Natural Increase Research Articles

Comparison of the life table and reproduction parameters of the Tetranychus urticae (Acari: Tetranychidea) on five strawberry varieties

ABSTRACTThe two-spotted spider mite (TSSM), Tetranychus urticae Koch, is an important pest of strawberries grown both in greenhouse and field, and also may be infested at high humid condition. In this study, we evaluated the life history and demographic parameters of TSSM on five varieties (Frenzo, Karsin-Berg, Klassica, Pajaro, and Ventana) of strawberry at a constant temperature of 25 ± 1°C, 75 ± 5% RH and a photoperiod of 16:8 h L: D. Egg-to-female adult development was faster on Karsin-Berg and slower on Klassica variety (17.4 vs. 21.1 days). The oviposition period was longer on Karsin-Berg and shorter on Pajaro variety (27.0 vs. 17.4 days). Fecundity and female adult longevity of TSSM were significantly different among the five varieties of strawberry. Life table parameters provide most comprehensive description on the survival, stage differentiation, and reproduction of the population and they were significantly affected by different varieties of strawberry. The net reproductive rate was the highest on Ventana and lowest on Pajaro. The intrinsic rate of natural increase varied from 0.1067 on Frenzo to 0.1212 day−1 on Ventana. The mean generation time of TSSM were considerably affected by strawberry varieties and the longer generation time was on Frenzo. Based on results of the present study, Frenzo and Pajaro is a less favourable variety for the population growth of TSSM. Research on these five strawberry varieties can be used to improve our understanding of the population dynamics of the pest and thereby develop effective pest management programmes against T. urticae.

Coinfection of the secondary symbionts, Hamiltonella defensa and Arsenophonus sp. contribute to the performance of the major aphid pest, Aphis gossypii (Hemiptera: Aphididae).

Bacterial endosymbionts play important roles in ecological traits of aphids. In this study, we characterize the bacterial endosymbionts of A. gossypii collected in Karaj, Iran and their role in the performance of the aphid. Our results indicated that beside Buchnera aphidicola, A. gossypii, also harbors both Hamiltonella defensa and Arsenophonus sp. Quantitative PCR (qPCR) results revealed that the populations of the endosymbionts increased throughout nymphal development up to adult emergence; thereafter, populations of Buchnera and Arsenophonus were diminished while the density of H. defensa constantly increased. Buchnera reduction caused prolonged development and no progeny production. Furthermore, secondary symbiont reduction led to reduction of the total life span and intrinsic rate of natural increase as well as appearance of the deformed dead offspring in comparison with the control insects. Reduction of the secondary symbionts did not affect parasitism rate of the aphid by the parasitic wasp Aphidius matricariae. Together these findings showed that H. defensa and Arsenophonus contributed to the fitness of A. gossypii by enhancing its performance, but not through parasitoid resistance.

Non-target toxicity of synthetic insecticides on the biological performance and population growth of Bracon hebetor Say.

Bracon hebetor Say (Hymenoptera: Braconidae) is an important biological control agent of various species of order Lepidoptera and extensively used in biological control program worldwide. Present study evaluated the lethal and sublethal effects of insecticides on B. hebetor using demographic and population growth parameters. Doses of all the tested insecticides were within a maximum range of their recommended field dosages and adults were treated using residual glass vials method. For control experiments adults were treated with distilled water. Among the tested insecticides, the survivorship of various stages of B. hebetor was considerably prolonged on cyantraniliprole followed by chlorantraniliprole and shortest on chlorpyrifos and profenofos treated group. Total immature development time was prolonged in chlorpyrifos and profenofos treated group. Population growth parameters like intrinsic rate of natural increase (rm), net reproductive rate (R0), finite rate of increase (λ) and mean generation time (Tc) were considerably reduced in B. hebetor groups treated with chlorpyrifos and profenofos. However, B. hebetor groups treated with chlorantraniliprole and cyantraniliprole showed a little or no much difference in population growth parameters when compared with untreated group. It was also observed that chlorpyrifos and profenofos modified the sex ratio, thereby female emergence get reduced. On the basis of present findings it can be concluded that all tested insecticides caused considerable ecotoxic effects on B. hebetor compared to control. However, comparisons among the tested insecticides on the basis of IOBC criteria showed that chlorantraniliprol and cyntraniliprol was less toxic as compared to other insecticides tested on this biological control agent.

Maternal effects of the English grain aphids feeding on the wheat varieties with different resistance traits

The maternal effects of the English grain aphid, Sitobion avenae on offspring phenotypes and performance on wheat varieties with different resistance traits were examined. We found that both conditioning wheat varieties(the host plant for over 3 months) and transition wheat varieties affected the biological parameters of aphid offspring after they were transferred between wheat varieties with different resistance traits. The conditioning varieties affected weight gain, development time (DT), and the intrinsic rate of natural increase (rm), whereas transition varieties affected the fecundity, rm, net reproductive rate, and fitness index. The conditioning and transition wheat varieties had significant interaction effects on the aphid offspring’s DT, mean relative growth rate, and fecundity. Our results showed that there was obvious maternal effects on offspring when S. avenae transferred bwteen wheat varieties with different resistance level, and the resistance traits of wheat varieties could induce an interaction between the conditioning and transition wheat varieties to influence the growth, development, reproduction, and even population dynamics of S. avenae. The conditioning varieties affected life-history traits related to individual growth and development to a greater extent, whereas transition varieties affected fecundity and population parameters more.

Population and House Prices in the United Kingdom

Real house prices rise in the United Kingdom amid growing concern of an impending correction. The rate of household formation has increased with strong population growth, due to elevated rates of natural increase and net migration, and lack of growth in average household size, due to a rise in single-person households with population ageing. This paper presents an overlapping generations model of housing, endogenous labour, savings and growth to analyse the effect of an increase in the household formation rate and speculative demand under rational expectations on house prices in a general equilibrium. We find that real house prices rise over time if the rate of household formation outstrips the rate of housing supply, but do not follow a speculative bubble path in the long run. The results explain why the upward trend in real house prices reflects market fundamentals and has continued despite population ageing as the number of working and retired households grows relative to the number of older people seeking to sell.

Rate of natural population increase as a paleodemographic measure of growth

The aim of this study was to provide a verifiable measure of population increase from age-at-death data. It was anticipated that the D0-14/D ratio would be a good predictor of the rate of natural increase (births minus deaths) due to its strong relationship with the total fertility rate. United Nations age-at-death data for 58 countries was used to calculate the rate of natural population increase and evaluate its relationship to the D0-14/D ratio. Additionally, the impact of migration on both the rate and the ratio was measured. A correlation of r = 0.863 (95% CI 0.777–0.917) between the D0-14/D ratio and rate of natural population increase was found. Linear regression provided a simple equation for calculating the rate of population increase. The rate of natural population increase accounts for the disparity (or lack of) between births and deaths, and provides a valuable measure for evaluating ancient population variability. While the rate does not factor in migration, we believe migration should be measured independently as it is not always of interest to bioarcheological research questions and has a negligible impact on the rate of natural increase and the D0-14/D ratio. Estimating the rate of natural population increase has the potential to provide significant insights into past populations and the human response to change.

Comparative Biology Parameters of Q1 and Q3 Genotypes ofBemisia tabaciMED (Hemiptera: Aleyrodidae) on Two Host Plants in Burkina Faso, West Africa

The biological parameters studies on Bemisia tabaci MED Q1 and Q3 genotypes in tropical areas are very scarce and could provide interesting insights for pest management programmes. The life history traits and demographic parameters of Q1 and Q3 genotypes of B. tabaci MED (Gennadius) were studied on Lantana camara (L.) and Solanum incanum (L.) plants under laboratory conditions (25 °C ± 2, 60 ± 5 % relative humidity (RH) and a photoperiod 12L:12D. In our study, L. camara and S. incanum were suitable forQ1whereasQ3 was able to develop on L. camara only. Q3 differs from Q1 by combination of several life history traits. Q3 has shorter developmental duration and higher fecundity than Q1 on L. camara. Sex ratio favouring Q1 genotype was observed. Longevity of females was more important than that of males for both genotypes. As for demographic parameters, values of intrinsic rates of natural increase (Rm) varied from 0.10 for Q1 to 0.18 for Q3 on L. camara and from 0.0 for Q3 to 0.13 for Q1 on S. incanum. The ne...

Comparative toxicity of pristine graphene oxide and its carboxyl, imidazole or polyethylene glycol functionalized products to Daphnia magna: A two generation study

To investigate the chronic toxicity of graphene oxide (GO) and its functionalized products (GO-carboxyl, GO-imidazole and GO-polyethylene glycol), a two-generation study was conducted using the aquatic model species Daphnia magna. Each generation of daphnids were exposed for 21 days to 1.0 mg L−1 graphene material, with body length, neonate number, time of first brood and the intrinsic rate of natural increase (r) assessed as endpoints. Chronic exposure to GO, GO-carboxyl, and GO-imidazole had no adverse effect on body length or offspring number in the daphnid F0 generation, however, this exposure paradigm led to significant growth or reproduction inhibition in the following generation. Meanwhile, GO was found to show the strongest inhibitory effect, sequentially followed by GO-carboxyl and GO-imidazole. With exposure to GO-polyethylene glycol, no significant effects on growth or reproduction were observed for both F0 and F1 generation daphnids. These results reveal that carboxyl, imidazole and polyethylene glycol functional attachments alleviate the bio-toxicity of GO, especially polyethylene glycol. The increased C/O atomic ratio present in GO-carboxyl, GO-imidazole and GO-polyethylene glycol due to functionalization may mainly explain the reduced toxicity.

The potential of Dicyphus hesperus as a biological control agent of potato psyllid and sweetpotato whitefly in tomato.

The potential of the mirid predator Dicyphus hesperus Knight (Heteroptera: Miridae) as a biological control agent of the sweetpotato whitefly, Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) and the potato psyllid, Bactericera cockerelli Sulcer (Hemiptera: Psyllidae) in tomato was investigated in two experiments. The first experiment focused on the study of the life history traits of D. hesperus when fed on nymphs of the potato psyllid compared with the factitious prey Ephestia kuehniella Zeller (Lepidoptera: Pyrallidae) eggs. Although reproductive and development rates were higher on E. kuehniella eggs, the predator exhibited a good intrinsic rate of natural increase (rm) when feeding on B. cockerelli nymphs (rm: B. cockerelli 0.069 ± 0.0001; E. kuehniella 0.078 ± 0.0001), thus reflecting good potential as a biocontrol agent of this pest. The second experiment focused on the efficacy of D. hesperus as a biocontrol agent of the potato psyllid and the sweetpotato whitefly in a tomato greenhouse. Prey species were offered individually or together in a series of five treatments in greenhouse cages. Results showed that the predator was able to establish and suppress populations of both pests inhabiting tomato plants when pests occurred alone or together. Thus, D. hesperus was demonstrated to be a suitable biocontrol agent of these two important pests that could be used in tomato greenhouses.

Reproduction, longevity and life table parameters of Monosteira unicostata (Hemiptera: Tingidae) at constant temperatures

Information on the effect of temperature on biological parameters of phytophagous insects is one of the tools in IPM programs, as it allows prediction of risk situations in the field. This work reports the effect of temperature on reproductive parameters and longevity of one of the most important current pests of almond orchards in the Mediterranean basin, the poplar lace bug, Monosteira unicostata (Mulsant & Rey) (Hemiptera: Tingidae). The temperatures tested were 22, 25, 28, 31, 34 and 37ºC, always at 60 ± 10% relative humidity and under a L16:D8 photoperiod. Extreme temperatures had an adverse effect on preoviposition period, total fecundity and daily fecundity while increasing values of oviposition period and adults longevity were registered for decreasing temperatures. Male longevity was higher than female longevity, and mortality pattern differed between sexes for all temperatures but 37ºC. The nonlinear Lactin model described accurately the effect of temperature on the intrinsic rate of natural increase of M. unicostata populations and predicted the optimum temperature for population increase at 34.1ºC, at which the population doubling time is 3.6 days. Produced values of lower and upper thresholds for M. unicostata populations were 14.8 and 38.8ºC, respectively. This characterizes the poplar lace bug as a very important pest in the Mediterranean basin, with an increasing potential risk in a global warming scenario.

Estimasi Potensi Pembibitan Ternak Kerbau di Kecamatan Ulakan Tapakis Kabupaten Padang Pariaman Provinsi Sumatera Barat, Indonesia (THE ESTIMATION POTENTIAL LIVESTOCK BREEDING OF BUFFALO IN ULAKAN TAPAKIS DISTRICT, PADANG PARIAMAN REGENCY, WEST SUMATRA PR

This study aimed to determine the potential of buffaloes in Ulakan Tapakis sub-district to produce calves and its viability as a source buffaloes. Casus and questionnaire are used in this study in which three sub-district characterized by high, medium and low buffalo population are chosen quota sampling. The observed variables in this study are the identity of the breeder and the buffalo. The development of buffalo population was analyzed using breeding theory approach. The average increase of the population was analyzed using a time series analysis. The results showed that Net Replacement Rate (NRR) value in male and female of 157.31% and 191.27% and the natural increase (NI) value of 23.66% indicating a moderate increase of the population. This study also shows that the population of buffaloes in the region is sufficient to cover its need. Male and female seed potencial of 4.55% and 5.33% of the population. On average the increase population of buffalo from 2011 to 2015 annual of as much as 172.75 head or 16.53%. Estimated population of buffaloes in 2016 and 2020 as in 1675 head and 2183 head eith average increase population as much as 63 head or 3.40%.

The Productivity and Natural Increase of Swamp Buffalo in District Malang

The purpose of this research was to collect the basic information needed to develop a sustainable breeding program, which includes the potential for production and reproduction of buffaloes. This research was conducted on swamp buffalo in Malang Regency East Java. The research method used was survey method. Primary data was obtained from direct observation on 323 tails owned by 98 breeders. Variables observed were population growth and reproductive performance. The data obtained were analyzed descriptively. The result showed that the initial population study of swamp Buffaloes in Malang as many as 1155 with male and female ratio 1: 2. The ratios of male and female swamp Buffalo 20 percent male and 80 percent female. Overall, the buffalo reproduction performance was still low. Service per conception 2.06 ± 0.88; Anestrus Postpartum 7.46 ± 3.83 months; calving interval distance 17.82 ± 4.86 months; 20.43 % birth rate and 4.33% mortality rate of Natural Increase (NI) population was about 16,1%. In conclusion, the value of NI of swamp Buffalo in Malang Regency is still low. To increase buffalo productivity, buffalo breeding program is continuously based on reproduction control.

Рождаемость и репродуктивные установки сельского населения Республики Калмыкия

The demographic situation in rural territories is currently characterized as ‘unfavorable’ and requires closer consideration of corresponding behaviors in the rural population. The republic of Kalmykia clusters with regions of natural population increase and negative migration balance. The trend is most evident in its rural areas. A statistical analysis shows that between 2012 and 2016 the natural increase rates in the country are lower than those of the urban population; which is contrary the traditional state of affairs with birthrates among the rural residents exceeding those among city dwellers. A comparison of cumulative birthrates of both the rural and urban populations testifies that the mentioned state of things existed till 2013, and in subsequent years the cumulative urban birthrate has been higher than the rural population. In an effort to estimate Kalmykia’s demographic potential, an opinion poll aimed to reveal the reproductive attitudes of the regional population was conducted. Most respondents declared they expected to have two or three children. Reproductive expectations of rural informants proved higher than those of city respondents. Our comparison of answers about expected and desired parities shows that with all circumstances required at hand the share or respondents inclined to have three and more children increases. While possession of many children is planned by 58,5 % of the respondents, this share may reach 68,5 % with all required conditions available. Analysis of answers given by urban and rural informants shows that provided they have all related opportunities, 59,8 % of urban residents and 71,7 % of rural dwellers do not exclude the possibility of giving birth to three and more children. The case study concludes that reproductive attitudes (expectations) of the rural population are higher than the ones developed by Kalmykia’s urban population.

Risk assessment and spread of the potentially invasive Ceratitis rosa Karsch and Ceratitis quilicii De Meyer, Mwatawala & Virgilio sp. Nov. using life-cycle simulation models: Implications for phytosanitary measures and management.

Integrative taxonomy has resolved the species status of the potentially invasive Ceratitis rosa Karsch into two separate species with distinct ecological requirements: C. rosa “lowland type” and the newly described species Ceratitis quilicii De Meyer, Mwatawala & Virgilio sp. nov. “highland type”. Both species are tephritid pests threatening the production of horticultural crops in Africa and beyond. Studies were carried out by constructing thermal reaction norms for each life stage of both species at constant and fluctuating temperatures. Non-linear functions were fitted to continuously model species development, mortality, longevity and oviposition to establish phenology models that were stochastically simulated to estimate the life table parameters of each species. For spatial analysis of pest risk, three generic risk indices were visualized using the advanced Insect Life Cycle Modeling software. The study revealed that the highest fecundity, intrinsic rate of natural increase and net reproductive rate for C. rosa and C. quilicii was at 25 and 30°C, respectively. The resulting model successfully fits the known distribution of C. rosa and C. quilicii in Africa and the two Indian Ocean islands of La Réunion and Mauritius. Globally, the model highlights the substantial invasion risk posed by C. rosa and C. quilicii to cropping regions in the Americas, Australia, India, China, Southeast Asia, Europe, and West and Central Africa. However, the proportion of the regions predicted to be climatically suitable for both pests is narrower for C. rosa in comparison with C. quilicii, suggesting that C. quilicii will be more tolerant to a wider range of climatic conditions than C. rosa. This implies that these pests are of significant concern to biosecurity agencies in the uninvaded regions. Therefore, these findings provide important information to enhance monitoring/surveillance and designing pest management strategies to limit the spread and reduce their impact in the invaded range.

Population and house prices in the United Kingdom

AbstractReal house prices rise in the United Kingdom amid growing concern of an impending correction. The rate of household formation has increased with strong population growth, due to elevated rates of natural increase and net migration, and lack of growth in average household size, due to a rise in single‐person households with population ageing. This paper presents an overlapping generations model of housing, endogenous labour, savings and growth to analyse the effect of an increase in the household formation rate and speculative demand under rational expectations on house prices in a general equilibrium. We find that real house prices rise over time if the rate of household formation outstrips the rate of housing supply, but do not follow a speculative bubble path in the long run. The results explain why the upward trend in real house prices reflects market fundamentals and has continued despite population ageing as the number of working and retired households grows relative to the number of older people seeking to sell.

Development of Tetranychus ludeni (Acari: Tetranychidae) on transgenic soybean cultivars

The aim of this study was to assess the influence of transgenic soybean [Glycine max L. (Fabaceae)] cultivars on the biological cycle of Tetranychus ludeni Zacher (Acari: Tetranychidae) in laboratory conditions. We used three cultivars: a conventional soybean (CO), a glyphosate-resistant with insertion of genes of Agrobacterium sp., Roundup Ready (RR), and a glyphosate-resistant with insertion of genes of Bacillus thuringiensis var. israelensis (BT). Duration of developmental stage, mite viability, number of laid eggs, and female longevity of T. ludeni were evaluated. The duration of the deutonymph phase was shorter in RR (2.1 ± 0.12 days) than in CO (2.6 ± 0.12) and BT (2.5 ± 0.08). The duration of egg, larval, and protonymph phases were similar for T. ludeni on the three cultivars. The mean duration of each generation (T), net reproduction rate (Ro), intrinsic rate of natural increase (rm), and doubling time (DT) were similar on the three cultivars. Results showed that population growth are not influenced by transgenesis at the laboratory level. Females died without a post-oviposition period on all soybean cultivars. The intrinsic rate of natural increase of T. ludeni on soybean cultivars was low (between 0.15 and 0.17).

Niezrównoważony przyrost naturalny w Europie, Afryce i na Bliskim Wschodzie

The aim of this article is to present the problem of unbalanced natural increase in Europe, Africa, and the Near East. The first part presents demographical trends occurring in the world in the twentieth century and a comparative analysis of the factors determining the natural increase. In the second part, it was carried out an analysis of demographic changes in sub-Saharan Africa and factors affecting the value of the birth (fertility) rate, which is the highest in the world on this subcontinent. The third part presents problems related to the internal unbalanced natural increase in the MENA region. In particular, it is an attempt to answer the question what factors influence the fact that, although the region is characterized by a far-reaching cultural-religious-civilization community, there are large differences between countries in term of natural increase and birth (fertility) rate, and what the effects may be. The last paragraph presents perspectives for further population growth in Sub-Saharan Africa and the MENA region, as well as the possible consequences of these trends, in particular concerning migration, destabilization, and new conflicts.

Is It Wrong to Apply the Intrinsic Rate of Natural Increase to Individuals and Compare It among Genotypes?

In order to gain insights into the seasonal dynamics of genetic variation in insecticide resistance within a natural population of Drosophila melanogaster during population growth, which we considered the most important ecological factor there, we conducted a series of genetic analyses of resistance factors involved in that population and compared individual-based intrinsic rates of natural increase among resistance genotypes. However, some researchers have argued that it is a misconception to apply the intrinsic rate of natural increase to individuals, because it is a population parameter. We consider that their criticisms were incorrect. In this article, I described our research briefly and set forth the reasons why we conducted these studies.

Biology and life table study of Spilarctia obliqua Walker (Arctiidae: Lepidoptera) on different bast fibre crops

The influence of different bast fibre crops i.e. jute (Corchorus olitorius and C. capsularis), mesta (Hibiscussabdariffa and H. cannabinus), ramie (Boehmeria nivea) and sunnhemp (Crotalaria juncea) on biology and life table parameters of jute hairy caterpillar, Spilarctia obliqua Walker was carried out to understand the host suitability under laboratory condition. Adult longevity and fecundity of S. obliqua and its life table parameters were differed significantly with bast fibre crops. The larval, pupal period and adult longevity of S. obliqua were shortest on C. olitorius and longest on H. sabdariffa. The larval survival and adult fecundity (eggs/female) significantly highest (80.68 ± 1.41%, 477.00 ± 21.12 eggs) in C. olitorius and the lowest (53.92 ± 1.20%, 260.00 ± 21.41 eggs) was on H. sabdariffa, respectively. The net reproductive rate was higher on C. olitorius (384.84 ± 21.56 females/female/generation) and minimum (163.80 ± 14.65 females/female/generation) on H. sabdariffa. The intrinsic rate of natural increase was higher on C. olitorius (0.15 ± 0.00 females/female/day) and lowest (0.12 ± 0.00 females/female/day) on H. cannabinus. The study indicated that C. olitorius was the most suitable host as compared to other crops for S. obliqua growth and reproduction.

Impaired reproduction and individual growth of the water flea Daphnia magna as consequence of exposure to the non-ester pyrethroid etofenprox.

The effect of the pesticide etofenprox (0.76, 0.95, 1.18, 1.48, and 1.85μgL-1) on survival, reproduction, and growth of Daphnia magna organisms was monitored using 21-day exposure tests. In order to test pesticide effects on D. magna, survival, length, mean total neonates per female, mean brood size, time to first reproduction, mean number broods per female, cumulative molting, and the population parameter intrinsic rate of natural increase (r) were used. Reproduction was seriously affected by etofenprox. Concentrations of etofenprox higher than 1.18μgL-1affected all the reproductive parameters analyzed as well as individual length. However, daphnids' survival after 21days of pesticide exposure did not exhibited differences among experimental and control groups. The no observed effect concentration (NOEC), the lowest observed effect concentration (LOEC), and the maximum acceptable toxicant concentration (MATC) were calculated for the different parameters. A MATC estimation of 1.32μgL-1 was calculated for mean brood size, mean number of broods per female, mean number of neonates per female, and the intrinsic rate of growth population. Etofenprox effect on the algae Nannochloris oculata was also evaluated. The selected etofenprox concentrations did not affect algal growth rate (μ) after 24h; however, N. oculata exposed during 48 and 72h to the highest etofenprox concentration showed a decreased in its population rate.