Food limitation of a Delaware salt marsh population of the mummichog, Fundulus heteroclitus (L.).

Food supply, grazing activity and growth rate in the limpet Patella vulgata L.: a comparison between exposed and sheltered shores.

The effects of predation by the mummichog, Fundulusheteroclitus (L.), on the abundance and distribution of the salt marsh snail, Melampus bidentatus (Say)

Field experiments were undertaken on the intertidal gastropod Bembicium auratum, which is one of the dominant organisms in sheltered bays and mangroves in New South Wales. Animals were caged at various densities ranging from natural levels to about four times normal density. Increased density resulted in increased mortality (particularly of juveniles), reduced body weight, and (less conclusively) a decline in growth rate. Chlorophyll levels of the mangrove mud within the cages were monitored as an index of food availability, and increased rapidly in the control cages in the absence of Bembicium, remained steady at normal Bembicium densities, and declined at higher densities. Parallel experiments were conducted on the effects of substratum on Bembicium. One series of animals was allowed access to a hard substratum and the other only to mud. Body weights and survivorship were proportionally lower in animals deprived of a hard substratum. Juveniles were particularly susceptible to a shortage of food and more dependent on a hard substratum than adults. The population structure also suggests a high juvenile mortality but high adult survival and longevity. Bembicium is very abundant low on the shore but numbers decline and body weights increase higher up. Chlorophyll levels and amounts of hard substratum also decline up the shore. Possibly juveniles settle selectively (or survive better) low on the shore where oysters provide a dense hard substratum. Adults are less dependent on the hard substratum and may disperse up the shore, explaining the patterns of abundance and size.As Bembicium limits its own food supply and seemingly is limited by it, predation is unlikely to play an important role in restricting population density.

(1) The development of biomass frequency distributions and mortality patterns was investigated in a dense, self-thinning, natural stand of Impatiens capensis. Densitydependent growth and mortality were also investigated by repeatedly censusing marked individuals in plots at natural and experimentally reduced densities. Morphological measurements permitted estimates of plant size and mean relative growth rate to be made for each individual. (2) At natural density, size distributions became more hierarchical as the plants grew, while in the thinned plots there was no such increase; size distributions therefore became significantly more hierarchical in the control plots than in the thinned plots. (3) In the control plots, the relative growth rate of individuals was positively correlated with initial plant size and many of the smaller plants had negative growth rates. In contrast, in the thinned plots, relative growth rate was negatively correlated with plant size and all the plants had positive growth rates. (4) Survivorship was significantly lower in the control plots than in the experimentally thinned plots. Individual longevity increased with plant size in both treatments, but the relationship was much stronger at natural density. (5) These results indicate that dominance and suppression influence size-hierarchy development in dense, natural Impatiens capensis populations. Small, suppressed plants lose biomass through leaf abcission and senesce more rapidly than large plants during selfthinning.

Growth rates of ovarian follicles during natural menstrual cycles, oral contraception cycles, and ovarian stimulation cycles

Annual stem and plant growth rates of Stenocereus thurberi and Lophocereus schottii in southern Arizona from 1970 through 1983 were related to plant size, age, and meteorological conditions with analysis of variance and regression analysis. In both species, size was the major factor in growth rates. Annual growth rates of individual stems decreased as stem size increased, whereas annual growth rates of individual plants increased as both plant size and stem number increased. Mean plant growth rates (±SD) were 0.07 ± 0.06 m/yr for S. thurberi <1 m tall and 0.62 ± 0.30 m/yr for plants >5 m tall. Corresponding mean plant growth rates for L. schottii were 0.06 ± 0.12 and 0.88 ± 0.67 m/yr. Age-size relationships derived from the plant size-growth models indicated that S. thurberi reached heights of 0.1 m in ca. 8 yr, 1 m in 19 yr, and 10 m in 45 yr. Lophocereus schottii attained heights of 0.1 m in 14 yr, 1 m in 27 yr, and 10 m in 42 yr. Interannual variation in mean growth rates of all plants in each sample was strongly related to both winter precipitation and freeze frequency. For both species, mean growth rates tended to be greater in growing seasons after unusually wet winters and lower after relatively dry winters. Freeze frequency was most strongly related to the mean growth rate the following summer in S. thurberi and to the mean growth rate two summers later in L. schottii. The more prolonged effect of severe winters on L. schottii growth rates resulted from the greater sensitivity of this species to subfreezing temperatures and its occurrence on flat terrain often affected by cold air drainage in the study area.

Tree cover in savannas is determined as much by disturbances from fire and herbivory as by rainfall and soil resources. Fire especially acts to limit tree cover via a demographic bottleneck, limiting the recruitment of tree saplings to adults. Because sapling growth rates determine rates of sapling to tree recruitment, predicting changes in tree cover requires data on sapling growth rates, commonly expressed as population means. Here, we discuss the variability in sapling growth rates in Acacia populations in a savanna in Hluhluwe iMfolozi Park in South Africa. Saplings growing at mean rates under typical fire regimes in African savannas would likely never escape the fire‐trap to become adults. Only the fastest growing saplings could grow above the flame zone between fires. We suggest that maximum growth rates are more ecologically relevant than mean growth rates in natural populations and experiments. Maximum growth rates are better than mean growth rates as predictors of sapling release within species, as shown here, and probably of which species are likely ‘winners’ in savanna tree communities.

Assuming the absence of a massive asteroid strike, gamma ray burst, or other globally devastating event, the survival of a species depends on its ability to adapt to environmental changes. To understand how such adaptations occur in nature, scientists study much simpler systems in the lab. A classic lab evolution experiment uses evolutionary responses to temperature as a model for studying how an environmental variable affects the physical expression (phenotype) of an organism's genes. Biologists have typically focused either on the range of physiological responses to temperature or on the genetic changes underlying variations in temperature. In a new study, Jennifer Knies, Christina Burch, Joel Kingsolver, and colleagues demonstrate the value of using a genetically tractable organism—the bacteria-infecting virus bacteriophage (or phage)—to study adaptive responses to temperature. By combining phenotypic and genetic analyses with a new statistical approach, the researchers show that the genetic changes they observed in phages undergoing thermal adaptations in the lab also play a role in thermal performance in natural populations. A graphical representation of the effect that temperature (the environmental variable) has on a population's growth rate (the performance indicator) is called a thermal reaction norm. (A continuous reaction norm shows these interactions as an ongoing, underlying relationship.) Thermal reaction norms usually have a common shape, showing performance increasing along with temperature, reaching a maximum at an intermediate temperature, and declining with additional temperature increases. Three basic variations on this curve reflect biological responses (see illustration): vertical shifts relate to average performance, horizontal shifts relate to optimal temperature (for growth rate, for example), and width shifts relate to changes in niche range. Using continuous reaction norms to characterize adaptive responses to temperature, the researchers reexamined a recent study that linked rapid adaptation to specific genetic changes. The study, by Holder and Bull, showed that phage populations quickly evolved higher growth rates at higher temperatures. But, Knies et al. explain, these growth rates were correlated with just one temperature point—the optimal temperature for the ancestral populations (used at the beginning of the experiment). Knies et al. reexamined phage thermal adaptation by measuring growth rate over a wider range of temperatures, then used a recently developed statistical method to identify the biological determinants of the shifts in the reaction norm shapes, quantify their relative contributions, and identify the genetic basis of the adaptations. In the evolution experiment, a population of phage clones was propagated through a series of 50 transfers—during each transfer, 1,000,000 phages were added to a culture of 1,000,000,000 reproducing Escherichia coli hosts—at 106.7 degrees Fahrenheit (41.5 °C), followed by 50 more transfers at 111.2 °F (44 °C). Knies et al. isolated phages from the evolving populations at the 20th, 50th, and 100th (last) transfer, and characterized their growth rates (and that of the ancestral population) across their entire thermal niche—six temperature points between 80.6 °F (27 °C) and 111.2 °F. The phages had evolved between each transfer, and their reaction norms had the characteristic shape for performance: growth rate increased with temperature until reaching a maximum at 95 °F (35 °C), and declined as temperatures further increased. Using the statistical model, the researchers estimated the biological components underlying the reaction norm shapes for each evolving population. Although the contributions of the components varied with temperature, Knies et al. found that optimal temperature explained the largest proportion of the variation in reaction norm shape, with smaller contributions from growth rate and niche width. The researchers knew from the previous study by Holder and Bull that ten adaptive mutations had spread through the population during adaptation to high temperature. By sequencing the genomes of several evolved phages at different transfer stages, they were able to confirm that many of these mutations contributed to adaptation in the laboratory. To determine the effects of these mutations in natural populations, they focused on one mutation that “unambiguously” contributed to adaptation in the lab and was also present in natural populations. In both laboratory and natural phage populations, the mutation was associated with increased growth rates at high, but not low, temperatures. The finding that shifts in optimal temperature underlie much of the adaptive response in phage populations supports human antiviral strategies that use cold-adapted vaccines, the researchers argue. These strategies adapt viral strains to grow at temperatures well below body temperature so they don't become virulent when injected as vaccines—a sound approach, based on these results. This study demonstrates a powerful method for integrating biological modes of adaptation to the underlying genetic changes—a method the researchers hope will inspire more collaborations between evolutionary geneticists, physiologists, and statisticians.

In terms of biomass, Sargassum lapazeanum (Phaeophyceae, Fucales) is one of the most important seaweeds in La Paz Bay, on the southeastern coast of the Baja California Peninsula, Mexico. This species can be found year‐round in shallow subtidal sites. Standing biomass is lowest between fall and winter and highest between spring and summer. We are currently studying the annual demography of fronds as a necessary step to understanding the mechanisms of population regulation. Work is being done on a bed of about 90 m in length and three m in width. At this stage of abstract submission, we can report results for winter only. Random samples were collected in February and in March 2000 to estimate stand biomass, frond density, and size (frond length) structure. In addition, we labeled fronds with numbered plastic tags to estimate their rates of growth and of mortality during this period. Rates of recruitment were estimated from a combined analysis of the above. In February, fronds were all shorter than 6.5 cm. Between February and March, mean total frond density increased from 122 to 776 fronds m−2 (n = 30 quadrats). The mean recruitment rate was 667 fronds m−2, the mean growth rate was 0.5 cm day−1 (n = 60 fronds), and the mean mortality rate was 43 fronds m−2. From last year's preliminary observations, we expect to observe peaks of biomass and of reproduction in late spring, followed by negative growth rates and high mortality rates during summer.

Individual growth rates, feeding rates (%BWd-1) and food conversions for cuttlefish (S. officinalis) hatchlings and juveniles were determined during this study. A flow-through system was used. Water temperature reached 30 degrees C during the hottest part of the day, gradually decreasing to 25 degrees C during the night; salinity varied between 37 +/- 3 ppt and lights were kept on for 14 h day(-1). Hatchlings were placed in separate compartments with a water volume of 1.2 L. Juvenile cuttlefish (from 0.5 to 25 g) were placed in bigger baskets, with a water volume of 5.2 L. Water flow was 120 L h(-1). The biggest cuttlefish used in these experiments (> than 25 g) were gathered in groups of five and placed in circular tanks (water volume of 250-300 L). Thus, results obtained in this case are means and not individual data. During the first 10, 20, 30 and 40 days, mean growth rates (of all individuals sampled by age group) decreased consistently (11.8 +/- 4.1, 9.8 +/- 1.8, 8.1 +/- 2.2 and 7.3 +/- 0.7%BW-1 respectively); in similar fashion, mean feeding rates decreased with age group (33.7 +/- 13.5, 22.0 +/- 7.9, 17.3 +/- 3.9 and 16.7%BWd-1 respectively). Mean food conversions varied between 3.6 and 2.5 between the age groups. When grouping results by weight class, similar patterns occur, as growth and feeding rates decrease consistently as cuttlefish grow bigger. Highest mean growth and feeding rates are obtained by hatchlings (< 0.1 g) with 12.4 +/- 4.5 and 35.3 +/- 15.1%BWd-1, respectively, while the lowest growth and feeding rates were recorded for the largest animals, between 15 and 25 g (3.4 +/- 1.1 and 10.8 +/- 4.1%BWd-1 respectively). For these weight classes, mean food conversions varied between 2.7 +/- 0.9 and 3.8 +/- 2.8.

Biodiversity indices often combine data from different species when used in monitoring programs. Heuristic properties can suggest preferred indices, but we lack objective ways to discriminate between indices with similar heuristics. Biodiversity indices can be evaluated by determining how well they reflect management objectives that a monitoring program aims to support. For example, the Convention on Biological Diversity requires reporting about extinction rates, so simple indices that reflect extinction risk would be valuable. We developed 3 biodiversity indices that are based on simple models of population viability that relate extinction risk to abundance. We based the first index on the geometric mean abundance of species and the second on a more general power mean. In a third index, we integrated the geometric mean abundance and trend. These indices require the same data as previous indices, but they also relate directly to extinction risk. Field data for butterflies and woodland plants and experimental studies of protozoan communities show that the indices correlate with local extinction rates. Applying the index based on the geometric mean to global data on changes in avian abundance suggested that the average extinction probability of birds has increased approximately 1% from 1970 to 2009.Conectando Índices para el Monitoreo de la Biodiversidad con la Teoría de Riesgo de ExtinciónResumenLos índices de biodiversidad combinan frecuentemente los datos de diferentes especies cuando se usan en los programas de monitoreo. Las propiedades heurísticas pueden sugerir índices preferidos, pero carecemos de medios objetivos para discriminar a los índices con propiedades heurísticas similares. Los índices de biodiversidad pueden evaluarse al determinar qué tan bien reflejan los objetivos de manejo que un programa de monitoreo busca apoyar. Por ejemplo, la Convención sobre la Diversidad Biológica requiere reportar las tasas de extinción, así que los índices que reflejan el riesgo de extinción serían valiosos. Desarrollamos 3 índices de biodiversidad que se basan en modelos sencillos de viabilidad de población y que relacionan el riesgo de extinción con la abundancia. Basamos el primer índice en la media geométrica de la abundancia de especies, y el segundo en una media de poder más general. En el tercer índice integramos la media geométrica y la tendencia. Estos índices requieren los mismos datos que índices previos, pero también se relacionan directamente con el riesgo de extinción. La información de campo sobre mariposas y plantas de bosque, y los estudios experimentales de comunidades protozoarias, muestran que los índices se correlacionan con las tasas locales de extinción. Al aplicar el índice basado en la media geométrica sobre los datos globales de los cambios en la abundancia de aves, sugirió que la probabilidad de extinción promedio de aves ha incrementado aproximadamente 1% desde 1970 hasta 2009.Palabras ClaveÍndice de biodiversidad, media geométrica, medida de la biodiversidad, riesgo de extinción

Fundulus heteroclitus is known to ascend onto the marsh surface to feed. Our study investigated whether the marsh surface food items are a necessary source of caloric intake for the Canary Creek, Delaware, USA population of this species. Enclosure techniques were used to restrict mummichogs from the marsh surface and the growth rates of these fish were compared to those having access to the marsh surface. Growth rates were significantly higher for mummichogs allowed access to the marsh surface. Food addition and density reduction experiments showed that food availability per fish, rather than behavioral responses due to fish crowding, was responsible for the increased growth. Although food was available in the subtidal portion of the habitat, it was of insufficient quantity for fish at natural density to grow at a normal rate, and mummichogs must utilize the marsh surface for at least a portion of their energy intake.

Small abdominal aortic aneurysms (AAAs; 3.0-5.4 cm in diameter) are usually asymptomatic and managed by regular ultrasound surveillance until they grow to a diameter threshold (commonly 5.5 cm) at which surgical intervention is considered. The choice of appropriate surveillance intervals is governed by the growth and rupture rates of small AAAs, as well as their relative cost-effectiveness. The aim of this series of studies was to inform the evidence base for small AAA surveillance strategies. This was achieved by literature review, collation and analysis of individual patient data, a focus group and health economic modelling. We undertook systematic literature reviews of growth rates and rupture rates of small AAAs. The databases MEDLINE, EMBASE on OvidSP, Cochrane Central Register of Controlled Trials 2009 Issue 4, ClinicalTrials.gov, and controlled-trials.com were searched from inception up until the end of 2009. We also obtained individual data on 15,475 patients from 18 surveillance studies. Systematic reviews of publications identified 15 studies providing small AAA growth rates, and 14 studies with small AAA rupture rates, up to December 2009 (later updated to September 2012). We developed statistical methods to analyse individual surveillance data, including the effects of patient characteristics, to inform the choice of surveillance intervals and provide inputs for health economic modelling. We updated an existing health economic model of AAA screening to address the cost-effectiveness of different surveillance intervals. In the literature reviews, the mean growth rate was 2.3 mm/year and the reported rupture rates varied between 0 and 1.6 ruptures per 100 person-years. Growth rates increased markedly with aneurysm diameter, but insufficient detail was available to guide surveillance intervals. Based on individual surveillance data, for each 0.5-cm increase in AAA diameter, growth rates increased by about 0.5 mm/year and rupture rates doubled. To control the risk of exceeding 5.5 cm to below 10% in men, on average a 7-year surveillance interval is sufficient for a 3.0-cm aneurysm, whereas an 8-month interval is necessary for a 5.0-cm aneurysm. To control the risk of rupture to below 1%, the corresponding estimated surveillance intervals are 9 years and 17 months. Average growth rates were higher in smokers (by 0.35 mm/year) and lower in patients with diabetes (by 0.51 mm/year). Rupture rates were almost fourfold higher in women than men, doubled in current smokers and increased with higher blood pressure. Increasing the surveillance interval from 1 to 2 years for the smallest aneurysms (3.0-4.4 cm) decreased costs and led to a positive net benefit. For the larger aneurysms (4.5-5.4 cm), increasing surveillance intervals from 3 to 6 months led to equivalent cost-effectiveness. There were no clear reasons why the growth rates varied substantially between studies. Uniform diagnostic criteria for rupture were not available. The long-term cost-effectiveness results may be susceptible to the modelling assumptions made. Surveillance intervals of several years are clinically acceptable for men with AAAs in the range 3.0-4.0 cm. Intervals of around 1 year are suitable for 4.0-4.9-cm AAAs, whereas intervals of 6 months would be acceptable for 5.0-5.4-cm AAAs. These intervals are longer than those currently employed in the UK AAA screening programmes. Lengthening surveillance intervals for the smallest aneurysms was also shown to be cost-effective. Future work should focus on optimising surveillance intervals for women, studying whether or not the threshold for surgery should depend on patient characteristics, evaluating the usefulness of surveillance for those with aortic diameters of 2.5-2.9 cm, and developing interventions that may reduce the growth or rupture rates of small AAAs. The National Institute for Health Research Health Technology Assessment programme.

Study question Can the growth of individual follicles during ovarian stimulation in medically assisted reproduction (MAR) cycles be modelled to enable prediction of final follicle profiles? Summary answer Mean follicle growth rate is 1.35 mm per day. Our model reliably forecasts follicle size profiles on the final scan within ±2mm with 75.1% accuracy. What is known already Follicle growth rates during ovarian stimulation are believed to be linear with various mean growth rates reported between 1 to 4 mm per day. Follicles are believed to grow faster during ovarian stimulation than in the natural menstrual cycle. The change in mean follicle size was 1.69 mm per day with ovarian stimulation in 131 MAR cycles, and 1.4 mm per day in 50 natural cycles. However, there are only very limited data using individual follicle sizes to model follicle growth to enable prediction of future follicle size profiles. Study design, size, duration We conducted a retrospective cohort study of 12,950 patients from 11 European clinics (2005-2023). First IVF/ICSI cycles with at least three follicles and two scans were analysed. Using 8,564 cycles with scans one or two days apart, 98,029 follicles were modelled to estimate follicle growth rates per day. Stratification by age, weight, total antral follicle count (AFC), initial FSH dose, and suppressant protocol was performed. Predictive modelling was conducted using 39,698 scans including 434,082 follicles. Participants/materials, setting, methods Assessment of Follicle Growth: Follicles were ranked and the difference in corresponding follicle sizes over consecutive scans estimated, and the impact of baseline characteristics evaluated. Prediction of follicle size profile on final scan: A kernel density estimator and random forest model were developed using the same training data. Both approaches estimated future follicle growth from the initial scan. The two predictions were combined using maximum-likelihood adjustments. Generalisation error was estimated using independent test data. Main results and the role of chance The mean growth rate of individual follicles was 1.350 mm per day (95% CI 1.346 – 1.353 mm per day), which was lower than the previously reported mean follicle growth rate during ovarian stimulation (1.7 mm per day). The large number of patient-cycles and follicles assessed enabled a precise estimate of follicle growth per day during ovarian stimulation. Age, total AFC, initial FSH dose, bodyweight, and suppressant protocol had no statistically significant effect on the estimated mean growth rate. Using only the follicle sizes from the initial scan during ovarian stimulation, our model had 75.1% accuracy for predicting follicle sizes on the final scan within ±2mm. Including follicle size data from the first two scans improved the accuracy of the model to predict the follicle sizes on the final scan to 80.4%. In a confirmatory analysis, we cross-validated our findings across each of 11 individual clinics, and similar estimates for the generalisation error as for the standard test/train split were maintained, suggesting suitable generalisability of these findings. Limitations, reasons for caution A key simplifying assumption in this study is that follicles demonstrate monotonic growth patterns. Specifically, the relative ordering of follicle sizes is preserved over the entire cycle. This assumption enables straightforward extraction of growth statistics from the observed data but assumes that follicles do not regress in size. Wider implications of the findings We have used a large high-quality dataset, allied to advanced modern machine learning techniques, to precisely estimate follicle growth rates during ovarian stimulation, and use this to reliably predict future follicle size profiles during ovarian stimulation. This supports the design, personalisation, streamlining and success of future assisted conception cycles. Trial registration number None

SUMMARY. Growth maybe divided conveniently into two well‐marked periods. (a) 1st period, from the seedling stage till the time that the plant regains its initial weight after the loss by respiration, i.e. the time during which a casual observer would say the plant “makes no growth.”(b) 2nd period, succeeding the former, during which the plant is obviously making growth, and which continues till the latter ceases and desiccation sets in. The length of the first period varies inversely with the mean maximum temperature, as the rate at which assimilation is able to make good the loss by respiration increases directly with rise of temperature, up to a certain limit. The possible amount of growth as measured by the dry matter produced depends directly upon the bright sunshine and temperature when the food supply is adequate, but when the latter is limited the total growth is much less owing to the lack of material for building up the tissues. Beyond a certain limit, however, the beneficial factors of heat and bright sunshine become harmful and result in the premature death of the plant. During the first period the rate of growth as shown by the efficiency index was associated with relatively warm days and nights, bright sunshine having little significant effect; the light, however, was good throughout for the season of the year. During the second period the rate was associated strongly with sunshine and warm days, but not significantly with the night temperatures, which did not fall below 32° F. During the greater part of the year the maximum rate of growth (highest efficiency index) is reached early in life, very soon after the second period begins. Under favourable environmental conditions a high rate of increase is then maintained for several weeks, but in less favourable circumstances the efficiency index rapidly falls. In winter, when temperatures rule low and there is little bright sunshine, the maximum rate of growth is not reached till several weeks after the beginning of the second period, and even then the efficiency index is not very great. Plants with a restricted food supply make less total growth than those with abundant food. The falling off in the amount of dry matter produced does not seem to be gradual but is marked by definite periods of which the incidence varies at different seasons. Broadly speaking the response of plants to the environmental conditions is similar whether the food supply is abundant or restricted, though the mean rate of growth is lower when food is scarce. During the first period the excess of food has no significant effect upon the rate of growth, but during the second period the mean differences in the rate of increase in the presence of abundance and of scarcity of food are strongly significant in favour of the well supplied plants. During the early weeks, corresponding approximately to the first period of growth, the shoot/root ratio falls, owing to the steady increase in root weight which is associated at first with a decrease and later with an increase in shoot weight. During the second period of active growth the shoot increases in weight far more rapidly than the root, and thus the shoot/root ratio rises steadily. Increase in shoot growth is closely associated with rise in temperature, though the lowest mean maximum attained in the experiments did not cause a cessation of growth. Root growth is much affected by low mean maximum temperatures and practically ceased, under the experimental conditions, when they were consistently below 60° F. Rise in maximum temperature had much less beneficial action upon the roots than upon the shoots. In early stages of growth the amount of nitrate absorbed by the plant is relatively large in comparison with the dry matter produced, but later on more dry matter is formed in proportion to the same amount of nitrate, owing to the accumulation of the products of assimilation.In conclusion I wish to express my indebtedness to Mr R. A. Fisher, who has examined the figures and has furnished me with the statistical information embodied in this paper.In each case the efficiency indices are percent per day.