scholarly journals Population decline of endangered lichen Erioderma pedicellatum in Nova Scotia, Canada

Botany ◽  
2016 ◽  
Vol 94 (7) ◽  
pp. 565-571 ◽  
Author(s):  
Robert P. Cameron ◽  
Brad Toms
Keyword(s):  
Nova Scotia ◽  
Population Growth ◽  
Life Stage ◽  
Population Decline ◽  
Mortality Rates ◽  
Population Viability ◽  
Adult Survival ◽  
Juvenile Survival ◽  
Atlantic Population ◽  
Future Viability

Erioderma pedicellatum (Hue) P.M. Jørg. (1972) is a globally endangered lichen known from only four countries worldwide. The Atlantic population in Nova Scotia, Canada, has been declining for at least the last few decades. The population was closely monitored between 2003 and 2012 to determine mortality rates by life stage and population growth. A population viability model was created to assess the future viability of this population. The population declined by 12.8% over the 10 year monitoring period. Mortality rates for juveniles were significantly lower than for adults. The population viability model suggests the population in Nova Scotia will decline by 49% within 25 years. Conservation measures aimed at prolonging adult survival or increasing juvenile survival is, according to the model, the best way to maintain the population.

scholarly journals Range expansion is associated with increased survival and fecundity in a long-lived bat species

2019 ◽  
Vol 286 (1906) ◽  
pp. 20190384 ◽  
Author(s):  
P.-L. Jan ◽  
L. Lehnen ◽  
A.-L. Besnard ◽  
G. Kerth ◽  
M. Biedermann ◽  
...  
Keyword(s):  
Life History ◽  
Population Growth ◽  
Range Expansion ◽  
Empirical Studies ◽  
Simulated Data ◽  
Adult Survival ◽  
Juvenile Survival ◽  
Average Growth ◽  
Population Growth Rates ◽  
Expanding Population

The speed and dynamics of range expansions shape species distributions and community composition. Despite the critical impact of population growth rates for range expansion, they are neglected in existing empirical studies, which focus on the investigation of selected life-history traits. Here, we present an approach based on non-invasive genetic capture–mark–recapture data for the estimation of adult survival, fecundity and juvenile survival, which determine population growth. We demonstrate the reliability of our method with simulated data, and use it to investigate life-history changes associated with range expansion in 35 colonies of the bat species Rhinolophus hipposideros . Comparing the demographic parameters inferred for 19 of those colonies which belong to an expanding population with those inferred for the remaining 16 colonies from a non-expanding population reveals that range expansion is associated with higher net reproduction. Juvenile survival was the main driver of the observed reproduction increase in this long-lived bat species with low per capita annual reproductive output. The higher average growth rate in the expanding population was not associated with a trade-off between increased reproduction and survival, suggesting that the observed increase in reproduction stems from a higher resource acquisition in the expanding population. Environmental conditions in the novel habitat hence seem to have an important influence on range expansion dynamics, and warrant further investigation for the management of range expansion in both native and invasive species.

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.

scholarly journals Cyclic dynamics of snowshoe hares on a small island in the Yukon

2002 ◽  
Vol 80 (8) ◽  
pp. 1442-1450 ◽  
Author(s):  
Charles J Krebs ◽  
Todd N Zimmerling ◽  
Claire Jardine ◽  
Kim A Trostel ◽  
Alice J Kenney ◽  
...  
Keyword(s):  
Population Decline ◽  
Survival Rates ◽  
Ground Squirrels ◽  
Adult Survival ◽  
Small Island ◽  
Juvenile Survival ◽  
Lower Amplitude ◽  
Arctic Ground Squirrels ◽  
Reproductive Rates ◽  
Survival Differences

Snowshoe hare (Lepus americanus) populations were monitored from 1977 to 2001 on Jacquot Island (5 km2) in Kluane Lake, southwestern Yukon, and on nearby mainland sites. Jacquot Island hares averaged twice the density of mainland control populations and, although they show 10-year cycles, fluctuate with much lower amplitude than mainland populations. Three separate intensive studies over 6 years attempted to determine what caused these differences. We tested two hypotheses to explain the dynamics. Reproductive rates of hares were similar on Jacquot Island and the mainland. Adult survival rates were higher on the island in most years, with the exception of years of population decline. Juvenile survival rates from 0 to 30 days of life were much higher on the island than on the mainland except for decline summers. The adult- and juvenile-survival differences between the island and the mainland were explained most consistently by predation. Improved survival on the island is correlated with a reduction in the numbers and types of predators found on Jacquot Island compared with the mainland. In particular, red squirrels were rare on Jacquot Island, arctic ground squirrels were absent, and the larger predators, like lynx and great-horned owls, were sporadic in occurrence on this small island.

scholarly journals Halfway to self-sustainability: Reintroduced migratory European Northern Bald Ibises (Geronticus eremita) still need management interventions for population viability

2021 ◽  
Author(s):  
Sinah Drenske ◽  
Viktoriia Radchuk ◽  
Cédric Scherer ◽  
Corinna Esterer ◽  
Ingo Kowarik ◽  
...  
Keyword(s):  
Population Growth ◽  
Life Stage ◽  
Survival Rates ◽  
Population Viability Analysis ◽  
Population Viability ◽  
Extinction Probability ◽  
Population Growth Rates ◽  
Viability Analysis ◽  
Management Interventions ◽  
Stochastic Events

Northern Bald Ibis (NBI) have disappeared from Europe already in Middle Age. Since 2003 a migratory population is reintroduced in Central Europe. We conducted demographic analyses of survival and reproduction of 384 NBI over a period of 12 years (2008-2019). These data also formed the basis for a population viability analysis (PVA) simulating the possible future development of the NBI population in different scenarios. We tested life-stage specific survival rates for differences between these stages, raising types and colonies as well as the influence of stochastic events and NBI supplements on the population growth. Stage specific survival rates ranged from 0.64 to 0.78. 61% of the mature females reproduce with a mean fecundity of 2.15 fledglings per nest. The complementary PVA indicated that the release population is close to self-sustainability with a given lambda 0.95 and 24% extinction probability within 50 years. Of the 326 future scenarios tested, 94 % reached the criteria of <5% extinction probability and population growth rates >1. In case of positive population growth, stochastic events had a limited effect. Of 820 sub-scenarios with different stochastic event frequencies and severities 87 % show population growth despite the occurrence of stochastic events. Predictions can be made based on the results of the individual-based model as to whether and under what circumstances the reintroduced NBI population can survive. This study shows that a PVA can support reintroduction success that should work closely together with the project in the field for mutual benefit, to optimize future management decisions.

Post-emergence survival and dispersal of juvenile Jefferson salamander (Ambystoma jeffersonianum) and their unisexual dependents

2020 ◽  
Vol 42 (1) ◽  
pp. 29-41
Author(s):  
Stephen G. Van Drunen ◽  
Jessica E. Linton ◽  
James P. Bogart ◽  
D. Ryan Norris
Keyword(s):  
Life Stage ◽  
Population Viability ◽  
Dispersal Distance ◽  
Juvenile Survival ◽  
Apparent Survival ◽  
Viability Assessment ◽  
Juvenile Dispersal ◽  
Ambystoma Jeffersonianum ◽  
Ambystoma Laterale ◽  
Jefferson Salamander

Abstract Understanding population demography and dispersal of species at risk is integral for evaluating population viability, identifying causes of decline, and assessing the effectiveness of recovery actions. In pond-breeding amphibians, juvenile survival and dispersal are key components linked to population and metapopulation stability but little is known about this life stage. We use mark-recapture methods to estimate juvenile daily apparent survival, dispersal distance, and initial dispersal orientation during summer and fall dispersal of endangered Ambystoma jeffersonianum and their unisexual dependents (Ambystoma laterale – jeffersonianum). Over four years (2015-2018), 1018 juveniles (612 bisexual, 406 unisexual) were marked and 192 (19%) were recaptured at least once. Total captures varied widely between years, with the highest number of captures (88% of all individuals) occurring in 2017. Cormack-Jolly-Seber estimates of daily apparent survival were low in all years (0.76-0.95) but was higher for unisexuals than bisexuals. The majority of juveniles (71%) did not disperse further than 10-40 m after which movement appeared to cease. While most juveniles remained close to their natal pond, at least 2% of juveniles in 2017 travelled further than 100 m. Dispersal orientation varied by year and there was no difference in either dispersal orientation or distance between bisexual and unisexual individuals. This work is the first to estimate and compare juvenile survival and dispersal of sympatric A. jeffersonianum and A. laterale – jeffersonianum individuals, the results of which help inform population viability assessment and increase our understanding of juvenile dispersal dynamics and habitat use.

Prédation on red squirrels during a snowshoe hare decline

1995 ◽  
Vol 73 (4) ◽  
pp. 713-722 ◽  
Author(s):  
A. Kari Stuart-Smith ◽  
Stan Boutin
Keyword(s):  
Breeding Season ◽  
Population Decline ◽  
Population Cycles ◽  
Tamiasciurus Hudsonicus ◽  
Adult Survival ◽  
Snowshoe Hare ◽  
Juvenile Survival ◽  
Red Squirrel ◽  
Red Squirrels ◽  
Snowshoe Hares

We examined the extent and impact of predation on red squirrels (Tamiasciurus hudsonicus) during a cyclic decline of snowshoe hares in the southwestern Yukon, Canada. We monitored survival of squirrels on three control grids and a predator exclosure from March 1991 through August 1993. On controls, adult survival during the breeding season decreased from 1991, when snowshoe hare populations were high, to 1992, when hare populations declined rapidly. Survival increased slightly in 1993, when hare and predator populations were very low. Similarly, adult survival during winter was lower in 1992 – 1993 than in 1991 – 1992. Adult survival on the exclosure remained similar in each breeding season but declined during winter 1992 – 1993. Adult survival was similar on the controls and the exclosure in each year except during winter 1991–1992 and the 1992 breeding season, when it was lower on the controls. There was no difference in juvenile survival between the controls and the exclosure. Despite the decrease in adult survival due to predation, there was no population decline on any of the control grids. We conclude that predation did not have a measurable impact on red squirrel densities at Kluane and that it is unlikely red squirrels show 10-year population cycles in conjunction with snowshoe hares.

scholarly journals Multiple life-stage inbreeding depression impacts demography and extinction risk in an extinct-in-the-wild species

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
A. E. Trask ◽  
G. M. Ferrie ◽  
J. Wang ◽  
S. Newland ◽  
S. Canessa ◽  
...  
Keyword(s):  
Life History ◽  
Inbreeding Depression ◽  
Wild Species ◽  
Life Stage ◽  
Population Decline ◽  
Population Viability ◽  
Life History Stages ◽  
Fitness Traits ◽  
In The Wild ◽  
Management Alternatives

AbstractInbreeding can depress individuals’ fitness traits and reduce population viability. However, studies that directly translate inbreeding depression on fitness traits into consequences for population viability, and further, into consequences for management choices, are lacking. Here, we estimated impacts of inbreeding depression (B, lethal equivalents) across life-history stages for an extinct-in-the-wild species, the sihek (Guam kingfisher, Todiramphus cinnamominus). We then projected population growth under different management alternatives with our B estimates incorporated, as well as without inbreeding depression (B = 0) or with a conventional default B. We found that inbreeding depression severely impacted multiple life-history stages, and directly translated into an effect on population viability under management alternatives. Simulations including our B estimates indicated rapid population decline, whereas projections without inbreeding depression or with default B suggested very gradual population decline. Further, our results demonstrate that incorporation of B across life-history stages can influence management decisions, as projections with our B estimates suggested a need to switch to increased breeding management to avoid species extinction and support wild releases. Our results demonstrate that magnitude of B across life-history stages can translate into demographic consequences, such that incorporation of multiple life-stage B into population models can be important for informed conservation management decision-making.

A Successful Population Policy: Potentials and Constraints (Distinguishedl Lecture)

1993 ◽  
Vol 32 (4I) ◽  
pp. 411-431
Author(s):  
Hans-Rimbert Hemmer
Keyword(s):  
Developing Countries ◽  
Economic Development ◽  
Population Growth ◽  
Capita Income ◽  
Population Policy ◽  
Mortality Rates ◽  
Per Capita Income ◽  
Access To Health Services ◽  
Industrial Countries ◽  
Per Capita

The current rapid population growth in many developing countries is the result of an historical process in the course of which mortality rates have fallen significantly but birthrates have remained constant or fallen only slightly. Whereas, in industrial countries, the drop in mortality rates, triggered by improvements in nutrition and progress in medicine and hygiene, was a reaction to economic development, which ensured that despite the concomitant growth in population no economic difficulties arose (the gross national product (GNP) grew faster than the population so that per capita income (PCI) continued to rise), the drop in mortality rates to be observed in developing countries over the last 60 years has been the result of exogenous influences: to a large degree the developing countries have imported the advances made in industrial countries in the fields of medicine and hygiene. Thus, the drop in mortality rates has not been the product of economic development; rather, it has occurred in isolation from it, thereby leading to a rise in population unaccompanied by economic growth. Growth in GNP has not kept pace with population growth: as a result, per capita income in many developing countries has stagnated or fallen. Mortality rates in developing countries are still higher than those in industrial countries, but the gap is closing appreciably. Ultimately, this gap is not due to differences in medical or hygienic know-how but to economic bottlenecks (e.g. malnutrition, access to health services)

scholarly journals Market Access and the Concentration of Economic Activity in a System of Declining Cities

REGION ◽  
2018 ◽  
Vol 5 (3) ◽  
pp. 97-109
Author(s):  
Luis Eduardo Quintero ◽  
Paula Restrepo
Keyword(s):  
Population Growth ◽  
Market Access ◽  
Population Decline ◽  
Market Potential ◽  
Population Loss ◽  
City Population ◽  
Alternative Measures ◽  
System Of Cities ◽  
The Impact ◽  
The City

Market access has been widely used as a measure of agglomeration spillovers in models that seek to explain productivity, economic or population growth at the city level. Most results have shown that having higher market access is beneficial to these outcomes. These results, both theoretical and empirical, have been obtained in a context of population growth. This article examines the impact that market access has on a system of cities that has suffered a negative population shock. An extended version of the Brezis and Krugman (1997) model of life cycle of cities predicts that a system of cities experiencing population loss will see a relative reorganization of its population from small to larger cities, and that higher market potential will make this movement stronger. We test these predictions with a comprehensive sample of cities in Eastern Europe and Central Asia. We find that having higher market access - when operating in an environment of population decline - is detrimental to city population growth. This result is robust to different measures of market access that use population. Alternative measures that use economic size rather population are tested, and the result weaker. A possible explanation is that using NLs restricts the sample to only using larger cities. 

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