Age-specific Survival Rates Research Articles

Environmental conditions during early life accelerate the rate of senescence in a short-lived passerine bird.

Environmental conditions experienced in early life may shape subsequent phenotypic traits including life history. We investigated how predation risk caused by domestic cats (Felis silvestris catus) and local breeding density affected patterns of reproductive and survival senescence in Barn Swallows (Hirundo rustica) breeding semicolonially in Denmark. We recorded the abundance of cats and the number of breeding pairs at 39 breeding sites during 24 years and related these to age-specific survival rate and reproductive senescence to test predictions of the life history theory of senescence. We found evidence for actuarial senescence for the first time in this species. Survival rate increased until reaching a plateau in midlife and then decreased later. We also found that survival rate was higher for males than females. Local breeding density or predation risk did not affect survival as predicted by theory. Barn Swallows with short lives did not invest more in reproduction in early life, inconsistent with expectations for trade-offs between reproduction and survival as theory suggests. However, we found that the rate of reproductive decline during senescence was steeper for individuals exposed to intense competition, and predation pressure accelerated the rate of reproductive senescence, but only in sites with many breeding pairs. These latter results are in accordance with one of the predictions suggested by the life history theory of aging. These results emphasize the importance of considering intraspecific competition and interspecific interactions such as predation when analyzing reproductive and actuarial senescence.

Temperature-dependent fecundity of overwintered Scirtothrips dorsalis (Thysanoptera: Thripidae) and its oviposition model with field validation.

A population model can be a useful tool to understand population dynamics under various environmental factors, and can be useful for evaluating the efficacy of new management practices. This study was conducted to construct an oviposition model of overwintered Scirtothrips dorsalis as a part of its whole population model. Adult longevity decreased with increasing temperature and ranged from 44.7 days at 13 °C to 9.9 days at 33 °C. S. dorsalis showed a maximum fecundity of 52.6 eggs female(-1) at 21 °C, which declined to 13.9 eggs female(-1) at 33 °C. Egg development time decreased from 28.41 days at 13 °C to 5.14 days at 29 °C and 5.5 days at 33 °C. An oviposition model was developed on the basis of three temperature-dependent submodels: total fecundity, age-specific oviposition rate and age-specific survival rate models The oviposition model outputs followed the field occurrence patterns of S. dorsalis egg populations well, with a peak time discrepancy of 3-4 days. Our model should be useful for population modelling of S. dorsalis in agricultural crops. Furthermore, the present model can be independently used for the timing of spraying against S. dorsalis in IPM programmes of various crops.

Dead before detection: addressing the effects of left truncation on survival estimation and ecological inference for neonates

SummaryNeonate survival is a key life history trait, yet remains challenging to measure in wild populations because neonates can be difficult to capture at birth. Estimates of survival from neonates that are opportunistically captured might be inaccurate because some individuals die before sampling, resulting in data that are left truncated. The resulting overestimation of survival rates can further affect ecological inference through biased estimates of covariate effects in survival models, yet is not addressed in most studies of animal survival. Here, we quantify the effects of left truncation on survival estimates and subsequent ecological inference.Vaginal implant transmitters (VITs) enable capture of ungulates at birth, yielding data without left truncation. The effects of left truncation on survival estimation were quantified using age‐dependent survival models for VIT and opportunistically captured neonatal deer. Differences in daily survival rates (DSRs) and cumulative survival probability were calculated for the first 70 days of life. In addition, left truncation was simulated by removing fawns that died during the first 1 or 2 days of life from the VIT‐caught sample, isolating the effect of left truncation.Cumulative probability of survival during the first 70 days of life was overestimated by 7–23% for fawns caught opportunistically compared with those caught by VIT, depending on model design. Differences in DSRs were large at age 1 day, but had converged by age 30 days. Simulated left truncation resulted in overestimates of survival of up to 31%. Model selection and covariate coefficients were strongly affected by left truncation, producing spurious ecological inference, including changes to sign and/or magnitude of inferred effects of all covariates.We recommend (i) every effort be made to capture neonates; (ii) consistent capture methods, using at least in part non‐truncating techniques, be implemented across years and study areas; and (iii) exclusion of left‐truncated data from survival estimates until DSRs converge with those calculated from non‐truncated data. This work emphasizes the importance of accounting for left truncation in survival estimation for any species with strong age‐dependent survival in order to prevent biased conclusions produced by sampling method rather than true ecological effects.

Oviposition model of Cnaphalocrocis medinalis Guenée (Lepidoptera: Pyralidae)

The longevity and fecundity of Cnaphalocrocis medinalis were investigated at temperatures of 15.0, 17.5, 20.0, 22.5, 25.0, 27.5, 30.0, 32.5, and 35.0°C. Adult longevity and fecundity were significantly influenced by temperature. Longevity decreased with increasing temperature: it was highest at 15.0°C (23.6±3.51days) and lowest at 35.0°C (6.4±0.48days). Fecundity was highest at 25.0°C (170.5±45.54 eggs) and lowest at 17.5°C (11.0±3.68 eggs). The oviposition period was longest at 20.0°C (8.0±1.09days) and shortest at 35.0°C (2.3±0.48days). The oviposition model presented in this study consisted of two reproductive components (total fecundity and age-specific cumulative oviposition rate) and a survival component (age-specific survival rate). The relationship between adult developmental rate and temperature was described by the Lactin 2 model (r2=0.98, p<0.0001). The age-specific survival rate was well explained by a sigmoid function (r2=0.97, p<0.00001). The age-specific cumulative oviposition rate was best described by the three-parameter Weibull function (r2=0.99, p<0.00001). Temperature-dependent fecundity was estimated using the Briere-2 model (r2=0.94, p<0.007). Daily egg production of C. medinalis in relation to adult age and temperature was estimated.

Analysis of age and lactation specific survival rate, stayability and expected herd life in Sahiwal cattle

Demographic analysis was carried out on 830 female calves and 473 cows of Sahiwal breed born between 1985 to 2009 and maintained at the National Dairy Research Institute, Karnal. Survival rate was lowest during 0–1 month of age and was highest during 9–12 months of age. The trend of stayability in female calves up to AFC was declining along with increase in age. Among adult cows the survival rate was 82.0 % in the first lactation and showed decreasing trend up to the fifth lactation. Stayability was noted as 0.421, 0.076 and 0.015 at fourth, eighth and eleventh lactation respectively, indicating that only 42.1, 7.6 and 1.5 % of cows retained in the herd during respective lactations. More than half (58%) of the total cows of first lactation left the herd by the time they completed third lactation; moreover, more than one-fourth (27.82%) of total herd comprised first calvers. It was observed that 79% of total cows present in the herd belonged to first 4 lactations and less than 3% cows belonged to 9 and above lactations, which indicated that this herd of Sahiwal mostly comprised younger cows. The probability of cows being lost from the herd due to their disposal was 0.18 at first lactation, indicating that 18.0 % replacements are required to maintain the herd size constant. Expected herd life was 2.59 lactations more at first lactation and showed decreasing trend along with increase in lactation number.

Individual fitness and phenotypic selection in age-structured populations with constant growth rates.

Powerful multiple regression-based approaches are commonly used to measure the strength of phenotypic selection, which is the statistical association between individual fitness and trait values. Age structure and overlapping generations complicate determinations of individual fitness, contributing to the popularity of alternative methods for measuring natural selection that do not depend upon such measures. The application of regression-based techniques for measuring selection in these situations requires a demographically appropriate, conceptually sound, and observable measure of individual fitness. It has been suggested that Fisher's reproductive value applied to an individual at its birth is such a definition. Here I offer support for this assertion by showing that multiple regression applied to this measure and vital rates (age-specific survival and fertility rates) yields the same selection gradients for vital rates as those inferred from Hamilton's classical results. I discuss how multiple regressions, applied to individual reproductive value at birth, can be used efficiently to estimate measures of phenotypic selection that are problematic for sensitivity analyses. These include nonlinear selection, components of the opportunity for selection, and multilevel selection.

Temperature-driven models of Aculops pelekassi (Acari: Eriophyidae) based on its development and fecundity on detached citrus leaves in the laboratory

This study was carried out to develop temperature-driven models for immature development and oviposition of the pink citrus rust mite Aculops pelekassi (Keifer). A. pelekassi egg development times decreased as the temperature increased, ranging from 6.6days at 16°C to 1.9days at 35°C. Total nymph development times decreased from 8.2days at 16°C to 3.3days at 35°C. The egg-to-adult development durations were 14.8, 11.6, 9.7, 8.0, 7.3, 6.1, and 5.2days at 16, 20, 24, 26, 28, 32, and 35°C, respectively. The lower developmental threshold temperatures for eggs, nymphs, and total egg-to-adult development were calculated as 9.3, 4.3, and 6.9°C, respectively. The thermal constants were 54.0, 101.8, and 153.8degree days for each of the above stages. The non-linear biophysical model fitted well for the relationship between the development rate and temperature for all stages. The Weibull function provided a good fit for the distribution of development times of each stage. Temperature affected the longevity and fecundity of A. pelekassi. Adult longevity decreased as the temperature increased and ranged from 24.2days at 16°C to 14.6days at 35.0°C. A. pelekassi had a maximum fecundity of 33.1 eggs per female at 28°C, which declined to 18.8 eggs per female at 16°C. In addition, three temperature-dependent components for an oviposition model of A. pelekassi were developed with sub-models estimated: total fecundity, age-specific cumulative oviposition rate, and age-specific survival rate. The oviposition model, coupled with the stage emergence model, should be useful to construct a population model for A. pelekassi in the future.

Estimating extinction risk under climate change: next-generation models simultaneously incorporate demography, dispersal, and biotic interactions

news and update ISSN 1948-6596 commentary Estimating extinction risk under climate change: next-generation models simultaneously incorporate demography, dispersal, and biotic interactions Estimating species-level extinction risk under pro- jected future climate change is challenging. About ten years ago, Chris Thomas and colleagues used correlative species distribution models (SDMs) and future climate scenarios to estimate extinc- tion risk for >1100 animal and plant species (Thomas et al. 2004). They predicted that 15–37% of their sample species will be ‘committed to ex- tinction’ by 2050. The validity of such results is highly questionable because implausible assump- tions in correlative SDMs introduce large un- knowns into extinction risk forecasts (e.g., Dor- mann 2007). For example, a key assumption is that species’ distributions are at equilibrium with climate and that observed correlations with cli- mate will extend into the future. A further limita- tion is that population-level processes such as demographic rates, dispersal distances, and an- tagonistic or mutualistic interactions among spe- cies are not incorporated into SDMs (e.g., Hampe 2004). Nevertheless, recent biogeographical re- search may finally resolve some of these out- standing challenges (Kissling et al. 2012, Schurr et al. 2012, Travis et al. 2013, Wisz et al. 2013). In a groundbreaking addition to this grow- ing area of research, Fordham et al. (2013) pro- vide a framework for a next-generation model which simultaneously incorporates demography, dispersal, and biotic interactions into estimates of extinction risk under projected climate change. The authors apply this model to one of Europe´s most endangered mammals, the Iberian lynx (Lynx pardinus), which is restricted to isolated popula- tions in southwestern Spain. The modeling frame- work (Figure 1) is centered on demographic (metapopulation) simulations for the Iberian lynx and the European rabbit (Oryctolagus cuniculus), the latter being the main food source of the lynx. Metapopulation models were implemented as age- and sex-structured models for the Iberian lynx (with age and sex specific survival rates and fecundity estimates for age of reproduction, litter size, etc.) and as scalar type stochastic models for the rabbit (to estimate population growth rates without the need to include population age or stage structure). For both species, outputs from correlative SDMs (in annual time steps from 2000 –2100, using ensemble projections based on seven different SDM methods, seven climate change models, and two emission scenarios) were only used to estimate the carrying capacity for the demographic models. In other words, they were used as spatial layers describing climate suitabil- ity, i.e. as one of the components of habitat suit- ability for the two species (Figure 1). The coupling of SDMs with demographic models is a recent ad- vance (Keith et al. 2008), and represents a major step forward in predicting species-level extinction risk under climate change. Dispersal for both species is modelled using functions to determine the proportion of each population that disperses between grid cells or subpopulations (Figure 1). For the lynx, a declining function between subpopulations was used for distances up to 45 km; the maximum dispersal distance which has been empirically reported for this species. Furthermore, a remotely-sensed map (CORINE) was used to identify land cover types with different degrees of suitability for lynx dis- persal (from very good to highly unsuitable). Lynx dispersal was assumed to be stage-specific (young individuals versus adults) and density dependent (based on number of breeding-age individuals in a population), allowing for more detailed simulation of movement. For rabbit dispersal, a declining function up to a maximum dispersal distance of 15 km was used, closely approximating a 1% move- ment at distances of >3 km. Dispersal and move- ment data for both species were based on previ- ously published studies, highlighting the utility of empirical estimates of maximum dispersal dis- tances, movement behavior and habitat selection frontiers of biogeography 5.3, 2013 — © 2013 the authors; journal compilation © 2013 The International Biogeography Society

Differential Performance of &lt;I&gt;Sitobion avenae&lt;/I&gt; (Hemiptera: Aphididae) Clones From Wheat and Barley With Implications for its Management Through Alternative Cultural Practices

Cultural control measures should play an important role in cereal aphid management on wheat and barley. Planting barley in fields adjacent to those of wheat and intercropping wheat with barley are cultural practices that might suppress the cosmopolitan cereal pest Sitobion avenae (F.). To evaluate the potential effects of these cultural measures on aphid outbreak risks, clones of S. avenae were collected from wheat and barley. Host-switch experiments for the collected clones were conducted in the laboratory to compare their life table parameters and other life history traits. Our results demonstrated that wheat clones of S. avenae had lower developmental times, higher fecundities, and higher growth rates compared with barley clones when tested on the plant of origin. When transferred to barley, the performance of wheat clones was decreased in terms of developmental times of nymphs and age at first reproduction of adults. Barley clones' performance was decreased in terms of reproductive time or lifespan of adult on wheat compared with that on barley. The age-specific survival rates of barley clones tended to be lower than wheat clones in the earlier part of their lives on wheat. The age-specific fecundity of barley clones on barley remained low and fluctuated significantly during their lifetime. Although quite a few significant correlations between developmental and reproductive traits were identified on both plants, no significantly negative correlations (i.e., trade-offs) for the traits were found between plants. The results suggested that barley clones could be generalized but wheat clones were more specialized to their host plant. The potential benefits of the abovementioned cultural measures were discussed.

Recent Declines in Apparent Survival and Survey Counts of Snowy Plovers Breeding in the Southern High Plains of Texas

Abstract We quantified changes in long-term Snowy Plover (Charadrius nivosus) survey counts and return rates, estimated current sex and age-specific apparent survival and encounter rates, and calculated recruitment thresholds needed to maintain a stable population in the Southern High Plains of Texas. Mean survey counts of adult Snowy Plovers decreased by 78% at one saline lake (from 80 adults/survey to 18 adults/survey) from 1999–2000 to 2008–2010 but remained consistent at an alternate lake (from 45 adults/survey to 41 adults/survey). Adult and juvenile return rates have similarly declined within this time frame by 25 and 62%, respectively. Long-term declines in return rates may be the result of increased mortality from declining habitat conditions either within or outside the breeding season. Current estimates of adult (65%) and juvenile (12%) apparent survival are lower than most other estimates for Snowy Plovers throughout their range. Current estimates of adult and juvenile apparent survival and ret...

Life Expectancy, Schooling, and Lifetime Labor Supply: Theory and Evidence Revisited

This paper presents a theoretical and empirical analysis of the role of life expectancy for optimal schooling and lifetime labor supply. The results of a simple prototype Ben-Porath model with age-specific survival rates show that an increase in lifetime labor supply is not a necessary, nor a sufficient, condition for greater life expectancy to increase optimal schooling. The observed increase in survival rates during working ages that follows from the ``rectangularization'' of the survival function is crucial for schooling and labor supply. The empirical results suggest that the relative benefits of schooling have been increasing across cohorts of US man born 1840-1930. A simple quantitative analysis shows that a realistic shift in the survival function can lead to an increase in schooling and a reduction in lifetime labor hours.

Life Expectancy, Schooling, and Lifetime Labor Supply: Theory and Evidence Revisited

This paper presents a theoretical and empirical analysis of the role of life expectancy for optimal schooling and lifetime labor supply. The results of a simple prototype Ben-Porath model with age-specific survival rates show that an increase in lifetime labor supply is not a necessary, or a sufficient, condition for greater life expectancy to increase optimal schooling. The observed increase in survival rates during working ages that follows from the rectangularization of the survival function is crucial for schooling and labor supply. The empirical results suggest that the relative benefits of schooling have been increasing across cohorts of U.S. men born between 1840 and 1930. A simple quantitative analysis shows that a realistic shift in the survival function can lead to an increase in schooling and a reduction in lifetime labor hours. [PUBLICATION ABSTRACT]

Annual survival of Red Knots (Calidris canutus rufa) wintering in Florida

ABSTRACT. Populations of Red Knots (Calidris canutus rufa) have declined an estimated 80% in the past 25 years. Declines are primarily attributed to dwindling food resources in Delaware Bay, their last migratory stopover before the breeding grounds. Red Knots wintering in Florida also decreased in numbers, prompting the need to estimate local vital rates to determine whether local factors contribute to declining trends. We estimated age-specific annual survival rates and compared them with estimates from populations of Red Knots wintering in South America using the Barker model. Adult annual survival rates between 2005 and 2010 averaged 0.89 ± 0.02 [SD]; range: 0.86–0.94) and were similar to estimates reported for Delaware Bay (0.87–0.92). Juvenile survival (0.95 ± 0.06 [SE]) and adult fidelity (0.81 ± 0.05 [SE]) were also high. However, juvenile survival did not include the period between fledging and arrival in Florida, a period of potentially high mortality. Similar adult survival rates suggested that ...

The Implications of Age and Comorbidity on Survival Following Epithelial Ovarian Cancer: Summary and Results from a Centers for Disease Control and Prevention Study

Advances in treatment have improved ovarian cancer survival for most women, although less for the elderly. We report on this disparity and add further evidence about the relationship among age, comorbidity, and survival after ovarian cancer. To examine age and comorbidity, Centers for Disease Control and Prevention (CDC)-funded cancer registries examined 2367 women residing in New York and Northern California diagnosed with epithelial ovarian cancer (1998-2000). Subjects were identified through tumor registries, treatment data were supplemented with physician survey, and comorbidity was identified through hospital discharge database linkages. Proportional hazards modeling was used to estimate the risk of death by age and comorbidity, adjusting for clinical and sociodemographic factors. Crude survival at 1 year and 3 years was 71.9% and 50.1%, respectively. Within stage, age-specific survival rates were lower in the oldest groups, particularly for those with advanced disease. For age 75+, 3-year survival was 13% vs. 50% in those <35 (stage IV). For all stages, women without comorbidity had higher survival rates than those with comorbidity. Older age and comorbidity were both associated with advanced stage and less aggressive treatment. The adjusted risk of death was 40%, and it was 80% higher for the 65-74 and 75+ groups, respectively, compared to women 35-64 (p<0.00). Comorbidity increased the risk of death by 40% (p<0.00). This study confirmed the independent adverse effects of age and comorbidity on survival following ovarian cancer. As the population ages, the co-occurrence of ovarian cancer and comorbidity will increase. Further work identifying critical conditions that impact survival could potentially inform complex treatment decisions.

Abstract 5499: A descriptive epidemiological study of lobular carcinoma of the breast and the effects of normal lobular regression at menopause

Abstract Background: Lobular carcinoma (LC) is a distinctive neoplasm originating in the milk producing glands and constituting about 12% of all breast cancer cases. LC differs from the more common invasive ductal carcinoma (IDC) by morphology and biology. We report the results of a descriptive epidemiological study of LC and a comparison of the pathogenesis of lobular and ductal carcinoma of the breast. Methods: A total of 86,846 cases of invasive LC (ILC) from women, aged 20 to 85, were obtained from NCI's SEER Program for the years 1973-2008 in the United States. There were 20,512 cases of LC in-situ (LCIS) and 66,634 cases of ILC. For comparison, 692,201 cases of IDC and 61,569 cases of ductal carcinoma in situ (DCIS) were collected. The analysis compared trends, age specific rates, log-log plots, age frequencies and relative survival rates. Results: From 1973-2008, the age-adjusted rate of LC progressively increased from 5.8 to 16.4/ 100,000 women. In an age frequency analysis of age versus rate, LCIS increased to 0.22/ 100,000 women at age 50, and then declined to 0.02/100,000 women at age 80. ILC increased to 0.11/100,000 women at age 50, and then plateaued after menopause but did not decline. Log-log plots revealed parallel curves between ILC and IDC in both pre-menopausal and post-menopausal age groups. At age 50, the age specific rate of LCIS increased to 11.3/100,000 women then progressively decreased. In contrast, the age specific rate of DCIS was 22.1/100,000 women at age 50 and continued to increase after menopause. Conclusions: At menopause, the incidence of LCIS decreases as a result of lobular involution of the breast. In contrast, DCIS continues to increase. ILC does not decline but plateaus suggesting that the initiation of ILC occurs before menopause, but the tumor becomes clinically apparent only after menopause. Although morphologically different, parallel log-log plots of age specific rates and age frequency analysis suggest a similar pathogenesis for IDC and ILC even though epidemiological patterns are different. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 5499. doi:1538-7445.AM2012-5499

Estimating survival rates with time series of standing age‐structure data

It has long been recognized that age-structure data contain useful information for assessing the status and dynamics of wildlife populations. For example, age-specific survival rates can be estimated with just a single sample from the age distribution of a stable, stationary population. For a population that is not stable, age-specific survival rates can be estimated using techniques such as inverse methods that combine time series of age-structure data with other demographic data. However, estimation of survival rates using these methods typically requires numerical optimization, a relatively long time series of data, and smoothing or other constraints to provide useful estimates. We developed general models for possibly unstable populations that combine time series of age-structure data with other demographic data to provide explicit maximum likelihood estimators of age-specific survival rates with as few as two years of data. As an example, we applied these methods to estimate survival rates for female bison (Bison bison) in Yellowstone National Park, USA. This approach provides a simple tool for monitoring survival rates based on age-structure data.

Demographic Parameters of &lt;I&gt;Spodoptera exigua&lt;/I&gt; (Lepidoptera: Noctuidae) on Different Soybean Cultivars

Life table, reproduction, and population growth parameters of the beet armyworm, Spodoptera exigua (Hübner) (Lepidoptera: Noctuidae), were determined on nine soybean (Glycine max L.) cultivars ('032', '033', 'Hill', 'M4', 'M7', 'M9', 'M11', 'TMS', and 'Zane') at 25°C. The age-specific survival rate of eggs and immature stages was higher on 033 in comparison with other cultivars. The gross fecundity rate ranged from 911 on M9 to 1,296 on Zane, but the differences were not statistically significant. The net fecundity rate was significantly higher on 033 (1,082 eggs per female) than on other cultivars. The gross fertility rate significantly differed on tested cultivars, and was the highest on Zane (1,257 eggs per female) and lowest on Hill (813 eggs per female). The net fertility rate varied from 532 on M11 to 1,082 eggs per female on 033. Both daily number of eggs and daily number of fertile eggs laid per female varied significantly among the different cultivars, and were the highest on TMS (90 for both parameter) and lowest on M7 (47 and 43), respectively. The values of net reproductive rate, intrinsic rate of increase, and finite rate of increase were significantly higher on 033. The shortest generation time (23 d), shortest doubling time (1.66 d), and highest percentage of female offspring (56%) also were obtained on 033. According to population growth parameters, 033 and Hill partially were susceptible and resistant, respectively, to S. exigua. The results of this study provide direction to design a more comprehensive integrated pest management program for this pest.

Gonadal and extragonadal germ cell tumours in the United States, 1973–2007

Germ cell tumours (GCTs) most often arise in the gonads, but some develop extragonadally. The aim of this study was to examine gender- and race-specific trends in incidence and survival of gonadal (GGCTs) and extragonadal GCTs (EGCTs) in the US from 1973 to 2007. We also examined the topographical distribution of EGCTs by race and gender. We estimated age-specific and age-standardized incidence rates and 5-year relative survival rates (RSR) of GCTs using the Surveillance, Epidemiology and End Results (SEER) Program (SEER nine registries). GCTs and their topographical sites were identified using ICD-O morphology and topography codes. Of 21,170 GCTs among males, 5.7% were extragonadal (Whites 5.5%; Blacks 16.3%). Of 2093 GCTs among females, 39.3% were extragonadal (Whites, 36.9%; Blacks 51.0%). The incidence of GGCT was much higher among White (56.3/1,000,000) than Black males (10.0/1,000,000), while there was no difference in incidence between White and Black females (3.2/1,000,000). The rates of EGCT among men and women of both races were similar (range:1.9-3.4/1,000,000). The most frequent extragonadal sites were mediastinum among males and placenta among females. The 5-year RSR of testicular GCT was higher among Whites (97%) than Blacks (90%), as was the 5-year RSR of ovarian GCT (Whites, 92%; Blacks 85%). In general, the 5-year RSRs of EGCTs were lower than the 5-year RSRs of GGCTs. The different incidence trends of GGCTs and EGCTs and distinct age-specific incidence patterns by anatomical site of EGCTs suggest that GGCTs and EGCTs may have different aetiologies.

Life history and demographic determinants of effective/census size ratios as exemplified by brown trout (Salmo trutta).

A number of demographic factors, many of which related to human-driven encroachments, are predicted to decrease the effective population size (Ne) relative to the census population size (N), but these have been little investigated. Yet, it is necessary to know which factors most strongly impact Ne, and how to mitigate these effects through sound management actions. In this study, we use parentage analysis of a stream-living brown trout (Salmo trutta) population to quantify the effect of between-individual variance in reproductive success on the effective number of breeders (Nb) relative to the census number of breeders (Ni). Comprehensive estimates of the Nb/N ratio were reduced to 0.16–0.28, almost entirely due to larger than binomial variance in family size. We used computer simulations, based on empirical estimates of age-specific survival and fecundity rates, to assess the effect of repeat spawning (iteroparity) on Ne and found that the variance in lifetime reproductive success was substantially higher for repeat spawners. Random family-specific survival, on the other hand, acts to buffer these effects. We discuss the implications of these findings for the management of small populations, where maintaining high and stable levels of Ne is crucial to extenuate inbreeding and protect genetic variability.

A New Definition of Aging?

A New Definition of Aging?