Intrinsic Population Growth Rate Research Articles

Sublethal and transgenerational effects of tetraniliprole on the tomato pinworm Phthorimaea (=Tuta) absoluta (Lepidoptera: Gelechiidae)

Invasive pest species of economic importance often require intensive pesticide use, leading to recurrent problems of pesticide resistance. Such is the case with the tomato pinworm, Phthorimaea (=Tuta) absoluta (Meyrick) (Lepidoptera: Gelechiidae), requiring the use of new insecticidal compounds for their management. Tetraniliprole, a novel insecticide effective against lepidopteran, coleopteran, and dipteran pests, is a potential alternative against the tomato pinworm. This study investigates the sublethal effects of tetraniliprole on the development and reproduction of the parental (F0) and progeny (F1) generations of P. absoluta while exploring the underlying mechanisms. Sublethal tetraniliprole exposure extended larval duration and reduced pupation rate, emergence rate, hatchability, and fecundity in both the F0 and F1 of P. absoluta. Additionally, the life-table parameters of the F1 generation were significantly altered, with decreases in net reproductive rate (R0) and increases in the mean generation time (T), leading to decreases in the intrinsic rate of population growth (r). The relative fitness of F1 insects exposed to tetraniloprole was reduced compared to unexposed insects (0.63 and 0.49, respectively). Furthermore, the mRNA expression levels of reproduction-related genes such as TaVg and TaVgR were down-regulated in the tetraniliprole-exposed insects. Finally, insect exposure to tetraniloprole increases the activity of the antioxidant enzymes such as glutathione S-transferase (GSTs), catalase (CAT), and superoxide dismutase (SOD). Taken together, these findings suggest that sublethal concentrations of tetraniloprole adversely affect both the development and reproduction of P. absoluta, providing a foundation for optimizing pest control strategies.

Exploring ocean pH dynamics via a mathematical modeling with the Caputo fractional derivative

AbstractGlobal warming is a complex problem with far-reaching global implications. One of its notable repercussions is the escalation of $$CO_2$$ C O 2 levels in the atmosphere, resulting in the phenomenon known as Ocean Acidification (OA). In this research, we have established a correlation between four key factors: marine species, human population, $$CO_2$$ C O 2 levels, and ocean pH. By formulating a Caputo fractional differential equation, we investigated the dynamics of these variables to evaluate the significance of this climatic phenomenon. The model analysis reveals that the rise in anthropogenic $$CO_2$$ C O 2 emissions causes a reduction in the ocean’s pH level and increases OA. This process, in turn, decreases the ocean’s ability to absorb $$CO_2$$ C O 2 , making it less effective in mitigating climate change. In this study, it was demonstrated that elevated levels of $$CO_2$$ C O 2 result in a reduction in pH levels, which in turn causes a decrease in the population of marine species that play a critical role in numerous economic sectors such as tourism, aquaculture, and fisheries. Moreover, we conducted a comprehensive analysis of the influence exerted by the intrinsic growth rate of the human population. We examined various theoretical aspects, including the assessment of existence and uniqueness. Numerical simulations are carried out to illustrate the effect of key parameters on the dynamics of the system using the generalized Adams–Bashforth–Moulton method.

On the deduction and quantification of irruptive dynamics in mountain pine beetle population and proxy data

AbstractIn attempting to develop a coherent description of the irruptive dynamics of mountain pine beetle (MPB) in North America, we examined a range of cases where authors described the dependency of intrinsic population growth rates on population attack levels. In some cases, detailed population data were used, but in most cases, investigators relied on operational aerial detection survey data. We found that study conclusions varied significantly depending on the type of data analysed and the spatial and temporal dimensions of the monitoring program. The ability to detect an intrinsic Allee effect (i.e., positive density‐dependent growth for low and rising population densities) depended on the type and the intensity of the sampling effort and the extent of sampling in space and time. Consequently, not all studies were able to quantify the irruption threshold (i.e., the population density at which endemic populations may transition towards the epidemic state). Notably, in every study where an Allee effect was demonstrated, investigators also identified at least one extrinsic environmental factor (e.g., winter weather, summer drought, microclimatic effect) that was regulating its strength. Our results suggest that population surveys conducted from the ground are a necessary complement to aerial survey data if the goal is to make inferences about the irruptive potential for MPB populations and the role of environmental factors in shaping that irruptive potential.

Examining Innovative Technologies: Nano-Chelated Fertilizers for Management of Wheat Aphid (Schizaphis graminum Rondani).

The use of nanofertilizers has both advantages and concerns. One benefit is that nano-fertilizers can enhance plant resistance against insect pests, making them a valuable strategy in integrated pest management (IPM). This study focused on the effect of wheat leaves treated with nano-chelated fertilizers and nitrogen (N) fertilizer on the wheat aphid (Schizaphis graminum Rondani), a harmful pest of wheat plants that transmits dangerous viruses. The nano-Cu treatment showed the longest pre-adult longevity. Additionally, the nano-Cu treatment resulted in the lowest adult longevity, fecundity, nymphoposition day number, intrinsic rate of population growth (r), finite rate of population increase (λ), and net reproductive rate (R0) and gross reproductive rate (GRR). Also, nano-Cu treatment led to the highest amount of (T). The N treatment led to the highest levels of fecundity, nymphoposition days, r, λ, and R0. Nano-Fe and nano-Zn demonstrated fewer negative effects on S. graminum life table parameters than nano-Cu. Our results indicate that N treatment yielded numerous advantageous effects on the wheat aphid while simultaneously impeding the efficacy of the aphid control program. Conversely, nano-Cu treatment exhibited a detrimental influence on various parameters of the aphid's life table, resulting in a reduction in the pest's fitness. Consequently, the integration of nano-Cu should be seriously considered as a viable option in the IPM of the wheat aphid.

Demography and life cycle of Daphnia Magna, subjected to the toxicity of andiroba oil used as a natural repelente

Daphnia magna is a common model organism used in toxicological testing because it is widely distributed in aquatic environments, has a short life cycle and is easy to rear in the laboratory. For the cultivation of cladocerans and for experiments, natural water and algae of the species Chlorella sorokiniana was used as diet. For Daphnia culture, modified EPA medium was used. And the general experimental conditions were: 50 mL transparent bottles, in a 1:1 ratio, of medium water and test substance, in treatments and control with medium water, where each test bottle received 10 neonates (<24 h) from the test organism, Daphnia magna. Calculations related to demographic analysis were determined, such as average lifespan, life expectancy, gross reproduction rate, net reproduction rate, generation time and intrinsic population growth rate. In general, the toxicity of andiroba oil promoted mortality in Daphnia magna compared to the control, regardless of any concentration tested. The fertility patterns of D. magna showed a decrease in the production of neonates with increasing andiroba oil concentration. The results of the experiment indicated that andiroba oil had toxic effects on Daphnia magna, being important to evaluate the safety of this chemical product, contributing significantly to the understanding of the risks associated with its use.

Effects of microbial-converted ancient permafrost organic carbon on the growth and reproduction of Daphnia magna.

Immense amounts of ancient (radiocarbon age over 200years) organic carbon (OC) from permafrost are released into aquatic systems. Ancient terrestrial OC exists in numerous aquatic ecosystems. It has been reported that ancient OC can be incorporated by consumers in aquatic ecosystems, but the effect of ancient OC on the growth of consumers has rarely been studied. In this study, we extracted ancient dissolved organic carbon (DOC) from frozen soils in an alpine lake catchment. After a 6-day microbial conversion period, the contents of ω3 and ω6 polyunsaturated fatty acids (PUFAs) in ancient DOC increased. Proteobacteria and Actinobacteria were the primary taxa consuming the permafrost DOC and generating fatty acids. In addition to the exclusive diet of soil DOC (containing bacteria) or Chlorella pyrenoidosa, mixed diets of Chlorella pyrenoidosa, and ancient DOC (containing bacteria) in ratios of 2:1, 1:1, and 1:2 (by carbon concentration) were used to feed Daphnia magna. We discovered that Daphnia reared on the mixture with the DOC:Chlorella ratio of 1:2 had the highest contents of ω3 PUFAs and FAs. Daphnia reared exclusively on Chlorella and the mixture with the DOC:Chlorella ratio of 1:2 had the largest body size (3.1-3.4mm) and the highest offspring production (95.5-96.2 ind-1). Daphnia fed on mixed diets exhibited higher intrinsic rates of population growth (0.48-0.53 d-1) compared to those fed exclusively on Chlorella pyrenoidosa, or ancient DOC plus bacteria. Overall, ancient soil OC converted by bacteria can act as a valuable supplement to algae food to promote Daphnia growth.

Gene drives for invasive wasp control: Extinction is unlikely, with suppression dependent on dispersal and growth rates.

Gene drives offer a potentially revolutionary method for pest control over large spatial extents. These genetic modifications spread deleterious variants through a population and have been proposed as methods for pest suppression or even eradication. We examined the influence of local dispersal, long-distance and/or human-mediated dispersal, and variation in population growth on the success of a gene drive for the control of invasive social wasps (Vespula vulgaris). Our simulations incorporated a spatially realistic environment containing variable habitat quality in New Zealand. Pest eradication was not observed, except in extreme and unrealistic scenarios of constant, widespread, and spatially intense releases of genetically modified individuals every year for decades. Instead, the regional persistence of genetically modified and wild-type wasps was predicted. Simulations using spatially homogeneous versus realistic landscapes (incorporating uninhabitable areas and dispersal barriers) showed little difference in overall population dynamics. Overall, little impact on wasp abundance was observed in the first 15 years after introduction. After 25 years, populations were suppressed to levels <95% of starting populations. Populations exhibited "chase dynamics" with population cycles in space, with local extinction occurring in some areas while wasps became abundant in others. Increasing the wasps' local dispersal distance increased the spatial and temporal variability of the occupied area and population suppression. Varying levels of human-associated long-distance dispersal had little effect on population dynamics. Increasing intrinsic population growth rates interacted with local dispersal to cause higher mean populations and substantially higher levels of variation in population suppression and the total amount of landscape occupied. Gene drives appear unlikely to cause a rapid and widespread extinction of this and probably other pests but could offer long-term and cost-effective methods of pest suppression. The predicted level of <95% pest suppression would substantially reduce the predation pressure and competitive interactions of this invasive wasp on native species. However, the predicted long-term persistence of genetically modified pests will influence the ethics and likelihood of using gene drives for pest control, especially given concerns that modified wasps would eventually be transported back to their home range.

Olfaction Response and Fertility Life Table Parameters of Tetrastichus howardi (Hymenoptera: Eulophidae) Parasitizing Plutella xylostella (Lepidoptera: Plutellidae) and the factitious host Tenebrio molitor (Coleoptera: Tenebrionidae).

Tetrastichus howardi (Olliff) (Hymenoptera: Eulophidae) parasitizes the diamond back moth Plutella xylostella (L.) (Lepidoptera: Plutellidae), but not much is known about its potential as a biocontrol agent. A rearing protocol has been established for this parasitoid on pupae of the factitious host Tenebrio molitor (L.) (Coleoptera: Tenebrionidae), with the aim of releasing it in the field to manage several lepidopteran species. The potential population growth of a parasitoid can be measured through fertility life tables and provide supporting information for using T. howardi in the management of P. xylostella. Also, the fitness and behavior of T. howardi reared on a factitious host can be indicators of its potential to control P. xylostella. Thus, in this study, the fertility life table parameters of T. howardi parasitizing P. xylostella were determined, as well as the effects of the natal host on the behavior of T. howardi towards host volatiles and parasitism rate. The results showed that net reproduction rate (Ro) and the intrinsic rate of population growth (rm) of T. howardi parasitizing P. xylostella were 13.6 (♀/♀) and 0.124 (♀/♀*day), respectively, whereas the mean generation time was 20.9days. Moreover, the natal host (T. molitor or P. xylostella) did not affect the fitness, parasitism rate, or olfactory response of T. howardi. In general, regardless of the natal host, parasitoid females responded to volatiles of both host species and exhibited the same rate of parasitism on P. xylostella. Therefore, T. howardi reared on the factitious host maintains its attraction and potential to parasitize P. xylostella, and can contribute to the biological control of this pest.

Tomato Aphid (Aphis gossypii) Secreted Saliva Can Enhance Aphid Resistance by Upregulating Signaling Molecules in Tomato (Solanum lycopersicum).

This study investigated the impact of Aphis gossypii watery saliva on the induction of tomato (Solanum lycopersicum) plant resistance. To examine the role of A. gossypii saliva, we collected watery saliva from A. gossypii after a 48 h feeding period on an artificial diet. SDS-PAGE resolving gel 12% was used to separate the salivary proteins. Relative expression of gene analysis revealed that the intrusion of A. gossypii saliva dripping onto S. lycopersicum leaves triggered robust defense responses mediated by a signaling molecule, i.e., salicylic acid, while the signaling molecule's jasmonic acid-dependent defense responses were moderately activated. Aphid saliva infiltrated S. lycopersicum leaves slowed the intrinsic rate of population growth of A. gossypii and significantly reduced the number of nymphs produced daily, compared to untreated leaves. During a choice test with untreated S. lycopersicum, aphids showed a repellent response towards saliva-infiltrated S. lycopersicum. Moreover, the (EPG) electrical penetration graph analysis demonstrated that the eating pattern of A. gossypii compared to untreated S. lycopersicum, that had been exposed to saliva was negatively impacted. These results provide compelling evidence for the involvement of salivary components of A. gossypii in inducing resistance against aphids in S. lycopersicum plants. Furthermore, the study underscores the crucial role of watery saliva in the intricate interactions between aphids and plants. The activation of pathways was also part of the defensive response (jasmonic acid (JA), salicylic acid (SA) signaling molecules). The findings of this research deliver valuable insights into the potential of watery aphid saliva as a natural defense mechanism against aphid infestations in S. lycopersicum crops.

Universal ontogenetic growth without fitted parameters: implications for life history invariants and population growth

Since the work of von Bertalanffy (Q Rev Boil 32:217–231, 1957), several models have been proposed that relate the ontogenetic scaling of energy assimilation and metabolism to growth, which are able to describe ontogenetic growth trajectories for living organisms and collapse them onto a single universal curve (West et al. in Nature 413:628–631, 2001; Barnavar et al. in Nature 420:626, 2002). Nevertheless, all these ontogenetic growth models critically depend on fitting parameters and on the allometric scaling of the metabolic rate. Using a new metabolic rate relation (Escala in Theor Ecol 12(4):415–425, 2019) applied to a Bertalanffy-type ontogenetic growth equation, we find that ontogenetic growth can also be described by a universal growth curve for all studied species, but without the aid of any fitting parameters (i.e., no fitting procedure is performed on individual growth curves). We find that the inverse of the heart frequency mathrm f_H, rescaled by the ratio of the specific energies for biomass creation and metabolism, defines the characteristic timescale for ontogenetic growth. Moreover, our model also predicts a generation time and lifespan that explain the origin of several “Life History Invariants’ (Charnov in Oxford University Press, Oxford, 1993) and predict that the Malthusian parameter should be inversely proportional to both the generation time and lifespan, in agreement with the data in the literature (Duncan et al. in Ecology 88:324–333 2007; Dillingham et al. in Paper 535, 2016; Hatton et al. in PNAS 116(43):21616–21622 2019). In our formalism, several critical timescales and rates (lifespan, generation time, and intrinsic population growth rate) are all proportional to the heart frequency mathrm f_H, and thus, their allometric scaling relations come directly from the allometry of the heart frequency, which is typically mathrm f_H propto M^{-0.25} under basal conditions.

Sublethal granulovirus infections in the tomato leafminer,Tuta absoluta: transmission and population‐level effects

AbstractGranuloviruses are insect viruses commonly used as biological insecticides for pest control in agriculture. Most pest control programs rely on the most virulent strains and doses to cause acute mortality events. However, we hypothesize that sublethal infections are key to maintaining persistent epidemics that regulate pest populations in the long‐term. The tomato leafminer (TLM),Tuta absoluta(Meyrick) (=Phthorimaea absolutaMeyrick) (Lepidoptera: Gelechiidae), is one of the most limiting pests of greenhouse and field tomatoes. Previous efforts have identified a strain ofPhthorimaea operculellagranulovirus (PhopGV), coded VG013, associated with field populations of the TLM, which causes significant acute mortalities and is being used as active ingredient of a biological insecticide. The aim of this study was to determine the effect of sublethal infections and transmission mechanisms of PhopGV‐VG013 on TLM populations. Six viral doses were tested for their virulence and effects on TLM development rate, and intrinsic population growth rate. A sublethal dose was selected to compare the density‐dependent mortality of TLM populations and vertical transmission was examined by testing for PhopGV in the offspring of surviving infected individuals. Horizontal transmission was assessed by testing for PhopGV in frass of infected larvae, and the infection of virus‐free larvae confined with infected larvae in the same leaf. We found that sublethal doses of PhopGV have slight effects on TLM population growth rates, and none on the strength of density‐dependent mortality. Although we found for the first time that PhopGV‐VG013 is transmitted to approximately 7.5% of the offspring of individuals that survive the virus challenge, we found no evidence suggesting horizontal transmission from sublethal infections. Our results show that sublethal infections of highly virulent ganulovirus strains may favor long‐term pathogen persistence but have a limited role in host population regulation.

Magnetized vermiculite as a tool for the treatment of produced water generated by oil companies: Effects on aquatic organisms before and after treatment.

Produced water (PW) generated by oil companies is a highly impacting waste that contains chemicals such as metals and organic and inorganic compounds. Given its polluting potential, PW requires effective treatment before being discharged into the environment. Conventional treatments have limited efficiency in removing PW toxicity, so alternative approaches must be developed and standardized. In this context, treatment with adsorbent materials like magnetized vermiculite (VMT-mag) is highlighted. This work aimed to evaluate the efficiency of treatment with VMT-mag in reducing PW toxicity to aquatic biota. For this purpose, three aquatic species (the midge Chironomus riparius, the planarian Girardia tigrina, and the crustacean Daphnia magna) were exposed to untreated PW and to PW treated with VMT-mag at laboratory conditions. The assessed endpoints included mortality, growth, emergence, and developmental time of C. riparius; mortality, locomotion, feeding, and head regeneration of G. tigrina; and intrinsic population growth rate (r) and reproductive output of D. magna. The results showed that all the species exposed to raw PW were impaired: C. riparius had delayed development, G. tigrina had reduced locomotor activity and delayed head regeneration, and D. magna had reduced reproduction and delayed intrinsic population growth rate (r). Most of the analyzed parameters showed that treatment with VMT-mag diminished PW toxicity. Therefore, using VMT-mag to treat PW may be the key to reducing the PW effects on aquatic organisms.

Forecasting the potential distribution of invasive leafminer pests, Liriomyza spp. (Diptera: Agromyzidae), and their natural enemies

AbstractThree species of polyphagous Liriomyza leafminers (Diptera: Agromyzidae), Liriomyza huidobrensis, L. sativae, and L. trifolii, are internationally significant pests of vegetable and nursery crops that have each been recently detected on the Australian mainland. Due to the early stages of these invasions in Australia, it is unclear how climatic conditions are likely to support and potentially restrict the distribution of these species as they expand into novel ranges and threaten agricultural production regions. Additionally, it is unclear how natural enemies, particularly parasitoid wasps, will mitigate the impacts of these pests. Here, we predicted the future establishment potential of L. huidobrensis, L. sativae and L. trifolii in Australia, as well as two cosmopolitan parasitoid wasps known to provide control of the flies in both field and glasshouse settings, Diglyphus isaea (Hymenoptera: Eulophidae) and Hemiptarsenus varicornis (Hymenoptera: Eulophidae). Global distribution data spanning 42 countries were compiled and used to validate a process‐based model of establishment potential based on intrinsic population growth rates. The modelling approach successfully captured the international distribution of the three Liriomyza species based on environmental variables and predicted the high suitability of non‐occupied ranges in Australia. The largely unfilled climatic niche available to these pests demonstrates the early stages of their Australian invasions and highlights locations where vegetable production regions are at particular risk. In addition to Australia, our results highlight many regions globally where L. sativae, L. trifolii and L. huidobrensis have the potential to spread in the future. Within Australia, D. isaea and H. varicornis are predicted to have a large spatial and seasonal overlap with each Liriomyza species and thus are expected to influence the future spread of these pests and play an important role in local pest management programs.

A predator-prey model for the optimal control of fish harvesting through the imposition of a tax

This paper is devoted to the study of ecosystem based fisheries management. The model represents the interaction between prey and predator population with Holling II functional response consisting of different carrying capacities and constant intrinsic growth rates. We have considered the continuous harvesting of predator only. It is observed that if the intrinsic growth rate of predator population crosses a certain critical value, the system enters into Hopf bifurcation. Our observations indicate that tax, the management object in fisheries system play huge impacts on this system. The optimal harvesting policy is disposed by imposing a tax per unit of predator biomass. The optimal harvest strategy is determined using Pontryagin's maximum principle, which is subject to state equations and control limitations. The implications of tax are also examined. We have derived different bifurcations and global stability of the system. Finally, numerical simulations are used to back up the analytical results.

Rapid evolution of unimodal but not of linear thermal performance curves in Daphnia magna.

Species may cope with warming through both rapid evolutionary and plastic responses. While thermal performance curves (TPCs), reflecting thermal plasticity, are considered powerful tools to understand the impact of warming on ectotherms, their rapid evolution has been rarely studied for multiple traits. We capitalized on a 2-year experimental evolution trial in outdoor mesocosms that were kept at ambient temperatures or heated 4°C above ambient, by testing in a follow-up common-garden experiment, for rapid evolution of the TPCs for multiple key traits of the water flea Daphnia magna. The heat-selected Daphnia showed evolutionary shifts of the unimodal TPCs for survival, fecundity at first clutch and intrinsic population growth rate toward higher optimum temperatures, and a less pronounced downward curvature indicating a better ability to keep fitness high across a range of high temperatures. We detected no evolution of the linear TPCs for somatic growth, mass and development rate, and for the traits related to energy gain (ingestion rate) and costs (metabolic rate). As a result, also the relative thermal slope of energy gain versus energy costs did not vary. These results suggest the overall (rather than per capita) top-down impact of D. magna may increase under rapid thermal evolution.

Effects of salinity on survival, reproductive performance, population growth, and life stage composition in the calanoid copepod Acartia bilobata

Copepods are a critical live prey item for most marine finfish larvae in the natural environment. The calanoid copepod belonging to species Acartia is a potential live food for the larval rearing of marine finfishes because of their higher productivity and tolerance to wide range of salinities. The present study was conducted to determine the effect of salinity on production parameters to standardize the optimal salinity for Acartia bilobata culture. For selecting the optimal salinity range, the adult copepods were exposed to abrupt salinity change from 30 g L−1 to ten salinity levels, including 0, 5, 10, 15, 20, 25, 30, 35, 40 and 45 g L−1 and their survival estimated after 24 h. Further, the effect of salinity (15, 20,25,30, and 35 g L−1) on egg production, hatching success and population growth were studied. Following sudden salinity change, A. bilobata could tolerate a wide range of salinities from 15 to 35 g L−1, and no copepod survived below 10 g L−1 and above 35 g L−1. Average daily egg production was significantly higher at 25 and 30 g L−1 (32 ± 1 and 34 ± 2 eggs female−1 day−1). A remarkably low egg hatching success was recorded at 15 g L−1 salinity; however, all other tested salinities showed similar egg hatching success. Different salinity levels did not affect the sex ratio of A. bilobata. A significantly higher total population number (1539 ± 75) and intrinsic population growth rate (0.50 ± 0.00) was observed at 30 g L−1, followed by 25 g L−1 salinity. The lowest mean population (518 ± 19) and population growth rate (0.39 ± 0.00) were recorded at 15 g L−1 salinity. The study results suggested that 25–30 g L−1 is the optimal salinity range to achieve maximal production of A. bilobata.

Time-lagged effects of habitat fragmentation on terrestrial mammals in Madagascar.

Biodiversity is severely threatened by habitat destruction. As a consequence of habitat destruction, the remaining habitat becomes more fragmented. This results in time-lagged population extirpations in remaining fragments when these are too small to support populations in the long term. If these time-lagged effects are ignored, the long-term impacts of habitat loss and fragmentation will be underestimated. We quantified the magnitude of time-lagged effects of habitat fragmentation for 157 nonvolant terrestrial mammal species in Madagascar, one of the biodiversity hotspots with the highest rates of habitat loss and fragmentation. We refined species' geographic ranges based on habitat preferences and elevation limits and then estimated which habitat fragments were too small to support a population for at least 100 years given stochastic population fluctuations. We also evaluated whether time-lagged effects would change the threat status of species according to the International Union for the Conservation of Nature (IUCN) Red List assessment framework. We used allometric relationships to obtain the population parameters required to simulate the population dynamics of each species, and we quantified the consequences of uncertainty in these parameter estimates by repeating the analyses with a range of plausible parameter values. Based on the median outcomes, we found that for 34 species (22% of the 157 species) at least 10% of their current habitat contained unviable populations. Eight species (5%) had a higher threat status when accounting for time-lagged effects. Based on 0.95-quantile values, following a precautionary principle, for 108 species (69%) at least 10% of their habitat contained unviable populations, and 51 species (32%) had a higher threat status. Our results highlight the need to preserve continuous habitat and improve connectivity between habitat fragments. Moreover, our findings may help to identify species for which time-lagged effects are most severe and which may thus benefit the most from conservation actions.

Evolution of population dynamics following invasion by a non-native predator.

Invasive predatory species are frequently observed to cause evolutionary responses in prey phenotypes, which in turn may lead to evolutionary shifts in the population dynamics of prey. Research has provided a link between rates of predation and the evolution of prey population growth in the lab, but studies from natural populations are rare. Here, we tested for evolutionary changes in population dynamics parameters of zooplankton Daphnia pulicaria following invasion by the predator Bythotrephes longimanus into Lake Kegonsa, Wisconsin, US. We used a resurrection ecological approach, whereby clones from pre‐ and post‐invasive periods were hatched from eggs obtained in sediment cores and were used in a 3‐month growth experiment. Based on these data, we estimated intrinsic population growth rates (r), the shape of density dependence (θ) and carrying capacities (K) using theta‐logistic models. We found that post‐invasion Daphnia maintained a higher r and K under these controlled, predation‐free laboratory conditions. Evidence for changes in θ was weaker. Whereas previous experimental evolution studies of predator–prey interactions have demonstrated that genotypes that have evolved under predation have inferior competitive ability when the predator is absent, this was not the case for the Daphnia. Given that our study was conducted in a laboratory environment and the possibility for genotype‐by‐environment interactions, extrapolating these apparent counterintuitive results to the wild should be done with caution. However, barring such complications, we discuss how selection for reduced predator exposure, either temporally or spatially, may have led to the observed changes. This scenario suggests that complexities in ecological interactions represents a challenge when predicting the evolutionary responses of population dynamics to changes in predation pressure in natural systems.

EXTINCTION AND PERSISTENCE OF A HARVESTED PREY–PREDATOR MODEL INCORPORATING GROUP DEFENCE AND DISEASE IN PREY: SPECIAL EMPHASIS ON STOCHASTIC ENVIRONMENT

In this paper, a nonlinear stochastic eco-epidemic model is presented to study the dynamics of harvested prey–predator model with group defence. One of the key roles of forming a group is to defend themselves from the attack of the predators. Since prey population spreads infection through direct contact; we consider two groups of prey population. Using some certain assumptions, a stochastic model is formulated by considering noisy intrinsic growth rate of susceptible pest population, death rate of infected pest and predator populations, respectively. Next, the existence and uniqueness of positive solution are performed using comparison theorem of stochastic differential equations (SDEs). The boundedness and uniform continuity of the system are analyzed. Then, the bionomic equilibrium and optimal harvesting policy are obtained by using stochastic maximum principle. We verify the conditions of extinction and persistence in mean with the numerical results. To verify our consideration with the reality, the effects of harvesting effort and catchability coefficient are observed. In addition, infected and uninfected regions are reported to specify the infection free system.

Estimating somatic growth of fishes from maximum age or maturity

Growth in body size is a key life-history trait that has coevolved and is interlinked with maturation, maximum age, mortality, generation time, and the intrinsic rate of population growth. Growth parameters are therefore required inputs in the majority of assessment models used in conservation or fisheries management. However, because of the difficulties involved in the proper aging of individuals, growth parameters are unknown for the vast majority of species. Here, two new data-limited methods are presented to estimate somatic growth from maximum length combined with either length or age at maturation or with maximum age. A comparison with existing growth parameters of fishes (Actinopterygii and Elasmobranchii) shows that the estimates of the new methods fall within the range of established methods. The new methods apply to species with indeterminate growth, such as fishes or invertebrates, and were used here to produce the first growth parameter estimates for 110 species of fishes.