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1.
Juan Carlos Alonso Carlos Palacín Alejandro Onrubia Rachid Aboulouafae Mohamed Amezian Abdelaziz El Idrissi Essougrati 《Ostrich》2016,87(3):277-280
A Great Bustard Otis tarda survey carried out in spring 2015 in Morocco confirmed the decline of this highly endangered population. Bustards were only seen at two of the seven leks occupied ten years ago. The total number of birds counted was 40-44, which represents a 40% decline over the last decade. The sex-ratio was still strongly female-biased (1 male: 3 females), but less than in previous surveys, which suggests that trophy hunting has not been the major mortality cause in recent times. The productivity was 0.29-0.33 juveniles per female, the highest ever recorded in this population, suggesting that breeding success doesn’t represent the main problem for the survival of this population. Based on the recent development of the power line network at some areas, the main threat today is probably collision with power lines. Reducing this mortality cause should be considered a high conservation priority. 相似文献
2.
Laurent Lehmann 《Genetics》2014,197(1):351-360
The neutral rate of allelic substitution is analyzed for a class-structured population subject to a stationary stochastic demographic process. The substitution rate is shown to be generally equal to the effective mutation rate, and under overlapping generations it can be expressed as the effective mutation rate in newborns when measured in units of average generation time. With uniform mutation rate across classes the substitution rate reduces to the mutation rate. 相似文献
3.
Jones OR Gaillard JM Tuljapurkar S Alho JS Armitage KB Becker PH Bize P Brommer J Charmantier A Charpentier M Clutton-Brock T Dobson FS Festa-Bianchet M Gustafsson L Jensen H Jones CG Lillandt BG McCleery R Merilä J Neuhaus P Nicoll MA Norris K Oli MK Pemberton J Pietiäinen H Ringsby TH Roulin A Saether BE Setchell JM Sheldon BC Thompson PM Weimerskirch H Jean Wickings E Coulson T 《Ecology letters》2008,11(7):664-673
Comparative analyses of survival senescence by using life tables have identified generalizations including the observation that mammals senesce faster than similar-sized birds. These generalizations have been challenged because of limitations of life-table approaches and the growing appreciation that senescence is more than an increasing probability of death. Without using life tables, we examine senescence rates in annual individual fitness using 20 individual-based data sets of terrestrial vertebrates with contrasting life histories and body size. We find that senescence is widespread in the wild and equally likely to occur in survival and reproduction. Additionally, mammals senesce faster than birds because they have a faster life history for a given body size. By allowing us to disentangle the effects of two major fitness components our methods allow an assessment of the robustness of the prevalent life-table approach. Focusing on one aspect of life history – survival or recruitment – can provide reliable information on overall senescence. 相似文献
4.
David E. Davis 《Human ecology: an interdisciplinary journal》1986,14(2):245-267
In northern France and Europe the population trebled after 1000 and then ceased to increase about 1300, before the Black Death caused an abrupt decline. The birthrate, as indicated by number of surviving children, increased and then declined. Death rates increased after 1250 and, of course, during the Black Death. Migration (assarting) was high after 1100 but ceased by about 1250. The evidence about resources, disease, and internecine strife is compatible with this scenario which can be predicted based on other animal populations. 相似文献
5.
Recently Mou et al. (J. Appl. Entomol., 139, 2015 and 00) recommended that in population studies in which hatch rates vary with maternal age, demographic parameters should be calculated excluding unhatched eggs. A mathematical proof was provided to support this. In this note, we expose a flaw in their proof and show that the demographic parameters do not differ by considering either all eggs or only viable ones, as long as the beginning and end of a generation are defined accordingly. 相似文献
6.
C. D. Phillips J. I. Hoffman J. C. George R. S. Suydam R. M. Huebinger J. C. Patton J. W. Bickham 《Ecology and evolution》2013,3(1):18-37
Patterns of genetic variation observed within species reflect evolutionary histories that include signatures of past demography. Understanding the demographic component of species' history is fundamental to informed management because changes in effective population size affect response to environmental change and evolvability, the strength of genetic drift, and maintenance of genetic variability. Species experiencing anthropogenic population reductions provide valuable case studies for understanding the genetic response to demographic change because historic changes in the census size are often well documented. A classic example is the bowhead whale, Balaena mysticetus, which experienced dramatic population depletion due to commercial whaling in the late 19th and early 20th centuries. Consequently, we analyzed a large multi‐marker dataset of bowhead whales using a variety of analytical methods, including extended Bayesian skyline analysis and approximate Bayesian computation, to characterize genetic signatures of both ancient and contemporary demographic histories. No genetic signature of recent population depletion was recovered through any analysis incorporating realistic mutation assumptions, probably due to the combined influences of long generation time, short bottleneck duration, and the magnitude of population depletion. In contrast, a robust signal of population expansion was detected around 70,000 years ago, followed by a population decline around 15,000 years ago. The timing of these events coincides to a historic glacial period and the onset of warming at the end of the last glacial maximum, respectively. By implication, climate driven long‐term variation in Arctic Ocean productivity, rather than recent anthropogenic disturbance, appears to have been the primary driver of historic bowhead whale demography. 相似文献
7.
Ehsan Ghaemmaghami Yaghoub Fathipour Abdoolnabi Bagheri Ali Asghar Talebi Gadi V.P. Reddy 《Journal of Asia》2021,24(2):166-174
Continuous mass rearing of Trichogramma brassicae (Bezdenko) at commercial mass-rearing insectaries may affect both quality and performance of natural enemies. In the present study, we studied the quality and performance of a colony of T. brassicae reared for over 45 generations (G) on Ephestia kuehniella Zeller using two-sex life table parameters and parasitism capacity. Our results revealed that although different generations showed no significant difference in terms of female longevity or total life span until G35, G5 and G10 had the highest values of fecundity, gross reproductive rate (GRR), net reproductive rate (R0), intrinsic rate of natural increase (r), and finite rate of increase (λ). No significant difference in male adult longevity was found among different generations. The longest and shortest mean generation times (T) were found in G10 (13.65 ± 2.31 d) and G45 (13.25 ± 3.37 d), respectively. The finite rate of parasitism (ω) ranged from 0.355 ± 2.332 host/parasitoid/day in G5 to 0.242 ± 0.017 host/parasitoid/day in G45. However, ω did not show any significant difference until G20. These results indicate that T. brassicae wasps held under continuous laboratory rearing declined in quality after 20 generations, and therefore periodical rejuvenation of the colony by adding feral parasitoids is strongly recommended. 相似文献
8.
9.
Ming‐Chih Chiu Ying‐Hsin Chen Mei‐Hwa Kuo 《Entomologia Experimentalis et Applicata》2012,142(3):216-222
Tropical invertebrates are currently living very close to their optimal temperature. Warming due to global climate change will likely exceed their physiological optima and have deleterious consequences for insects living at low latitudes. In this study, we assess the effects of various levels of summer warming predicted for the late 21st century (+1.2 and +3.7 °C, with the same diel oscillation as the current regime) on the physiology and demography of the aphid Myzus varians Davidson (Hemiptera: Aphididae) in subtropical and tropical Taiwan. Aphids subjected to a moderate (3.7 °C) increase in temperature did not reach adulthood and thus left no offspring, meaning that wild populations could go extinct during the summer. Slight (+1.2 °C) warming did not significantly affect development time and generation time. However, warming reduced nymphal survival, adult longevity, and reproduction, and, thus, reduced the fitness of aphid populations. Aphids have a number of adaptations for surviving or avoiding unfavorable conditions. However, predicted increases in global temperatures will likely decrease their survival and reproduction, which could increase the frequency of local extinction. 相似文献
10.
Larval dispersal may have an important effect on genetic structure of benthic fishes. To examine the population genetic structure of spottedtail goby Synechogobius ommaturus, a 478 base pair (bp) fragment of the hypervariable portion of the mtDNA control region was sequenced and used to interpret life‐history characteristics and larval dispersal strategy. Individuals (n = 186) from 10 locations on the coasts of China and Korea were analysed and 44 haplotypes were obtained. The levels of haplotype and nucleotide diversity were higher in East China Sea populations than in other populations. Both the phylogenetic tree and the minimum spanning tree showed that no significant genealogical structures corresponding to sampling locations existed. AMOVA and pair‐wise FST revealed significant genetic differentiation between populations from Korea and China. A significant isolation by distance pattern was observed in this species (r = 0·53, P < 0·001). Both mismatch distribution analysis and neutrality tests showed S. ommaturus to have experienced a recent population expansion. These results suggest that the Pleistocene ice ages had a major effect on the phylogeographic pattern of S. ommaturus, that larvae might avoid offshore dispersal and that dispersal of larvae may maintain a migration–drift equilibrium. 相似文献
11.
植物亲缘地理学的研究现状与发展趋势 总被引：2，自引：0，他引：2
新生代以来剧烈的地质和气候变化,特别是第四纪冰期和间冰期的反复交错对温带植物类群的地理分布格局、种群结构和物种分化造成了深刻影响。近20年来,随着分子标记技术的发展和分析方法的成熟,植物亲缘地理学利用基因谱系关系和在种群中的时空分布来追溯种群的进化历史,在探讨植物类群对地质气候变迁的响应以及种群分化的历史成因等方面开展了大量工作,取得了一些重要进展。在取得这些成绩的同时,作者也注意到了被研究者所忽略的一些问题。试图对这些问题进行初步的总结,着重于分析方法和几个常用软件的使用,并对今后的发展趋势进行了展望。 相似文献
12.
The vaquita, Phocoena sinus, is one of two critically endangered cetacean species, and is listed as an endangered species in both the United States and Mexico. These listings result from a small population size, estimated to be 224 animals, and a rapid decline in abundance (18% per annum) thought to be caused by human activities. To characterize the genetic composition of the vaquita, we have sequenced a portion of the mitochondrial DNA control region from 43 individuals collected between 1985 and 1993. All animals had identical sequences. While low genetic variability has been reported for cetacean species, this complete lack of polymorphism in the control region is unique. This result is concordant with the hypothesis that the evolutionary history of the species includes a bottleneck or founder event, possibly at species inception, followed by a small long-term effective population size. We recommend parallel studies of nuclear variability, which could provide understanding of the basic biology of the vaquita for use in conservation efforts. 相似文献
13.
SUMMARY 1. Temporary ponds are inhabited by a variety of invertebrates, of which anostracans are an important group. We studied the lifetables of male and female anostracan Streptocephalus mackini at 3 algal concentrations (0.5 × 106 , 1.0 × 106 and 1.5 × 106 cells mL−1 ).
2. Regardless of sex, S. mackini showed better survivorship at lower food levels. The longest average lifespan observed was 85 ± 2 days for males fed Chlorella at 0.5 × 106 cells mL−1 .
3. Both net reproductive rate and generation time decreased with increasing food level. The highest net reproductive rate was about 120 cysts per female. The longest generation time of about 40 days, observed at 0.5 × 106 cells mL−1 , was more than three times that at 1.5 × 106 cells mL−1 .
4. The rate of population increase ( r ) was nearly the same (0.31 ± 0.06) at high (1.5 × 106 cells mL−1 ) and intermediate (1.0 × 106 cells mL−1 ) food levels. The r -value at low food level (0.5 × 106 cells mL−1 of Chlorella ) was 0.20 ± 0.01 per day. 相似文献
2. Regardless of sex, S. mackini showed better survivorship at lower food levels. The longest average lifespan observed was 85 ± 2 days for males fed Chlorella at 0.5 × 10
3. Both net reproductive rate and generation time decreased with increasing food level. The highest net reproductive rate was about 120 cysts per female. The longest generation time of about 40 days, observed at 0.5 × 10
4. The rate of population increase ( r ) was nearly the same (0.31 ± 0.06) at high (1.5 × 10
14.
Shripad Tuljapurkar Jean-Michel Gaillard Tim Coulson 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2009,364(1523):1499-1509
Environmental stochasticity is known to play an important role in life-history evolution, but most general theory assumes a constant environment. In this paper, we examine life-history evolution in a variable environment, by decomposing average individual fitness (measured by the long-run stochastic growth rate) into contributions from average vital rates and their temporal variation. We examine how generation time, demographic dispersion (measured by the dispersion of reproductive events across the lifespan), demographic resilience (measured by damping time), within-year variances in vital rates, within-year correlations between vital rates and between-year correlations in vital rates combine to determine average individual fitness of stylized life histories. In a fluctuating environment, we show that there is often a range of cohort generation times at which the fitness is at a maximum. Thus, we expect ‘optimal’ phenotypes in fluctuating environments to differ from optimal phenotypes in constant environments. We show that stochastic growth rates are strongly affected by demographic dispersion, even when deterministic growth rates are not, and that demographic dispersion also determines the response of life-history-specific average fitness to within- and between-year correlations. Serial correlations can have a strong effect on fitness, and, depending on the structure of the life history, may act to increase or decrease fitness. The approach we outline takes a useful first step in developing general life-history theory for non-constant environments. 相似文献
15.
Charles E. Zartman July A. Amaral José N. Figueiredo Cristian de Sales Dambros 《Biotropica》2015,47(2):172-178
Understanding how changing precipitation patterns impact the population dynamics of Amazonian plants is necessary for predicting their long‐term survival. Most terrestrial plants are characterized by life cycles intractably slow for evaluating such demographic consequences. Due to the demands of surviving on an ephemeral substrate such as a leaf surface, epiphyllous (leaf‐inhabiting) bryophytes have some of the fastest generation times for terrestrial plants. Considering these advantages, we investigated the demographic consequences of seasonality in precipitation during one‐year of the epiphyllous bryophyte Radula flaccida Gott. (Radulaceae) in a central Amazonian rain forest. In a 1‐ha sized study area, 154 epiphyll colonies from 18 phorophytes of the understory shrub Naucleopsis ulei (Warb.) Ducke (Moraceae) were marked and colony growth, extinction, recolonization, as well as rates of sexual and asexual expression were measured in nine demographic censuses. The probability of survivorship decreased in the dry season due to the synergistic effects of both increased leaf fall (e.g., loss of occupied patches) and colony mortality on persisting leaves. Asexual expression also declined significantly during the driest months; however, sexual expression, as measured by sporophyte density, was not related to seasonality. Logistic regression probabilities also indicate a minimum threshold colony size for optimal sporophyte expression. Lower survivorship and colony growth in the dry season along with reduced sporophyte production in smaller colonies implies that both demographic stability as well as population structure of Amazonian epiphyll species may be compromised whether climate models projecting prolonged droughts for the region are accurate. 相似文献
16.
Threatening processes, such as disease, can drive major changes in population demographics of the host. Chytridiomycosis, caused by the fungal pathogen Batrachochytrium dendrobatidis (Bd), has led to the decline of at least 500 amphibian species across the globe and has been shown to truncate host age structure by lowering adult survival rates. This results in heavy reliance on annual recruitment and the inability to recover in the event of periodic recruitment failure. We used skeletochronology to determine the age structure, growth, and survival rates of populations of an endangered amphibian, Litoria raniformis, with endemic chytridiomycosis, across two climatically disparate regions in south‐eastern Australia: semi‐arid and temperate. Contrary to predictions, populations in the semi‐arid region (in which chytrid prevalence is substantially lower due to high temperatures) displayed a more truncated age structure than populations in the temperate study regions. Maximum recorded age was only two years in the semi‐arid region compared with up to four years in the temperate region. Wetland hydroperiod and average seasonal air temperature were correlated with age, and males had a slightly higher survival rate than females (0.31 for males and 0.27 for females). Despite the previously documented differences in chytrid prevalence between the two climatic regions, water availability and wetland hydroperiods appear the over‐riding determinants of the age structure and survival rates of L. raniformis. Targeted management which ensures water availability and improves survival of 1‐year‐old frogs into their second and third breeding season would reduce the impact of stochastic events on L. raniformis, and this may be true for numerous frog species susceptible to chytridiomycosis. 相似文献
17.
A major challenge in ecology is to understand how populations are affected by increased climate variability. Here, we assessed the effects of observed climate variability on different organismal groups (amphibians, insects, mammals, herbaceous plants and reptiles) by estimating the extent to which interannual variation in the annual population growth rates (CVλ) and the absolute value of the long-term population growth rate (|log λ|) were associated with short-term climate variability. We used empirical data (≥ 20 consecutive years of annual abundances) from 59 wild populations in the Northern Hemisphere, and quantified variabilities in population growth rates and climatic conditions (temperature and precipitation in active and inactive seasons) calculated over four- and eight-year sliding time windows. We observed a positive relationship between the variability of growth rate (CVλ) and the variability of temperature in the active season at the shorter timescale only. Moreover, |log λ| was positively associated with the variability of precipitation in the inactive season at both timescales. Otherwise, the direction of the relationships between population dynamics and climate variability (if any) depended largely on the season and organismal group in question. Both CVλ and |log λ| correlated negatively with species' lifespan, indicating general differences in population dynamics between short-lived and long-lived species that were not related to climate variability. Our results suggest that although temporal variation in population growth rates and the magnitude of long-term population growth rates are partially associated with short-term interannual climate variability, demographic responses to climate fluctuations might still be population-specific rather than specific to given organismal groups, and driven by other factors than the observed climate variability. 相似文献
18.
Bertram G. Murray 《Austral ecology》2000,25(4):297-304
I constructed age‐structured populations by drawing numbers from a random numbers table, the constraints being that within a cohort each number be smaller than the preceding number (indicating that some individuals died between one year and the next) and that the first two‐digit number following 00 or 01 ending one cohort’s life be the number born into the next cohort. Populations constructed in this way showed prolonged existence with total population numbers fluctuating about a mean size and with long‐term growth rate (r) ≈ 0. The populations’ birth rates and growth rates and the females’ per capita fecundity decreased significantly with population size, whereas the death rates showed no significant relationship to population size. These results indicate that age‐structured populations can persist for long periods of time with long‐term growth rates of zero in the absence of negative‐feedback loops between a population’s present or prior density and its birth rate, growth rate, and fecundity, contrary to the assumption of density‐dependent regulation hypotheses. Thus, a long‐term growth rate of zero found in natural populations need not indicate that a population’s numbers are regulated by density‐dependent factors. 相似文献
19.
The numbat has been reduced to two populations in Western Australia. To better understand the effects of range reduction on gene flow and genetic variation, and to address questions crucial for the species' management, we analysed mitochondrial DNA (mtDNA) sequences of free-ranging individuals and museum specimens. The results suggest recent connectivity between the remnant populations, although one of those may have lost significant amounts of genetic diversity during the recent population size reduction. We propose that for management purposes the remnant populations should be treated as a single historical lineage and that, subject to certain caveats, consideration should be given to population augmentation by translocation. 相似文献