Finite Growth Rate Research Articles

Functional roles of nicotinic acetylcholine receptors in dinotefuran and flupyrimin toxicity and their sublethal effects on Sogatella furcifera (Hemiptera: Delphacidae)

Abstract Sogatella furcifera (Horváth) (Hemiptera: Delphacidae), a serious rice pest, has developed significant resistance to a wide range of pesticides. Neonicotinoid insecticides are currently the primary choice for controlling S. furcifera, yet their impact on the species remains poorly understood. In this study, we investigated the binding sites of a conventional insecticide (dinotefuran) and a novel insecticide (flupyrimin), and evaluated their sublethal effects on S. furcifera. Our results revealed that the LC50 of dinotefuran and flupyrimin were 2.51 mg/L and 2.80 mg/L in third-instar S. furcifera, respectively. RNA interference (RNAi) knockdown of S. furcifera nicotinic acetylcholine receptor (nAChR) alpha2 subunit (Sfα2) and S. furcifera nAChR beta1 subunit (Sfβ1) significantly reduced the susceptibility to dinotefuran by 18.7% and 16.8%, respectively, but had no effect on flupyrimin. Reproduction of the F0 and F1 generations was significantly inhibited by the LC25 of both dinotefuran and flupyrimin. In the dinotefuran treatment at LC25, the intrinsic growth rate (r) and finite growth rate (λ) were reduced to 0.15 and 0.16 days, respectively; the mean generation time (T) increased to 27.77 days, and the relative fitness was only 0.76 compared to the control. Additionally, the relative fitness (Rf) of the flupyrimin-treated group was reduced to 0.93 and 0.86 times that of the control group. The population dynamics of S. furcifera are significantly affected by both dinotefuran and flupyrimin, making these insecticides valuable tools for integrated pest management and the rational use of insecticides.

Nonlinear modulation of dispersive fast magnetosonic waves in an inhomogeneous rotating solar low-β magnetoplasma

Abstract We study the modulation of fast magnetosonic waves (MSWs) in rotating inhomogeneous low-β magnetoplasmas with the effects of gravitation and the Coriolis force. By employing the standard multiple-scale reductive perturbation technique (RPT), we derive a nonlinear Schrödinger (NLS) equation that governs the evolution of slowly varying MSW envelopes. The fast MSW becomes dispersive by the effects of the Coriolis force in the fluid motion, and the magnetic field and density inhomogeneity effects favor the Jeans instability in self-gravitating plasmas in a larger domain of the wave number (k, below the Jeans critical wave number, kJ) than homogeneous plasmas. The relative influence of the Jeans frequency (ωJ, associated with the gravitational force) and the angular frequency (Ω0, relating to the Coriolis force) on the Jeans carrier MSW mode and the modulational instability (MI) of the MSW envelope is studied. We show that the MSW envelope (corresponding to the unstable carrier Jeans mode with ωJ > 2Ω0 and k < kJ) is always unstable against the plane wave perturbation with no cut-offs for growth rates. In contrast, the stable Jeans mode with ωJ > 2Ω0 but k > kJ manifests either modulational stability or MI having a finite growth rate before being cut off. We find an enhancement of the MI growth rate by the influence of magnetic field or density inhomogeneity. The case with constant gravity force (other than the self-gravity) perpendicular to the magnetic field is also briefly discussed to show that the fast magnetosonic carrier mode is always unstable, giving MI of slowly varying envelopes with no cut-offs for the growth rates. Possible applications of MI in solar plasmas, such as those in the X-ray corona, are also briefly discussed.

Population Parameters of Haplaxius crudus (Hemiptera: Cixiidae) under Semi-Controlled Conditions.

The palm leafhopper, Haplaxius crudus, is a possible vector of the pathogen that causes the Lethal Wilt of oil palms in Colombia. This disease represents the biggest phytosanitary problem in the eastern palm zone. From 2010 to 2021, more than 7700 ha have been eradicated, with economic losses exceeding 154 million USD. Therefore, knowing the biology of this insect and its population parameters is necessary for developing population control tools. To evaluate these parameters, a cohort of 100 eggs obtained from H. crudus adults from the breeding unit established in the Campo Experimental Palmar de las Corocoras de Cenipalma in Paratebueno, Cundinamarca, was monitored to record the life cycle and the population parameters using a life table under semi-controlled conditions in an oil palm plantation. The life cycle from egg to adult was 62.7 ± 15.5 days (26.1 ± 2.9 °C; HR: 89.8 ± 14.0%). The egg stage lasted 14.6 ± 0.6 days, the nymphal stage 48.1 ± 2.8 days through five instars, and the adult longevity was 14.8 ± 8.4 days. The specific mortality rate (qx) calculated in the life table was 0.14 (for the egg stage), 0.05 (for I instar), 0.05 (for II instar), 0.03 (for III instar), 0.04 (for IV instar), and 0.07 (for V instar). The population parameters' values were as follows: net reproductive rate Ro = 10.96; generation time T = 62.3 days, intrinsic natural growth rate rm = 0.03, and finite growth rate λ = 1.03. These results help us to understand the population dynamics of this insect in the field and for the development of population control studies.

Using state‐space models to estimate recreational angling effort and infer processes that regulate angler dynamics

AbstractObjectiveState‐space models are a flexible modeling approach and are often fit to ecological time series data exhibiting temporal autocorrelation. Traditionally, angler effort data collected using on‐site creel surveys are analyzed using design‐based methods. With some exceptions, state‐space models are rarely used to model creel survey data that are also generally a time series of temporally autocorrelated counts.MethodsIn this study, we demonstrated how to fit state‐space models to a time series of angler counts in 11 sections of three trout fisheries in Idaho. The basic model was extended to make inference about processes that may regulate angling dynamics, such as “population growth rate” of angling effort and recreational carrying capacity.ResultEstimated angling effort varied from 21,179 h in the lowermost section of the Henrys Fork Snake River to 199,457 h in the uppermost section of the South Fork Snake River. The finite population growth rate of angling effort was 1.82 when transitioning from a weekday to a weekend, suggesting that angling effort was 1.82 times greater, on average, on Saturdays than on Fridays, and the population growth rate was 0.38 (i.e., 0.38 times smaller) when transitioning from a Sunday to a Monday. Estimated carrying capacity among fishery sections varied from 129 daily hours of angling effort on the Big Lost River to 693 h on the middle section of the South Fork Snake River. Carrying capacity was 1.88 times higher on fishery sections that had ≥0.5 access points/km than on sections with <0.5 access points/km.ConclusionThe state‐space models used in this study can be modified or extended to fit a variety of data types or can be used to evaluate additional hypotheses regarding the angling process.

Hidden demographic impacts of fishing and environmental drivers of fecundity in a sea turtle population.

Fisheries bycatch is a critical threat to sea turtle populations worldwide, particularly as turtles are vulnerable to multiple gear types. The Canary Current is an intensely fished region, yet there has been no demographic assessment integrating bycatch and population management information of the globally significant Cabo Verde loggerhead turtle (Caretta caretta) population. Using Boa Vista island (Eastern Cabo Verde) subpopulation data from capture-recapture and nest monitoring (2013-2019), we evaluated population viability in combination with estimated regional bycatch rates (2016-2020) in longline, trawl, purse-seine and artisanal fisheries. We further evaluated current nesting trends in the context of bycatch estimates, existing hatchery conservation measures, and environmental (net primary productivity) variability in turtle foraging grounds. Current bycatch mortality rates present a risk of near extinction this century, when projecting the Boa Vista subpopulation with matrix population models. Bycatch reduction could increase finite population growth rate by 1.95%, and 1.76% for longline fisheries alone. Hatchery conservation increases hatchling production and reduces extinction risk, but cannot achieve population growth alone. Short-term increases in nest counts (2013-2021), putatively driven by temporary increases in net primary productivity, may be crucially masking ongoing long-term population declines. When fecundity was linked to net primary productivity, our hindcast models simultaneously predicted these opposing long-term and short-term trends. Consequently, our results show conservation management must diversify from land-based management. The masking effect we found has broad-reaching implications for monitoring sea turtle populations worldwide, demonstrating the importance of directly estimating adult survival and that nest counts might inadequately reflect underlying population trends. This article is protected by copyright. All rights reserved.

Effect of the type of citrus fruit on the biological parameters of Panonychus citri (Acari: Tetranychidae) under laboratory conditions

The citrus red mite, Panonychus citri (McGregor, 1916), is considered a very important pest in most citrus-growing countries. The developmental periods, reproduction rates, and population growth parameters of P. citri were evaluated using the fruit peel under experimental conditions (25 ± 1 °C, 50 ± 5% RH and 14:10 h photoperiod) on five Citrus species: Mexican lime (C. ×aurantiifolia (Christm.) Swingle), grapefruit (C. ×paradisi Macfad.), sweet orange (C. ×sinensis (L.) Osbeck), mandarin (C. reticulata Blanco), and tangelo fruit (C. ×tangelo J.W. Ingram & H.E. Moore). The developmental period of the immature stages of P. citri averaged 26.64, 25.93 and 25.75 d for sweet orange, mandarin, and tangelo fruit, respectively. The adult stage was not achieved in Mexican lime and grapefruit. Immature survival was less than 50% in mandarin and tangelo fruit, in contrast, in sweet orange it was 57%. On average, oviposition was 3.55, 4.95 and 5.00 eggs female-1, on sweet orange, mandarin, and tangelo fruit, respectively. The intrinsic natural growth rate (rm), net reproduction rate (R0), generation time (T), and finite growth rate (λ) of P. citri showed significant differences among the tested species (p < 0.05). The rm and R0 values were 0.005 and 1.209 for sweet orange, 0.026 and 2.474 for mandarin and 0.020 and 2.000 for tangelo fruit. The results indicated that mandarin was the most suitable species for the P. citri population growth, whereas sweet orange was less suitable to proliferate. These differences are important in the integrated management of P. citri on citrus.

Demographic analyses reveal differential biological vulnerability in four Southwestern Atlantic skates

More than 33 skate species have been registered in the Southwestern Atlantic Ocean (SAO) 34°S, where hotspots of the endemic threatened marine chondrichthyans with high scientific and conservation priorities have been detected. The lack of species-specific landing data highlights the importance of biological data-based methods to determine the vulnerability and productivity of skate species. In this work, we estimated the demographic parameters for the skates Atlantoraja castelnaui, Rioraja agassizi, Sympterygia bonapartii, and Zearaja brevicaudata in SAO, by implementing Leslie matrix models. The finite rate of population growth ( ʎ) for the four skate's species ranged from 1.036 ( Z. brevicaudata) to 1.196 ( R. agassizi). Elasticity analyses and the performance of different harvest strategies show that reducing juvenile catches appears to be one of the most effective management actions for these species since they result in higher survivorship of age classes with more influence in λ. Differences in the biological productivity of the skates suggest that, to achieve sustainable exploitation of skates, the commitment of all stakeholders to improve species-level information is necessary.

Electrostatic Plasma Wave Excitations at the Interplanetary Shocks

Over the last few decades, different types of plasma waves (e.g., the ion acoustic waves (IAWs), electrostatic solitary waves, upper/lower hybrid waves, and Langmuir waves) have been observed in the upstream, downstream, and ramp regions of the collisionless interplanetary (IP) shocks. These waves may appear as short-duration (only a few milliseconds at 1 au) electric field signatures in the in-situ measurements, with typical frequencies of ∼1–10 kHz. A number of IAW features at the IP shocks seem to be unexplained by kinetic models and require a new modeling effort. Thus, this paper is dedicated to bridging this gap in understanding. In this paper, we model the linear IAWs inside the shock ramp by devising a novel linearization method for the two-fluid magnetohydrodynamic equations with spatially dependent shock parameters. It is found that, for parallel propagating waves, the linear dispersion relation leads to a finite growth rate, which is dependent on the shock density compression ratio, as Wind data suggest. Further analysis reveals that the wave frequency grows towards the downstream region within the shock ramp, and the wave growth rate is independent of the electron-to-ion temperature ratio, as Magnetospheric Multiscale (MMS) in-situ measurements suggest, and is uniform within the shock ramp. Thus, this study helps in understanding the characteristics of the IAWs at the collisionless IP shocks.

Climate‐driven stream‐flow impacts on bull trout metapopulation dynamics revealed by quantitative assessment of 22 years of tag–recapture data

Abstract Climate change has altered annual hydrologic cycles globally. Where stream flows are dominated by snow melt in western North America, climate change has resulted in peak flows that occur earlier in the runoff season and reduced flows during the non‐runoff season. Such changes can negatively affect the reproduction success and first‐year survival of stream‐dependent, autumn‐spawning salmonid fishes. We annually sampled bull trout (Salvelinus confluentus Suckley) populations in the St. Mary River catchment in north‐central Montana, U.S.A. Bull trout (≥ age 3; n = 3,502) electrofished from six creeks during 1998–2018 were given passive integrated transponder tags and 739 (21.1%) of those fish were recaptured through 2019 (tag loss c. 4.5%). We used tag–recapture data to (1) determine the spatial extent of the bull trout metapopulation; (2) fit a Bayesian Jolly–Seber model to identify the temporal trends in the sizes, finite growth rates (λ), and apparent survival and detection probabilities of the three main populations; and (3) assess the statistical associations between λ and flow. Bull trout movements among creeks defined the metapopulation's almost catchment‐wide spatial extent. Statistical correlations between λ and flow were clumped in the month × flow variable space at flow lags of 3–7 years, which corresponded with production of the dominant age classes in our tagged populations. Positive correlations occurred during June–September (the bull trout spawning season) and negative correlations during October–May (the embryo‐incubation period). Declining spawning‐season flow could have degraded bull trout spawning habitat, whereas increasing incubation‐period flow could have physically disturbed embryos affecting their survival. This study revealed associations between bull trout population dynamics and climate change as indexed by stream flow. Although the spawning habitats of these bull trout are protected within Glacier National Park and the occurrence of multiple local populations supports metapopulation persistence, that persistence is diminished because flow‐regime change has a strong negative influence on each population. Given the region's apparent climate trajectory, further decline in the bull trout metapopulation is anticipated.

Demographic Analysis of Shortfin Mako Shark (Isurus oxyrinchus) in the South Pacific Ocean.

The shortfin mako shark (Isurus oxyrinchus) demonstrates low productivity and is thus relatively sensitive to fishing. Natural mortality (M) and fishing mortality (F) data are critical to determine their population dynamics. However, catch and fishing effort data are unavailable for this species in the South Pacific Ocean, making stock assessments difficult. Demographic quantitative methods aid in analyzing species with limited data availability. We used a two-sex stage-structured matrix population model to examine the demographic stock status of mako sharks. However, data-limited models to determine fishery management strategies have limitations. We performed Monte Carlo simulations to evaluate the effects of uncertainty on the estimated mako shark population growth rate. Under unfished conditions, the simulations demonstrated that the mako sharks showed a higher finite population growth rate in the 2-year reproductive cycle compared to the 3-year reproductive cycle. Protecting immature mako sharks led to a higher population growth rate than protecting mature mako sharks. According to the sex-specific data, protecting immature male and female sharks led to a higher population growth rate than protecting mature male and female sharks. In conclusion, sex-specific management measures can facilitate the sustainable mako shark conservation and management.

Development and reproductive potential of Plutella xylostella (Lepidoptera: Plutellidae) in five Brassicaceae hosts

Plutella xylostella (L.) is one of the main pests in Brassicaceae crops, although, information regarding its biology on alternative hosts is scarce, crucial for its mass rearing. We studied the development, biology, and population parameters of P. xylostella, fed with different Brassicaceae. In laboratory conditions, P. xylostella was reared from larva 1 to adult. Larvae were fed with B. napus (rapeseed), Brassica carinata (Ethiopian rape), Brassica oleracea var. capitata (cabbage), Rapistrum rugosum (turnipweed) and Raphanus raphanistrum (radish). The development time of immature stages was longer in B. oleracea var. capitata (19.19 ± 0.43d) and shorter in R. raphanistrum (15.44 ± 0.37d). In R. rugosum, the highest survival of individuals that reached adult stage was achieved. The highest value of oviposited eggs was recorded in R. rugosum (300.82 ± 24), and highest hatching percentage in R. raphanistrum (79.7%). The highest values of net reproductive rate, intrinsic rate of increase and finite rate of growth, were obtained with R. rugosum. P. xylostella complete their whole cycle in any of the five hosts, being R. rugosum most suitable host for an efficient mass rearing system.

Gravity Wave Generation in Balanced Sheared Flow Revisited

Abstract The generation of internal gravity waves from an initially geostrophically balanced flow is diagnosed in nonhydrostatic numerical simulations of shear instabilities for varied dynamical regimes. A nonlinear decomposition method up to third order in the Rossby number (Ro) is used as the diagnostic tool for a consistent separation of the balanced and unbalanced motions in the presence of their nonlinear coupling. Wave emission is investigated in an Eady-like and a jet-like flow. For the jet-like case, geostrophic and ageostrophic unstable modes are used to initialize the flow in different simulations. Gravity wave emission is in general very weak over a range of values for Ro. At sufficiently high Ro, however, when the condition for symmetric instability is satisfied with negative values of local potential vorticity, significant wave emission is detected even at the lowest order. This is related to the occurrence of fast ageostrophic instability modes, generating a wide spectrum of waves. Thus, gravity waves are excited from the instability of the balanced mode to lowest order only if the condition of symmetric instability is satisfied and ageostrophic unstable modes obtain finite growth rates. Significance Statement We aim to understand the generation of internal gravity waves in the atmosphere and ocean from a flow field that is initially balanced, i.e., free from any internal gravity waves. To examine this process, we use simulations from idealized numerical models and nonlinear flow decomposition method to identify waves. Our results show that a prominent mechanism by which waves can be generated is related to symmetric or ageostrophic instabilities of the balanced flow possibly occurring during frontogenesis. This process can be a significant mechanism to dissipate the energy of the geostrophic flow in the ocean.

Pareto-optimal trade-off for phenotypic switching of populations in a stochastic environment

Finding optimal survival strategies of living systems embedded in fluctuating environments generally involves a balance between phenotypic diversification and sensing. If we neglect sensing mechanisms, it is known that slow, resp. fast, environmental transitions favor a regime of heterogeneous, resp. homogeneous, phenotypic response. We focus here on the simplest non-trivial case, i.e. two randomly switching phenotypes subjected to two stochastically switching environments. The optimal asymptotic (long term) growth rate of this model was studied elsewhere; we further expand these results by discussing finite time growth rate fluctuations. An exact asymptotic expression for the variance, alongside with approximations valid in different regimes, are tested numerically in details. Our simulations of the dynamics suggest a close connection between this variance and the extinction probability, understood as risk for the population. Motivated by an earlier trade-off analysis between average capital growth rate and risk in Kelly’s gambling model, we study the trade-off between the average growth rate and the variance in the present model. Despite considerable differences between the two models, we find similar optimal trade-off curves (Pareto fronts), suggesting that our conclusions are robust, and broadly applicable in various fields ranging from biology/ecology to economics.

Intraspecific competition and persistence in Acanthoscelides macrophthalmus (Coleoptera: Chrysomelidae): an experimental analysis in a stage‐structured population

AbstractIntraspecific competition is an ecological process that can affect the structure of populations with important consequences for population persistence. In this study, we investigated (in the larval stage) the effect of intraspecific competition in the seed‐feeding beetle Acanthoscelides macrophthalmus on its population structure and persistence. By using Leslie matrices, which are useful to project future population sizes of structured populations, we conducted demographic analysis when competition was (more than one larva per seed) and was not (one larva per seed) present. The hypothesis that competition reduces the finite rate of population growth, the survival of the immatures and the fecundity of females, influencing population persistence, was tested. To understand whether intraspecific competition is a common process in this system, the oviposition pattern was also studied. We found that in the presence of competition, the larvae from the third instar were smaller than those in the absence of competition and, in the presence of competition, fewer larvae reached the adult stage. Larval survival was lower in the presence of competition, particularly from the third larval stage until the pupal stage, and the fecundity of females was also reduced in the presence of competition, which affected the population structure. Although we showed that populations may either grow geometrically or go extinct in absence and presence of competition, respectively, the finite rates of population increase did not differ from 1.0 when compared to the estimated confidence intervals. Therefore, although larval competition may affect the structure of this seed‐feeding beetle, there is no clear evidence that this ecological process can negatively affect its persistence. Furthermore, most seeds with eggs had just one egg per seed, which suggests that competition should occur with low frequency under natural conditions.

Callosobruchus chinensis (Coleoptera: Chrysomelidae): Biology, life table parameters, host preferences, and evaluation of green gram germplasm for resistance

Pulse beetle (Coleoptera: Chrysomelidae) is a notable insect pest of green grams, garden peas, chickpeas, cowpeas, lentils, black grams, and pigeon peas. Callosobruchus chinensis L. can cause huge quantitative and qualitative losses and also decrease the nutritional values of stored grains/pulses. The biology, life table parameters, and host preference of C. chinensis were studied in three pulses - green grams, lentils, and cowpeas. We also evaluated the green gram germplasms for resistance to C. chinensis. Cowpea was the most appropriate host for the culturing of C. chinensis under laboratory conditions among the three pulses. C. chinensis exhibited higher fecundity, shorter development period, and longer female longevity in cowpeas than green grams and lentils. The relative growth rate of C. chinensis was 0.101 ± 0.006 mg/day. The finite growth rate, intrinsic rate of increase, and net reproduction rate demonstrated a faster increase in the C. chinensis population in cowpeas than green grams and lentils. We observed the overlapping patterns in the life expectancy, survival rate, and reproductive results of C. chinensis on cowpea, green gram, and lentil; this universal pattern is important in assessing the life table parameters. Based on growth index, we graded 20 green gram germplasms as resistant (6), moderately resistant (7), moderately susceptible (2), susceptible (3), and highly susceptible (2). The green gram germplasms resistant to C. chinensis, EC920900, IC616111, IC616247, IC616161, IC616258, and IC616138 have the potential in reducing the loss of green grams during storage. To summarize, cowpeas can be utilized for continuous mass rearing of C. chinensis in the laboratory and the resistant germplasms can be used as donor in future breeding programmes.

The Finite Size Lyapunov Exponent and the Finite Amplitude Growth Rate

The finite size Lyapunov exponent (FSLE) has been used extensively since the late 1990s to diagnose turbulent regimes from Lagrangian experiments and to detect Lagrangian coherent structures in geophysical flows and two-dimensional turbulence. Historically, the FSLE was defined in terms of its computational method rather than via a mathematical formulation, and the behavior of the FSLE in the turbulent inertial ranges is based primarily on scaling arguments. Here, we propose an exact definition of the FSLE based on conditional averaging of the finite amplitude growth rate (FAGR) of the particle pair separation. With this new definition, we show that the FSLE is a close proxy for the inverse structural time, a concept introduced a decade before the FSLE. The (in)dependence of the FSLE on initial conditions is also discussed, as well as the links between the FAGR and other relevant Lagrangian metrics, such as the finite time Lyapunov exponent and the second-order velocity structure function.

Long‐term abundance dynamics of the South American sea lion (Otaria flavescens) in the most important breeding colony in central Chile

AbstractLong‐term studies that monitor changes in the abundance of pinnipeds are particularly relevant given that these long‐lived species are considered to be indicators of the quality of the ecosystems around them. We report a continuous record of the total abundance by sex and age‐classes of the South American sea lion (Otaria flavescens) in Cobquecura, the most important breeding colony in central Chile over a twelve‐year period (2008 to 2020). We also analysed the demographic trends in South American sea lion abundance at this location. A total of 110 and 43 sea/land based and aerial censuses were performed over the studied period, respectively. The number of sea lions on land was highest in the summer months, which corresponds to the breeding season of the species. The abundance ranged from a minimum of 870 to a maximum of 4,531 individuals from sea/land‐based observations, and from 796 to 4,854 from aerial censuses. This variation was mainly influenced by the number of adult females, the most abundant age‐class in the colony. On the contrary, adult and sub‐adult males were least abundant in the population. The highest numbers of pups were registered in February of each year, ranging from 448 in February 2009 to 1,214 in February 2017. During the study period, we estimated a finite growth rate (λ) of 1.031, suggesting an increase in the population size in the colony, especially in the number of pups. Considering Cobquecura is highly susceptible to anthropogenic disturbance, developing effective long‐term protection through adequate management is critical to better conserve the South American sea lion in the most important breeding colony in central Chile.

Effect of RNAi targeting CYP6CY3 on the growth, development and insecticide susceptibility of Aphis gossypii by using nanocarrier-based transdermal dsRNA delivery system

RNA interference (RNAi) has been proved to be a viable method for agricultural pest control. Due to the limited uptake of dsRNA in hemiptera insects, this study used nanocarrier SPc (star polycation) transdermal delivery systems to deliver two truncated fragments (P1/P2) dsRNA of the CYP6CY3 for silencing this target gene in Aphis gossypii. After the cotton aphid was sprayed with the SPc + dsP1/P2 mixture, the expression level of target gene in SPc + dsP1 treatment group was not different from that in dsP1 group at 24 h, 48 h, and significantly lower than that in dsP1 group at 60 h, 72 h, respectively; and the expression level of target gene in SPc + dsP2 treatment group was not different from that in dsP2 group at 24 h, and significantly lower than that in dsP2 group from 48 h, 60 h, 72 h, respectively. In addition, the expression level was continuously silenced after spraying the SPc + dsP1/P2 mixture and significant reduced by 79.7% and 84.3% at 48 h compared with the H2O control group, the mortality rate reached 48.09% and 43.18% at 84 h, respectively. And the cumulative reproduction number of cotton aphids also decreased, but the cumulative death number of newborn nymphs had an increase trend, compared with the control groups. Bioassays after RNAi showed that the silencing of CYP6CY3 increased the susceptibility of the 4th instar aphid to imidacloprid, and increased mortality by 67.21% and 58.69% at 96 h, respectively. The life table parameters of the offspring from the 4th instar cotton aphids from the SPc + dsP1/P2 treatment groups showed that the offspring had a longer pre-reproductive period and post-reproductive period. The intrinsic growth rate was 0.231 ± 0.005, 0.210 ± 0.013 and the finite growth rate was 1.260 ± 0.007 and 1.234 ± 0.016 in the SPc + dsP1/P2 treatment group, these two parameters of the two groups were lower than that of the corresponding control，the population doubling time of the two groups was prolonged and the developmental duration was delayed. These results indicate that CYP6CY3 plays a key role in the growth, development, reproduction and detoxification ability in cotton aphids, and may be as a potential RNAi target for controlling aphids, laying the foundation for the development of new environmentally-friendly RNA pesticides in this field.

Some Population Aspects of Common Tern Sterna hirundo Breeding in Algeria at a Small Mediterranean Island (East Coast of Algeria)

Abstract We present the first detailed study of population dynamics, breeding biology and egg measurement of Common Terns. During six years (from 2004 to 2009) of monitoring, from mid-May to mid-August, 74 Common Terns individual were recorded at Laouinet small island, El Tarf, northeast of Algeria, witha finite population growth rate that indicated an alarming population decline(λ = -0.62: Lambda). Sterna hirundo build its nests (n = 37) in the northeast at a mean distance of 7.58 m from the closest edge of rocks. The nests were closed and ovoid, constituted mainly of mussel shells Sandpit, stems and leaves. Incubation was performed by pairs of common tern and lasted 25.5 ±3.4 days. We recorded a clutch size of 1 to 3 eggs with mean clutch size of 2.45±0.65 (41.24±0.83 × 30.46±0.62 mm). The egg parameters (volume, mass, shape index) varied between the six years of the study. The egg volume (19.24±0.87) depended more on egg width (30.46±0.62), however the egg shape (0.73±0.20) depended negatively on the egg length (41.24±0.83) but not on the egg width. Our results also showed a stabilized hatching success and a best estimation of breeding success. The hatching success did not vary between years: 70.5% in 2004, 68.75% in 2005, 71.42% in 2006, 71.42% in 2007, 69.23% in 2008 and 69.23% in 2009.

Better alone? A demographic case study of the hemiparasite Castilleja tenuiflora (Orobanchaceae): A first approximation

AbstractCastilleja tenuiflora is a facultative root hemiparasitic plant that has colonized a disturbed lava field in central Mexico. To determine the effects of hemiparasitism on the population dynamics of the parasite, we identified a set of potential hosts and quantified their effects on the vital rates of C. tenuiflora during 2016–2018. Connections between the roots of the hemiparasite and the hosts were confirmed with a scanning electron microscope. Annual matrices considering two conditions (with and without potential hosts) were built based on vital rates for each year, and annual stochastic finite rate growth rates (λs) were calculated. Plants produced more reproductive structures with hosts than without hosts. A Life Table Response Experiment (LTRE) was performed to compare the contributions of vital rates between conditions. We identified 19 species of potential hosts for this generalist hemiparasite. Stochastic lambda with hosts λs = 1.02 (CI = 0.9999, 1.1) tended to be higher than without them λs = 0.9503 (CI = 0.9055, 0.9981). The highest elasticity values correspond to survival. LTRE indicated that the most important parameters are survival and fecundity; the total contribution of fecundity (0.0192) to the difference in growth was three times lower than that of survival (0.0603). Piqueria trinervia was the most abundant host, and C. tenuiflora had a higher lambda with it than with other species. Individuals can grow alone, but hosts can have a positive effect on the vital parameters of C. tenuiflora and on λ.