of warming may be compounded by dramatic reductions in winter snow cover. Cheatgrass (Bromus tectorum) is arguably the most destructive biological invader in basins of the North American Intermountain West, and warming could increase its performance through direct effects on demographic rates or through indirect effects mediated by loss of snow. We conducted a two-year experimental manipulation of temperature and snow pack to test whether 1) warming increases cheatgrass population growth rate and 2) reduced snow cover contributes to cheatgrass’ positive response to warming. We used infrared heaters operating continuously to create the warming treatment, but turned heaters on only during snowfalls for the snowmelt treatment. We monitored cheatgrass population growth rate and the vital rates that determine it: emergence, survival and fecundity. Growth rate increased in both warming and snowmelt treatments. The largest increases occurred in warming plots during the wettest year, indicating that the magnitude of response to warming depends on moisture availability. Warming increased both fecundity and survival, especially in the wet year, while snowmelt contributed to the positive effects of warming by increasing survival. Our results indicate that increasing temperature will exacerbate cheatgrass impacts, especially where warming causes large reductions in the depth and duration of snow cover.

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Effects of territorial status and life history on Sandhill Crane (Antigone canadensis) population dynamics in south-central Wisconsin, USA

Canadian Journal of Zoology ◽

10.1139/cjz-2018-0135 ◽

2019 ◽

Vol 97 (2) ◽

pp. 112-120 ◽

Cited By ~ 2

Author(s):

Michael E. Wheeler ◽

Jeb A. Barzen ◽

Shawn M. Crimmins ◽

Timothy R. Van Deelen

Keyword(s):

Growth Rate ◽

Population Growth ◽

Population Growth Rate ◽

Demographic Data ◽

Bird Species ◽

Adult Survival ◽

Vital Rates ◽

Management Actions ◽

South Central ◽

Sandhill Cranes

Population growth rate in long-lived bird species is often most sensitive to changes in adult survival. Sandhill Cranes (Antigone canadensis (Linnaeus, 1758)) have long life spans, small broods, and delayed first reproduction. Only territorial adult Sandhill Cranes participate in breeding, and territory acquisition reflects the interplay between the availability of suitable territories and the variation in mortality of adult birds occupying those territories. We estimated vital rates of a population at equilibrium using long-term resightings data (2000–2014; n = 451 marked individuals) in a multistate mark–resight model and used a stage-structured projection matrix to assess how strongly territorial adult survival affects population growth rate. Elasticity analysis indicated territorial birds surviving and retaining territories had a 2.58 times greater impact on population growth compared with the next most important transition rate (survival of nonterritorial adults remaining nonterritorial). Knowing how changes in vital rates of various stage classes will differentially impact population growth rate allows for targeted management actions including encouraging growth in recovering populations, assessing opportunity for recreational harvest, or maintaining populations at a desired level. This study also highlights the value of collecting demographic data for all population segments, from which one can derive reproductive output or growth rate.

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Estimating the effects of 17α-ethinylestradiol on stochastic population growth rate of fathead minnows: a population synthesis of empirically derived vital rates

Ecotoxicology ◽

10.1007/s10646-016-1688-9 ◽

2016 ◽

Vol 25 (7) ◽

pp. 1364-1375 ◽

Cited By ~ 6

Author(s):

Adam R. Schwindt ◽

Dana L. Winkelman

Keyword(s):

Growth Rate ◽

Population Growth ◽

Population Growth Rate ◽

Fathead Minnows ◽

Population Synthesis ◽

Vital Rates ◽

Stochastic Population Growth

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Drivers of large-scale spatial demographic variation in a perennial plant

10.1101/2020.02.29.969428 ◽

2020 ◽

Author(s):

Gesa Römer ◽

Ditte M. Christiansen ◽

Hendrik de Buhr ◽

Kristoffer Hylander ◽

Owen R. Jones ◽

...

Keyword(s):

Growth Rate ◽

Population Dynamics ◽

Environmental Factors ◽

Population Growth ◽

Spatial Variation ◽

Population Growth Rate ◽

Forest Understory ◽

Environmental Drivers ◽

Vital Rates ◽

The Impact

AbstractTo understand how the environment drives spatial variation in population dynamics, we need to assess the effects of a large number of potential drivers on the vital rates (survival, growth and reproduction), and explore these relationships over large geographical areas and long environmental gradients. In this study, we examined the effects of a broad variety of abiotic and biotic environmental factors, including intraspecific density, on the demography of the forest understory herb Actaea spicata between 2017 and 2019 at 40 sites across Sweden, including the northern range margin of its distribution. We assessed the effect of potential environmental drivers on vital rates using generalized linear mixed models (GLMMs), and then quantified the impact of each important driver on population growth rate (λ) using integral projection models (IPMs). Population dynamics of A. spicata were mostly driven by environmental factors affecting survival and growth, such as air humidity, soil depth and forest tree species composition, and thus those drivers jointly determined the realized niche of the species. Soil pH had a strong effect on the flowering probability, while the effect on population growth rate was relatively small. In addition to identifying specific drivers for A. spicata’s population dynamics, our study illustrates the impact that spatial variation in environmental conditions can have on λ. Assessing the effects of a broad range of potential drivers, as done in this study, is important not only to quantify the relative importance of different drivers for population dynamics but also to understand species distributions and abundance patterns.

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Spatiotemporal dynamics in vital rates of Humboldt’s flying squirrels and Townsend’s chipmunks in a late-successional forest

Journal of Mammalogy ◽

10.1093/jmammal/gyz204 ◽

2019 ◽

Vol 101 (1) ◽

pp. 187-198

Author(s):

Matt Weldy ◽

Clinton W Epps ◽

Damon B Lesmeister ◽

Tom Manning ◽

Eric D Forsman

Keyword(s):

Growth Rate ◽

Population Growth ◽

Pacific Northwest ◽

Population Growth Rate ◽

Habitat Associations ◽

Spatiotemporal Variability ◽

Life History Strategies ◽

Vital Rates ◽

Annual Survival ◽

Flying Squirrels

Abstract Knowledge of the spatiotemporal variability of abundance and vital rates is essential to the conservation of wildlife populations. In Pacific Northwest forests, previous small mammal research has focused on estimating abundance; few studies have focused on vital rates. We used robust design temporal symmetry models and live-trapping data collected 2011–2016 at nine sites to estimate apparent annual survival, population growth rate, and recruitment of Humboldt’s flying squirrels (Glaucomys oregonensis) and Townsend’s chipmunks (Neotamias townsendii) in a late-successional forest of the Cascade Mountains of Oregon, United States. We also estimated the proportional contribution of apparent annual survival and recruitment to population growth rate. Covariates previously associated with abundance were also associated with vital rates for Townsend’s chipmunks, but less so for Humboldt’s flying squirrels. Apparent annual survival was nearly constant (range = 0.47 to 0.51) among years and sites for Humboldt’s flying squirrels but was consistently lower and more variable among years for Townsend’s chipmunks (range = 0.13 to 0.31). Recruitment was variable among years for both species. Apparent annual survival generally contributed more than recruitment to the population growth rate of Humboldt’s flying squirrels. For Townsend’s chipmunks, recruitment consistently contributed more than apparent annual survival to population growth rate. These findings suggest that life history strategies differed for these co-occurring species. This study demonstrates substantial temporal variation in vital rates and some differences in abundance and vital rate habitat associations, suggesting that habitat suitability inferences based on short time series or variation in abundance could be misleading.

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Demographic analysis of the shortfin mako shark, Isurus oxyrinchus, in the Northwest Pacific using a two-sex stage-based matrix model

ICES Journal of Marine Science ◽

10.1093/icesjms/fsu056 ◽

2014 ◽

Vol 71 (7) ◽

pp. 1604-1618 ◽

Cited By ~ 12

Author(s):

Wen-Pei Tsai ◽

Chi-Lu Sun ◽

André E. Punt ◽

Kwang-Ming Liu

Keyword(s):

Growth Rate ◽

Population Growth ◽

Matrix Model ◽

Population Growth Rate ◽

Future Research ◽

Northwest Pacific ◽

Vital Rates ◽

Mako Shark ◽

Shortfin Mako ◽

The Impact

Most demographic models are single sex, and assume both sexes have the same vital rates. However, many species, including the shortfin mako shark, are sexually dimorphic in vital rates, which suggests the need for two-sex models. In this study, a two-sex stage-structured matrix model was constructed to estimate shortfin mako shark demography and population dynamics. Monte Carlo simulations were used to evaluate the impact of uncertainties on the estimate of population growth rate. The number of shortfin mako sharks is found to be dropping under current conditions, but will stabilize if size-limit management is implemented. The simulations indicated that population growth rate estimates are mainly influenced by the uncertainty related to survival rate and fecundity. The effects of uncertainty regarding the age at maturity and longevity were found to be relatively minor. Future research should focus on obtaining estimates of natural mortality and reproductive traits for this species to improve the accuracy of demographic estimates.

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