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Long-lived Species (long-lived + species)
Selected AbstractsNoninvasive Stress and Reproductive Measures of Social and Ecological Pressures in Free-Ranging African ElephantsCONSERVATION BIOLOGY, Issue 4 2001C. A. H. Foley This, coupled with political pressures to delist the elephant, has created a need for noninvasive physiological measures that can quantify the long-term effects of past mortality patterns of this long-lived species. We collected fresh fecal samples from 16 female elephants in three different groups over 23 months at Tarangire National Park, Tanzania, and analyzed them for fecal progesterone and cortisol metabolites. Social and ecological measures were collected concurrently. Fecal progesterone metabolite measures corresponded significantly with stage of gestation, and appear to be able to confirm pregnancy in female elephants from as early as 3 months of gestation. We found that progesterone metabolite concentrations were significantly lower during the dry season than during the wet season after controlling for stage of gestation. Fecal cortisol metabolite concentrations showed the opposite seasonal pattern, being significantly higher in the dry season and inversely correlated with rainfall across seasons. Fecal cortisol metabolite concentrations also increased with group size and were correlated positively with dominance rank in the largest group. Our results suggest that measures of progesterone and cortisol metabolites in feces provide indices of reproductive function and physiological stress that can quantify both natural and human disturbances in African elephants. These measures are ideally suited for monitoring the long-term effects of social disruption from poaching and a variety of other management concerns. Resumen: Debido a la cacería furtiva, la población de elefante africano ( Loxodonta africana) declinó en un 60%, principalmente adultos, entre 1979 y 1988. Esto, aunado a presiones políticas para eliminar al elefante de las listas de especies en peligro, ha creado la necesidad de medidas fisiológicas no invasivas que puedan cuantificar efectos a largo plazo de patrones de mortalidad en el pasado de esta especie longeva. Recolectamos muestras fecales de 16 elefantes hembras en tres grupos diferentes en el Parque Nacional Tarangire, Tanzania a lo largo de 23 meses, y las analizamos para detectar metabolitos de progesterona fecal y de cortisol. Al mismo tiempo se recolectaron medidas sociales y ecológicas. Las medidas de metabolitos de progesterona fecal correspondieron significativamente con la etapa de gestación, y parecen permitir la confirmación de preñez en elefantes hembras tan temprano como a los tres meses de gestación. Las concentraciones de metabolitos de progesterona fueron significativamente menores durante la época de sequía que en la de lluvias después de controlar para la etapa de gestación. Las concentraciones de metabolitos de cortisol fecal mostraron un patrón estacional opuesto, siendo significativamente más altas en la época de sequía e inversamente correlacionados con la precipitación en todas las estaciones. Las concentraciones de metabolitos de cortisol fecal también incrementaron con el tamaño del grupo y se correlacionaron positivamente con el rango de dominancia en el grupo más grande. Nuestros resultados sugieren que las medidas de metabolitos de progesterona y cortisol en las heces proporcionan índices de la función reproductiva y del estrés fisiológico que puede cuantificar perturbaciones, tanto naturales como humanas, en elefantes africanos. Estas medidas son idealmente adecuadas para monitorear efectos a largo plazo de la disrupción social por la cacería furtiva y así como una variedad de aspectos del manejo. [source] The effect of short fire cycles on the cover and density of understorey sprouting species in South African mountain fynbosDIVERSITY AND DISTRIBUTIONS, Issue 5 2000J. H. J. Vlok Abstract. Two South African mountain fynbos sites were studied to determine the effect of short fire cycles on the cover and density of understorey sprouting species and their subsequent effect on plant-species richness. Frequent fires (4,6 years between burns) increased the cover of sprouting species by 32% when compared to an adjacent site where the penultimate fire was 28 years previously. There was little or no effect of fire frequency on the densities of understorey sprouters; however, individuals were larger at sites with short fire cycles. The response of individual species of sprouters was variable with one species, Hypodiscus striatus, showing no response to fire frequency. The impact of sprouting species on the species richness of the plant community was great. The mean number of species recorded in quadrats with a high cover of sprouters was 60% lower in comparison to quadrats with low covers or under the burned skeletons of overstorey proteas. The effect of sprouters was consistent for all functional groups of species (i.e. sprouters, non-sprouters, short-lived and long-lived species), in each case reducing the number of species present. [source] Estimating the growth of a newly established moose population using reproductive valueECOGRAPHY, Issue 3 2007Bernt-Erik Sæther Estimating the population growth rate and environmental stochasticity of long-lived species is difficult because annual variation in population size is influenced by temporal autocorrelations caused by fluctuations in the age-structure. Here we use the dynamics of the reproductive value to estimate the long-term growth rate s and the environmental variance of a moose population that recently colonized the island of Vega in northern Norway. We show that the population growth rate was high (,=0.26). The major stochastic influences on the population dynamics were due to demographic stochasticity, whereas the environmental variance was not significantly different from 0. This supports the suggestion that population growth rates of polytocous ungulates are high, and that demographic stochasticity must be assessed when estimating the growth of small ungulate populations. [source] Environmental variation and experience-related differences in the demography of the long-lived black-browed albatrossJOURNAL OF ANIMAL ECOLOGY, Issue 1 2007MARIE NEVOUX Summary 1It has been largely demonstrated that demographic performances of animals increase with age or experience as a result of an improvement of foraging skills, an increasing reproductive effort or a selection process. However, little is known about the age or experience-related response of populations to environmental variations. Theoretical studies consider that age-related variations of the performances are greater under more restricting conditions, but this has rarely been tested. 2We tested this hypothesis on a long-lived species, black browed albatross Thalassarche melanophrys Temminck, using a long-term capture,mark,recapture data set. We investigated the responses of a population to climate, by studying the effects of climatic factors and breeding experience on survival and breeding success. 3First-time breeders appear to be poorer performers compared with experienced adults, with lower reproductive success and lower survival. In addition, interannual variations of demographic traits were partly explained by climatic indices, reflecting environmental variations. The survival probability of black-browed albatrosses varied with experience and climate, and differences being greater under harsh conditions. By contrast, the reproductive success of inexperienced individuals was affected by climatic fluctuations in the same way as the experienced ones. 4First breeding event acts as a strong selective process on the highly heterogeneous class of inexperienced individuals, suggesting the increase in survival and breeding success with experience may mainly reflect a reduction in the heterogeneity among individual qualities. [source] Matrix models for a changeable world: the importance of transient dynamics in population managementJOURNAL OF APPLIED ECOLOGY, Issue 3 2010Thomas H. G. Ezard Summary 1.,Matrix population models are tools for elucidating the association between demographic processes and population dynamics. A large amount of useful theory pivots on the assumption of equilibrium dynamics. The preceding transient is, however, of genuine conservation concern as it encompasses the short-term impact of natural or anthropogenic disturbance on the population. 2.,We review recent theoretical advances in deterministic transient analysis of matrix projection models, considering how disturbance can alter population dynamics by provoking a new population trajectory. 3.,We illustrate these impacts using plant and vertebrate systems across contiguous and fragmented landscapes. 4.,Short-term responses are of fundamental relevance for applied ecology, because the time-scale of transient effects is often similar to the length of many conservation projects. Investigation of the immediate, post-disturbance phase is vital for understanding how population processes respond to widespread disturbance in the short- and into the long term. 5.,Synthesis and applications.,Transient analysis is critical for understanding and predicting the consequences of management activities. By considering short-term population responses to perturbations, especially in long-lived species, managers can develop more informed strategies for species harvesting or controlling of invasive species. [source] Population structure and establishment of the threatened long-lived perennial Scorzonera humilis in relation to environmentJOURNAL OF APPLIED ECOLOGY, Issue 2 2002Guy Colling Summary 1The intensification of agriculture has resulted in the decline of many plant species of nutrient-poor wet grasslands. At some sites local populations of long-lived characteristic species have persisted and might benefit from recent extensification schemes. However, little is known about the population biology of these plants, and the prospects for the populations are uncertain. 2We studied the population structure and establishment of the long-lived Scorzonera humilis in 23 populations in Luxembourg and neighbouring Belgium. Two types of populations could be distinguished according to their population structure: regenerating populations, with a high proportion of plants with only one or a few rosettes, and aged populations, with a low proportion of small, young plants but a high proportion of individuals with many rosettes. The total density of Scorzonera individuals was higher in regenerating than in aged populations. 3Within sites, S. humilis was restricted to more open and nutrient-poor patches. The composition of the vegetation in plots where S. humilis was present was significantly different from that of plots without the species, indicating that S. humilis is restricted to particular microhabitats. 4In multiple regression analyses, environmental variables explained a large part of the variation in the total density of genets, the density of genets of different size and the density of rosettes. The main variables of influence were site productivity and soil moisture. With increasing productivity and decreasing soil moisture the proportion of small genets decreased and that of large genets increased. Increased productivity had contrasting effects at the genet and ramet (rosette) levels. While genet density decreased, ramet density increased, indicating that if a site is fertilized, recruitment of new genets and survival of genets is reduced, but growth of surviving genets is increased. 5The results of a sowing experiment indicated that an aged population structure was due to a lack of recruitment. The number of seeds that germinated and the proportion of seedlings that survived until the next summer were positively correlated with soil moisture and negatively with productivity. Germination rate and establishment success were significantly higher in Molinion grassland than in the Calthion grasslands. 6The results suggest that for long-lived species the size and number of populations may not be good indicators of the status of a species. In S. humilis large populations (> 1000 genets) still exist, but all are of the aged type. In order to preserve existing populations of S. humilis, management should aim to reduce productivity and increase soil moisture. [source] Dynamics of black spot sea bream (Pagellus bogaraveo) mean length: evaluating the influence of life history parameters, recruitment, size selectivity and exploitation ratesJOURNAL OF APPLIED ICHTHYOLOGY, Issue 3 2006K. Erzini Summary Stochastic simulations were used to evaluate the influence of recruitment pattern (log-normal, decreasing), size selectivity (normal, logistic model) and fishing mortality pattern (abrupt, continuous increase in fishing mortality) on the evolution of mean length and the dispersion of mean length for a relatively long-lived deep-water species, the black spot sea bream (Pagellus bogaraveo). An abrupt increase in fishing mortality resulted in mean size decreasing and stabilizing at a lower level while a steady increase in fishing mortality caused the continuous decrease in mean size that has been reported for many long-lived species. Decrease in mean size was greatest for logistic model simulations and for cases where fish were susceptible to capture at a small size. Logistic selectivity, with decreasing recruitment and increasing fishing mortality over time, resulted in mean length and variability in mean length trends similar to that observed for the Strait of Gibraltar fishery. Furthermore, it was found with the declining recruitment that moderate increases in fishing mortality can result in significant decreases in mean length. Given the importance of mean size as an indicator of the state of a resource, these simulations are a useful alternative or complement to standard fisheries assessment methods, helping to provide information on exploitation patterns and rates that can be used for conservation and management. [source] Insights from comparative analyses of aging in birds and mammalsAGING CELL, Issue 2 2010Robert E. Ricklefs Summary Many laboratory models used in aging research are inappropriate for understanding senescence in mammals, including humans, because of fundamental differences in life history, maintenance in artificial environments, and selection for early aging and high reproductive rate. Comparative studies of senescence in birds and mammals reveal a broad range in rates of aging among a variety of taxa with similar physiology and patterns of development. These comparisons suggest that senescence is a shared property of all vertebrates with determinate growth, that the rate of senescence has been modified by evolution in response to the potential life span allowed by extrinsic mortality factors, and that most variation among species in the rate of senescence is independent of commonly ascribed causes of aging, such as oxidative damage. Individuals of potentially long-lived species, particularly birds, appear to maintain high condition to near the end of life. Because most individuals in natural populations of such species die of aging-related causes, these populations likely harbor little genetic variation for mechanisms that could extend life further, or these mechanisms are very costly. This, and the apparent evolutionary conservatism in the rate of increase in mortality with age, suggests that variation in the rate of senescence reflects fundamental changes in organism structure, likely associated with the rate of development, rather than physiological or biochemical processes influenced by a few genes. Understanding these evolved differences between long-lived and short-lived organisms would seem to be an essential foundation for designing therapeutic interventions with respect to human aging and longevity. [source] Spatio-temporal dynamics and local hotspots of initial recruitment in vertebrate-dispersed treesJOURNAL OF ECOLOGY, Issue 4 2008Arndt Hampe Summary 1Initial recruitment, or the arrival and establishment of propagules, is the most variable period in the life cycle of long-lived plants, and the extent to which studies of initial recruitment can be used to predict patterns of regeneration remains unresolved. 2We investigated the spatio-temporal dynamics of initial recruitment across five populations of three fleshy-fruited tree species from contrasting environments. Among-year variation in total seedfall, dispersed seedfall and seedling distributions was examined using analytical approaches that are new to the field and that explicitly incorporate space and allow comparisons among studies. 3Observed patterns ranged from remarkable across-year consistency in seedfall distributions and strong spatial coupling between seed and seedling stages to extensive variation and almost complete independence of stages. Spatial distributions of frugivore-mediated seedfall were markedly more consistent than those of the total seedfall in two of the five populations. Seedling distributions were generally more variable among years than seedfall distributions. 4All populations showed a positive relationship between the long-term mean density of recruitment at a given microsite and its year-to-year consistency. This relationship remained valid when considering only microsites away from fruiting tree canopies (i.e. those receiving actually dispersed seeds), and was virtually independent of their distance to the nearest fruiting tree. 5Synthesis. Our results point to the existence of some general rules behind the idiosyncratic recruitment dynamics of perennial plant populations, which should help with projecting spatial patterns of plant establishment in long-lived species. In particular, those microsites that combine a great intensity with a high year-to-year consistency of recruitment should represent potential regeneration ,hotspots' whose identification and characterization can be of great use for the management and conservation of naturally regenerating tree populations. [source] Low complex I content explains the low hydrogen peroxide production rate of heart mitochondria from the long-lived pigeon, Columba liviaAGING CELL, Issue 1 2010Adrian J. Lambert Summary Across a range of vertebrate species, it is known that there is a negative association between maximum lifespan and mitochondrial hydrogen peroxide production. In this report, we investigate the underlying biochemical basis of the low hydrogen peroxide production rate of heart mitochondria from a long-lived species (pigeon) compared with a short-lived species with similar body mass (rat). The difference in hydrogen peroxide efflux rate was not explained by differences in either superoxide dismutase activity or hydrogen peroxide removal capacity. During succinate oxidation, the difference in hydrogen peroxide production rate between the species was localized to the ,pH-sensitive superoxide producing site within complex I. Mitochondrial ,pH was significantly lower in pigeon mitochondria compared with rat, but this difference in ,pH was not great enough to explain the lower hydrogen peroxide production rate. As judged by mitochondrial flavin mononucleotide content and blue native polyacrylamide gel electrophoresis, pigeon mitochondria contained less complex I than rat mitochondria. Recalculation revealed that the rates of hydrogen peroxide production per molecule of complex I were the same in rat and pigeon. We conclude that mitochondria from the long-lived pigeon display low rates of hydrogen peroxide production because they have low levels of complex I. [source] Reduced reproductive success and offspring survival in fragmented populations of the forest herb Phyteuma spicatumJOURNAL OF ECOLOGY, Issue 6 2005ANNETTE KOLB Summary 1Habitat fragmentation, which reduces the size and increases the isolation of populations, is a major threat to biodiversity. For Phyteuma spicatum, a self-incompatible, rare understorey herb in deciduous forests of north-western Germany, I tested the hypotheses that: (i) fitness (in terms of reproductive success) is reduced in small or isolated populations, (ii) reproduction in small populations is reduced by pollen limitation and (iii) genetic effects cause fitness reductions in small populations. 2I compared the reproductive success of plants of Phyteuma in 14 populations of different size and degree of isolation. Seed production was, as predicted, positively related to population size but was also influenced by plant size, although not by population isolation, density or habitat quality. 3I performed supplemental hand-pollinations in 10 of the 14 populations using pollen from the same population (test for pollen quantity) or from another large population (pollen quality). The proportional difference in seed production between hand-pollinated plants and open-pollinated controls increased with decreasing population size, indicating pollinator limitation of reproduction in small populations. There was no difference between the two hand-pollination treatments, suggesting that a sufficient number of cross-compatible mates was available even in the smallest populations. 4Progeny from the 14 populations were grown for 32 weeks in a common environment. There was no effect of population size on germination, but final seedling survival was positively related to population size, and this relationship was more pronounced in the glasshouse than under more favourable growing conditions in a common garden. Genetic effects may thus reduce fitness (here measured in terms of survival) in plants from small populations, making them more susceptible to environmental stress. 5The results suggest that both reproduction and offspring performance may be reduced in small populations even of long-lived species such as Phyteuma spicatum. Different processes, such as pollen limitation and genetic deterioration, may interact and affect local population dynamics and the persistence of species in fragmented landscapes. [source] High hybrid fitness at seed and seedling life history stages in Louisiana irisesJOURNAL OF ECOLOGY, Issue 3 2003Jill A. Johnston Summary 1,Relative fitness of hybrid genotypes will determine the role that hybrids can play in the evolution of a plant species complex. To realistically evaluate hybrid fitness and how environmental variation affects fitness in a long-lived species, all life stages must be considered. 2,We evaluated germination, seedling survival and growth of two Louisiana iris species and their early generation hybrids in several experimental environments created by manipulating light and water levels. 3,Species and hybrids all required similar moist conditions for germination. The proportion of germinated seeds was highest in shade and seedling survival highest in sun. 4,Iris brevicaulis exhibited the lowest germination and seedling survival overall, yet those individuals that survived grew vigorously. Iris fulva had high levels of germination and seedling survival, but yielded the smallest plants at the end of one season of growth. 5,Germination rates, seedling survival and seedling growth of hybrids equalled or exceeded one or both parent species, indicating that hybrids in this system have high relative fitness at seed and seedling stages in several environmental conditions. 6,We conclude that Iris fulva and I. brevicaulis share a common regeneration niche and similar early stage relative fitness with their hybrids. Thus, environment-dependent fitness in this system is due primarily to selection at adult stages. [source] Skin-derived fibroblasts from long-lived species are resistant to some, but not all, lethal stresses and to the mitochondrial inhibitor rotenoneAGING CELL, Issue 1 2007James M. Harper Summary Fibroblast cell lines were developed from skin biopsies of eight species of wild-trapped rodents, one species of bat, and a group of genetically heterogeneous laboratory mice. Each cell line was tested in vitro for their resistance to six varieties of lethal stress, as well as for resistance to the nonlethal metabolic effects of the mitochondrial inhibitor rotenone and of culture at very low glucose levels. Standard linear regression of species-specific lifespan against each species mean stress resistance showed that longevity was associated with resistance to death induced by cadmium and hydrogen peroxide, as well as with resistance to rotenone inhibition. A multilevel regression method supported these associations, and suggested a similar association for resistance to heat stress. Regressions for resistance to cadmium, peroxide, heat, and rotenone remained significant after various statistical adjustments for body weight. In contrast, cells from longer-lived species did not show significantly greater resistance to ultraviolet light, paraquat, or the DNA alkylating agent methylmethanesulfonate. There was a strong correlation between species longevity and resistance to the metabolic effects of low-glucose medium among the rodent cell lines, but this test did not distinguish mice and rats from the much longer-lived little brown bat. These results are consistent with the idea that evolution of long-lived species may require development of cellular resistance to several forms of lethal injury, and provide justification for evaluation of similar properties in a much wider range of mammals and bird species. [source] Long-lived intermediates in reversible addition,fragmentation chain-transfer (RAFT) polymerization generated by , radiationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 8 2002Christopher Barner-Kowollik Abstract A novel experimental procedure is presented that allowed probing of reversible addition,fragmentation chain-transfer (RAFT) free-radical polymerizations for long-lived species. The new experimental sequence consisted of gamma irradiation of a mixture of initial RAFT agent (cumyl dithiobenzoate) and monomer at ambient temperature, a subsequent predetermined waiting period without initiation source also at ambient temperature, and then heating of the reaction mixture to a significantly higher temperature. After each sequence step, the monomer conversion and molecular weight distribution were determined, indicating that controlled polymer formation occurs only during the heating period. The results indicated that stable intermediates (either radical or nonradical in nature) are present in such experiments because thermal self-initiation of the monomer can be excluded as the reason for polymer formation. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1058,1063, 2002 [source] Support for a metapopulation structure among mammalsMAMMAL REVIEW, Issue 3 2009PIETER I. OLIVIER ABSTRACT 1The metapopulation metaphor is increasingly used to explain the spatial dynamics of animal populations. However, metapopulation structure is difficult to identify in long-lived species that are widely distributed in stochastic environments, where they can resist extinctions. The literature on mammals may not provide supporting evidence for classic metapopulation dynamics, which call for the availability of discrete habitat patches, asynchrony in local population dynamics, evidence for extinction and colonization processes, and dispersal between local populations. 2Empirical evidence for metapopulation structure among mammals may exist when applying more lenient criteria. To meet these criteria, mammals should live in landscapes as discrete local breeding populations, and their demography should be asynchronous. 3We examined the literature for empirical evidence in support of the classical criteria set by Hanski (1999), and for the more lenient subset of criteria proposed by Elmhagen & Angerbjörn (2001). We suggest circumstances where metapopulation theory could be important in understanding population processes in mammals of different body sizes. 4The patchy distribution of large (>100 kg) mammals and dispersal often motivate inferences in support of a metapopulation structure. Published studies seldom address the full suite of classical criteria. However, studies on small mammals are more likely to record classic metapopulation criteria than those on large mammals. The slow turnover rate that is typical for medium-sized and large mammals apparently makes it difficult to identify a metapopulation structure during studies of short duration. 5To identify a metapopulation structure, studies should combine the criteria set by Hanski (1999) and Elmhagen & Angerbjörn (2001). Mammals frequently live in fragmented landscapes, and processes involved in the maintenance of a metapopulation structure should be considered in conservation planning and management. [source] Limitation of population recovery: a stochastic approach to the case of the emperor penguinOIKOS, Issue 9 2009Stéphanie Jenouvrier Major population crashes due to natural or human-induced environmental changes may be followed by recoveries. There is a growing interest in the factors governing recovery, in hopes that they might guide population conservation and management, as well as population recovery following a re-introduction program. The emperor penguin Aptenodytes forsteri population in Terre Adélie, Antarctica, declined by 50% during a regime shift in the mid-1970s, when abrupt changes in climate and ocean environment regimes affected the entire Southern Ocean ecosystem. Since then the population has remained stable and has not recovered. To determine the factors limiting recovery, we examined the consequences of changes in survival and breeding success after the regime shift. Adult survival recovered to its pre-regime shift level, but the mean breeding success declined and the variance in breeding success increased after the regime shift. Using stochastic matrix population models, we found that if the distribution of breeding success observed prior to the regime shift had been retained, the emperor penguin population would have recovered, with a median time to recovery of 36 years. The observed distribution of breeding success after the regime shift makes recovery very unlikely. This indicates that the pattern of breeding success is sufficient to have prevented emperor penguin population recovery. The population trajectory predicted on the basis of breeding success agrees with the observed trajectory. This suggests that the net effect of any facors other than breeding success must be small. We found that the probability of recovery and the time to recovery depend on both the mean and variance of breeding success. Increased variance in breeding success increases the probability of recovery when mean success is low, but has the opposite effect when the mean is high. This study shows the important role of breeding success in determining population recovery for a long-lived species and demonstrates that demographic mechanisms causing population crash can be different from those preventing population recovery. [source] Female-biased dispersal, low female recruitment, unpaired males, and the extinction of small and isolated bird populationsOIKOS, Issue 2 2001Svein Dale Small and isolated populations are usually assumed to be at a high risk of extinction due to environmental or demographic stochasticity, genetic problems, or too little immigration. In birds, natal dispersal is usually female-biased, but the consequences of such a pattern on vulnerability to extinction of isolated populations has not received much attention before. In this paper I derive predictions as to how female-biased natal dispersal may differentially affect the extinction risk of populations and species with contrasting distributions, migratory behaviours, life histories and mating systems. Female-biased dispersal will lead to male-biased sex ratios in small, isolated or fragmented populations, in particular because recent research has shown that females often have a limited ability to search for mates and may therefore effectively be lost from the breeding population if they disperse into areas empty of conspecifics. I reviewed published studies on birds and found that a high proportion of unpaired males is common in isolated populations or populations in small habitat fragments. Dispersal of females may therefore increase the vulnerability to extinction of small or isolated populations, or populations at the periphery of a species' distribution range. I also predict that vulnerability to extinction should be greater for migratory than for resident species and greater for short-lived than for long-lived species because of differences in the time available for females to locate unpaired males. Further, extinction risk may also be greater for birds than for mammals due to differences in which sex disperses and patterns of parental care. Finally, mating system will also affect vulnerability to extinction when natal dispersal leads to biased sex ratios. I review available evidence for these predictions (e.g. songbird declines in North America) and discuss implications for conservation. [source] Fetal origins of developmental plasticity: Are fetal cues reliable predictors of future nutritional environments?AMERICAN JOURNAL OF HUMAN BIOLOGY, Issue 1 2005Christopher W. Kuzawa Evidence that fetal nutrition triggers permanent adjustments in a wide range of systems and health outcomes is stimulating interest in the evolutionary significance of these responses. This review evaluates the postnatal adaptive significance of fetal developmental plasticity from the perspective of life history theory and evolutionary models of energy partitioning. Birthweight is positively related to multiple metabolically costly postnatal functions, suggesting that the fetus has the capacity to distribute the burden of energy insufficiency when faced with a nutritionally challenging environment. Lowering total requirements may reduce the risk of negative energy balance, which disproportionately impacts functions that are not essential for survival but that are crucial for reproductive success. The long-term benefit of these metabolic adjustments is contingent upon the fetus having access to a cue that is predictive of its future nutritional environment, a problem complicated in a long-lived species by short-term ecologic fluctuations like seasonality. Evidence is reviewed suggesting that the flow of nutrients reaching the fetus provides an integrated signal of nutrition as experienced by recent matrilineal ancestors, which effectively limits the responsiveness to short-term ecologic fluctuations during any given pregnancy. This capacity for fetal nutrition to minimize the growth response to transient ecologic fluctuations is defined here as intergenerational "phenotypic inertia," and is hypothesized to allow the fetus to cut through the "noise" of seasonal or other stochastic influences to read the "signal" of longer-term ecologic trends. As a mode of adaptation, phenotypic inertia may help the organism cope with ecologic trends too gradual to be tracked by conventional developmental plasticity, but too rapid to be tracked by natural selection. From an applied perspective, if a trait like fetal growth is designed to minimize the effects of short-term fluctuations by integrating information across generations, public health interventions may be most effective if focused not on the individual but on the matriline. Am. J. Hum. Biol. 17:5,21, 2005. © 2004 Wiley-Liss, Inc. [source] Simulation of the population dynamics and social structure of the Virunga mountain gorillasAMERICAN JOURNAL OF PRIMATOLOGY, Issue 4 2004Martha M. Robbins Abstract An agent-based model was developed to simulate the growth rate, age structure, and social system of the endangered mountain gorillas (Gorilla beringei beringei) in the Virunga Volcanoes region. The model was used to compare two types of data: 1) estimates of the overall population size, age structure, and social structure, as measured by six censuses of the entire region that were conducted in 1971,2000; and 2) information about birth rates, mortality rates, dispersal patterns, and other life history events, as measured from three to five habituated research groups since 1967. On the basis of the research-group data, the "base simulation" predicted a higher growth rate than that observed from the census data (3% vs. 1%). This was as expected, because the research groups have indeed grown faster than the overall population. Additional simulations suggested that the research groups primarily have a lower mortality rate, rather than higher birth rates, compared to the overall population. Predictions from the base simulation generally fell within the range of census values for the average group size, the percentage of multimale groups, and the distribution of females among groups. However, other discrepancies predicted from the research-group data were a higher percentage of adult males than observed, an overestimation of the number of multimale groups with more than two silverbacks, and an overestimated number of groups with only two or three members. Possible causes for such discrepancies include inaccuracies in the census techniques used, and/or limitations with the long-term demographic data set obtained from only a few research groups of a long-lived species. In particular, estimates of mortality and male dispersal obtained from the research groups may not be representative of the entire population. Our final simulation addressed these discrepancies, and provided a better basis for further studies on the complex relationships among individual life history events, group composition, population age structure, and growth rate patterns. Am. J. Primatol. 63:201,223, 2004. © 2004 Wiley-Liss, Inc. [source] Assessment of demographic risk factors and management priorities: impacts on juveniles substantially affect population viability of a long-lived seabirdANIMAL CONSERVATION, Issue 2 2010M. E. Finkelstein Abstract Predicting population-level effects from changes in demographic rates of different life stages is critical to prioritize conservation efforts. Demographic modeling and sensitivity analysis in particular, has become a standard tool to evaluate how management actions influence species' survival. Demographic analyses have resulted in the robust generalization that, for long-lived species with delayed reproduction, population growth rates will be most sensitive to changes in survivorship of older-aged individuals. Although useful in guiding management, this simple maxim may limit options for conservation by causing managers to overlook actions that, although possibly not the most effective in terms of increasing a population's growth rate in an ideal world, can nonetheless more feasibly and rapidly slow a population's decline. We examine the population-level benefits of increasing chick survival in a long-lived seabird, the Laysan albatross Phoebastria immutabilis. Specifically, we use a simple deterministic modeling approach to evaluate the impact of chick mortality (from ingestion of lead-based paint) on the population growth rate (,) for Laysan albatross that breed on Sand Island, Midway Atoll (part of the Hawaiian Archipelago). We estimate that up to 7% of chicks on Sand Island fail to fledge as a result of lead poisoning, which will create a 16% reduction in the Laysan albatross population size (,190 000 less birds) at 50 years into the future. We demonstrate how straightforward management actions that increase juvenile survivorship (e.g. removal of lead-based paint) can help slow population declines while efforts are underway to reduce politically and logistically challenging threats to adult survivorship (e.g. mortality from international fisheries bycatch). Our work exemplifies a situation where overgeneralizations about demography can stifle useful conservation actions and highlights the need to consider the population-level benefits from multiple management strategies. [source] | |||||||||||||||||||||||||