scholarly journals Demographic compensation does not rescue populations at a trailing range edge

2017 ◽  
Author(s):  
Seema Nayan Sheth ◽  
Amy Lauren Angert
Keyword(s):  
Climate Change ◽  
Life History ◽  
Population Growth ◽  
Growth Rates ◽  
Time Lags ◽  
Vital Rates ◽  
Low Latitude ◽  
Species Ranges ◽  
Population Growth Rates ◽  
Range Edge

ABSTRACTAs climate change shifts species' climatic envelopes across the landscape, equilibrium between geographic ranges and niches is likely diminishing due to time lags in demography and dispersal. If a species' range and niche are out of equilibrium, then population performance should decrease from cool, “leading” range edges, where populations are expanding into recently ameliorated habitats, to warm, “trailing” range edges, where populations are contracting from newly unsuitable areas. Population contraction signals that compensatory changes in vital rates are insufficient to buffer population growth from deteriorating environments. Life history theory predicts tradeoffs between fast development, high reproduction, and short longevity at low latitudes and slow development, less frequent but multiple bouts of reproduction, and long lifespan at high latitudes. If demographic compensation is driven by life history evolution, compensatory negative correlations in vital rates may be associated with this fast-slow continuum. An outstanding question is whether range limits and range contractions reflect inadequate compensatory life history shifts along environmental gradients, causing population growth rates to fall below replacement levels at range edges. We surveyed demography of 32 populations of the scarlet monkeyflower (Erythranthe cardinalis) spanning 11° latitude in western North America and used integral projection models to infer population dynamics and assess demographic compensation. Population growth rates decreased from north to south, consistent with leading-trailing dynamics. Southern populations are declining due to reduced survival, growth, and recruitment, despite compensatory increases in reproduction and faster life history characteristics, suggesting that demographic compensation will not rescue populations at the trailing range edge.SIGNIFICANCE STATEMENTWhile climate change is causing poleward shifts in many species' geographic distributions, some species' ranges have remained stable, particularly at low-latitude limits. One explanation for why some species' ranges have not shifted is demographic compensation, whereby declines in some demographic processes are offset by increases in others, potentially buffering populations from extinction. However, we have limited understanding of whether demographic compensation can prevent collapse of populations facing climate change. We examined the demography of natural populations of a perennial herb spanning a broad latitudinal gradient. Despite increases in reproduction, low-latitude populations declined due to diminished survival, growth, and recruitment. Thus, demographic compensation may not be sufficient to rescue low-latitude, warm-edge populations from extinction.

Life history and environmental influences on population dynamics in sockeye salmon

2014 ◽  
Vol 71 (8) ◽  
pp. 1198-1208 ◽  
Author(s):  
Douglas C. Braun ◽  
John D. Reynolds
Keyword(s):  
Population Dynamics ◽  
Life History ◽  
Population Growth ◽  
Growth Rates ◽  
Environmental Conditions ◽  
Sockeye Salmon ◽  
Life History Traits ◽  
Relative Importance ◽  
Population Growth Rates ◽  
Habitat Variables

Understanding linkages among life history traits, the environment, and population dynamics is a central goal in ecology. We compared 15 populations of sockeye salmon (Oncorhynchus nerka) to test general hypotheses for the relative importance of life history traits and environmental conditions in explaining variation in population dynamics. We used life history traits and habitat variables as covariates in mixed-effect Ricker models to evaluate the support for correlates of maximum population growth rates, density dependence, and variability in dynamics among populations. We found dramatic differences in the dynamics of populations that spawn in a small geographical area. These differences among populations were related to variation in habitats but not life history traits. Populations that spawned in deep water had higher and less variable population growth rates, and populations inhabiting streams with larger gravels experienced stronger negative density dependence. These results demonstrate, in these populations, the relative importance of environmental conditions and life histories in explaining population dynamics, which is rarely possible for multiple populations of the same species. Furthermore, they suggest that local habitat variables are important for the assessment of population status, especially when multiple populations with different dynamics are managed as aggregates.

Characterization of elasticity patterns of North American freshwater fishes

2006 ◽  
Vol 63 (9) ◽  
pp. 2050-2066 ◽  
Author(s):  
Luis A Vélez-Espino ◽  
Michael G Fox ◽  
Robert L McLaughlin
Keyword(s):  
Population Growth ◽  
North American ◽  
Growth Rates ◽  
Freshwater Fishes ◽  
Adult Survival ◽  
Juvenile Survival ◽  
Vital Rates ◽  
Population Growth Rates ◽  
North American Freshwater ◽  
Trade Offs

We applied elasticity analysis to 88 North American freshwater fishes to assess the relative impacts of changes in the vital rates on asymptotic population growth. Variance in vital rates was summarized for four distinct functional groups: (i) species with population growth rates strongly sensitive to perturbations in adult survival; (ii) species with population growth rates sensitive to perturbations in overall survival; (iii) species with population growth rates most sensitive to perturbations in juvenile survival; and (iv) species with population growth rates sensitive to perturbations in juvenile survival and fecundity. The results of the present study also showed that (a) elasticity patterns cannot be inferred in a straightforward manner from trade-offs between life-history traits, (b) the sensitivity of a population's growth rate to changes in adult survival and fecundity can be predicted empirically from life span and age at maturity, respectively, (c) elasticities are highly conserved among genera within the same taxonomic family, and (d) there are key divergences between elasticity patterns of freshwater fish and other vertebrate taxa.

Demography of Sooty Fox Sparrows (Passerella unalaschcensis) following a shift from a migratory to resident life history

2018 ◽  
Vol 96 (5) ◽  
pp. 436-440 ◽  
Author(s):  
Hannah Visty ◽  
Scott Wilson ◽  
Ryan Germain ◽  
Jessica Krippel ◽  
Peter Arcese
Keyword(s):  
British Columbia ◽  
Life History ◽  
Population Growth ◽  
Vital Rates ◽  
Population Growth Rates ◽  
Probability Of Survival ◽  
Georgia Basin ◽  
Passerella Iliaca ◽  
Resident Populations ◽  
Established Population

Identifying causes and consequences of variation in species life history has the potential to improve predictions about how climate and land-use change may affect the demography and distribution of species in future. Sooty Fox Sparrows (Passerella unalaschcensis (J.F. Gmelin, 1789); or commonly grouped within the Fox Sparrow, Passerella iliaca (Merrem, 1786)) were migrants that rarely bred in the Georgia Basin of British Columbia prior to ∼1950 but have since established resident populations. Data on 270 color-banded birds and 54 nests on Mandarte Island, British Columbia, allowed us to estimate demographic vital rates and population growth in one recently established population. Annual fecundity (F), estimated as the product of the number of broods initiated (1.5 ± 0.01; mean ± SD), clutch size (2.82 ± 0.44), and probability of survival to fledging (0.68 ± 0.02), exceeded values reported for migrants, supporting the hypothesis that residents invest more in reproduction, on average, than migrants within species. Estimating juvenile and adult overwinter survival (Sj = 0.32 ± 0.06 and Sa = 0.69 ± 0.05) next allowed us to simulate an expected distribution of population growth rates as λexp = Sa + (Sj × F), given parameter error. Our estimate of λexp (1.61 ± 0.57) implies expeditious population growth, consistent with the species’ recent colonization of the region.

scholarly journals Swimming against the tide: resilience of a riverine turtle to recurrent extreme environmental events

2014 ◽  
Vol 10 (3) ◽  
pp. 20130782 ◽  
Author(s):  
Abigail M. Jergenson ◽  
David A. W. Miller ◽  
Lorin A. Neuman-Lee ◽  
Daniel A. Warner ◽  
Fredric J. Janzen
Keyword(s):  
Climate Change ◽  
Population Growth ◽  
Growth Rates ◽  
Chrysemys Picta ◽  
Population Parameters ◽  
Flood Events ◽  
Population Growth Rates ◽  
Painted Turtles ◽  
Annual Population ◽  
Environmental Events

Extreme environmental events (EEEs) are likely to exert deleterious effects on populations. From 1996 to 2012 we studied the nesting dynamics of a riverine population of painted turtles ( Chrysemys picta ) that experienced seven years with significantly definable spring floods. We used capture–mark–recapture methods to estimate the relationships between more than 5 m and more than 6 m flood events and population parameters. Contrary to expectations, flooding was not associated with annual differences in survival, recruitment or annual population growth rates of the adult female segment of the population. These findings suggest that female C. picta exhibit resiliency to key EEE, which are expected to increase in frequency under climate change.

scholarly journals The evolution of growth rates on an expanding range edge

2009 ◽  
Vol 5 (6) ◽  
pp. 802-804 ◽  
Author(s):  
Ben L. Phillips
Keyword(s):  
Life History ◽  
Population Growth ◽  
Growth Rates ◽  
Life History Theory ◽  
Common Garden ◽  
Individual Growth ◽  
Dispersal Ability ◽  
Invasion Front ◽  
Range Edge ◽  
Theoretical Predictions

Individuals in the vanguard of a species invasion face altered selective conditions when compared with conspecifics behind the invasion front. Assortment by dispersal ability on the expanding front, for example, drives the evolution of increased dispersal, which, in turn, leads to accelerated rates of invasion. Here I propose an additional evolutionary mechanism to explain accelerating invasions: shifts in population growth rate ( r ). Because individuals in the vanguard face lower population density than those in established populations, they should (relative to individuals in established populations) experience greater r -selection. To test this possibility, I used the ongoing invasion of cane toads ( Bufo marinus ) across northern Australia. Life-history theory shows that the most efficient way to increase the rate of population growth is to reproduce earlier. Thus, I predict that toads on the invasion front will exhibit faster individual growth rates (and thus will reach breeding size earlier) than those from older populations. Using a common garden design, I show that this is indeed the case: both tadpoles and juvenile toads from frontal populations grow around 30 per cent faster than those from older, long established populations. These results support theoretical predictions that r increases during range advance and highlight the importance of understanding the evolution of life history during range advance.

Effect of experimental manipulation on survival and recruitment of feral pigs

2009 ◽  
Vol 36 (3) ◽  
pp. 185 ◽  
Author(s):  
Laura B. Hanson ◽  
Michael S. Mitchell ◽  
James B. Grand ◽  
D. Buck Jolley ◽  
Bill D. Sparklin ◽  
...  
Keyword(s):  
Population Growth ◽  
Growth Rates ◽  
Experimental Manipulation ◽  
Vital Rates ◽  
Manipulative Experiment ◽  
Intensity Effect ◽  
Population Growth Rates ◽  
Harvest Intensity ◽  
Effect Model ◽  
Feral Pig

Lethal removal is commonly used to reduce the density of invasive-species populations, presuming it reduces population growth rate; the actual effect of lethal removal on the vital rates contributing to population growth, however, is rarely tested. We implemented a manipulative experiment of feral pig (Sus scrofa) populations at Fort Benning, Georgia, USA, to assess the demographic effects of harvest intensity. Using mark–recapture data, we estimated annual survival, recruitment, and population growth rates of populations in a moderately harvested area and a heavily harvested area for 2004–06. Population growth rates did not differ between the populations. The top-ranked model for survival included a harvest intensity effect; model-averaged survival was lower for the heavily harvested population than for the moderately harvested population. Increased immigration and reproduction likely compensated for the increased mortality in the heavily harvested population. We conclude that compensatory responses in feral pig recruitment can limit the success of lethal control efforts.

scholarly journals Density-independent processes decouple component and ensemble density feedbacks

2021 ◽  
Author(s):  
Corey J. A. Bradshaw ◽  
Salvador Herrando-Perez
Keyword(s):  
Population Growth ◽  
Growth Rates ◽  
Carrying Capacity ◽  
Census Data ◽  
Growth Models ◽  
Structured Populations ◽  
Logistic Growth ◽  
Feedback Signal ◽  
Vital Rates ◽  
Population Growth Rates

Analysis of long-term trends in abundance provide insights into population dynamics. Population growth rates are the emergent interplay of fertility, survival, and dispersal, but the density feedbacks on some vital rates (component) can be decoupled from density feedback on population growth rates (ensemble). However, the mechanisms responsible for this decoupling are poorly understood. We simulated component density feedbacks on survival in age-structured populations of long-living vertebrates and quantified how imposed nonstationarity (density-independent mortality and variation in carrying-capacity) modified the ensemble feedback signal estimated from logistic-growth models to the simulated abundance time series. The statistical detection of ensemble density feedback was largely unaffected by density-independent processes, but catastrophic and proportional mortality eroded the effect of density-dependent survival on ensemble-feedback strength more strongly than variation in carrying capacity. Thus, phenomenological models offer a robust approach to capture density feedbacks from nonstationary census data when density-independent mortality is low.

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