Intrinsic Rate Of Population Increase Research Articles

Testing the Effects of Prey Type on the Life History and Population-Level Parameters of Chrysoperla externa (Neuroptera: Chrysopidae)

Green lacewings are valuable predators, utilized in augmentative biological control against various agricultural pests. However, further studies are required to comprehend the performance of these predators when consuming natural prey. We investigated the capacity of Chrysoperla externa (Hagen) to utilize the following three distinct prey types: the pupae of the coffee leaf miner Leucoptera coffeella (Guérin-Mèneville & Perrottet), the eggs of the sugarcane borer Diatraea saccharalis (F.), and the eggs of the Mediterranean flour moth Ephestia kuehniella (Zeller). The first two of these species are naturally occurring prey found in field crops, while the last serves as a factitious prey species for the mass rearing of natural enemies. We hypothesized that the type of prey would differentially affect the life history and population-level parameters of C. externa. Laboratory experiments were conducted to compare the pre-imaginal survival and developmental times, adult longevity and reproduction, and population growth of C. externa when larvae were provided with each of the three prey items. Results indicated that C. externa utilized the two natural prey items, L. coffeella pupae and D. saccharalis eggs, for its development, reproduction, and population growth. However, larvae developed significantly faster and females exhibited higher reproductive parameters, including fecundity and daily oviposition, when consuming the factitious prey, E. kuehniella eggs. This resulted in a higher intrinsic rate of population increase, as well as shorter times for the population to double in size. Understanding the population dynamics of C. externa when consuming different prey items is crucial for optimizing their utilization in augmentative biological control programs.

Projection of Interspecific Competition (PIC) Matrices: A Conceptual Framework for Inclusion in Population Risk Assessments.

Accounting for intraspecific and interspecific competition when assessing the effects of chemical and nonchemical stressors is an important uncertainty in ecological risk assessments. We developed novel projection of interspecific competition (PIC) matrices that allow for analysis of population dynamics of two or more species exposed to a given stressor(s) that compete for shared resources within a landscape. We demonstrate the application of PIC matrices to investigate the population dynamics of two hypothetical fish species that compete with one another and have differences in net reproductive rate and intrinsic rate of population increase. Population status predictions were made under scenarios that included exposure to a chemical stressor that reduced fecundity for one or both species. The results of our simulations demonstrated that measures obtained from the life table and Leslie matrix of an organism, including net reproductive rate and intrinsic rate of increase, can result in erroneous conclusions of population status and viability in the absence of a consideration of resource limitation and interspecific competition. This modeling approach can be used in conjunction with field monitoring efforts and/or laboratory testing to link effects due to stressors to possible outcomes within an ecosystem. In addition, PIC matrices could be combined with adverse outcome pathways to allow for ecosystem projection based on taxonomic conservation of molecular targets of chemicals to predict the likelihood of relative cross-species susceptibility. Overall, the present study shows how PIC matrices can integrate effects across the life cycles of multiple species, provide a linkage between endpoints observed in individual and population-level responses, and project outcomes at the community level for multiple generations for multiple species that compete for limited resources. Environ Toxicol Chem 2024;00:1-17. Published 2024. This article is a U.S. Government work and is in the public domain in the USA.

Evolution of migration processes in Cladocera populations

An intrinsic rate of population increase (r) in a local habitat is determined by the birth-to-death ratio and by migration processes. In natural populations, including Cladocera, r is estimated as the logarithm difference of population densities at the end and at the beginning of time interval. Under this method of evaluation, migration processes are already included in the final population density. A realized intrinsic rate of population increase (rmax) can be determined from the data on age-related mortality and fecundity by the life table method. The high regression relation (R2 = 0.867) was found between rmax, the first time of reproduction (Drepr) and mean fecundity during the reproduction period (mean_mx). Drepr is known for most of Cladocera, the mean_mx analog can be easily determined in their natural populations; these parameters can be used to evaluate a possible intrinsic rate of population increase (rcalc). The differences between r and rcalc can be used to evaluate migration processes. If these differences are positive, then individuals are emigrating from the population, if they are negative, then there occurs the influx of immigrants.

Effects of pasture intensification and sugarcane cultivation on non-target species: A realistic evaluation in pesticide-contaminated mesocosms

Conventional soil management in agricultural areas may expose non-target organisms living nearby to several types of contaminants. In this study, the effects of soil management in extensive pasture (EP), intensive pasture (IP), and sugarcane crops (C) were evaluated in a realistic-field-scale study. Thirteen aquatic mesocosms embedded in EP, IP, and C treatments were monitored over 392 days. The recommended management for each of the areas was simulated, such as tillage, fertilizer, pesticides (i.e. 2,4-D, fipronil) and vinasse application, and cattle pasture. To access the potential toxic effects that the different steps of soil management in these areas may cause, the cladoceran Ceriophania silvestrii was used as aquatic bioindicator, the dicot Eruca sativa as phytotoxicity bioindicator in water, and the dipteran Chironomus sancticaroli as sediment bioindicator. Generalized linear mixed models were used to identify differences between the treatments. Low concentrations of 2,4-D (<97 μg L−1) and fipronil (<0.21 μg L−1) in water were able to alter fecundity, female survival, and the intrinsic rate of population increase of C. silvestrii in IP and C treatments. Similarly, the dicot E. sativa had germination, shoot and root growth affected mainly by 2,4-D concentrations in the water. For C. sancticarolli, larval development was affected by the presence of fipronil (<402.6 ng g−1). The acidic pH (below 5) reduced the fecundity and female survival of C. silvestrii and affected the germination and growth of E. sativa. Fecundity and female survival of C. silvestrii decrease in the presence of phosphorus-containing elements. The outcomes of this study may improve our understanding of the consequences of exposure of freshwater biota to complex stressors in an environment that is rapidly and constantly changing.

Pollen provisioning attenuates pesticide side-effects on a phytoseiid predator.

Biological control with predatory mites is applied against pests in greenhouse crops. Chemical control with the use of selective, reduced-risk pesticides, is an important component of Integrated Pest Management (IPM) programs, that often needs to be combined with biological control. Here, we evaluated the effect of plant pollen when used as supplementary food on the survival, reproduction and predation of the predatory mite Amblydromalus limonicus (Acari: Phytoseiidae) after exposing young larvae and adults to flonicamid, an insecticide of moderate toxicity to phytoseiids. Pollen is an important alternative food for generalist phytoseiids ensuring survival and supporting populations build-up during periods of prey scarcity. Two regimes of cattail (Typha angustifolia L.) pollen differing in application frequency were used. In the first, the total amount of pollen was supplied once, within 30 min after insecticide application, whereas in the second regime, the same amount of pollen was supplied gradually, i.e., every 48 h. Regardless of the frequency of application, pollen provisioning results in a reduction in prey (thrips) consumption relative to the control (no pollen provisioning). Nevertheless, when adult mites were directly exposed to flonicamid residues, pollen provisioning attenuated the reduction in prey consumption as compared to the control. In addition, the gradual (every 48 h) provisioning of pollen to adult predators exposed to flonicamid residues impacted positively the intrinsic rate of population increase (rm) of A. limonicus as compared to when feeding on prey. Our results reveal an unexpected role of pollen provisioning in alleviating pesticides side-effects on phytoseiids. © 2024 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Facultative endosymbionts modulate the aphid reproductive performance on wheat cultivars differing in contents of benzoxazinoids.

Facultative bacterial endosymbionts have the potential to influence the interactions between aphids, their natural enemies, and host plants. Among the facultative symbionts found in populations of the grain aphid Sitobion avenae in central Chile, the bacterium Regiella insecticola is the most prevalent. In this study, we aimed to investigate whether infected and cured aphid lineages exhibit differential responses to wheat cultivars containing varying levels of the benzoxazinoid DIMBOA (2,4-dihydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one), which is a xenobiotic compound produced by plants. Specifically, we examined the reproductive performance responses of the most frequently encountered genotypes of Sitobion avenae when reared on wheat seedlings expressing low, medium, and high concentrations of DIMBOA. Our findings reveal that the intrinsic rate of population increase (rm ) in cured lineages of Sitobion avenae genotypes exhibits a biphasic pattern, characterized by the lowest rm and an extended time to first reproduction on wheat seedlings with medium levels of DIMBOA. In contrast, the aphid genotypes harbouring Regiella insecticola display idiosyncratic responses, with the two most prevalent genotypes demonstrating improved performance on seedlings featuring an intermediate content of DIMBOA compared to their cured counterparts. This study represents the first investigation into the mediating impact of facultative endosymbionts on aphid performance in plants exhibiting varying DIMBOA contents. These findings present exciting prospects for identifying novel targets for aphid control by manipulating the presence of aphid symbionts. © 2023 Society of Chemical Industry.

Metabolism, population growth, and the fast‐slow life history continuum of marine fishes

AbstractThe maximum intrinsic rate of population increase (rmax) represents a population's maximum capacity to replace itself and is central to fisheries management and conservation. Species with lower rmax typically have slower life histories compared to species with faster life histories and higher rmax. Here, we posit that metabolic rate is related to the fast–slow life history continuum and the connection may be stronger for maximum metabolic rate and aerobic scope compared to resting metabolic rate. Specifically, we ask whether variation in rmax or any of its component life‐history traits – age‐at‐maturity, maximum age, and annual reproductive output – explain variation in resting and maximum metabolic rates and aerobic scope across 84 shark and teleost species, while accounting for the effects of measurement temperature, measurement body mass, ecological lifestyle, and evolutionary history. Overall, we find a strong connection between metabolic rate and the fast‐slow life history continuum, such that species with faster population growth (higher rmax) generally have higher maximum metabolic rates and broader aerobic scopes. Specifically, rmax is more important in explaining variation in maximum metabolic rate and aerobic scope compared to resting metabolic rate, which is best explained by age‐at‐maturity (out of the life history traits examined). In conclusion, teleosts and sharks share a common fast–slow physiology/life history continuum, with teleosts generally at the faster end and sharks at the slower end, yet with considerable overlap. Our work improves our understanding of the diversity of fish life histories and may ultimately improve our understanding of intrinsic sensitivity to overfishing.

Inhibitory effects of cold atmospheric plasma on population growth of the carob moth, Ectomyelois ceratoniae (Lepidoptera: Pyralidae) in laboratory.

Potential sterilizing effects of the atmospheric cold plasma on the carob moth, Ectomyelois ceratoniae Zeller (Lepidoptera: Pyralidae) was studied under laboratory conditions by means of life history experimentation. The results showed that the population growth parameters of the carob moth decreased in all periods of 15 to 60 sec of plasma treatments applied on 1 -day-old eggs. Overall, 19.5% and 23.8% of reproduced eggs were fertile when the experimental males and females mated with normal moths in indirect treatments of 15 and 30 sec, respectively. The highest intrinsic rate of population increase, r, was in control (0.11 day-1) and the highest decrease in this parameter was in the 30 sec direct treatment (- 0.073 day-1). The results showed that cold plasma had an acceptable potential to sterilize the pest if plasma was applied at egg stage. This potential will be explored from the perspective of insect sterility technique and the genetical / physiological mechanisms involved should be studied in future.

Properties and interpretation of the Skellam model—A discrete‐time contest competition population model

AbstractThe Skellam model describes discrete‐time population dynamics of a single species assuming uniform (i.e., random or Poissonian) individual distribution and intraspecific contest competition. Apart from studies on individual‐based models derived from first principles it has been rarely applied in ecological research although in specific situations it may be more appropriate than, for instance, the frequently used Ricker model, which is derived assuming scramble competition among the individuals. In this article, we offer an insight into the first principles underlying the Skellam model and provide an alternative parameterization of the model in terms of two commonly used parameters: intrinsic rate of population increase and carrying capacity. We also provide guidelines and software for fitting the Skellam model to discrete population time series data. In light of these findings, the Skellam model may be a useful alternative for a range of purposes where it has been earlier overlooked.

Saxitoxin-Producing Raphidiopsis raciborskii (Cyanobacteria) Constrains Daphnia Fitness and Feeding Rate despite High Nutritious Food Availability.

Changes in food quality can dramatically impair zooplankton fitness, especially in eutrophic water bodies where cyanobacteria are usually predominant. Cyanobacteria are considered a food with low nutritional value, and some species can produce bioactive secondary metabolites reported as toxic to zooplankton. Considering that cyanobacteria can limit the survival, growth and reproduction of zooplankton, we hypothesized that the dietary exposure of neotropical Daphnia species (D. laevis and D. gessneri) to saxitoxin-producing cyanobacteria impairs Daphnia feeding rates and fitness regardless of a high availability of nutritious algae. Life table and grazing assays were conducted with different diets: (1) without nutritional restriction, where neonates were fed with diets at a constant green algae biomass (as a nutritious food source), and an increasing cyanobacterial concentration (toxic and poor food source), and (2) with diets consisting of different proportions of green algae (nutritious) and cyanobacteria (poor food) at a total biomass 1.0 mg C L-1. In general, the presence of high proportions of cyanobacteria promoted a decrease in Daphnia somatic growth, reproduction and the intrinsic rate of population increase (r) in both diets with more pronounced effects in the nutritionally restricted diet (90% R. raciborskii). A two-way ANOVA revealed the significant effects of species/clone and treatments in both assays, with significant interaction between those factors only in the second assay. Regarding the grazing assay, only D. laevis was negatively affected by increased cyanobacterial proportions in the diet. In the life table assay with constant nutritious food, a reduction in the reproduction and the intrinsic rate of the population increase (r) of all species were observed. In conclusion, we found adverse effects of the toxic cyanobacterial strain R. raciborskii on Daphnia fitness, regardless of the constant amount of nutritious food available, proving the toxic effect of R. raciborskii and that the nutritional quality of the food has a greater influence on the fitness of these animals.

Side effects of insecticides alone or in a mixture with acaricide on life history traits and demographic parameters of Brevipalpus yothersi

Brevipalpus yothersi is an important pest to citrus crop due to its ability to transmit the virus that causes citrus leprosis. The exposure of target and non-target organisms to different pesticides is a reality in field conditions. For successful management, it is essential to determine the effects of citrus commonly used pesticides on leprosis mites to determine how pesticides can interfere with the leprosis mite population. Therefore, this study aimed to evaluate the impact of insecticides, alone or associated with spirodiclofen, on B. yothersi life history traits and demographic parameters under laboratory and greenhouse conditions. Results suggest that cypermethrin and imidacloprid, both alone and in a mixture with spirodiclofen, phosmet in a mix with spirodiclofen and spirodiclofen alone did not interfere significantly in the fecundity and fertility of B. yothersi in laboratory conditions. In the same condition, only phosmet at 15.6, 125.0, and 250.0 mg.L-1 reduced the fecundity of the mites. Brevipalpus yothersi population varied with the insecticide and mixture type in the greenhouse condition. Most insecticides and acaricide, alone or in a mixture, decreased pre-adult development, whereas female adult longevity was similar to control. Spirodiclofen combined with phosmet and imidacloprid decreased female adult longevity. Only spirodiclofen in a mixture with cypermethrin and phosmet alone did not interfere significantly with the intrinsic rate of population increase. The other insecticides and mixtures reduced that parameter. The mean time of one mite generation was decreased when the mites were exposed to all insecticides and acaricide combinations, spirodiclofen and phosmet alone. Therefore, cypermethrin, phosmet, imidacloprid, and spirodiclofen, alone or in a mixture, negatively impacted the development time and demographic parameters of B. yothersi.

The elevated toxicity of the biodegradation product (guanylurea) from metformin and the antagonistic pattern recognition of combined toxicity: Insight from the pharmaceutical risk assessment and the simulated wastewater treatment

The emerging contaminants metformin (MET) and its degradation product guanylurea (GUA) are released into aquatic environments through wastewater treatment plants (WWTPs). Thus, the environmental risks of wastewater with more treatments may be underestimated due to the lower effect concentration of GUA and the higher detected concentration of GUA in treated wastewater in comparison with MET. In this study, we aimed to investigate the combined toxicity mode of MET and GUA to Brachionus calyciflorus by simulating the degrees of wastewater treatments through adjustments to the ratio of MET and GUA in medium. The results showed that the 24 h-LC50 of MET, GUA, their mixtures of equal concentrations and the mixtures of equal toxic units to B. calyciflorus were 907.44, 544.53, 1185.82 and 940.52 mg/L, respectively, demonstrating GUA is significantly more toxic than MET. An antagonistic interaction between MET and GUA was found in mixture toxicity assessments. Compared with the control, MET treatments only significantly affected the intrinsic rate of population increase of rotifers (rm), while all life-table parameters were significantly affected by GUA. In addition, at medium and high concentrations (120 and 600 μmol/L), the net reproductive rate (R0) and rm of rotifers under GUA were significantly lower than those under MET. Notably, increased proportion of GUA relative to MET in binary-mixture treatments resulted in increased survival risk and reduced fecundity of rotifers. Moreover, the responses of population dynamics to exposures of MET and GUA were mainly attributed to the reproduction of rotifer, indicating that an improved wastewater treatment process is necessary to protect aquatic ecosystems. The study highlights the importance of considering the combined toxicity of emerging contaminants and degradation product in environmental risk assessment, especially the unintentional transformations of parent compound in treated wastewater.

Population Growth Parameters of Helicoverpa armigera (Hübner) on Various Legume Seeds Reveal Potential Tolerance Traits

Helicoverpa armigera (Hübner) is a key polyphagous pest with global spread that causes economic damage to agricultural crops. It is commonly managed by synthetic insecticides, which can cause negative impacts on the environment and human health, as well as toxicity to natural enemies. Hence, investigations into alternative pest management approaches such as the use of resistant host plant cultivars against H. armigera is important. In this study, the effects of various legume seeds based on meridic diets were evaluated using biology and population growth parameters of H. armigera under laboratory conditions. The results indicated that the shortest developmental time and pupal incubation periods occurred on white kidney bean Dehghan, while the longest periods occurred on broad bean Mahta. The intrinsic rate of population increase (r) was highest when H. armigera was reared on white kidney bean Dehghan and cowpea Arabi, and the lowest when reared on broad bean Mahta and common bean Khomein. Furthermore, the highest net reproductive rate (R0) occurred on white kidney bean Dehghan and the lowest on common bean Khomein. Cluster analysis revealed that white kidney bean Dehghan and cowpea Arabi were the most susceptible hosts, while common bean Khomein, and broad beans Feyz and Mahta were the poorest and perhaps least susceptible hosts for population growth of H. armigera. Our results suggest that the selective use of certain bean cultivars as potential sources of antibiosis against this pest may be useful as part of an integrated management program.

Temperature dependent development and population performance of Tetranychus fijiensis Hirst (Acari: Tetranychidae) on Papaya

Developmental biology and life table characteristics of Tetranychus fijiensis Hirst (Acari: Tetranychidae) on papaya were studied at four distinct constant temperatures (20, 24, 28, and 32°C) and relative humidity (70-85%) conditions. With the increase in rearing temperature conditions, the length of T. fijiensis life cycle decreased from 34.46 to 8.58 days. At 20, 24, 28, and 32°C, the Net Reproduction Rate (R0) was 23.48, 39.06, 33.75, and 23.48 and; the intrinsic rate of population increase (rm) was 0.0694, 0.2003, 0.2281, and 0.1902 females/ female/day, respectively. The optimum temperature for mite development was observed to be between 24 and 28°C, while favourable temperature for optimal reproduction capacity of the mite was 28°C.

Tropical rays are intrinsically more sensitive to overfishing than the temperate skates

Overfishing, habitat loss, and climate change are driving population declines in many species. Understanding a species' capacity to recover from these and other threats is necessary for prioritising management. The maximum intrinsic rate of population increase (rmax) can be used to compare which species or groups are particularly sensitive to ongoing threats. To investigate global patterns of intrinsic sensitivity of rays and skates (superorder Batoidea), we calculated rmax of 85 species using a modified Euler-Lotka model that accounts for survival to maturity. We examined how rmax varies with body mass, temperature, and depth using an information-theoretic approach through model selection, accounting for phylogenetic non-independence. Although we observed an overall positive relationship between rmax and temperature, we found that warm, shallow-water rays were more intrinsically sensitive to exploitation (lower rmax) than cold, deep-water skates (higher rmax). We hypothesise that this pattern is likely driven by their different reproductive strategies as live-bearing rays have fewer offspring compared to egg-laying skates, and caution that future research should focus on understanding differences in the mortality schedule of juveniles and sub-adults to understand if survival to maturity is comparable. Our findings highlight the high vulnerability of warm, shallow-water ray species to overexploitation and other threats due to their intrinsically low maximum population growth rates. These differences in rmax have conservation implications for our understanding of the geographic patterns in extinction risk, suggesting that tropical rays are more intrinsically sensitive.

Interaction between life history parameters of Callosobruchus maculatus (F.) (Coleoptera: Chrysomelidae) with physical and biochemical properties of legumes species

The cowpea beetle, Callosobruchus maculatus, is a highly damaging and destructive pest of pulse seeds, which is widely distributed in tropical and subtropical areas. In this research, the effects of the seeds of six pulse species (broad bean, cowpea, lentil, green gram, chickpea, and soybean) were assessed on life history and energy content of C. maculatus under controlled conditions, 27 ± 2 °C, 60 ± 5% relative humidity, and a photoperiod of 10:14 (L:D) h. Some biochemical (protein, starch, phenol, total anthocyanin, flavonoids and condensed tannin contents) and physical (humidity, seed volume and area) characteristics of legume seeds were measured and their interactions with population growth parameters of C. maculatus were assessed. The results showed that biological properties of C. maculatus were significantly different when fed on various legume seeds. The developmental time of cowpea beetle fed on broad bean (32.08 day) was longer compared with other seeds. The lowest immature survival rate was observed on broad bean. The pupal weight on cowpea, chickpea and green gram was significantly higher than on broad bean and lentil seeds. The lowest intrinsic rate of population increase (r) and net reproductive rate (R0) were recorded on soybean (r = 0.055 d−1, R0 = 14.02 offspring). The intrinsic rate of increase and the finite rate of increase (λ) of C. maculatus reared on cowpea (r = 0.145 d−1, λ = 1.16 d−1) and green gram (r = 0.144 d−1, λ = 1.15 d−1) seeds were significantly higher than those reared on other legumes. Significant correlations were detected between life history parameters of C. maculatus with biochemical and physical traits of legume seeds. The results showed that cowpea and green gram were relatively susceptible legume seeds and that soybean was a relatively resistant host for feeding of C. maculatus, which can be useful in the development or improvement of IPM programs for C. maculatus.

Population growth and respiration in the dust mite Dermatophagoides farinae under different temperature and humidity regimes.

Dermatophagoides farinae is an important house dust mite species that causes allergies in humans worldwide. In houses, these mites are commonly found in actively used mattresses and pillows, which provide food (i.e. sloughed skin and microorganisms), moisture, and increased temperature for faster mite development. In mattresses, feeding mites prefer the upper sector, as close as possible to the resting human (temperature 32-36°C, humidity between 55 and 59%). However, mites that are not actively feeding prefer staying at deeper zones of the mattress. Here, we analyzed mite responses to different temperatures (15-35°C) and relative humidity (62-94% RH) in terms of their population size growth and respiration (CO2 production) using lab mite cultures. The intrinsic rate of population increase had a single maximum at approximately 28°C and 85% RH. At 30°C, there were two respiration peaks at RH 90% (smaller peak) and 65% (larger peak). Therefore, there is a mismatch between the optimal temperature/humidity for the population size increase vs. respiration. We propose preliminary hypotheses explaining the two respiration peaks and suggest that future research should be done to elucidate the nature of these peaks.

Body mass, temperature, and depth shape the maximum intrinsic rate of population increase in sharks and rays.

An important challenge in ecology is to understand variation in species' maximum intrinsic rate of population increase, r max , not least because r max underpins our understanding of the limits of fishing, recovery potential, and ultimately extinction risk. Across many vertebrate species, terrestrial and aquatic, body mass and environmental temperature are important correlates of r max . In sharks and rays, specifically, r max is known to be lower in larger species, but also in deep sea ones. We use an information-theoretic approach that accounts for phylogenetic relatedness to evaluate the relative importance of body mass, temperature, and depth on r max . We show that both temperature and depth have separate effects on shark and ray r max estimates, such that species living in deeper waters have lower r max . Furthermore, temperature also correlates with changes in the mass scaling coefficient, suggesting that as body size increases, decreases in r max are much steeper for species in warmer waters. These findings suggest that there are (as-yet understood) depth-related processes that limit the maximum rate at which populations can grow in deep-sea sharks and rays. While the deep ocean is associated with colder temperatures, other factors that are independent of temperature, such as food availability and physiological constraints, may influence the low r max observed in deep-sea sharks and rays. Our study lays the foundation for predicting the intrinsic limit of fishing, recovery potential, and extinction risk species based on easily accessible environmental information such as temperature and depth, particularly for data-poor species.

The Cost of Resistance to Diamide Insecticide Varies With the Host Plant in Spodoptera frugiperda (Lepidoptera: Noctuidae).

Fitness costs associated with insect resistance to insecticides can be exploited to implement resistance management programs. However, most of these studies are restricted to evaluating biological traits on artificial diets. Here, we investigated the fitness cost associated with chlorantraniliprole in Spodoptera frugiperda (J.E. Smith) feeding on corn, soybean, and cotton plants. We used a near-isogenic strain of S. frugiperda resistant to chlorantraniliprole (Iso-RR), a susceptible strain (SS), and heterozygotes strains (H1 and H2) to evaluate several biological and population growth parameters. Larval survival of the Iso-RR strain was on average 90% on corn, 65% on soybean, and 57% on cotton plants. Development time of the larval stage also differed among host plants, Iso-RR strain took on average 14, 17, and 26 days to reach the pupal stage on corn, soybean, and cotton plants respectively. Net reproductive rate, intrinsic rate of population increase, and finite rate of population increase were higher for Iso-RR strain feeding on corn plants than other host plants. The relative fitness, based on the intrinsic rate of population increase, of S. frugiperda resistant strain on corn, soybean, and cotton plants were 1.04, 0.85, and 0.88, respectively. Therefore, no fitness cost was observed for S. frugiperda feeding on corn plants, but a significant fitness cost was observed when this pest fed on soybean and cotton plants. We showed that the food source influences the fitness cost of S. frugiperda resistant to diamide. Such information may help to implement resistance management strategies based on each crop.

Combined effects of temperature and algal density on the life history characteristics in Brachionus angularis and Keratella Valga

Temperature and food density are the most important factors influencing the population dynamics of rotifers. In the present study, the effects of temperature and food concentration on the developmental durations, egg ratio, and life-table demography in Brachionus angularis and Keratella valga were studied at four temperatures (15 °C, 20 °C, 25 °C and 30 °C) and four food levels (0.5 × 106, 1.0 × 106, 2.0 × 106 and 3.0 × 106 cells/mL Scenedesmus obliquus). The results showed significant effects of both temperature and food concentration, independently and interactively on the embryonic development (ED), juvenile period (JP), average lifespan (LS), generation time (T) and intrinsic rate of population increase (rm) in B. angularis, while the ED, life expectancy at hatching (e0), LS, T and rm in K. valga. In all conditions, the number of eggs per female and rm in B. angularis were higher than those in K. valga. These results suggested that B. angularis might be more suitable to mass culture in aquaculture than K. valga, and a potential prey for fish larvae in freshwater aquaculture.