Natural Increase Research Articles

Development and demographic parameters of Fall Armyworm (Spodoptera frugiperda J.E. Smith) when feeding on rice (Oryza sativa)

Fall Armyworm (FAW), Spodoptera frugiperda (Lepidoptera: Noctuidae), native to the Americas, is a polyphagous insect pest feeding on more than 350 plant species. We studied the developmental and demographic parameters of the maize (Zea mays) strain of FAW on rice (Oryza sativa), and compared the results with its prime host, maize. The developmental period from egg to adult among rice varieties did not differ significantly; however, it did differ significantly between rice and maize, as feeding on rice rather than maize extends development duration of FAW larvae by 15.15%. FAW larvae collected and reared on maize were found to be of significantly higher weight than those reared on rice at two sequential dates of their development; pupal weight however was observed as statistically similar between these two host crops. Regardless of the host, female adults always emerged before males; in maize, female FAW appeared 3.36 days earlier than males. Females derived from rice had longer pre-oviposition periods and shorter oviposition ones than those derived from maize. In rice and maize, the age-specific fecundity rate (mx) peaked at 40 days and 33 days, respectively. When the Fall Armyworm consumed maize instead of rice, there was an increase in the reproduction rate (R0), the intrinsic rate of natural increase (rm), and the finite rate of increase (λ). For instance, when FAW fed on rice, the rm value was 0.121, whereas it rose to 0.173 when FAW fed on maize. Feeding on rice instead of maize resulted in significantly longer mean length of generation (tG) and doubling time (tD) for the fall armyworm (FAW). This suggests that it took a longer time for the FAW population to double when it was fed rice under controlled greenhouse conditions. In summary, our research suggests that FAW can survive and complete its life cycle on rice plants and on multiple varieties of rice in Bangladesh. However, field verification is necessary before drawing strong conclusions as to the risk posed by FAW in rice. This requires additional studies of FAW and associated insect community dynamics under non-controlled conditions and in the context of multi-species interactions in Asian rice fields.

Sustainable management of rainforest in cross river state, nigeria

The study evaluate the matric models using trees stand parameters such as stem density, in-growth, rates of growth and mortality rate to predict the tree stand structure of the most complex tropical rainforest ecosystem in Cross River State, Nigeria. The model represented all tree species covering matrix for 6 years. The forest decline due to dominant eigenvalue (A) of the matrix R was 0.977, which is the intrinsic rate of natural increase with less than zero. A sensitivity analysis revealed that large recruitment rate of 87% was required to restore stability to the forest while only 16% improvement in growth rate would ensure sustenance and hence stabilized the forest.

Modeling population growth of a proto-city: A new urban accretion growth hypothesis and its P-CPAG model

The population growth of a proto-city (P–C, the initial stage of city-forming) is fundamental for shaping the subsequent pattern of population growth in city evolution. This study proposed a mathematical model, the P–C Population Accretion Growth (P-CPAG) model, to simulate key processes of population growth over a P–C period, based on the Urban Accretion Growth hypothesis (the UAG hypothesis). In the P-CPAG model, several parameters, e.g., natural increase rate of population(k), accretion rate (ρ), accretion radius(r), and initial population size (Pt0o), are vital for population growth. In the model examination, we determined the potential value for all parameters by the universal laws and the collected literature about the worldwide ancient cities. Based on observation and evaluation of 64 simulation scenarios, a promising plan of optimal parameters was suggested, that is, k = 0.008, ρ = 0.01, kρ = 0.003, Pt0o = 2000, Pt0i = 3.6, r = 5, N = 200000, Ni = 300. The proposed P-CPAG model sheds new light on population simulation in the critical but limited-mentioned P–C stage and has the potential to simulate population growth in other periods of city evolution. The unique perspectives on urban accretion growth and the P-CPAG model are meaningful for understanding the complicated and mysterious history of cities' evolution back about 5000 years ago.

Population Dynamics of Emerging Spider Mite Pest <i>Tetranychus Udaipurensis</i> gupta & Gupta

Temperature related development and demography of emerging spider mite pest Tetranychus udaipurensis Gupta and Gupta were studied on two vegetable host plants ridge gourd and French bean at four different temperature (22º-34ºC)and humidity conditions (67-80%). Development of T. udaipurensis female was faster-7.31 days on French bean and 7.42 days on ridge gourd, respectively at 34ºC. For reproduction (female longevity, fecundity and sex ratio) and demography, the favourable temperature range was 26º-30ºC. Chief demographic parameters viz., mean generation time, doubling time, net reproduction rate and intrinsic rate of natural increase on the preferred host French bean was 16 to 20 and 2.98 to 3.80, 42 to 48 mites and 0.200 to 0.248 female offsprings/ day, respectively. Under the consequence of changing climatic conditions, T.udaipurensis might emerge as potential pest of vegetable crops, more particularly of French bean.

Reproductive potential of the black bean aphid (Aphis fabae Scop.) on a range of faba bean (Vicia faba L.) accessions

AbstractThe black bean aphid is one of the main insect pests of faba bean, leading to yield losses in many countries. The aphid inflicts damage to faba bean through direct phloem feeding and indirectly by transmission of several viruses. Sources of genetic resistance or tolerance to the aphid have been hard to identify and to use in breeding because of the high environmental variability of the attack, the weak and partial nature of the resistance when found, and the low repeatability of experiments. A range of molecular genotyping tools is now available for identifying the genes underlying key traits in faba bean. Hence, we screened the responses of eight inbred lines (Columbo, Albus, Closed‐flower, Diana, Hedin/2, Icarus, ILB938/2, and Mélodie/2) of faba bean, derived from commercial cultivars and experimental germplasm, to aphid infestation in controlled (no‐choice‐test) and field (preference test) conditions. In the controlled environment, aphid performance was assessed by measuring fecundity and determining the intrinsic rate of natural increase (rm). In the field experiment, population growth was examined on Columbo, Closed‐flower, Hedin/2, and ILB938/2 during June and July. Each week, 10 plants in each plot, randomly chosen at the start, were screened for aphid colonization and number of plants attacked. For each plant, an index number was given reflecting the severity of aphid presence. Our results demonstrate a clear conformity between the results obtained from the indoor pot experiments and the field experiments. In both experiments, ILB938/2 showed partial resistance with significantly lower fecundity, rm, and field infestation when compared with the known susceptible line Columbo. The consistently strong performance of ILB938/2 against the black bean aphid suggests that it carries a factor or factors rendering it unconducive to aphid landing, feeding, and/or reproduction. Further investigation into the resistance mechanisms of ILB938/2 is planned.

Unstable fipronil resistance associated with fitness costs in fipronil-selected Aedes aegypti L.

Mosquitoes are very serious household and medically important pests transmitting many diseases of humans and animals. Among mosquitoes, Aedes aegypti L., is an active transmitter of dengue and lumpy skin disease virus, horrible and terrifying diseases, causing human and animal death throughout the world. Fipronil is a new chemistry insecticide used to control agriculture and medically important insect pests. It affects the GABA receptors in the nervous system and consequently causes the death of the pests. A laboratory experiment was conducted to investigate the onset of fipronil resistance and associated fitness costs in Ae. Aegypti. Moreover, the stability of fipronil resistance was evaluated after five generations of rearing without selection pressure. The population of Ae. Aegypti was exposed continuously for 12 generations to fipronil under controlled conditions. The fipronil selected population (Fipro-Sel Pop) had a 317 and 115.7-fold level of resistance compared to a susceptible and field population, respectively. Relative fitness for Fipro-Sel Pop was 0.57, with a significant disadvantage in larval duration, developmental time, percent hatchability, intrinsic rate of natural increase (rm), net reproductive rate (Ro), number of larvae in the next generation, and mean relative growth rate (MRGR) when compared to the Unselected population (Un-Sel Pop). However, the relative fitness value of Cross1 (Un-Sel Pop ♂ × Fipro-Sel Pop ♀) and Cross2 (Fipro-Sel Pop ♂ × Un-Sel Pop ♀) was 1.69 and 1.12, respectively. It is evident from the results that fipronil resistance comes with a fitness disadvantage, and it is unstable in the Fipro-Sel Pop of Ae. Aegypti. Therefore, the alternation of fipronil with other chemicals or suspension of fipronil usage for some time could improve its efficacy by delaying resistance development in Ae. Aegypti. Further research should be performed to investigate the field applicability of our findings.

Impact learning: A learning method from feature’s impact and competition

Machine learning is the study of computer algorithms that can automatically improve based on data and experience. Machine learning algorithms build a model from sample data, called training data, to make predictions or judgments without being explicitly programmed to do so. A variety of well-known machine learning algorithms have been developed for use in the field of computer science to analyze data. This paper introduced a new machine learning algorithm called impact learning. Impact learning is a supervised learning algorithm that can be consolidated in both classification and regression problems. It can furthermore manifest its superiority in analyzing competitive data. This algorithm is remarkable for learning from the competitive situation and the competition comes from the effects of autonomous features. It is prepared by the impacts of the highlights from the intrinsic rate of natural increase (RNI). We, moreover, manifest the prevalence of impact learning over the conventional machine learning algorithm.

High-Voltage Electrostatic Fields Adversely Affect the Performance of Diamondback Moths over Five Consecutive Generations

Changing electrical environments can influence the performance of herbivorous insects and adversely affect their control strategies. The diamondback moth, Plutella xylostella (L.), is a pest that devastates cruciferous vegetables. An age–stage, two-sex life table of P. xylostella over multiple generations was established to describe the effect of varying high-voltage electrostatic field (HVEF) exposure on their performance after the age-cohort eggs were exposed to HVEF at an intensity of 5.0 kV/cm for different durations. The results show that direct HVEF exposure adversely affected the population dynamics parameters of P. xylostella over multiple generations. In particular, the net reproduction rate, intrinsic natural increase rate, and finite increase rate of the P. xylostella population significantly decreased in the third and fifth generations under HVEF exposure for 10 min, while the mean generation time and doubling time significantly increased. Similarly, HVEF exposure for 10 min rapidly reduced the survival rate of adult P. xylostella in the first generation, and subsequently, it declined evenly and slowly. Meanwhile, the fecundity parameters of P. xylostella revealed that HVEF exposure for 10 min had the strongest inhibition effect on reproduction over five consecutive generations. In addition, HVEF exposure significantly increased the superoxide dismutase activity to produce extra hydrogen peroxide; however, increased catalase and peroxidase activity or reduced peroxidase activity triggered the accumulation of malondialdehyde in instar P. xylostella, especially after 10 min of treatment. The present findings provide experimental evidence and a theoretical basis for developing control strategies for P. xylostella under new HVEF environments.

Biological parameters of Muscidifurax raptorellus (Hymenoptera: Pteromalidae) on Bactrocera oleae (Diptera: Tephritidae), the key pest of olives

ABSTRACT The olive fruit fly, Bactrocera oleae, is one of the main pests of this crop and its control requires the development of methods environmentally safer than those used mostly nowadays, being biological control a possible alternative. Accordingly, the capacity of parasitisation and the biological parameters of Muscidifurax raptorellus, a generalist parasitoid of dipteran pupae, were evaluated on B. oleae at 25°C, 80% RH and a 16:08 h light/dark photoperiod. In a development assay, the rates of parasitism ranged 60% to 72% and the duration of the preimaginal period was between 17.0 and 18.5 days. The total mean number of adult wasps produced per pair in a reproduction assay was 50.7, with a mean daily production of 7 individuals and a mean rate of parasitism of 32.6%. The moment of maximum offspring production was estimated at 2.6 days after the beginning of the oviposition. The intrinsic rate of natural increase of M. raptorellus on B. oleae was 0.147, what determines a population doubling time of 4.7 days. The functional response was type II and the maximum attack rate in 24 h was 19.6 pupae. At host densities ranging 20–80 pupae per female, the number of adult wasps produced was around 20–22. The results obtained show the potential of M. raptorellus to be used for the biological control of B. oleae.

In vitro life table of the storage mite Tyrophagus putrescentiae (Acari: Acaridae)

Introduction: The mite Tyrophagus putrescentiae is a common contaminant of stored products and an important pest in plant tissue culture laboratories, because they diseminate fungi and bacteria. Objective: To describe the reproduction and life table of T. putrescentiae in vitro. Methods: We reared the mites with its associated fungus Leptosphaerulina sp., recording growth and development every 12h. Results: The duration of the egg, larva, protonymph, and tritonymph stages of cohort 1 was 4,52; 1,57; 1,37 and 1,29 days (cohort 2: 4,54; 1,44; 1,31 and 1,45 days, respectively). Cohort 1 periods of pre-oviposition, oviposition and post-oviposition were 1,86; 7,21 and 1,35 days (most cohort 2 individuals did not reach maturity). The intrinsic rate of natural increase (rm) was 0,11 individuals per female per day, the net reproduction rate (Ro) was 29,21; the generation time was 29,47 days, and the finite rate of increase (λ) was 1,12 times per female per day. Conclusion: Under the typical laboratory conditions, T. putrescentiae can multiply its initial population in a single day, which explains the population explosions observed in these laboratories.

Lighting in Dark Periods Reduced the Fecundity of Spodoptera frugiperda and Limited Its Population Growth

Light is a crucial environmental factor implicated in the temporal regulation of important biological events of insects, and some insects are usually sexually active in dark periods. However, the effects of light during dark periods on the growth, development, and fecundity of Spodoptera frugiperda, an important agricultural pest, remain unknown. In this study, we evaluated the effects of lighting in dark periods on the biological parameters of S. frugiperda in laboratory conditions. Our results showed that lighting in dark periods significantly prolonged the pre-adult stage and reduced the pupal survival and emergence rate. Moreover, the results indicated that the adult stage is the photoperiod-sensitive stage of S. frugiperda, and the fecundity and longevity of adults significantly reduced under lighting in dark periods, and the number of eggs per female moth decreased by 99% compared with the control. The mean generation time (T) of S. frugiperda population was the longest, and the intrinsic rate of natural increase (r) and finite rate of increase (λ) were the smallest under lighting in dark periods, and the population growth of S. frugiperda was significantly limited. Our findings may provide valuable insights to develop effective integrated pest management strategies to control S. frugiperda.

Assessment of the growing demographic threats to economic security in the regions of the North Caucasian Federal District

The article is devoted to the study and assessment of demographic threats to the economic security of the regions of the North Caucasian Federal District. A brief overview of periodical publications covering pressing demographic challenges and their impact on economic security is provided. Methods of economic analysis were used as follows: generalization, absolute and relative value method, comparison, index and tabular methods, etc. To assess the threats, the authors used data collected by the Federal State Statistics Service, such as birth and death data, the rate of natural increase (decrease), and the rate of migration increase. The data on the population before and after the sharp aggravation of demographic problems caused by the spread of the coronavirus disease (COVID-19) were compared. An initial assessment of demographic processes that had jeopardized the economic security of the regions was made. Based on the analysis of the statistical data showing a change in the number of births and deaths in years 2019–2021, the authors point out a certain decrease in the birth rate and a dramatic increase in mortality, which caused a drop in the rate of natural increase up to negative values, in the federal district under study as a result of the pandemic. The decline in the intensity of migration flows was identified. The interdependence of the territory’s population decline trend and the able-bodied population decline trend was noted. A set of conclusions on the top demographic policy priorities of the state in the current realities were made, and the need to develop measures aimed at ensuring economic security in the demographic sphere was stressed.

Growth and maturity of belugas (Delphinapterus leucas) in Cumberland Sound, Canada, and in captivity: evidence for two growth layer groups (GLGs) per year in teeth

The beluga (Delphinapterus leucas) is one of the few cetaceans to adapt, year-round, to an Arctic environment, one of the most challenging marine habitats, incorporating shallow estuaries, high turbidity, shifting pack-ice and extreme tidal ranges. Adaptation is attributed in part, to year-round herd integrity and synchrony, occupying a sequence of restricted seasonal habitats and calving sites, which are reflected in tooth laminae. Field research, 1966–1969, led to the conclusion that females are sexually mature at 5.75 years and males at 8.75 years, gestation is 15–16 months, reproductive cycle 3 years, with a lifespan of 30–35 years. Newborn and the first four year-classes are recognisable by length, body colour and morphology. The two-year nursing period results in rapid growth, coincident with a training period to acquire social, feeding, and crucial under-ice navigational skills. Belugas in Cumberland Sound had been reduced through exploitation, thus it is unlikely that present numbers are food limited, reflecting maximum rate of increase. We examine growth indices for captive belugas, either captured as calves, or first and second generations born in captivity, to compare known-age animals. Onset of sexual maturity in males and females is similar to findings for Cumberland Sound, which was based on two growth layer groups per year in the teeth, or GLG/2. We analyse studies where previous oral doses of tetracycline, as well as bomb radiocarbon 14C from 1958 were used to argue for single annual GLGs or GLG/1. Dedicated field studies, using appropriate dosage of intramuscular tetracycline, provide evidence for GLG/2. The 14C study appears to have been compromised by preparation technique and burdens sampled in the 1990s may have been of maternal origin, transferred during foetal growth and nursing, or from recent fallout to 1980. Fundamental to the issue of growth-at-age: arguments for GLG/1 are based on back-calculation from adults of unknown age, while GLG/2 is based on projection from newborn to known-age young and adults. Direct observations and cross-referenced parameters do not substantiate GLG/1, which requires halving the growth rate, thus doubling the age of sexual and physical maturity as well as lifespan, resulting in a 40% reduction of the intrinsic rate of natural increase, substantially lower than the present rate of recovery observed.

Biodemographic parameters of spodoptera frugiperda smith, 1797 (Lepidoptera: Noctuidae), a pest of maize crop, zea mays linnaeus, 1753 in sub-sudanese zone of Côte d'Ivoire

Spodoptera frugiperda is one of the main pests of maize (Zea mays L.) in Côte d'Ivoire. The control of this insect requires knowledge of biological and demographic parameters. The need to know the effect of seasons on the biodemographic parameters of Spodoptera frugiperda in Côte d'Ivoire led us to carry out work in the Sub-sudanese zone. The study was carried out in dry and rainy seasons on a maize plot from 2020 to 2021. The monitoring of newly emerged individuals on 3-week-old early variety with semi-serrated grains (EV 87/28-SR) maize plants under semi-natural conditions. The development cycle consisted of six larva stages. The development time was 27.93 ± 1.01 days in dry season and 32.47 ± 1.83 days in rainy season. Larval survival rates ranged from 85.79 to 100% in dry season and from 74.64 to 94.7% in rainy season. The average egg fertility rate was 21.19 ± 5.89% in dry season and 40.36 ± 8.49% in rainy season. The sex ratio was in favour of females. The net reproduction rate (Ro) and intrinsic rate of natural increase (rm) were highest in rainy season at 27.67 ± 7.82 and 0.26 ± 0.01 respectively. Spodoptera frugiperda performs much better in rainy season at temperatures between 25.1°C - 26.2°C due to a slow development time of 32.47 ± 1.83 days, a short population doubling time (D.T.) of 2.62 ± 0.13 and a high net reproduction rate (Ro) of 27.67 ± 7.82.

Dentinal growth layer counts of captive, known-age, mother and daughter belugas (Delphinapterus leucas): confirming two growth layer groups (GLG/2) per year; consequences for recovery and management

Captive mother and daughter belugas (Delphinapterus leucas) of Hudson Bay origin died at the Vancouver Aquarium, in November 2016, aged29.25 and 21.25 years. Aurora, captured at age three and captive since 1990, gave birth to Qila in 1995. Age and histories being known, the focusof this study was on total number of tooth growth layer groups (GLGs) present; one (GLG/1) or two (GLG/2) per year. Teeth from Aurora indicatedtwo growth layers per year (GLG/2) during pre-capture and captivity. Qila deposited GLG/2 throughout her captive life. Clearly an assumption ofGLG/1 over GLG/2 doubles the duration of all life stages, including lifespan and age at attainment of sexual maturity. Arguments for GLG/1 havebeen based on inferences (e.g. from fallout of bomb radio carbon) from adults of unknown age and history, while those for GLG/2 are based on theprojection of direct observations from newborn, known-age young to 21 and 29 year-old adults from captivity. Use of radiocarbon is ingenious butsuch analyses have not been rigorously tested on marine mammals and the sensitivity to necessary correction factors not addressed. The newinformation from this study contradicts the GLG/1 hypothesis in that such an assumption would place Aurora’s birth at the 1958 peak fallout ofbomb radiocarbon (14C) yet she was born 29 years later in 1987, while the birth of her daughter Qila would pre-date the birth of her mother by 13years. This paper re-assesses three studies that assigned GLG/1 based ages to older adults using GLG/2 and concludes that their supposed birthswould also pre-date the realistic births of their own mothers plus as many as two previous generations. Proponents of GLG/1 have overestimatedthe ages of previous calves-at-capture by 200–800%. Given the growth pattern in teeth of these 21 year and 29 year old female belugas, withincreasingly finer dentine GLGs deposited as the pulp tissue diminishes, it is difficult to envisage the GLG/1 tooth structures of those assumed tobe 60–80 years; none are as yet available. An holistic analysis using direct observations and cross-referenced parameters does not substantiateGLG/1which implies a 40% reduction of the intrinsic rate of natural increase; as a consequence, overestimating historical population size as wellas recovery target population and the predicted date of recovery in Cumberland Sound.

Modern İktisat Okulları Açışından Makroekonomik Dengeye Ulaşmada Beklentilerin Rolü

New Classicals have developed “Rational Expectations Hypothesis”. This means all economic agents are rational, optimizing and maximizing; they all have access to full information for the decisions they will take, and they will predict future prices correctly, hence make correct maximizing decisions.
 Friedman and Monetarists came up with “Adaptive Expectations Hypothesis” assuming that the workers, when there is an inflation will err in the first period and keep their wages the same; but in the next period they will realize the exact magnitude of the price rise and the fall in their real wage, hence will raise their wages correspondingly. Thus, the effects of monetary policy in reducing unemployment below natural rate of unemployment point will live only for one period; the economy will return to natural rate of unemployment and money supply increase will have only raised prices and wages; with the value of real parameters the same as one period ago.
 New Keynesians have also accepted Rational Expectations Hypothesis, which is obviously contrary to the Keynesian assumptions in this regard, namely, systematic under-estimation of future prices on the part of workers, as well as uncertainty and non-ergodicity.
 Post-Keynesians presented their assumptions in “Heterogeneous Expectations Hypothesis”. According to Post-Keynesians, entrepreneurs are in a better position than workers to obtain full information and estimate future prices correctly. The workers are less knowledgeable and generally end up under-estimating future prices.

Effects of temperature on life table parameters of a newly described phytoseiid predator, Neoseiulus neoagrestis (Acari: Phytoseiidae) fed on Tyrophagus putrescentiae (Acari: Acaridae)

The predatory mite, Neoseiulus neoagrestis Khaustov and Döker (Acari: Phytoseiidae), recently described as new species for science, but seems to have a great potential to be used in biological control. In this study, as a first step to determine the optimum temperature (between three temperatures tested) for its mass rearing, we studied its biological characteristics and life table parameters fed on Tyrophagus putrescentiae (Schrank) (Acari: Acaridae) at three different temperatures (20, 25, and 30 °C) under laboratory conditions. Results show that immature development, oviposition period as well as reproductive potential of this predator are significantly vary depending on the temperature. The immature developmental times and adult longevity for females, are ranged between 5.42 to 10.42 days and 39.88 to 74.12 days, based on the temperature, respectively. Average total number of eggs laid by per female at 25 °C (62.29) and 30 °C (58.65) are more or less similar but higher than that determined at 20 °C (41.46). The highest net reproductive rate (R<sub>0</sub>) is 29.066 (offspring/individual) at 25 °C. In addition, the highest intrinsic rate of natural increase (r) is 0.241 day<sup>-1</sup> at 30 °C. Furthermore, the highest finite rate of increase (λ = 1.272 day<sup>-1</sup>), and the shortest mean generation time (T = 13.416 days) and doubling time (DT = 2.874 days) are also determined at 30 °C. Our results demonstrate that N. neoagrestis successfully completed immature development, and can survive and reproduce at all tested temperatures. Nevertheless, a series of biological characteristics of this predator are differentially affected by the temperature. Finally, 25 °C and 30 °C seems to be more suitable for mass rearing of this predator on T . putrescentiae. Further studies should be conducted to determine biological characteristics and life table parameters of N. neoagrestis on several important pests such as spider mites, whiteflies and thrips.

Effects of parental age on salt stress tolerance in an aquatic plant

Parental age influences components of offspring fitness in many species. The ability to tolerate stress also affects fitness, but less is known regarding changes in offspring stress tolerance with increasing parental age, especially in plants. We examined first and fifth‐born clonal offspring (using birth order as a proxy for parental age), and compared their fitness in several sub‐lethal concentrations of salt (NaCl), to investigate the interactive effects of birth order and salt stress on the offspring of the aquatic plant Lemna minor L. We found that increasing salt concentration reduced reproduction particularly at early ages, which detrimentally affected fitness, as measured by the intrinsic rate of natural increase. Fifth offspring had greater fitness than first offspring, potentially due to the hump‐shaped relationship between offspring fitness and birth order observed in other studies on Lemna, with fifth offspring near the peak of the hump. We found no interactive effect of birth order and salt concentration on offspring fitness; however, there were interactive effects on the time to first reproduction and the size of fronds. Specifically, first offspring exposed to increasing salt concentrations exhibited longer delays to first reproduction and grew to a greater size, while fifth offspring showed little change in either variable with increasing salt concentration. Thus, variation in birth order affected offspring response to salt stress, although not in terms of fitness. These results help illuminate factors impacting the age‐specific strength of natural selection and stress responses, and may be environmentally relevant in the context of environmental salinization.

Has urbanization slowed down in Pakistan?

ABSTRACT Pakistan is the seventh largest contributor to world urban growth and exhibits high levels of urbanization. The recent 2017 Population Census results show a slowing of urban growth. We question whether this apparent slowdown reflects lowering of the rate of natural increase and migration, or is the result of a disconnect between the administrative definition of urban and actual reality. Alternative estimates presented here suggest that the 2017 Census may have underestimated urbanization by as much as 22.2 per cent, that is, the actual level of urbanization may be 44.5 per cent compared to 36.4 per cent reported in the census. We decompose the urban growth to assess the relative impact of natural increase, reclassification and migration and we utilize alternative methods of classification of urban areas to assess urbanization levels for Pakistan and its provinces. Continuing high levels of urban fertility and natural increase are the major contributors to urban growth. Internal migration is the next biggest contributor, however directions of movements may be changing. These findings have implications for the forthcoming 2022 census to improve the enumeration of urban areas and for urban planning to take advantage of the beneficial effects of building connectivity between small, medium, and large cities.

Sublethal effects of growth-regulating insecticides of synthetic and botanical origins on the biological parameters of Spodoptera frugiperda (Lepidoptera: Noctuidae).

The objective of this study was to evaluate the effects of growth-regulating insecticides of synthetic (e.g., Certero 480 SC, Intrepid 240 SC, Match EC and Mimic 240 SC) and botanical origins (e.g., Azamax 1.2 EC, Agroneem 850 EC, Azact 2.4 EC and Fitoneem 850 EC) on the biological parameters and fertility life table of Spodoptera frugiperda (J.E. Smith) under laboratory conditions. Larvae were fed insecticides that were incorporated into artificial diets. To develop the fertility life table, the following biological parameters were evaluated: survival at 7 days after infestation (d.a.i) and survivorship at adult eclosion, duration of the neonate-to-adult eclosion period, larval and pupal weights and total fecundity (number of total eggs per female). The results indicated that S. frugiperda neonates surviving LC25 or LC50 concentrations of the evaluated insecticides showed longer larval and egg-to-adult periods, lower larval and pupal weights and reduced fecundity, when compared to the control treatment. Larvae exposed to Azamax at LC25 or LC50 concentrations showed the greatest increase in generation duration (75 d). In addition, S. frugiperda adults emerged from pupae when larvae reared on an artificial diet containing growth regulating insecticides of synthetic and botanical origins produced fewer females per female per generation (Ro). As well as, lower rates of natural population increase per day (rm) compared to insects fed the control diet. Our findings indicated that, neem-derived products and growth-regulating insecticides of synthetic origin may be employed within integrated management strategies that aim to keep populations of S. frugiperda below levels that cause economic damage. Similarly, they offer alternatives for insecticide resistance management programs.