Constant Survival Rates Research Articles

A Comparative Analysis of Age-Stage Two Sex Life Tables in Distinct Forms of Callosobruchus maculatus (F.): Insights into Population Dynamics and Reproductive Strategies

Callosobruchus maculatus, the bean weevil, is a fascinating insect that showcases remarkable adaptations for survival. Found in tropical and subtropical regions, it has become a global pest due to its adaptability and hitchhiking capabilities, causing substantial grain losses. This small beetle, part of the Chrysomelidae family, serves as a valuable model organism in entomology and agricultural research. One of the key aspects of Callosobruchus maculatus that captures the attention of scientists is its dichotomy between active and inactive forms. These two forms represent distinct survival strategies employed by the beetle to navigate its ever-changing environment. The present study provides a comprehensive overview of the study on Callosobruchus maculatus, highlighting the two distinct forms of the species, their adaptations, and the significance of understanding their lifetable parameters. It emphasizes the ecological, practical, and research-oriented implications of this study, ranging from ecological insights to pest management strategies and the optimization of mass multiplication protocols. These forms exhibited notable differences in various life history parameters and survival characteristics. Flightless-inactive females had longer preoviposition and oviposition period and laid a significantly higher average of eggs per female with higher reproduction potential. Female fecundity (eggs/female) was much lower in the flight-active form (18.6) than in the flightless-inactive form (84.10) and maintained constant survival rate. Life expectancy values were generally lower for the flightless-inactive form compared to the flight-active form across different stages and sexes. Both males and females in the flight-active form exhibited a consistent and relatively high life expectancy, with a 100% chance of survival throughout all age intervals. Overall, these findings provide a comprehensive understanding of the differences in life history traits, reproductive strategies, and survival patterns between the flight-active and flightless-inactive forms of Callosobruchus beetles in a controlled laboratory environment.

Egg Clutch Survival under Prolonged Paternal Care in a Glass Frog, Hyalinobatrachium talamancae

Previous studies have reported egg attendance as the most common protective behavior among the Neotropical frog family Centrolenidae. However, research on the effect of parental care and other factors thought to affect offspring survival is still missing for a great number of species. Here, we performed field observations during day and night to associate male-only care, habitat characteristics, and environmental variables with egg clutch survival in the understudied glass frog, Hyalinobatrachium talamancae. We conducted 34 nest survival models for 39 egg clutches considering constant daily survival rates, temporal variation in the survival probability, and other biotic and abiotic variables thought to affect the survival of embryos. We found that egg attendance was strongly associated with egg clutch survival in H. talamancae. Our results showed similar degrees of parental investment during day and night, accounting for extensive caring periods over one or multiple clutches as paternal care did not hinder re-mating in this species. Egg clutches exhibited daily survival rates of 0.93±0.02, often reaching pre-hatching stages when attended by males. Our results may thus suggest that egg attendance is a major, if not predominant, determining factor of embryo survival in H. talamancae. This study contributes to the understanding of the natural history associated with paternal care in H. talamancae and provides insight into the evolution of prolonged male-only care in the family Centrolenidae.

AUTOMATED VITRIFICATION AND WARMING OF OOCYTES MEDIATED BY A NOVEL MICROFLUIDICS DEVICE

The purpose of this study is to develop a microfluidic device to automate the critical process of vitrification and thawing procedures, providing standardization, minimizing inter and intra-center variability, and reducing hands on time. Experimental comparative study of both vitrification and warming of bovine and human oocytes using an automated microfluidics device (Davitri, Overture Life). a microfluidics system has been developed that infuses the solutions required in a central well, where the oocytes are placed, and withdraws the spent solutions. The system and the protocols were first tried in bovine oocytes, which are of similar size as human, and later on human donated oocytes. After 24 hours of maturation the cumulus oocyte complex (COCs) were denuded manually and vitrified using the palm-size Davitri device. The scripts controlling the process are based on the Kitazato protocol. Once the procedure was validated with bovine, frozen human oocytes from donors were warmed and vitrified automatically and fresh human oocytes were vitrified and warmed automatically. 100 fresh bovine oocytes were vitrified automatically and warmed manually, 5 of them were lost during the procedure and 84 oocytes survive after culture (88%), compared to 80% for a control group. Also 50 fresh bovine oocytes were vitrified manually and warmed with the microfluidics device, and 48 of them survived (96%). Donated frozen human oocytes (N=19) were warmed automatically, and 12 survived (63.15%) compared to 80% expected (1,2). Those 12 were re-vitrified automatically and 71% survived thawing compared to 70% expected after re-vitrification (3). After these promising results 4 fresh human mature oocytes from an egg donor were automatically vitrified and manually warmed of which 100% survived. Also, 13 fresh immature oocytes were automatically vitrified and manually warmed of which 11/13 (86.6%) survived. The automation of vitrification and thawing of eggs is an improvement in assisted reproduction by allowing constant high survival rates with reduced hands-on time. Here we provide proof of concept that the Davitri microfluidics device is able to vitrify and warm both bovine and human oocytes with high survival rates.

Influence of body condition on the population dynamics of Atlantic salmon with consideration of the potential impact of sea lice.

Atlantic salmon Salmo salar is an iconic species of high conservation and economic importance. At sea, individuals typically are subject to sea lice infestation, which can have detrimental effects on their host. Over recent decades, the body condition and marine survival in NE Atlantic stocks have generally decreased, reflected in fewer adults returning to rivers, which is partly attributable to sea lice. We developed a deterministic stage-structured population model to assess condition-mediated population dynamics resulting in changing fecundity, age at sexual maturation and marine survival rate. The model is parameterized using data from the North Esk system, north-east Scotland. Both constant and density-dependent juvenile survival rates are considered. We show that even small sea lice-mediated changes in mean body condition of MSW can cause substantial population declines, whereas 1SW condition is less influential. Density dependence alleviates the condition-mediated population effect. The resilience of the population to demographic perturbations declines as adult condition is reduced. Indirect demographic changes in salmonid life-history traits (e.g., body condition) are often considered unimportant for population trajectory. The model shows that Atlantic salmon population dynamics can be highly responsive to sea lice-mediated effects on adult body condition, thus highlighting the importance of non-lethal parasitic long-term effects.

Use of mistletoes by the Grey Go‐away‐bird (Corythaixoides concolor, Musophagidae) in a semi‐arid savannah, south‐west Zimbabwe

AbstractMistletoes are preferred nesting sites for many bird species in a range of habitats. However, no studies have examined the use of mistletoes by nesting birds in the semi‐arid savannah. We studied nesting in mistletoe and its role in determining nesting success in the Grey Go‐away‐bird in south‐west Zimbabwe. We modelled the effects of mistletoe, mistletoe abundance, nest microclimate, concealment and nest height on daily survival rates (DSR) using program MARK. A constant survival model was best fitted for the Grey Go‐away‐bird suggesting a constant nest survival rate across the nesting period. Mistletoe nests had lower DSR than nests placed elsewhere in the canopy. Mistletoe abundance and nest height had a positive association with DSR whereas visibility distance, microclimate and concealment were negatively associated with DSR. Overall, survival for nests in mistletoe was 22.1% compared with 90.5% for nests in other substrates over the 50‐day nesting period. In conclusion, the low nest survival in mistletoe suggests either that the factors used to select mistletoe as nest sites by these birds are poor predictors of nest success or that nesting in mistletoe may be maladaptive.

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.

Survival and abundance of short‐finned pilot whales in the archipelago of Madeira, NE Atlantic

AbstractEstimates of population parameters for the short‐finned pilot whale, Globicephala macrorhynchus, are scarce in literature, contributing to an International Union for Conservation of Nature (IUCN) status of Data Deficient. In this study, photo‐identification data collected over 7 yr from Madeira were used to estimate for the first time survivorship, capture probability, and abundance in this species using mark‐recapture methodology. The Cormack‐Jolly‐Seber model estimated that the adult island‐associated (i.e., resident and regular visitor) whales had a constant survival rate of 0.960 (95% CI: 0.853–0.990) and an annual capture probability varying between 0.372 (CI: 0.178–0.619) and 0.843 (CI: 0.619–0.947). A parameterization of the Jolly‐Seber model estimated that 140 island‐associated whales (CI: 131–151) used the area throughout the course of the study. Based on a closed population model, the most precise (lower CV) annual estimate of the total number of pilot whales using the southern and eastern waters of Madeira (~900 km2) in a 3 mo period covering summer/autumn was 334 animals (CI: 260–437). No trend was observed. Despite including biases, the approach used in this study provided plausible estimates of population parameters, which can contribute to the regional conservation strategies.

Survival and Recovery Estimates of Male Elk in a Harvested Inter‐Jurisdictional Population

Demographic rates are critical pieces of information for understanding ungulate population dynamics and effectively managing populations. In harvested elk Cervus elaphus canadensis populations, human harvest is often the greatest source of adult male mortality. In the Cypress Hills of southeast Alberta and southwest Saskatchewan, Canada, hunting is a tool to mitigate conflicts between elk and agricultural producers in the area. We estimated survival (S) and animal recovery (f) rates based on individually marked male elk (n = 47) using hunter‐returned ear tags from 1998–2001. Recovery rate differed between jurisdictions and was substantially lower in Saskatchewan (f = 0.16, SE = 0.05) compared to Alberta (f = 0.31, SE = 0.08). A constant survival rate (S = 0.61, SE = 0.15) was most supported. The average longevity for male elk in the Cypress Hills was 2.02 (SE = 0.51) years after surviving their first year of life. This research highlights the importance of considering regulatory regimes and requirements when investigating and interpreting demographic and population dynamics of populations managed across jurisdictions.

Higher than expected growth rate of the Endangered West African giraffeGiraffa camelopardalis peralta: a successful human–wildlife cohabitation

AbstractThe West African giraffe is a genetically unique population represented only by the subspeciesGiraffa camelopardalis peralta, categorized as Endangered on the IUCN Red List. These giraffes live outside protected areas, without natural predators and share their habitat with local people and their livestock. This study provides demographic data on this poorly studied megaherbivore and documents its recovery. We analysed the results of photo-identification censuses from 1996 to 1999 (count data) and from 2005 to 2008 (count and demographic data). From 1996 to 1999 the annual growth rate was c. 19% because of an unbalanced population structure after a period of severe poaching. From 2005 to 2008 an annual growth rate of c. 12–13% was estimated from both count data and demographic parameters. This value fits with the maximum growth rate calculated for a browser species based on the allometric relationship linking growth rate and body mass. During the period 2005–2008 adult and subadult females had a constant survival rate of 0.94 and a constant recapture rate of 0.97. Annual calf survival rate was 1. Observed sex ratio at birth was 0.57 and mean reproductive success was 0.257. Generation time was estimated to be 9.66 years. This spectacular population growth was mostly attributed to the absence of predators and the ongoing monitoring to limit illegal hunting.

Constant breeding and low survival rates in the subtropical Striped Frog in southern Brazil

AbstractSurvival and consequent implications for population dynamics in the subtropical Striped Frog Hypsiboas leptolineatus was studied for 1 year in the southern Brazilian state of Paraná. By means of capture‐marking‐recapture, we estimated survival and capture probabilities in an open population. A total of 583 captures of 374 individuals, comprising 96% male (n = 353) and 4% females (n = 21), resulted in daily survival estimates ranging from 0.808 to 0.998 day−1. The number of individuals captured per capture session varied from 8 to 37 (mean = 21) and was correlated with night length, after a two session lag time (r = 0.78). Males were found vocalizing throughout the year, while females were less common and gravid females were only found in November, March and June. Recapture probability was relatively constant at 25% for males, 24% for females and, overall, 29% of males were recaptured at least once. Young individuals were encountered in all months but one and, being extremely small, were impossible to quantify. Thus, the Striped Frog is active and breeding year‐round as indicated by the constant singing of adult males, the few gravid females found at different times and the frequent encounters of young frogs at all times of year. While survival and captures varied throughout the year, the only seasonality was in the number of captures that increased during longer nights. Nonetheless, recapture probability was constant. These dynamics contrast strongly with most anuran species and especially subtropical and temperate species in other places. This first detailed study of population parameters of a subtropical species with its unusual dynamics may suggest that once studied, other species of anurans may also have surprising population dynamics.

Demographic effects of live shearing on a guanaco population

Live shearing of wild guanacos (Lama guanicoe) is promoted as an alternative to livestock production and a conservation tool in the Argentinean Patagonia. However, biological sustainability of guanaco shearing has not been evaluated. We studied movements, population trends, survival, and yearling recruitment of guanacos, comparing sections with and without roundups on a Patagonian sheep ranch. A total of 2900 guanaco captures occurred in 10 roundups from 2003 to 2007. We estimated guanaco density and yearling/adult ratios with line transect surveys. We evaluated if guanacos left the section with roundups through direct observation of tagged guanacos and radiotelemetry. We estimated survival rate of shorn guanacos using 1334 capture–recapture histories. Guanaco population trends in sections with and without roundups were stable throughout a normal-rainfall period and declined during the drought that followed. Roundups were followed by temporary declines in density estimates probably associated with altered guanaco behavior. Tagged guanacos were rarely observed outside the section with roundups and none of the radiocollared guanacos permanently left the section. We estimated a constant annual survival rate for shorn guanacos (82% SE=0.01) that was independent of sex and age. Yearling proportions declined in the section with roundups 2–3 months after summer roundups. Our results suggest that, under conditions similar to those of our study (i.e. following animal welfare practices in a ranch with moderate livestock densities and sections without livestock), live shearing would not imperil wild guanacos if roundups were conducted in spring and during normal-rainfall periods.

Breast Ductal Carcinoma In Situ

Ductal carcinoma in situ (DCIS) of the breast is becoming one of the most important diseases diagnosed in preventive medicine screening. The current age-adjusted incidence rate of DCIS is 32.5 per 100,000 women. For women 50–64 years of age, the incidence is approximately 88 per 100,000. Currently, for every 4 diagnoses of invasive breast cancer, there is 1 diagnosis of DCIS. Risk of DCIS is rare in women younger than 30 years of age and is low in women under 40 years of age, but increases steadily from ages 40–50. The risk of DCIS increases much more slowly after the age of 50, and it plateaus after the age of 60. Assuming constant incidence and survival rates, it is estimated that more than 1 million women will be living with diagnosed DCIS by 2020, with obvious social and political health ramifications. The question scientists are facing now, and the question women are beginning to ask their breast surgeons, is whether we are overdiagnosing and overtreating this disease. Should we be less aggressive and more tolerant toward this disease? We are aware that DCIS is a spectrum of different diseases and that we may have overdiagnosed and overtreated to a point, but we have also likely undertreated others. Despite randomized clinical trials and evidence-based recommendations, there are important regional and geographic differences in clinical management, reflecting both a cultural bias regarding, and the heterogeneity of, this disease. In this current issue, the authors present a detailed overview of the state of the art of the diagnosis and treatment of this disease as well as an overview of future tendencies and research. M. Badruddoja extensively reviews the most recent knowledge of epidemiology and risk factors for DCIS. L. Fortunato et al. and M. Amichetti et al. review all the randomized clinical trials on DCIS, giving an unbiased interpretation of the data that is helpful in the daily management of DCIS patients. K. Lambert et al., in their literature review facilitated by the Medline, PubMed, Embase, and Cochrane databases, consider randomized, nonrandomized, prospective, and retrospective studies with the goal of increasing understanding of the most important predictive factors for local recurrence, and of better selection of the use of radiation therapy and tamoxifen. The still debatable issue of sentinel node biopsy in DCIS is addressed by D. Boler et al., who present their experiences and discuss literature evidence. G. Scripcaru and I. M. Zardawi investigate the occurrence of each architectural growth pattern in mammary DCIS. Correlating the architecture with nuclear grade, they postulate that the comedo pattern can ultimately occur in all types of DCIS and therefore should not be regarded as a separate DCIS type. D. Coradini et al., in an elegant experiment, investigate the expression patterns of a selected panel of genes associated with cell polarity and the apical junction complex. They are able to confirm that atypical ductal hyperplasia and DCIS are part of a tumorigenic, multistep process with possible chemoprevention implications. E. Bastiaannet et al., analyzing 8421 patients with DCIS, found no excess mortality irrespective of treatment in women older than 50 years of age, with the important clinical implication that local relapse in these women may not impact prognosis. K. Van Zee and D. Choi et al. from Memorial Sloan-Kettering Cancer Center investigate many aspects of the biology, diagnosis, and treatment of DCIS over a 20-year period with the final development of a nomogram that incorporates many factors simultaneously to estimate the risk of local relapse in DCIS treated with conservation therapy. Several recent patterns-of-care studies have identified substantial variation in surgeon decision making regarding the optimal management of DCIS [1–5]. In September 2009, the National Institutes of Health convened a conference to discuss the diagnosis and management of patients with DCIS because of the complexity and discrepancy in its management [6]. The papers presented here represent important contributions toward a better understanding of this disease and its treatment, and emphasize the need for a multidisciplinary approach to DCIS. Virgilio Sacchini Lucio Fortunato Hiram S. Cody III Kimberly J. Van Zee Bruno Cutuli Bernardo Bonanni

Effects of fire and grazing on grasshopper sparrow nest survival

AbstractPatch‐burn grazing is a management framework designed to promote heterogeneity in grasslands, creating more diverse grassland structure to accommodate the habitat requirements of many grassland species, particularly grassland birds. Published studies on the effects of patch‐burn grazing on passerines have been conducted on relatively large (430–980 ha pastures), contiguous grasslands, and only 1 of these studies has investigated the reproductive success of grassland birds. We assessed the effects of the patch‐burn grazing and a more traditional treatment on the nesting ecology of grasshopper sparrows (Ammodramus savannarum) in small (<37 ha pastures) grasslands located in southern Iowa from May to August of 2008 and 2009. The study pastures were grazed from May to September and prescribed burns were conducted in the spring. We investigated the effects of treatments on clutch size and modeled grasshopper sparrow nest survival as a function of multiple biological and ecological factors. We found no difference in clutch size between treatments; however, we did find a reduction in clutch size for nests that were parasitized by brown‐headed cowbirds (Molothrus ater). Constant daily survival rates were greater in patch‐burn grazed pastures than in grazed‐and‐burned pastures (patch‐burn grazed rate ${\bar {x}} = 0.930$ and grazed‐and‐burned rate ${\bar {x}} = 0.907$). Competitive survival models included year, stage of nest, nest age, and cool‐season grass (csg) abundance within 5 m of the nest. Overall, csg abundance had the greatest effect on survival and had a negative influence. Although survival rates were highest in patch‐burn grazed pastures, multiple factors influenced grasshopper sparrow survival. Nest survival rates for both treatments were relatively low, and variables other than treatment were more instrumental in predicting grasshopper sparrow survival. We recommend decreasing overall vegetation cover if increasing nesting habitat for grasshopper sparrows is a management goal. In addition, we recommend further investigation of heterogeneity management in fragmented landscapes to better understand how it affects biodiversity in relatively small management units that typify grassland habitats in the Midwest. © 2011 The Wildlife Society.

Analysis of Prinobius myardi Mulsant population dynamics in a Mediterranean cork oak stand

The dehesa is a silvopastoral system of a high economic and ecological significance in the Iberian Peninsula that is protected under the EEC/92/43 Habitat Directive. One of the most serious problems the dehesa system is currently facing is oak decline. This tree decay process is largely caused by three xylophagous cerambycids of which Prinobius myardi is the least known. In this study, we used a capture-mark-recapture method to identify the models best fitting the behaviour of this species with a view to estimating basic population parameters such as survival rate (phi), recapture rate (p) and transiency index (T). Prinobius myardi adults were captured by hand following visual detection in the trees of a cork oak (Quercus suber) plot located in the close vicinity of the Doñana National Park (SW Spain). Males exhibited a constant survival rate exceeding 85.4% throughout their flight period, a maximum transiency index of 1.82% and a recapture rate ranging from 42.50% to 76.90%. These results are suggestive of a sedentary behaviour in P. myardi males. By contrast, the small number of females captured precluded calculation of the previous parameters for this gender; in any case, field observations revealed a fleeing, less sedentary behaviour with respect to the males.

Short-Term Effects of Fire and Fire-Surrogate Treatments on Avian Nest Survival: A National-Scale Analysis

We examined the initial response of avian nest success to mechanical thinning, prescribed fire, and thinning/ prescribed fire combination treatments, designed to reduce fuel loads, at study sites throughout the continental USA as part of the National Fire and Fire Surrogate (FFS) Project. We modeled the daily nest survival of ground-, shrub-, tree-, and snag-nesting bird species to test for effects of: (1) overall treatment (2) specific treatment category (i.e., burn, thin, thin/burn); (3) time since treatment; and (4) study site. Of the 7 species examined, only 2 had top models that included effects of the FFS treatments, the remainder had either constant survival rates, or rates that varied only by study site. The Eastern Towhee had top models that included effects of treatment and study site, while the Red-bellied Woodpecker had top models that included effects of treatment category, time since treatment, and study site. All estimates of treatment, treatment category, and study site were statistically weak with confidence intervals including zero. The lack of clear response patterns observed in this study is likely a consequence of the variability inherent across forest types and taxonomic groups we examined. Forest managers should use our results cautiously and also be encouraged to facilitate opportunities for studies of avian nest survival as a function of fire-surrogate treatments that are regional specific, encompass longer time frames and larger spatial scales.

Exotic shrubs as ephemeral ecological traps for nesting birds

Certain exotic plants may increase risk of nest predation, and, in this way, may act as ecological traps. We hypothesized that the greater vulnerability to predation was a consequence of either (1) reduced nest height due to architectural differences among plant species or (2) seasonal changes in the distribution of nests among forest strata. To test this, we examined temporal variation in nest survival of 888 nests of Northern Cardinal (Cardinalis cardinalis) in native substrates and two exotic shrubs (Lonicera maackii and Rosa multiflora) in Ohio, USA, 2001–2006. We evaluated evidence for an ecological trap by monitoring the annual reproductive productivity of 245 breeding pairs of cardinals. Only nests in Rosa experienced relatively constant survival rates across the season, whereas probability of survival increased over the season for nests in other substrates. Interestingly, the relative vulnerability of nests in different substrates varied across the season. Most strikingly, nests in Lonicera in early spring showed the lowest survival rates but exceeded survival rates of nests in native substrates late in the season. Nest height failed to explain seasonal changes in nest survival, as only nests in native plants significantly increased in height as the season progressed. Rather, predation risk seemed to be a function of the proportion of nests within each substrate, as illustrated by the decreased predation in Lonicera as the relative proportion of nests in native substrates increased. The patterns of temporal variation in predation risk that we detected show that impacts of Lonicera are not a function of plant architecture alone and may be related to leaf phenology, changes in nest density, nest site location, and/or nest synchrony. Examination of the reproductive productivity of cardinals showed that pairs that made their first nest attempt in Lonicera fledged 20% fewer cardinal young than birds that began the season using other substrates. Thus, we suggest that exotic plants may represent an ephemeral ecological trap for certain nesting birds, where negative effects persist only during certain periods.

Demography of perennial grassland plants: survival, life expectancy and life span

Summary Survival, life expectancy and life span are key demographic parameters that are essential for understanding life‐history evolution and forecasting population dynamics, but empirical data on these parameters is extremely limited for herbaceous species. We used long‐term data from annually mapped permanent quadrats in a Kansas, USA, grassland to estimate survival, life expectancy and life span for 29 perennial forbs (herbaceous dicots) and 11 perennial grasses. In the cases of both forbs and grasses, they were the most common species at the research site. We developed computer programs to track the identity of individual genets based on their spatial locations in the permanent quadrats. The programs distinguished between new recruits and surviving individuals, and calculated the ages and life spans of the survivors. Most herbaceous perennials die young; life expectancy at age 1 year ranged from 0.6 to 6.5. However, forbs are more likely to die young than grasses. Survival from age 1 to 2 years for forbs ranged from 0.11 to 0.49 with an average of 0.30, whereas for grasses it ranged from 0.30 to 0.63 with an average of 0.44. Maximum observed life spans ranged from 3 to 25 years for forbs and 5 to 39 years for grasses. All species tended towards Type III survivorship curves, but grasses were more strongly Type III while many forbs had relatively constant survival rates with age. Therefore, population models must account for increasing survival with age, especially for grasses. Age was a better predictor of grass survival than size, raising questions about the use of size‐based methods to indirectly estimate survival and life span. Maximum observed life span was positively and significantly related with species importance. Synthesis. The higher survival, life expectancy and life span of grasses compared to forbs may provide a demographic explanation for community‐level differences in the dominance and turnover of these two functional groups in grassland plant communities.

Constant relative survival rates in Sweden and Norway when adjusting for screening‐related overdiagnosis

Constant relative survival rates in Sweden and Norway when adjusting for screening‐related overdiagnosis

“Comments to IJC‐06‐2150, Zahal PH, Mæhlen J. Constant relative survival rates in Sweden and Norway when adjusting for screening‐related overdiagnosis”

“Comments to IJC‐06‐2150, Zahal PH, Mæhlen J. Constant relative survival rates in Sweden and Norway when adjusting for screening‐related overdiagnosis”

Apparent Survival of Adult Magnificent Frigatebirds in the Breeding Colony of Isla Isabel, Mexico

Abstract Annual apparent survival rates of the Magnificent Frigatebird (Fregata magnificens) were estimated from 1998 to 2003 using a capture-resight model with 870 marked adult birds on Isla Isabel, Mexico (21°51’N, 105°54’W). The most parsimonious model was a time since marking model (or two age class model) with constant resighting rate for males and females (pm and pf), constant apparent survival rate for males in both age classes (ϕ1m and ϕ2+m), and time-dependent apparent survival rate for females (ϕ1f and ϕ2+f) in both age classes. We found higher resighting rates in males than in females, a tendency of higher apparent survival in females than in males in 1999, a clear higher apparent survival rates in females than in males in 2000, nearest the same apparent survival rates of the two age classes of males throughout, and differences in apparent survival between age classes of females showing considerable annual variation within age classes. The results suggest permanent emigration of females from th...