Probability Of Reproduction Research Articles

Bet hedging in stochastic habitats: an approach through large branchiopods in a temporary wetland.

Organisms evolve to maintain fitness across generations, while short-term fitness in stochastic habitats such as temporary wetlands may be highly varied. As typical temporary wetland inhabitants, large branchiopods rely on bet hedging hatching that helps them survive throughout generations. An optimal hatching rate is predicted to be approximate to the successful reproduction probability (SRP). We tested the difference between hatching rate and SRP of large branchiopods Branchinella kugenumaensis and Eulimnadia braueriana in a temporary wetland in Taiwan, through field surveys and climatic records to evaluate their SRP. Comparisons were performed under two proposed scenarios, where a population's hatching was bet hedged for a hydroperiod or for a wet season (with several hydroperiods), respectively. Population size fluctuations were simulated for these two scenarios under assumed egg mortalities and reproductive replenishments. Results showed that the hatching rates only fitted to SRP for E. braueriana under the scenario of bet hedging on a wet season, not for B. kugenumaensis, nor for both species under the scenario of bet hedging on a hydroperiod. Bet hedging on a wet season would have a smaller range of population size fluctuation and a lower rate of population size decrease. This implies that large branchiopods adopt a conservative hatching strategy, lowering the hatching fraction in each hydroperiod to reduce long-term egg bank size fluctuation. Bet hedging strategies could occur during other life cycle stages, coexist with other life history strategies, and lead to the diversified hatching fraction distribution rather than a single, optimal fraction throughout hydroperiods.

Chronic leaf harvesting reduces reproductive success of a tropical dry forest palm in northern Mexico.

Palm leaves represent one of the most important non-timber forest products in tropical and subtropical regions. Brahea aculeata is an endemic palm of northwest Mexico, whose leaves are intensively exploited for roof thatch and handcrafts. As part of a long-term defoliation experiment, we evaluated the effects of different leaf harvest on foliar and reproductive traits of adults and attributes of their progeny. We conducted a six-year manipulative experiment and applied three harvesting treatments to adults: high harvest, low harvest and no harvest (control). We recorded leaf production and size, flower and fruit production, seed germination and seedling growth. We also explored trade-offs among foliar and reproductive traits.Harvested palms exhibited drastically reduced reproductive activity, producing fewer flowers and fruits (up to 80 and 90% fewer than unharvested palms). However, individuals in both harvest treatments had larger leaves and increased leaf production rates, compared to control palms. For harvested palms, we registered first a slight increase in leaf traits and a decline in reproductive attributes. These traits showed a gradual reduction and for six period attained very low proportional values compared to control palms (~0.10), however individuals in the harvested treatments maintained the greatest leaf lengths and leaf production rates. Seed germination and seedling growth rates of progeny from harvested palms were significantly lower than control palms, with seeds from the high harvest treatment having the lowest seed production and germination rates. Relationships among leaf (size/production) and reproductive traits (flower/fruit production) were positive during the fourth year, but showed negative relationships for the fifth year suggesting a trade-off between reproduction and growth functions. Leaf harvesting in B. aculeata seems to alter patterns of resource allocation away from reproduction as reflected in a decrease in the probability of reproduction, seed number, germination, and vigor, causing a strong decrease in the reproductive success of this species. Results showed that the consequences of long-term leaf harvest not only affect harvested individuals, but also the fitness and vigor of progeny. This type of long-term studies is essential to understand the population dynamics of non-timber forest products and helps inform sustainable harvesting programs considering intensity, frequencies and periods for recovery from defoliation. Also results may help to explain how intensive and non-planned management schemes may negatively affect vital rates and long-term dynamics of populations from non-timber forest products and other components of the ecosystem.

Demographic costs and benefits of natural regeneration during tropical forest restoration

For tropical forest restoration to result in long-term biodiversity gains, native trees must establish self-sustaining populations in degraded sites. While many have asked how seedling recruitment varies between restoration treatments, the long-term fate of these recruits remains unknown. We address this research gap by tracking natural recruits of 27 species during the first 7years of a tropical forest restoration experiment that included both planted and naturally regenerating plots. We used an individual-based model to estimate the probability that a seedling achieves reproductive maturity after several years of growth and survival. We found an advantage for recruits in naturally regenerating plots, with up to 40% increased probability of reproduction in this treatment, relative to planted plots. The demographic advantage of natural regeneration was highest for mid-successional species, with relatively minor differences between treatments for early-successional species. Our research demonstrates the consequences of restoration decision making across the life cycle of tropical tree species.

Variation in the vital rates of an Antarctic marine predator: the role of individual heterogeneity.

Variation in life-history traits such as lifespan and lifetime reproductive output is thought to arise, in part, due to among-individual differences in the underlying probabilities of survival and reproduction. However, the stochastic nature of demographic processes can also generate considerable variation in fitness-related traits among otherwise-identical individuals. An improved understanding of life-history evolution and population dynamics therefore depends on evaluating the relative role of each of these processes. Here, we used a 33-yr data set with reproductive histories for 1,274 female Weddell seals from Erebus Bay, Antarctica, to assess the strength of evidence for among-individual heterogeneity in the probabilities of survival and reproduction, while accounting for multiple other sources of variation in vital rates. Our analysis used recent advances in Bayesian model selection techniques and diagnostics to directly compare model fit and predictive power between models that included individual effects on survival and reproduction to those that did not. We found strong evidence for costs of reproduction to both survival and future reproduction, with breeders having rates of survival and subsequent reproduction that were 3% and 6% lower than rates for non-breeders. We detected age-related changes in the rates of survival and reproduction, but the patterns differed for the two rates. Survival rates steadily declined from 0.92 at age 7 to 0.56 at the maximal age of 31yr. In contrast, reproductive rates increased from 0.68 at age 7 to 0.79 at age 16 and then steadily declined to 0.37 for the oldest females. Models that included individual effects explained more variation in observed life histories and had better estimated predictive power than those that did not, indicating their importance in understanding sources of variation among individuals in life-history traits. We found that among-individual heterogeneity in survival was small relative to that for reproduction. Our study, which found patterns of variation in vital rates that are consistent with a series of predictionsfrom life-history theory, is the first to provide a thorough assessment of variation in important vital rates for a long-lived, high-latitude marine mammal while taking full advantage of recent developments in model evaluation.

Demographic strategies of a dominant tree species in response to logging in a degraded subtropical forest in Southeast China

The demography of pioneer tree species ( Pinus massoniana Lamb.) is significantly affected by logging in Southeast China. Logging negatively affects the population growth rate of P. massoniana , which facilitates the growth of individual trees but has no effect on reproduction probability. The survival and growth of seedlings contribute the most to population growth. Subtropical forest degradation caused by unreasonable disturbances is closely related to anthropogenic activities in Southeast China, and the frequent small-scale logging activity by local people was the dominated disturbance regime in forests in this region over the past several decades. The objective of this study is to evaluate the demographic consequences of logging on Pinus massoniana, a pioneer tree species, at individual level (survival, growth, and fecundity) and population level (the population growth rate and size distribution) over short-term period. The size of tree individuals was combined with vital rates using various modeling approaches based on demographic data from three annual censuses. The integral projection model (IPM) was constructed and used to conduct comparative demographic analyses. Logging negatively affected the population growth rate: from a slight expansion before logging to a moderate decline after logging. This study found a significant reduction in seedling recruitment after logging, and plant growth and mortality were slightly enhanced. The survival of seedlings greatly contributes to population growth rate compared to other life stages for both periods (before and after logging) while its relative importance decreases after logging. Seedling growth is also important to population growth, and its relative importance increased after logging. Shrinkage and fecundity have a minimal contribution effect on the population growth rate. Growing plants in a nursery with a similar demography to P. massoniana could be beneficial for pioneer species regeneration in that this will improve the survival rate and growth of small individuals after logging.

Mate‐searching behavior in the invasive German wasp, Vespula germanica, in Patagonia

AbstractIn order to increase the probability of reproduction, social insects can adopt various mate‐finding strategies, such as increasing densities of males at specific locations, and/or visual and chemical cues that attract the opposite sex. In field and laboratory studies we investigated strategies used by the invasive eusocial wasp Vespula germanica (Fabricius) (Hymenoptera: Vespidae). In tethered flight assays, we established contrasting flight patterns in females and males that may partly explain how related individuals distribute spatially during the mating period. We also determined experimentally, in the field and in the laboratory via olfactometer assays, that gynes produce airborne pheromonal cues that attract drones and are important during mate location. Our field trials also suggest that visual cues play a role in mate location. We conclude that in addition to aspects of the social biology of the species, an efficient mate‐location strategy can partly explain the invasion success of the species. Tools to mitigate the damage caused by yellowjackets may be developed by focusing on reproductive castes, in addition to workers.

On the development of a predictive functional trait approach for studying terrestrial arthropods.

The characterization of ecological communities with functional traits allows to consider simultaneously the ability of a species to survive and reproduce in an environment, its interactions with other species and its effects on the ecosystem. Functional traits have been studied mainly by plant ecologists, but are increasingly common in the study of other taxa including arthropods. Arthropods represent a group for which a functional trait approach could be highly profitable because of their high diversity, abundance, ubiquity and role in many important ecological processes. This review synthesizes two decades of functional trait research on terrestrial arthropods. We show that while the approach has gained popularity, particularly in the last decade, the absence of clearly postulated hypotheses is a recurrent problem limiting generalization. Furthermore, studied traits are often poorly related to studied functions. To address these problems, we propose a step-by-step protocol to postulate clear hypotheses prior to trait selection and emphasize the need for a common set of more generalizable traits in future studies. Extending the functional trait approach to arthropods opens the door to improving our understanding of interspecific interactions and potential links between response and effect traits. We present the concept of trait-matching with several examples of arthropod traits known to be effective predictors of consumer-resource interactions. The development of a successful functional trait approach for terrestrial arthropods will necessitate an understanding of relevant traits, standardized measurement protocols and open access databases to share this information. Such progress will provide ecologists with a new set of tools to answer broad questions in several fields including the study of community assembly, ecological networks and multitrophic functionality.

Out of sight, out of mind? Testing the effects of overwinter habitat alterations on breeding territories of a migratory endangered species

AbstractAnthropogenic activities are one of the main threats to species living in human‐dominated landscapes and can promote behavioral changes in birds. This paper presents a novel approach to test how a migratory species responds to habitat alterations occurring in nesting territories during winter, when the species is absent. From 2000 to 2016, we collated territory and nest monitoring data for the endangered Egyptian vulture Neophron percnopterus in the north of Spain, to test the effects of overwinter habitat alterations (OHA) around breeding territories on the species reproductive output. We monitored 70 different nest sites and observed OHA around the nesting area in 39 cases. Probability of switching to another nesting site almost tripled after OHA. Pairs that switched experienced substantially decreased breeding success and avoided reusing the nest for 4.8 ± 4.64 years. The presence of determinate landscape elements that provide screening, such as forest patches, increased nest reoccupancy probability after OHA by more than 0.3, to 0. 55 (compared to 0.24 when no screening was present). We also found that the distance and the situation of the OHA were critical factors explaining reproduction probabilities at nest sites. Our results demonstrate how OHA can strongly impact the breeding behavior of long‐lived species. This highlights the need to examine the long‐term impact of OHA rather than focusing only on disturbances during sensitive periods, as is often the case with habitual mitigation measures.

Periodic events of Potamogeton alpinus in NW Poland (Pomerania region)

Abstract We have determined the timing of periodic events, such as leaf formation, flowering, fruiting and wintering of the aquatic plant Potamogeton alpinus. This study was performed in 15 watercourses situated in NW Poland in 2014–2015. Characteristics of the age stages were determined on the basis of 728 modules and phenological data were collected from permanent plots. In the study area, the plant appeared in week 12 of the calendar year, when water temperature in the streams was 5.4 ± 0.16°C. At that time, the first leafy juvenile shoots developed from winter buds. In week 22 (water temperature 13.9 ± 0.85°C), juvenile shoots became mature, whereas the first flowers were formed in week 24 (15.6 ± 1.04°C). The generative phase lasted twelve weeks with water temperature from 15.6 ± 1.04°C to 18.9 ± 3.23°C. Between weeks 37 and 44 (water temperature from 13.7 ± 0.77°C to 6.3 ± 1.05°C), senile shoots dominated in the population. From week 45 until week 11 of the next year (water temperature < 5.4 ± 0.16°C), the plants were in the winter resting stage. In our view, climate warming might disturb the phenology of P. alpinus, decreasing the probability of sexual reproduction of the species and the phenological distance between the Central European Plain and the Scandinavian populations.

A probabilistic cellular automata model for the dynamics of a population driven by logistic growth and weak Allee effect

We propose and investigate a one-parameter probabilistic mixture of one-dimensional elementary cellular automata under the guise of a model for the dynamics of a single-species unstructured population with nonoverlapping generations in which individuals have smaller probability of reproducing and surviving in a crowded neighbourhood but also suffer from isolation and dispersal. Remarkably, the first-order mean field approximation to the dynamics of the model yields a cubic map containing terms representing both logistic and weak Allee effects. The model has a single absorbing state devoid of individuals, but depending on the reproduction and survival probabilities can achieve a stable population. We determine the critical probability separating these two phases and find that the phase transition between them is in the directed percolation universality class of critical behaviour.

Life-history trade-offs vary with resource availability across the geographic range of a widespread plant.

Trade-offs between reproduction, growth and survival arise from limited resource availability in plants. Environmental stress is expected to exacerbate these negative correlations, but no studies have evaluated variation in life-history trade-offs throughout species geographic ranges. Here we analyse the costs of growth and reproduction across the latitudinal range of the widespread herb Plantago coronopus in Europe. We monitored the performance of thousands of individuals in 11 populations of P.coronopus, and tested whether the effects of growth and reproduction on a set of vital rates (growth, probability of survival, probability of reproduction and fecundity) varied with local precipitation and soil fertility. To account for variation in internal resources among individuals, we analysed trade-offs correcting for differences in size. Growth was negatively affected by previous growth and reproduction. We also found costs of growth and reproduction on survival, reproduction probability and fecundity, but only in populations with low soil fertility. Costs also increased with precipitation, possibly due to flooding-related stress. In contrast, growth was positively correlated with subsequent survival, and there was a positive covariation in reproduction between consecutive years under certain environments, a potential strategy to exploit temporary benign conditions. Overall, we found both negative and positive correlations among vital rates across P.coronopus geographic range. Trade-offs predominated under stressful conditions, and positive correlations arose particularly between related traits like reproduction investment across years. By analysing multiple and diverse fitness components along stress gradients, we can better understand life-history evolution across species' ranges, and their responses to environmental change.

Spatial patterns in occupancy and reproduction of Golden Eagles during drought: Prospects for conservation in changing environments

ABSTRACT We used a broad-scale sampling design to investigate spatial patterns in occupancy and breeding success of territorial pairs of Golden Eagles (Aquila chrysaetos) in the Diablo Range, California, USA, during a period of exceptional drought (2014–2016). We surveyed 138 randomly selected sample sites over 4 occasions each year and identified 199 pairs of eagles, 100 of which were detected in focal sample sites. We then used dynamic multistate modeling to identify relationships between site occupancy and reproduction of Golden Eagles relative to spatial variability in landscape composition and drought conditions. We observed little variability among years in site occupancy (3-yr mean = 0.74), but the estimated annual probability of successful reproduction was relatively low during the study period and declined from 0.39 (± 0.08 SE) to 0.18 (± 0.07 SE). Probabilities of site occupancy and reproduction were substantially greater at sample sites that were occupied by successful breeders in the previous ...

Reproductive Decisions in a “Fast-Living” Sciurid: A Case Study of the Yellow Ground Squirrel (Spermophilus fulvus)

The problem of the optimal distribution of time and energy between reproduction and the other vital functions and the choice of optimal reproductive tactics concerns all animals. The sequence of decisions largely determines overall individual reproductive success and fitness. The goal of the study was to summarize the factors determining the reproductive decision of the yellow ground squirrel (Spermophilus fulvus). Despite its relatively large size and extremely long hibernation, the yellow ground squirrels is characterized by rapid growth and maturation, in combination with a short life-span; the life cycle of the yellow ground squirrel proceeds according to the “fast” scenario. Analysis of the relationship between breeding indices of females and their individual characteristics has shown that the reproductive investment and success of females do not depend on the age, body condition, or previous reproductive history of the female. The only factor found to influence female reproduction is the date of emergence from hibernation: the later a female emerges, the lower the offspring mass is and the fewer offspring survive. At the same time, female annual investment in reproduction is very large and close to the mean lifetime reproductive investment estimated for female mammals. With a short life-span (approximately 2–3 years), females do not have the opportunity to distribute the reproductive effort across many breeding attempts, they seem to be able to recover quickly after reproduction. Nevertheless, a substantial portion of mature females (about 30%) annually do not produce litters for unknown reasons. The sex ratio among reproductively active individuals during the mating period is strongly biased toward females. This is due to the lower survival of males, the late maturation of young males in comparison with females, and the fact that, even in adult males, individuals in poor physical condition are not very active and hardly search for sexual partners, i.e., males demonstrate a trade-off in the distribution of costs for somatic processes and reproduction. When there is a surplus of females emerging from hibernation, there are more receptive females in the population than reproductively active males, and operational sex ratio (OSR, the ratio between females and males ready to mate) is skewed toward females. Since females live sparsely and are sedentary during the mating period, the probability of breeding for them depends on the availability of sexual partners: the females’ breeding chances increase with an increase in the local density of males and the proportion of males in the population at the time of the female’s estrus; the only explanation for the large proportion of non-breeding females is the shortage of sexual partners. Thus, the negative effect of the shortage of males on the probability of female reproduction is shown for the first time for a natural population of mammals; this opens a new perspective on the theory of sexual conflict. This phenomenon, which is not so typical of species in which the parental investment of the female far exceeds the male’s investment, is explained by the combination of sociodemographic conditions and the life-history patterns of the yellow ground squirrel.

长汀侵蚀退化区砍伐迹地马尾松种群动态

PDF HTML阅读 XML下载 导出引用 引用提醒 长汀侵蚀退化区砍伐迹地马尾松种群动态 DOI: 10.5846/stxb201706261148 作者: 作者单位: 湿润亚热带山地生态国家重点实验室培育基地,湿润亚热带山地生态国家重点实验室培育基地,福建师范大学地理科学学院,福建师范大学地理科学学院,湿润亚热带山地生态国家重点实验室培育基地,湿润亚热带山地生态国家重点实验室培育基地,湿润亚热带山地生态国家重点实验室培育基地,中国科学院植物研究所植被与环境变化国家重点实验室 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金面上项目（31470633）；国家重点研发计划（2017YFC05054） Population dynamics of Pinus massoniana in the logged forestland of Changting's eroded and degraded region Author: Affiliation: State Key Laboratory of Subtropical Mountain Ecology (Founded by Ministry of Science and Technology and Fujian Province),State Key Laboratory of Subtropical Mountain Ecology (Founded by Ministry of Science and Technology and Fujian Province),School of Geographical Science, Fujian Normal University,School of Geographical Science, Fujian Normal University,State Key Laboratory of Subtropical Mountain Ecology (Founded by Ministry of Science and Technology and Fujian Province),State Key Laboratory of Subtropical Mountain Ecology (Founded by Ministry of Science and Technology and Fujian Province),State Key Laboratory of Subtropical Mountain Ecology (Founded by Ministry of Science and Technology and Fujian Province), Fund Project: Population dynamics and maintenance mechanisms of pioneer species in subtropical red soil hilly region 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:砍伐是人类对植物种群最常见的干扰形式之一，种群结构及其动态在砍伐后会经历快速变化和调整时期。以长汀侵蚀退化地为研究区，基于砍伐迹地上马尾松种群4年生活史调查，利用积分投影模型（IPM，Integral Projection Model）结合传统种群统计分析方法，揭示砍伐迹地上马尾松种群增长率变化过程及个体生命率对种群的影响。结果表明：砍伐迹地上马尾松种群处于衰退状态（λ < 1），且衰退程度不断加深。4年内幼苗数量大幅度减少，幼年树和成树数量增加。死亡在生活史各个阶段均有出现，幼苗是死亡的主要来源；植株生长量随着个体的增大和时间的增加而增加，生长增量由大到小依次为：成年树，幼年树和幼苗；植株繁殖概率逐年提升，但新生幼苗数量逐年下降。弹性分析显示，个体尤其是幼苗的存活对种群至关重要，小径级植株的正生长有利于种群恢复，大径级植株的正生长不利于种群发展，而负增长和繁殖贡献均十分有限。 Abstract:Logging is one of the most common forms of human disturbance for plants. Population structure and its dynamics experience rapid changes and regulates following logging. We studied the life history traits and population dynamics of a long-lived dominant tree Pinus massoniana in the red soil eroded and degraded region of China. Demographic data from four annual censuses (2013-2016) were used to parameterize integral projection model (IPM) to determine changes in population growth rate and their contributions to population development. The results showed that:the population growth rate (λ) declined gradually (λ < 1) over time in the logged forestland. During the censuses periods, the number of seedlings decreased substantially, whereas juveniles and adults increased slightly. Mortality was observed during all life stages, mainly in seedlings and small individuals. Diameter growth increased with individual's size, with adult individuals showing faster growth than those at other life stages. Reproduction probability increased gradually, but the number of new recruits declined. In addition, elasticity analysis revealed that the survival of individuals, especially seedlings, was the key for population growth. The growth of the small individuals positively affected population development, while the growth of large plants had negative effects. There were minimal contributions of shrinkage and fecundity to population growth rate. 参考文献 相似文献 引证文献

From gestation to weaning: Combining robust design and multi‐event models unveils cost of lactation in a large herbivore

The cost of current reproduction on survival or future reproduction is one of the most studied trade-offs governing resource distribution between fitness components. Results have often been clouded, however, by the existence of individual heterogeneity, with high-quality individuals able to allocate energy to several functions simultaneously, at no apparent cost. Surprisingly, it has also rarely been assessed within a breeding season by breaking down the various reproductive efforts of females from gestation to weaning, even though resource availability and energy requirements vary greatly. We filled this gap by using an intensively monitored population of Pyrenean chamois and by expanding a new methodological approach integrating robust design in a multi-event framework. We distinguished females that gave birth or not, and among reproducing females whether they lost their kid or successfully raised it until weaning. We estimated spring and summer juvenile survival, investigated whether gestation, lactation or weaning incurred costs on the next reproductive occasion, and assessed how individual heterogeneity influenced the detection of such costs. Contrary to expectations if trade-offs occur, we found a positive relationship between gestation and adult survival suggesting that non-breeding females are in poor condition. Costs of reproduction were expressed through negative relationships between lactation and both subsequent breeding probability and spring juvenile survival. Such costs could be detected only once individual heterogeneity (assessed as two groups contrasting good vs. poor breeders) and time variations in juvenile survival were accounted for. Early lactation decreased the probability of future reproduction, providing quantitative evidence of the fitness cost of this period recognized as the most energetically demanding in female mammals and critical for neonatal survival. The new approach employed made it possible to estimate two components of kid survival that are often considered practically unavailable in free-ranging populations, and also revealed that reproductive costs appeared only when contrasting the different stages of reproductive effort. From an evolutionary perspective, our findings stressed the importance of the temporal resolution at which reproductive cost is studied, and also provided insights on the reproductive period during which internal and external factors would be expected to have the greatest fitness impact.

Extreme allomaternal care and unequal task participation by unmated females in a cooperatively breeding spider

Division of reproductive behaviour and alloparental care are key aspects of many animal societies. In cooperatively breeding species, variation in helping effort and unequal task participation are frequently observed. However, the extent to which the reproductive state of an individual affects the tasks performed during offspring care remains poorly understood. In the social spider Stegodyphus dumicola, approximately 40% of females reproduce, and mothers show extended maternal care including eggsac tending, regurgitation feeding and matriphagy, in which they are consumed by the offspring. We asked whether and to what extent virgin females participate in extreme maternal care and whether they differ from reproducing females in foraging activity. We show that virgin females contributed to all aspects of extended brood care, including regurgitation feeding and matriphagy. This suggests a physiological adaptation in virgin females to cooperative breeding, since in the subsocial Stegodyphus lineatus only mated females provide extended maternal care. Although virgin females and mothers are behaviourally totipotent, we found evidence for task differentiation as virgins engaged less in brood care and more in prey attack than mothers. High relatedness among nestmates and low probability of future reproduction in virgin helpers suggest alignment of reproductive interests between mothers and allomothers. Therefore, extreme allomaternal care by virgin helpers can be considered an adaptation to cooperative breeding in social spiders.

Assessing the resistance potential of Phytophthora nicotianae, the causal agent of black shank of tobacco, to oxathiopropalin with laboratory mutants

Black shank, caused by Phytophthora nicotianae van Breda de Haan, is a devastating disease of tobacco (Nicotiana tabacum L.) throughout the world. The newly-discovered fungicide, oxathiapiprolin has shown efficacy against P. nicotianae, but the potential for fungicide resistance is unknown. Production of oxathiapiprolin resistant P. nicotianae isolates was attempted through mass selection of zoospores, UV light mutagenesis, and mycelial adaptation through repeated culturing on oxathiapiprolin-amended medium. No resistant isolates were detected from mass zoospore selection. UV light mutagenesis of mycelium generated two isolates, EdgeB7-M1 and YadA28-M1, with stable mycelial and sporangial resistance to oxathiapiprolin. Isolate EdgeB7-M1 remained pathogenic to tobacco, while YadA28-M1 was nonpathogenic. For mycelial adaptation, 48 colonies, 12 replicate colonies from four isolates, were transferred 15 times on oxathiapiprolin-amended medium. Twelve of the 48 colonies had a significant increase in mycelial insensitivity to oxathiapiprolin; however, mycelial adaptation was not stable. Mycelial growth and sporangia production of the adapted isolates was significantly less compared to the wild-type whereas only one remained pathogenic to tobacco. In summary, the generation of oxathiapiprolin resistant P. nicotianae isolates was feasible. Constant exposure to oxathiapiprolin increased insensitivity, however fitness costs associated with insensitivity reduced the probability of isolate reproduction and survival.

High and variable mortality of leatherback turtles reveal possible anthropogenic impacts.

The number of nesting leatherback turtles (Dermochelys coriacea) in the eastern Pacific Ocean has declined dramatically since the late 1980s. This decline has been attributed to egg poaching and interactions with fisheries. However, it is not clear how much of the decline should also be ascribed to variability in the physical characteristics of the ocean. We used data on individually marked turtles that nest at Playa Grande, Costa Rica, to address whether climatic variability affects survival and inter-breeding interval. Because some turtles might nest undetected, we used capture-recapture models to model survival probability accounting for a detection failure. In addition, as the probability of reproduction is constrained by past nesting events, we formulated a new parameterization to estimate inter-breeding intervals and contrast hypotheses on the role of climatic covariates on reproductive frequency. Average annual survival for the period 1993-2011 was low (0.78) and varied over time ranging from 0.49 to 0.99 with a negative temporal trend mainly due to the high mortality values registered after 2004. Survival probability was not associated with the Multivariate ENSO Index of the South Pacific Ocean (MEI) but this index explained 24% of the temporal variability in the reproductive frequency. The probability of a turtle to permanently leave after the first encounter was 26%. This high proportion of transients might be associated with a high mortality cost of the first reproduction or with a long-distance nesting dispersal after the first nesting season. Although current data do not allow separating these two hypotheses, low encounter rate at other locations and high investment in reproduction, supports the first hypothesis. The low and variable annual survival probability has largely contributed to the decline of this leatherback population. The lack of correlation between survival probability and the most important climatic driver of oceanic processes in the Pacific discards a climate-related decline and point to anthropogenic sources of mortality as the main causes responsible for the observed population decline.

Influence of Early Reproductive Success on Longevity and Late Reproductive Success in an Alpine Ungulate.

The life-history theories of aging predict lifetime trade-offs between early reproductive allocation and late-life survival, reproduction, or both components of fitness. Recent studies in wild populations have found evidence for these early-late life trade-offs, but rarely have they been found across multiple traits while exploring the additional effects of variation in environmental conditions and individual quality. Benefiting from longitudinal data on adult female mountain goats (Oreamnos americanus), we investigated the influence of age at first reproduction (AFR) and early reproductive success (ERS) on longevity, late reproductive success, and senescence rates while accounting for the influence of natal environmental conditions and individual quality. Contrary to predictions, we did not find evidence for early-late life trade-offs. Instead, an earlier AFR and a greater ERS had positive but weak direct effects on late reproductive success. Natal population density, however, was the strongest determinant of all life-history traits, having a direct negative effect on female longevity, late reproductive success, AFR, and ERS. Although natal density reduced the probability of annual reproduction and annual survival during adulthood, higher allocation to reproduction in early life and poorer natal conditions did not lead to accelerated rates of senescence during adulthood. The results of this investigation provide an integrated picture of early-late life trade-offs, underscoring the importance of accounting for environmental conditions because of their potentially strong implications for population dynamics.

Physiological condition and migratory experience affect fitness‐related outcomes in adult female sockeye salmon

AbstractRelating fish physiology, behaviour and experience to fitness‐related outcomes at the individual scale is ecologically significant, but presents difficulties for free‐ranging fishes in natural systems. Physiological state (e.g. level of stress or maturity) and experience (e.g. habitat use or exposure to stressors) may alter the probability of survival or reproduction. This study examined the relative influence of physiology and migratory experience on survival, migration duration, reproductive longevity, and egg retention in adult female sockeye salmon (Oncorhynchus nerka) from a Fraser River population. One hundred and thirty‐five females were plasma sampled and tagged with radio transmitters and archival temperature loggers. Fish were tracked 55 km through two natal lakes to spawning grounds, following passage of a hydroelectric dam. For 39 females, we assessed the proportion of time within an optimal temperature (ToptAS) window (13.4–19.5°C), which provides ≥90% of maximum aerobic scope. Females with lower plasma glucose concentrations were more likely to reach spawning grounds. Early migrants spent longer in natal lakes. More time in the ToptAS window was associated with greater reproductive longevity and lower probability of egg retention. Later arriving females had reduced longevity on spawning grounds, as did females that retained eggs. Exposure to higher dam discharge was associated with reduced reproductive longevity and greater probability of egg retention, but not lower survival, indicating a delayed effect of dam passage. Our results underscore the complexity of factors governing fitness‐related outcomes for salmonids, particularly the importance of female experience in the days and weeks prior to spawning.