Demographic consequences of artificial selection at the LAP locus in voles (Microtus townsendii)

1975 ◽  
Vol 53 (12) ◽  
pp. 1825-1840 ◽  
Author(s):  
Janice LeDuc ◽  
Charles J. Krebs
Keyword(s):  
Population Density ◽  
Demographic Variables ◽  
Control Area ◽  
Experimental Population ◽  
Population Fluctuations ◽  
Genetic Composition ◽  
Gene Frequencies ◽  
Survival And Reproduction ◽  
Altered Gene ◽  
Microtus Townsendii

A number of studies on small mammals have shown that changes in the frequency of alleles at polymorphic loci are correlated with population fluctuations. To determine whether the genetic composition of a population affected its density changes, we altered gene frequencies in two field populations of the vole Microtus townsendii. The fast allele, LAPF, was present in a control population at a frequency of about 35% from July 1971 to July 1973. By removing homozygous LAPS/LAPS voles from one experimental population we maintained an LAPF frequency of about 75%. Removal of LAPF/LAPF homozygotes from a second population resulted in an LAPF frequency of about 25%. We monitored demographic variables of the populations while the selection was being applied. The populations went through increasing and peak phases and then declined sharply during the spring of 1973. Different genotypes had an advantage in survival and reproduction during different phases of population density on the control area, and the selection that maintained the polymorphism on the control area could be correlated with population density. The altered allelic frequencies on the experimental areas did not produce any consistent effects on demography.

scholarly journals A fencing experiment on a high-density population of Microtus townsendii

1977 ◽  
Vol 55 (7) ◽  
pp. 1166-1175 ◽  
Author(s):  
Rudy Boonstra ◽  
Charles J. Krebs
Keyword(s):  
Survival Rate ◽  
Breeding Season ◽  
Population Regulation ◽  
Control Area ◽  
High Density ◽  
Low Density ◽  
Vole Population ◽  
Sharp Decline ◽  
Density Population ◽  
Microtus Townsendii

If dispersal is prevented, a low-density vole population will increase to unusually high densities. A mouse-proof fence was constructed around a vole population that had already reached high density and both this population and one on a control area were live-trapped from January 1975 to November 1975. The population on the control remained at peak densities. The enclosed population increased to even higher density once the breeding season had started and had a higher survival rate than the control population. By midsummer the enclosed population had severely overgrazed the vegetation and went into a sharp decline. Dispersal losses from the control were estimated at 32% for males and 31% for females in these high-density populations. Microtus townsendii populations thus responded to a fence in a manner similar to that of other species that have been studied. This experiment indicates the importance of dispersal to population regulation in voles even at peak densities.

Breeding characteristics of Townsend's vole (Microtus townsendii) during population fluctuations

1980 ◽  
Vol 58 (4) ◽  
pp. 623-625 ◽  
Author(s):  
Terry D. Beacham
Keyword(s):  
British Columbia ◽  
Sexual Maturity ◽  
Fraser River ◽  
Population Fluctuations ◽  
Peak Density ◽  
Decline Phase ◽  
Early Maturing ◽  
Fraser River Delta ◽  
Peak Phase ◽  
Microtus Townsendii

A 2-year livetrapping study on Townsend's vole (Microtus townsendii) on Reifel Island in the Fraser River delta in British Columbia, Canada, showed that there was an early stop to summer breeding in the peak phase summer compared with the increasing phase summer. Selective dispersal and death of early-maturing voles may account for this result. A delay occurred in the onset of breeding in the decline phase. Voles in peak density populations had the highest median weights at sexual maturity, and males matured at heavier weights than did females.

scholarly journals Quantifying the effect of genetic, environmental and individual demographic stochastic variability for population dynamics in Plantago lanceolata

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ulrich K. Steiner ◽  
Shripad Tuljapurkar ◽  
Deborah A. Roach
Keyword(s):  
Population Dynamics ◽  
Population Growth ◽  
Population Change ◽  
Adaptive Dynamics ◽  
Plantago Lanceolata ◽  
Environmental Parameters ◽  
Experimental Population ◽  
Stochastic Variation ◽  
Survival And Reproduction ◽  
Stochastic Events

AbstractSimple demographic events, the survival and reproduction of individuals, drive population dynamics. These demographic events are influenced by genetic and environmental parameters, and are the focus of many evolutionary and ecological investigations that aim to predict and understand population change. However, such a focus often neglects the stochastic events that individuals experience throughout their lives. These stochastic events also influence survival and reproduction and thereby evolutionary and ecological dynamics. Here, we illustrate the influence of such non-selective demographic variability on population dynamics using population projection models of an experimental population of Plantago lanceolata. Our analysis shows that the variability in survival and reproduction among individuals is largely due to demographic stochastic variation with only modest effects of differences in environment, genes, and their interaction. Common expectations of population growth, based on expected lifetime reproduction and generation time, can be misleading when demographic stochastic variation is large. Large demographic stochastic variation exhibited within genotypes can lower population growth and slow evolutionary adaptive dynamics. Our results accompany recent investigations that call for more focus on stochastic variation in fitness components, such as survival, reproduction, and functional traits, rather than dismissal of this variation as uninformative noise.

Demography, behavior, and genetics of a colonizing population of blue grouse

1977 ◽  
Vol 55 (12) ◽  
pp. 1948-1957 ◽  
Author(s):  
Fred C. Zwickel ◽  
James A. Redfield ◽  
John Kristensen
Keyword(s):  
Population Density ◽  
Esterase Activity ◽  
Control Area ◽  
Behavioral Differences ◽  
Experimental Area ◽  
Dendragapus Obscurus ◽  
Reproductive Rates ◽  
Starch Gels ◽  
Two Populations ◽  
Subsequent Replacement

The demography, behavior, and genetics of a population of blue grouse (Dendragapus obscurus) that colonized an area from which most grouse were removed were compared with those of grouse on a nearby control area. Population density increased on the removal area from 1971 to 1974 but remained essentially stable on the control area. Although there were some differences in survival and reproductive rates among years and between areas, none appeared related to the experimental removal and subsequent replacement by new founders.No consistent differences in potentially aggressive behavior were observed between birds in the two populations. Behavioral differences that occurred were likely related to differences in age structures of the two populations or to the synchronous settling of a cohort of mostly young birds on the experimental area.There was no excess of Ng (Birdsall, α., J. A. Redfield, and D. G. Cameron. White bands on starch gels stained for esterase activity; a new polymorphism. Biochem. Genet. 4: 655–658 (1970)) homozygotes among recruits to the experimental area, in contrast with Redfield's (Demography and genetics in colonizing populations of blue grouse (Dendragapus obscurus). Evolution, 27(4): 576–592 (1974)) report of such an excess among birds colonizing new habitat.The increase in the population on the experimental area compared with the control area must have resulted from an increased recruitment of yearlings. No clear evidence was found that this increase was related to qualitative differences between stocks on the two areas.

The Life System of Cardiaspina Albitextura (Psyllidae), 1950-74.

1975 ◽  
Vol 23 (4) ◽  
pp. 523 ◽  
Author(s):  
LR Clark ◽  
MJ Dallwitz
Keyword(s):  
Population Density ◽  
Natural Enemies ◽  
Average Rate ◽  
The Other ◽  
Population Densities ◽  
Insect Abundance ◽  
Complete Development ◽  
Rate Of Increase ◽  
Adverse Weather ◽  
Survival And Reproduction

In 1958-63 and 1964-71 the life systems of four kinds of test-forming psyllid that coexist on Eucalyptus blakelyi were investigated intensively in a comparative study of insect abundance. This paper deals mainly with C. albitextura, which was kept under observation from 1950 to 1974. (The others were two species of Glycaspis, Spondyliaspis sp, and Creiis costatus.) The results indicate that the differences in maximal abundance reached by the four kinds of psyllid are mainly the outcome of differences in their ability tg utilize the leaves of the host plant as a source of food, C. albitextura being much more effective than the other species. For the latter, it appears that the principal environmental determinant of abundance was the number of feeding places where nymphs could survive long enough to complete development. That number varied according to foliage and weather. C. albitextura also differed from the other species by having its population densities held for long periods far below the levels at which the food supply would be limiting, by restrictions imposed upon reproduction by adverse weather and foliage conditions (the latter being due partly to poor synchronization between the emergence of adults in spring and the occurrence of foliage attractive for oviposition), and by high mortalities due to natural enemies. The life system of C. albitextura lacks an element that can stabilize abundance at low population densities, but adverse environmental influences usually limit the rate of increase greatly when abundance is low. The magnitude of the average rate of increase to high levels of population density, and the length of time for which high average densities are maintained, depend upon the frequency with which favourable conditions of weather, foliage and predation combine to promote both survival and reproduction.

scholarly journals Causes and consequences of variation in early-life telomere length in a bird metapopulation

2021 ◽  
Author(s):  
Michael Le Pepke ◽  
Thomas Kvalnes ◽  
Peter Sjolte Ranke ◽  
Yimen G. Araya-Ajoy ◽  
Jonathan Wright ◽  
...  
Keyword(s):  
Reproductive Success ◽  
Population Density ◽  
Telomere Length ◽  
Environmental Conditions ◽  
Early Life ◽  
Morphological Traits ◽  
Weather Conditions ◽  
Population Fluctuations ◽  
Individual Quality ◽  
Pace Of Life

1.Environmental conditions during early-life development can have lasting effects on individual quality and fitness. Telomere length (TL) may correlate with early-life conditions and may be an important mediator or biomarker of individual quality or pace-of-life, as periods of increased energy demands can increase telomere attrition due to oxidative stress. Thus, knowledge of the mechanisms that generate variation in TL, and the relation between TL and fitness, is important in understanding the role of telomeres in ecology and life-history evolution. 2.Here, we investigate how environmental conditions and morphological traits are associated with early-life TL and if TL predicts natal dispersal probability or components of fitness in two populations of wild house sparrows (Passer domesticus). 3.We measured morphological traits and blood TL in 2746 nestlings from 20 cohorts (1994-2013) and retrieved data on weather conditions. We monitored population fluctuations, and individual survival and reproductive output using field observations and genetic pedigrees. We then used generalized linear mixed-effects models to test which factors affected TL in early-life, and if TL predicted dispersal propensity, or was associated with recruitment probability, mortality risk, or reproductive success.4.We found a negative effect of population density on TL, but only in one of the populations. There was a curvilinear association between TL and the maximum daily North Atlantic Oscillation (NAO) index during incubation, suggesting that there are optimal weather conditions that result in the longest TL. Dispersers tended to have shorter telomeres than non-dispersers. TL did not predict survival, but we found a tendency for individuals with short telomeres to have higher annual reproductive success.5.Our study showed how early-life TL is shaped by effects of growth, weather conditions and population density, supporting that environmental stressors negatively affect TL in wild populations. In addition, TL may be a mediator or biomarker of individual pace-of-life, with higher dispersal rates and annual reproduction tending to be associated with shorter early-life TL in this study. However, clear associations between early-life TL and individual fitness seems difficult to establish and may differ between different populations in the wild.

scholarly journals Where have all the spiders gone? Observations of a dramatic population density decline in the once very abundant garden spider, Araneus diadematus (Araneae: Araneidae), in the Swiss midland

2020 ◽  
Author(s):  
Martin Nyffeler ◽  
Dries Bonte
Keyword(s):  
Population Density ◽  
Trophic Cascade ◽  
Western Europe ◽  
Negative Impact ◽  
Normal Population ◽  
Late Summer ◽  
Population Fluctuations ◽  
Population Densities ◽  
Flying Insects ◽  
Araneus Diadematus

AbstractAerial web-spinning spiders (including large orb-weavers) depend, as a group of insectivores, completely on flying insects as a food source. The recent widespread loss of flying insects across large parts of western Europe, both in terms of diversity and biomass, can therefore be anticipated to have a drastic negative impact on survival and abundance of this type of spiders. To test the putative importance of such a to date neglected trophic cascade, a survey of population densities of the European garden spider Araneus diadematus – a large orb-weaving spider – was conducted in late summer 2019 on twenty sites of the Swiss midland. The data from this survey were compared with published population densities for this species from the previous century. The study verifies above-mentioned hypothesis that this spider’s present-day overall mean population density has declined alarmly to densities much lower than can be expected from normal population fluctuations (0.7% of the historical densities). Review of other available records suggests this pattern is widespread and not restricted to this region. In conclusion, the here documented abundance decline of this once so abundant spider in the Swiss midland is evidently revealing a bottom-up trophic cascade in response to the widespread loss of flying insect prey in recent decades.

scholarly journals Population density shapes patterns of survival and reproduction in Eleutheria dichotoma (Hydrozoa: Anthoathecata)

2018 ◽  
Vol 165 (3) ◽  
Author(s):  
Aleksandra Dańko ◽  
Ralf Schaible ◽  
Joanna Pijanowska ◽  
Maciej J. Dańko
Keyword(s):  
Population Density ◽  
Survival And Reproduction

scholarly journals Where Have All the Spiders Gone? Observations of a Dramatic Population Density Decline in the Once Very Abundant Garden Spider, Araneus diadematus (Araneae: Araneidae), in the Swiss Midland

Insects ◽  
2020 ◽  
Vol 11 (4) ◽  
pp. 248
Author(s):  
Martin Nyffeler ◽  
Dries Bonte
Keyword(s):  
Population Density ◽  
Trophic Cascade ◽  
Western Europe ◽  
Negative Impact ◽  
Normal Population ◽  
Late Summer ◽  
Population Fluctuations ◽  
Population Densities ◽  
Flying Insects ◽  
Araneus Diadematus

Aerial web-spinning spiders (including large orb-weavers), as a group, depend almost entirely on flying insects as a food source. The recent widespread loss of flying insects across large parts of western Europe, in terms of both diversity and biomass, can therefore be anticipated to have a drastic negative impact on the survival and abundance of this type of spider. To test the putative importance of such a hitherto neglected trophic cascade, a survey of population densities of the European garden spider Araneus diadematus—a large orb-weaving species—was conducted in the late summer of 2019 at twenty sites in the Swiss midland. The data from this survey were compared with published population densities for this species from the previous century. The study verified the above-mentioned hypothesis that this spider’s present-day overall mean population density has declined alarmingly to densities much lower than can be expected from normal population fluctuations (0.7% of the historical values). Review of other available records suggested that this pattern is widespread and not restricted to this region. In conclusion, the decline of this once so abundant spider in the Swiss midland is evidently revealing a bottom-up trophic cascade in response to the widespread loss of flying insect prey in recent decades.

Sublethal parasites in white-footed mice: impact on survival and reproduction

1991 ◽  
Vol 69 (2) ◽  
pp. 398-404 ◽  
Author(s):  
James C. Munger ◽  
William H. Karasov
Keyword(s):  
Population Density ◽  
Peromyscus Leucopus ◽  
Parasitic Infection ◽  
Reproductive Season ◽  
Natural Experiments ◽  
Bot Fly ◽  
Impact On Survival ◽  
Survival And Reproduction ◽  
Potential Impact ◽  
The Impact

The potential impact of two parasites on the population density of host white-footed mice (Peromyscus leucopus) was assessed by measuring effects on survival and reproduction in field populations. Thirty-eight mice infected with larvae of the bot fly Cuterebra angustifrons had their larvae removed, another 41 mice remained infected, and 46 other mice were naturally uninfected during the experiment. No effect of bot larvae removal was detected on either survival (measured as attrition) or reproduction (measured as end of reproductive season). However, contrary to expectation, naturally infected mice had lower attrition and a marginally longer reproductive season than naturally uninfected mice. This latter result is probably an artifact, due to underlying differences between naturally infected and uninfected mice. Sixty-seven mice were experimentally infected with the tapeworm Hymenolepis citelli (64 mice were controls), but no effect was detected on attrition from the trappable population nor on the cessation of the reproductive season. Our results indicate that (i) these parasites are unlikely to have any effect on population density of white-footed mice, and (ii) it is potentially misleading to use "natural experiments" (comparison of naturally infected hosts with uninfected hosts) to study the impact of parasitic infection.

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