Mean Population Density Research Articles

The effects of combining modified sowing methods with herbicide mixtures on weed interference in wheat crops

In India, wheat is prone to being heavily infested with weeds, which cause considerable yield losses. Agronomic practices, including sowing method, influence weed interference in wheat growth. A herbicide mixture is usually more effective than a single herbicide for controlling a broad-spectrum of weeds. It may prevent weed species shift and delay resistance development in weeds. This study attempted to develop an integrated approach, combining a modified sowing method with applying a herbicide mixture for efficient weed management in wheat. We found that flat bed missing-row sowing resulted in significant reductions in: (i) the three-year mean population densities of grassy, broad-leaved and total weeds at 40 days after sowing (d.a.s), (ii) total weed population density and biomass (dry weight) at 60 d.a.s., compared to a mainly, furrow-irrigated raised bed system. Applying a tank-mix of fenoxaprop-p-ethyl at 0.08 kg/ha and isoproturon at 0.4 kg/ha applied 30 d.a.s. resulted in significant reductions in total weed population density and biomass, leading to a significant improvement in wheat growth and yield compared to either a weedy check or a regime of fenoxaprop-p-ethyl applied at 0.10 kg/ha. However, a combination of the flat bed missing-row sowing and tank-mix application of fenoxaprop-p-ethyl 0.08 kg/ha and isoproturon 0.4 kg/ha 30 d.a.s. resulted in higher wheat yield through better management of weeds compared with other sowing/ weed control combinations.

Allometric scaling of population variance with mean body size is predicted from Taylor’s law and density-mass allometry

Two widely tested empirical patterns in ecology are combined here to predict how the variation of population density relates to the average body size of organisms. Taylor's law (TL) asserts that the variance of the population density of a set of populations is a power-law function of the mean population density. Density-mass allometry (DMA) asserts that the mean population density of a set of populations is a power-law function of the mean individual body mass. Combined, DMA and TL predict that the variance of the population density is a power-law function of mean individual body mass. We call this relationship "variance-mass allometry" (VMA). We confirmed the theoretically predicted power-law form and the theoretically predicted parameters of VMA, using detailed data on individual oak trees (Quercus spp.) of Black Rock Forest, Cornwall, New York. These results connect the variability of population density to the mean body mass of individuals.

Culture experiments with a freshwater cladoceran, <i>Ceriodaphnia quadrangula</i> (O. F. Müller, 1785), as suitable live food for Mayan cichlid (Cichlasoma urophthalmus) larvae

Effects of five different diets of green microalgae, Scenedesmus quadricauda (S), poultry manure (P), cattle manure (C), and two mixed diet of P+C (PC) and S+P+C (SPC); and interaction effects of water temperature (20, 25, 30°C) and photoperiod (24:0, 0:24, and 12:12, hours light: hours dark) on production and growth of Ceriodaphnia quadrangula were examined separately. Then, mass cultivation of C. quadrangula and its application for rearing of an ornamental fish larva, Mayan cichlid (Cichlasoma urophthalmus) were carried out. Results showed that mean population density and specific growth rate (SGR) of C. quadrangula obtained 0.15-3.70 ind. mL-1 (150-3700 ind. mL-1) and 0.019-0.18 day-1, respectively, maximum with S diet and minimum with C diet. The better mean population density and SGR for C. quadrangula determined at interactions 25 ºC with 24:0 and 12: 12, L:D, respectively, which was significantly higher than that at interactions 20 ºC and 30 ºC. Nutritional analyses showed that protein and lipid contents of C. quadrangula were 54% and 12.3% dry weight, respectively. The fatty acid contents of C. quadrangula were 27.3% and 63.7% of saturated and unsaturated fatty acids, respectively. Among PUFAs (Polyunsaturated Fatty Acids) content, 18:2n-6 and 18:3n-3 were in highest level. Early cichlid larvae (5-weeks-old, 15.8 mm length and 110 mg weight) and advanced larvae (10-weeks-old, 25.6 mm length and 240 mg weight) consumed C. quadrangula at range 220–584 ind. day-1 larvae-1 and 528–1956 ind. day-1 larvae-1, respectively, as well as suitable growth and survival rate. This study demonstrated that C. quadrangula could be used as live feed purposes for larval rearing in aquaculture.

English

This study attempts to provide an overview of the benthic macroinvertebrate assemblages of Yousmarg streams. For studying the distribution of macroinvertebrate assemblages in the two streams, that is, Doodganga and Khanshah manshah canal, a total of 4 study sites were selected. During the period of investigation, 24 species of macrozoobenthos in Yousmarg streams were recorded. Arthropoda was found to be the most dominant group, comprising of 23 species followed by Annelida with 1 species. The phylum Arthropoda was represented by class Insecta (5 orders) and Crustacea (1 orders). The diversity of benthic invertebrates was high in Doodhganga stream (21 taxa) as compared to Khanshah-manshah canal (18 taxa). An inter-site comparison revealed maximum mean population density for Doodhganga stream as compared to Khanshah-manshah canal. Besides, it was observed that boulders and cobbles provided a stable habitat for macroinvertebrates dwelling. Also, greater diversity in the summers as against winters was recorded in both the streams. On the basis of the biotic indices, the Doodhganga stream is being adjudged pristine with no organic pollution, however slight organic pollution in Khanshah–manshah canal was recorded.   Key words: Kashmir Himalayas, benthic macroinvertebrates, Diversity

Spatial distribution and diet of Cephalopholis fulva (Ephinephelidae) at Trindade Island, Brazil

In this study we analyze the population structure and diet of the coney Cephalopholis fulva at Trindade Island, Brazil, through direct observation with SCUBA diving in 11 reef sites around the Island, up to 50 m deep. Diet was based on 77 individuals collected with speargun. Mean population density and biomass were estimated at 29 individuals/100 m² and 13 kg/100 m², respectively. This species is regularly distributed along the costal environments of the Trindade Island, with no significant differences in densities and biomass detected among the different collection habitats (reef crest, reef slope, and reef plateau). However, significantly higher densities were observed micro-habitats with greater structural complexity, which may offer more shelter and food to C. fulva. Four food item groups were identified from the gut contents of C. fulva: Annelida, Crustacea, Teleostei, and Testudinata. It is the first record of predation of the green turtle Chelonia mydas hatchlings by the coney. Trindade Island seems to present the densest concentration of C. fulva in all Brazilian and Caribbean ecosystems inhabited by this species. Scarcity of competitors, predators, and fishing pressure may explain the high densities observed in the Island.

Population density but not stability can be predicted from species distribution models

Summary1. Species distribution models (SDMs) are increasingly used in applied conservation biology, yet the predictive ability of these models is often tested only on detection/non‐detection data. The probability of long‐term population persistence, however, depends not only upon patch occupancy but upon more fundamental population parameters such as mean population density and stability over time.2. Here, we test estimated probability of occurrence scores generated from SDMs built using species occupancy data against independent empirical data on population density and stability for 20 bird and butterfly species across 1941 sites over 15 years. We devised a measure of population stability over time which was independent of mean density and time‐series duration, yet positively correlated with risk of local extinction. This may be a useful surrogate measure of population persistence for use in applied conservation.3. We found that probability of occurrence scores were significantly positively correlated with mean population density for both butterflies and birds. In contrast, probability of occurrence scores were at best weakly positively correlated with population stability. Referring to established ecological theory, we discuss why SDMs may be appropriate for predicting population density but not stability.4. Synthesis and applications.Species distribution models are often constructed using species occupancy data because, for the majority of species and regions, these are the best data available. The models are then often used for projecting species’ distributions in the future and identifying areas where management could be targeted to improve species’ prospects. However, our results suggest that an overreliance on these SDMs may result in an exclusive focus on landscape management approaches that promote patch occupancy and density, but may overlook features important for long‐term population persistence such as population stability. Other landscape metrics that take into account habitat heterogeneity or configuration may be required to predict population stability. To understand species persistence under rapid environmental change, count data from standardised monitoring schemes are an invaluable resource. These data provide additional insights into the factors affecting species’ extinction risks, which cannot easily be inferred from species’ occupancy data.

Bacterial microcosms obey Taylor's law: effects of abiotic and biotic stress and genetics on mean and variance of population density

Abstract Introduction According to the empirical regularity called Taylor's law, the variance of population density in samples of populations is a power of the mean population density. The exponent is often between 1 and 2. Our experiments investigated how genetics, evolution, and environment shape Taylor's law. Methods Genetically different strains (wild type and hypermutator) of the bacterium Pseudomonas fluorescens evolved and were assayed under different environmental conditions (with and without antibiotic rifampicin and bacteriophage SBW25φ2, separately and in combination). Results Experimental treatments altered the exponent b, but not the power law form, of the relation between variance and mean population density. Bacterial populations treated only with rifampicin had a narrow range of mean population densities and exponent b = 5.43. Populations exposed to rifampicin plus phage had b = 1.51. In ancestral, control, and phage-exposed populations, mean abundance varied widely and b was not significantly different from 2. Evolutionary factors (mutation rate, selection) and ecological factors (abiotic, biotic) jointly influenced b. Conclusions Taylor's power law relationship accurately and robustly described variance as a function of mean population density, with overall exponent b = 1.89. These and other experiments with different factors acting on bacterial population size support the relevance of models that predict 'universal' patterns of fluctuation scaling.

Turfgrass Performance of Diploid Buffalograss [Buchloe dactyloides (Nutt.) Engelm.] Half-sib Populations

Hybridization and selection has been one of the methods used to generate turfgrass cultivars in buffalograss improvement. Three half-sib populations were developed by crossing three buffalograss female genotypes, NE 3296, NE 2768, and NE 2769, with NE 2871, a male genotype, to 1) investigate the pattern of genetic variability generated for turfgrass characteristics through hybridization; 2) assess the effect of parental change on the level of genetic variability generated in a buffalograss diploid population; and 3) predict the performance of a progeny generated from two heterozygous parents for turfgrass performance. The four parents and 20 random F1 progeny selected from each population were established in 2006 at the John Seaton Anderson Turfgrass Research Facility located near Mead, NE. A randomized complete block design (RCBD) was used with the progeny nested in the crosses. A visual rating scale of 1–9 was used to evaluate the population. Mean population lateral spread, genetic color, density, and turfgrass quality from early summer to fall ranged from 3.5 to 4.5, 7.1 to 7.9, 6.9 to 8.1, and 5.2 and 6.8, respectively. There were significant differences among the crosses and the parents for all the traits studied except quality in June and August. The progeny nested within crosses differed for turfgrass genetic color and quality. Best linear unbiased prediction (BLUP) indicated a high improvement potential for turfgrass lateral spread and spring density in NE 2768 × NE 2871 and for turfgrass genetic color in NE 3296 × NE 2871. From these findings, it can be concluded that hybridization breeding is a worthwhile approach for generating and identifying transgressive segregants for specific buffalograss traits.

Conservation in Sustainable-Use Tropical Forest Reserves

trialspecies,therelativemeritsofdifferentapproachesto ensure the long-term persistence of those species remain highly contentious. Most would agree, however, that both establishing protected areas and exercising some form of restraint on extraction of forest resources are among the most effective of all viable conservation measures. Deforestation, wildfires, logging, and hunting are among the leading drivers of species losses in tropical forests, and de facto or de jure protection from these threats can be conferred by either effective enforcement of regulations or physical remoteness. Attempts to assess conservation success of protected areasatlargescaleshaverestedprimarilyonconventional use of remote sensing to quantify spatial or temporal differences in rates of change in land cover due to deforestation and wildfires, rather than on empirical demographic or community-level metrics (Gaston et al. 2008). Q2 However, the former approaches fail to detect most types of subcanopy anthropogenic disturbances that also result, directly or indirectly, in species losses (Peres et al. 2006). Moreover, the effects of habitat loss and degradation on population extirpations and declines are nonlinear, so vegetation cover alone is rarely a robust proxy for the viability of terrestrial biotas. Remotesensing data show vast tracts of apparently intact tropical forests, but in reality levels of hunting and other forms of extraction in these areas are often unsustainable (Peres & Lake 2003). Fundamental questions yet to be answered include whether ostensibly intact protected areas retain full complements of forest species and how the extent of cryptic patterns of disturbance is related to human population density in both protected and unprotected areas. I considered the global to regional emergence of sustainable-use reserves, emphasizing the world’s largest tropical forest region, Amazonia. Sustainable-use reserves often have intermediate levels of disturbance, so I examined the degree of use of natural resources by resident communities and used human population density as a proxy for level of extraction. In both protected and unprotected areas, I also estimated responses of game vertebrate assemblages to hunting on the basis of the relative biomassextractedfromasubsetoftheforestfauna.Iused analysesofcovariance(ANCOVA)toexaminetheassociationbetweenhumandensityandgamebiomassharvested across different reserve categories. Finally, I considered the long-term capacity of sustainable-use forest reserves to maintain populations of all resident species.

Communal nesting, activity patterns, and population characteristics in the near-threatened monito del monte, Dromiciops gliroides

The “living fossil,” Dromiciops gliroides (monito del monte), is an endemic marsupial inhabiting the temperate rain forests of South America. It is cavity-dependent and faces high energetic costs associated with thermoregulation during the austral winter. Although D. gliroides is well known for seed dispersal in temperate rain forests, its ecology, behavior, and long-term population dynamics have received little attention. We monitored a population of D. gliroides and studied variation in abundance and density and seasonal changes in body mass and body condition index (BCI). In addition, we monitored activity and communal nesting with camera traps and nest boxes, respectively. Over 4 years we documented a mean population density of 26 (95% confidence interval = 19–32) individuals/ha. We found significantly greater body mass and BCI for females than for males, suggesting different energetic strategies during the prehibernation period. Animals were nocturnal and active until dawn. Communal nesting occurred during summer and early fall, but torpor by single individuals and small groups was increasingly frequent during winter. Communal nesting could be a key behavioral strategy affecting survival. However, given the greater frequency in warm seasons and groups composed of postreproductive females and juveniles, communal nesting might be more related to parental care associated with kin selection than to thermoregulation.

Survival and distribution of Escherichia coli on diverse fresh-cut baby leafy greens under preharvest through postharvest conditions.

Escherichia coli O157:H7 has been associated in multiple outbreaks linked to the consumption of whole produce and fresh-cut leafy vegetables. However, plant-based foods had not been traditionally recognized as a host for enteric pathogens until the elevated incidence of produce-related outbreaks became apparent. The survival dynamics of two cocktails of generic E. coli (environmental water, plant and soil isolates) and E. coli O157:H7 within the phyllosphere of Mizuna, Red Chard and Tatsoi during their production, harvest, minimal processing, packaging and storage over two greenhouse production cycles were studied. Genotyping of applied generic E. coli strains to evaluate their comparative survival and relative abundance in the phyllosphere by REP-PCR is also reported. The Mizuna, Red Chard and Tatsoi shoots were grown under standard greenhouse conditions and fertility management. Both E. coli cocktails were spray-inoculated separately and determined to result in an initial mean population density of log 4.2 CFU/cm². Leaves were harvested as mini-greens approximating commercial maturity, minimally processed in a model washing system treated with 3 mg/L of ClO₂ and stored for 7 days at 5 °C. Rapid decline of generic E. coli and E. coli O157:H7 populations was observed for all plant types regardless of the leaf age at the time of inoculation and the irrigation type across both seasonal growth cycle trials. The decline rate of the surviving populations for the fall season was slower than for the summer season. The minimal processing with 3 mg/L of ClO₂ was not sufficient to fully disinfect the inoculated leaves prior to packaging and refrigerated storage. Viable populations of E. coli and E. coli O157:H7 were confirmed throughout storage, including the final time point at the end of acceptable visual leaf quality. In this study, the ability of low populations of E. coli to survive during production and postharvest operations in selected mini-greens has been demonstrated. However, further field-based trials are needed to expand understanding of the post-contamination fate of enteric bacterial pathogens on leafy vegetables. In summary, this research work provides baseline data upon which to develop food safety preventive control guidance during the production and minimal processing of these crops.

Global interannual variability in terrestrial ecosystems: sources and spatial distribution using MODIS-derived vegetation indices, social and biophysical factors

Variations in global vegetation activity were measured at a global scale, from 2000 to 2006, based on the Enhanced Vegetation Index (EVI) extracted from the 1km resolution Moderate Resolution Imaging Spectroradiometer (MODIS) satellite data. Interannual variations in phenology and/or in annual integrated vegetation index are mapped using change metrics. The relationships between interannual variability and climate, ecosystem disturbances and land use are also examined. Around 14% of the study area experienced high interannual variability in land surface attributes over the six years. The ecosystems most subjected to large fluctuations in surface conditions were the boreal ecosystems, temperate ecozones, and subtropical and tropical steppes. These changes were largely related to rainfall variability and were associated with mean annual rainfall, agriculture, fire regimes and population density. Large population concentrations were mostly found in more stable ecozones. Rainfall and natural fire regimes explained more than half of the land surface variability in Australia. An additional global analysis on trends in vegetation activity also shows that around 4.5% of the vegetated surface of the Earth, excluding deserts and frequently cloudy regions, experienced a continuous decrease in vegetation activity over the six years. This represents more than twice the area experiencing a greening trend over this time period and concerns mostly tropical, subtropical and temperate forest ecozones. The total change in vegetation activity at a global scale and per year amounted to –2% of the annual integrated EVI aggregated across all ecosystems of the study area, on average for the years 2001–2006.

Evapotranspiration of a drip‐irrigated, film‐mulched cotton field in northern Xinjiang, China

AbstractEddy covariance flux measurements were performed at a cotton crop site of an oasis in northern Xinjiang, northwest China from 2008 to 2010 in order to study ecosystem evapotranspiration (ET). The soil surface area was approximately 80% covered by plastic film mulch and a cotton crop was grown with a mean population density of around 24 plants m−2 under drip irrigation. The total annual ET was measured to be 560 mm, which was 350 mm more than the average annual mean precipitation for the time period 1963–2006. Due to the low vapor pressure deficit associated with low temperatures, the ET was low from November to March. The ET totaled 538 mm during the cotton crop growing season, generally from early‐April through mid‐October. Mean daily ecosystem ET was 1·4–1·6 mm day−1 in April and May, 3·4–4·7 mm day−1 from June through August, 1·8–2·3 mm day−1 in September and 0·7–0·8 mm day−1 in October. The diurnal variations of ET in all months were consistent with those of net radiation, although the leaf area index (LAI) and climate conditions changed substantially. Soil water content was not a limiting factor for ET during the period from April through September, as the crop was regularly irrigated. Therefore, ET was mainly controlled by the available energy in April and May, and by leaf area from June through September. Due to a complete lack of irrigation, ET was constrained by soil water in October. These results of ET variability are helpful for improved allocation of water resources and agricultural water use practices in the region. Copyright © 2011 John Wiley & Sons, Ltd.

Population densities in relation to bladder cancer mortality rates in America from 1950 to 1994

Previous studies have reported that bladder cancer risks are elevated in industrial and urban areas. The cause is believed to be the result of occupational exposure from industries located in urban areas. Recent studies suggest that traffic air pollution may also increase bladder cancer risks. The study purpose is to investigate the relationship between bladder cancer mortality and population density of counties in America. Another objective is to explore traffic air pollution and industrial exposures as risk factors. Bladder cancer mortality rates for white men and women from 1950 to 1994 and population densities (population per 10 square miles) of 2,248 counties were the basis of the study. A linear regression analysis was performed to evaluate the relationship between bladder cancer mortality rates and population densities after log transforming the population density data set. In addition, the counties were divided into quartiles based on bladder cancer mortality rates. Mean population density values with 95% confidence intervals for the quartiles were computed. Correlation coefficients (R) between bladder cancer mortality rates and the population densities were R = .37, P < .001 for men and R = .28, P < .001 for women. In addition, population densities increased with increasing bladder cancer mortality rates across all quartiles. The mean population density of the highest quartile was more than ten times higher than the lowest. In this study, we found a strong association between bladder cancer mortality and population density. Traffic air pollution is a potential cause.

Using simulation to explore the functional relationships of terrestrial carnivore population indices

Population indices based on visits to detection stations commonly are used to monitor wildlife populations. Inferences about populations are based on 1 of 2 measures: (1) change in the proportion of stations visited at least once or (2) change in the cumulative number of visits by unique individuals. The functional relationships between index responses and population density is poorly understood and can lead to misinterpretation of index data when an incorrect functional relationship (e.g. linear) is assumed. We created a flexible simulation environment to study the response of detection-based population indices under a wide variety of conditions meant to reflect species life history and study design. Proportional indices exhibited non-linear saturating responses to changes in population density while cumulative indices responded linearly. Shapes of responses were functions of home range sizes, individual detection probabilities, and spatial arrangement of animals and sampling stations. Non-linear relationships of proportional indices lead to under-estimation of mean population density when data are aggregated from multiple detection stations deployed in a heterogeneous landscape. Cumulative indices have significant statistical advantages over proportional indices including smaller sample sizes required to detect density change, linearity, consistent index responses across a wide range of densities, and ability to aggregate data to meet minimum sample size requirements. Our simulation provides a flexible tool for the interpretation of station-based population indices.

Comparison of Pellet-Group Counting Methods to Estimate Population Density of White-Tailed Deer in a Mexican Tropical Dry Forest

Wildlife species population density estimation is important from both ecological and management perspectives. The pellet-group counting method has been used to evaluate density of the white-tailed deer ( Odocoileus virginianus). This species is an important component of human diet in tropical habitats. The objectives of this study were to: 1) compare density estimates using four methods: counts in circular plots (FSC, Fecal Standing Crop and FAR, Fecal Accumulation Rate), and counts in transects (LT, Line Transect and ST, Strip Transect); 2) simulate the effect of increased sampling effort on density and precision, and; 3) evaluate the effort required to detect changes in population density using LT. From 2006 to 2007, we intensively sampled a 1 km2quadrant in a Mexican tropical dry forest. The results indicate that all four methods produce similar mean population density estimates. However, estimates of precision were dependent on sample size which in turn was associated with the particular counting method used. In descending order of estimate precision, the methods ranked as: LT, ST, FSC, and FAR. To detect population changes of &lt; 20%, we suggest the establishment of 5 to 22 transects (LT) of 390 m during the dry season. To reduce bias in density estimation, it is important to obtain defecation and pellet decomposition rates in the study site.

Stream Nutrient Concentrations on the Windward Coast of Hawai‘i Island and Their Relationship to Watershed Characteristics

Dissolved inorganic and organic nutrients and physiochemical parameters were measured in 24 Hawai‘i Island streams. Particulate nutrients and instantaneous nutrient and sediment fluxes were measured in half of these streams. Stream waters were dilute and slightly alkaline and had low concentrations of ammonium, orthophosphate, dissolved organic phosphorus, and total suspended solids. Particulate matter comprised 45%, 73%, and 28% of nitrogen, phosphorus, and carbon pools, respectively. Dissolved nitrogen was comprised primarily of organic nitrogen (54%) and nitrate (34%). In some streams, nitrate and total nitrogen concentrations were slightly elevated relative to Hawai‘i Department of Health (HDOH) water quality standards. Instantaneous nitrate yields for the streams plus 26 HDOH stations were calculated, and the average from the combined data set was 7.1 (SD 11.1) moles N day −1 km −2 . Nitrate concentrations and yields were 2.1 and 3.5 times higher, respectively, in Kohala watersheds than in Mauna Kea watersheds. Regression analysis was used to evaluate whether water quality parameters are predicted by watershed area, mean annual rainfall, population density, or percentage of agricultural land. Many water quality parameters were not predicted by these variables. In Mauna Kea streams, concentrations of dissolved organic nitrogen and dissolved organic carbon increased with increasing watershed area, nitrate concentrations increased with increasing population density, and both specific conductivity and nitrate yield increased with increasing percentage of agricultural lands. In Kohala streams, nitrate concentrations and yields were not predicted by watershed characteristics. Overall, watershed characteristics, as quantified in this study, were not strong predictors of water quality.

Density compensation, species composition, and richness of ants on a neotropical elevational gradient

The distribution of species on elevational gradients challenges our understanding of ecological processes, particularly in the context of biotic responses to climate change. We report here the distribution of leaf-litter ants on the Barva Transect, a continuous gradient of wet forest on Costa Rica's Atlantic slope. Seven sites were sampled, distributed from 50 to 2000 m. Worker density and microsite occupancy were high and relatively constant from 50 m to 1500 m and then abruptly dropped to near zero at 2000 m. Species density at the 1 m2 scale was high and constant to 1070 m and then declined at higher elevations. Species richness of assemblages at the 1 km2 scale was constant or rose slightly from 50 m to 500 m and then steeply declined. Because assemblage richness and species density declined more rapidly than worker density, density compensation with elevation is suggested and supported by a measure of mean population density. Statistically, temperature was the best predictor of both species richness and worker density. Relative humidity, soil nutrients, elevation-specific regional area, and the mid-domain effect were poor predictors of richness. Sites from 50 m to 500 m were similar in species composition. In contrast, assemblages at 1070 m, 1500 m, and 2000 m were highly differentiated. Thus elevational ranges were narrow for species at mid to upper elevations and broad for those at the lowest elevations. Density compensation at higher elevation suggests that if temperature or productivity are influencing the decline in diversity it must be indirectly through speciation and extinction processes, rather than by greater numbers of individuals. The broad ranges of lowland species may be a response to as yet unmeasured environmental factors (e.g., NPP) or to climate changes associated with the current interglacial period. Interglacial warming may have driven species to higher elevations, but the lack of competitors at the lower range margins may have allowed the lowest-elevation species to move upslope without a concomitant contraction of the lower range boundary. Global warming threatens a loss of narrowly-distributed montane species, but lowland biotic attrition may be ameliorated by range expansion among lowland species.

A large‐scale approach can help detect general processes driving the dynamics of brown trout populations in extensive areas

Abstract – Most studies on the population dynamics of stream‐living salmonids have been conducted at the scale of a reach, a stream or a river basin. This can lead to overestimating the importance of local factors acting on a reduced scale compared to the more general factors that drive the dynamics of several populations. Two models were built on the basis of a data set from 60 sampling stations representing separated populations inhabiting a large heterogeneous area encompassing 18 years of quantifications. Our analyses showed the following: (i) Population growth rate (pgr) of a set of independent brown trout populations can be described by means of a single model; (ii) the youngest and the oldest year classes of these populations seem to be limited by the same constraints; (iii) there is a climatic control of the recruitment because of spring weather conditions, but also the abundance of oldest age class may be controlled by the climate, (iv) there is a nonlinear positive effect of winter North Atlantic Oscillation on pgr; (v) there is a 3‐year lagged positive feedback tracing the upward trend of a stock‐recruitment curve, and 1‐year lagged negative feedback showing the downward trend of the curve; (vi) a strong cohort has a positive effect on the whole population that can be detected throughout the time. Our fitted models allowed to predict the mean population densities at a regional scale with &lt;10% error and shed light onto the main factors and associated ecological processes that control these large‐scale dynamics.

Population dynamics of Rana macrocnemis Boulenger, 1885 at Uludağ, Western Turkey

In a study on the population dynamics of the Uludağ Frog, Rana macrocnemis Boulenger, 1885 at Uludağ, 4,952 individuals were marked with toeclipping, visible implant elastomer and vi alpha tags between 2006 and 2008. 47.1% of the population consisted of males, 39.0% of females and 13.8% of juveniles, and a male-biased sex ratio was observed. According to the formula of Jolly-Seber, the mean population size was calculated for individual study plots as 1,535 in Kirazlıyayla, 1,578 in Sarıalan, 1,481 in the Hotels District, 823 in Lake Kilimli, 742 in Lake Kara, 675 in Lake Aynalı, 658 in Lake Koğukdere, and 151 in Lake Heybeli. The total population size was estimated at 7,643 individuals (3,113 in forest, 4,530 in the subalpine belt) in 1.30 ha areas (0.14 ha in forest, 1.16 ha in the subalpine belt) in study plots of Uludağ ranging between 1,476 to 2,450 m a.s.l. The capture probability ranged from 0.21 to 0.93 and the survival rate ranged from 0.57 to 0.98 among the populations, and the mean population density was calculated as 0.19–2.52 individuals/m2. The age in the population varied between 2 and 11 years, and the median age was calculated as 4 in males, 4.5 in females. The sexual maturity age ranged from 2nd to 6th years depending on altitude (from 1,476 to 2,450 m). It was found that the breeding period commenced in early April upon the melting of the snow and extended until the end of June, depending on altitude. The mean number of eggs in an egg mass was calculated to be 987±326. Spawned eggs hatched in 7 to 32 days depending on weather conditions and metamorphosis was completed in 46 to 130 days.