scholarly journals Linking individual phenotype to density-dependent population growth: the influence of body size on the population dynamics of malaria vectors

2011 ◽  
Vol 278 (1721) ◽  
pp. 3142-3151 ◽  
Author(s):  
Tanya L. Russell ◽  
Dickson W. Lwetoijera ◽  
Bart G. J. Knols ◽  
Willem Takken ◽  
Gerry F. Killeen ◽  
...  
Keyword(s):  
Population Dynamics ◽  
Body Size ◽  
Population Growth ◽  
Vector Control ◽  
Anopheles Gambiae ◽  
Phenotypic Expression ◽  
Phenotypic Traits ◽  
Density Dependent ◽  
Individual Fitness ◽  
The Impact

Understanding the endogenous factors that drive the population dynamics of malaria mosquitoes will facilitate more accurate predictions about vector control effectiveness and our ability to destabilize the growth of either low- or high-density insect populations. We assessed whether variation in phenotypic traits predict the dynamics of Anopheles gambiae sensu lato mosquitoes, the most important vectors of human malaria. Anopheles gambiae dynamics were monitored over a six-month period of seasonal growth and decline. The population exhibited density-dependent feedback, with the carrying capacity being modified by rainfall (97% w AIC c support). The individual phenotypic expression of the maternal ( p = 0.0001) and current ( p = 0.040) body size positively influenced population growth. Our field-based evidence uniquely demonstrates that individual fitness can have population-level impacts and, furthermore, can mitigate the impact of exogenous drivers (e.g. rainfall) in species whose reproduction depends upon it. Once frontline interventions have suppressed mosquito densities, attempts to eliminate malaria with supplementary vector control tools may be attenuated by increased population growth and individual fitness.

scholarly journals Modelling the impact of vector control interventions on Anopheles gambiae population dynamics

2011 ◽  
Vol 4 (1) ◽  
Author(s):  
Michael T White ◽  
Jamie T Griffin ◽  
Thomas S Churcher ◽  
Neil M Ferguson ◽  
María-Gloria Basáñez ◽  
...  
Keyword(s):  
Population Dynamics ◽  
Vector Control ◽  
Anopheles Gambiae ◽  
Gambiae Population ◽  
The Impact

scholarly journals Contrasting size and fate of juvenile crown-of-thorns starfish linked to ontogenetic diet shifts

2020 ◽  
Vol 287 (1931) ◽  
pp. 20201052
Author(s):  
Jennifer C. Wilmes ◽  
Andrew S. Hoey ◽  
Morgan S. Pratchett
Keyword(s):  
Population Dynamics ◽  
Body Size ◽  
Coralline Algae ◽  
Phenotypic Traits ◽  
Diet Shift ◽  
Growth And Survival ◽  
Ontogenetic Diet Shift ◽  
Individual Fitness ◽  
Ontogenetic Diet Shifts ◽  
Diet Shifts

Population dynamics of organisms are shaped by the variation in phenotypic traits, often expressed even among individuals from the same cohort. For example, individual variation in the timing of ontogenetic shifts in diet and/or habitat greatly influences subsequent growth and survival of some organisms, with critical effects on population dynamics. Few studies of natural systems have, however, demonstrated that marked phenotypic variation in growth rates or body size among individuals within a modelled cohort is linked to dietary shifts and food availability. Population irruptions of the crown-of-thorns starfish are one of the foremost contributors to the global degradation of coral reefs, but causes of irruptions have been debated for decades. Here we demonstrate, based on extensive field sampling of juvenile starfish ( n = 3532), that marked variation in body size among juvenile starfish is linked to an ontogenetic diet shift from coralline algae to coral. This transition in diet leads to exponential growth in juveniles and is essential for individuals to reach maturity. Because smaller individuals experience higher mortality and growth is stunted on an algal diet, the ontogenetic shift to corallivory enhances individual fitness and replenishment success. Our findings suggest that the availability of coral prey facilitates early ontogenetic diet shifts and may be fundamental in initiating population irruptions.

scholarly journals Assessing the acoustic behaviour of Anopheles gambiae (s.l.) dsxF mutants: implications for vector control

2020 ◽  
Vol 13 (1) ◽  
Author(s):  
Matthew P. Su ◽  
Marcos Georgiades ◽  
Judit Bagi ◽  
Kyros Kyrou ◽  
Andrea Crisanti ◽  
...  
Keyword(s):  
Anopheles Gambiae ◽  
Population Control ◽  
Beat Frequency ◽  
Phenotypic Traits ◽  
Gene Drive ◽  
Anopheles Gambiae S.L ◽  
Female Genotype ◽  
Female Specific ◽  
The Impact ◽  
Dose Dependent

Abstract Background Release of gene-drive mutants to suppress Anopheles mosquito reproduction is a promising method of malaria control. However, many scientific, regulatory and ethical questions remain before transgenic mosquitoes can be utilised in the field. At a behavioural level, gene-drive carrying mutants should be at least as sexually attractive as the wildtype populations they compete against, with a key element of Anopheles copulation being acoustic courtship. We analysed sound emissions and acoustic preference in a doublesex mutant previously used to collapse Anopheles gambiae (s.l.) cages. Methods Anopheles rely on flight tones produced by the beating of their wings for acoustic mating communication. We assessed the impact of disrupting a female-specific isoform of the doublesex gene (dsxF) on the wing beat frequency (WBF; measured as flight tone) of males (XY) and females (XX) in homozygous dsxF− mutants (dsxF−/−), heterozygous dsxF− carriers (dsxF+/−) and G3 dsxF+ controls (dsxF+/+). To exclude non-genetic influences, we controlled for temperature and wing length. We used a phonotaxis assay to test the acoustic preferences of mutant and control mosquitoes. Results A previous study showed an altered phenotype only for dsxF−/− females, who appear intersex, suggesting that the female-specific dsxF allele is haplosufficient. We identified significant, dose-dependent increases in the WBF of both dsxF−/− and dsxF+/− females compared to dsxF+/+ females. All female WBFs remained significantly lower than male equivalents, though. Males showed stronger phonotactic responses to the WBFs of control dsxF+/+ females than to those of dsxF+/− and dsxF−/− females. We found no evidence of phonotaxis in any female genotype. No male genotypes displayed any deviations from controls. Conclusions A prerequisite for anopheline copulation is the phonotactic attraction of males towards female flight tones within mating swarms. Reductions in mutant acoustic attractiveness diminish their mating efficiency and thus the efficacy of population control efforts. Caged population assessments may not successfully reproduce natural mating scenarios. We propose to amend existing testing protocols to better reflect competition between mutants and target populations. Our findings confirm that dsxF disruption has no effect on males; for some phenotypic traits, such as female WBFs, the effects of dsxF appear dose-dependent rather than haplosufficient.

scholarly journals Increased natural mortality at low abundance can generate an Allee effect in a marine fish

2014 ◽  
Vol 1 (2) ◽  
pp. 140075 ◽  
Author(s):  
Anna Kuparinen ◽  
Jeffrey A. Hutchings
Keyword(s):  
Population Dynamics ◽  
Population Growth ◽  
Density Dependence ◽  
Gadus Morhua ◽  
Allee Effect ◽  
Population Regulation ◽  
Atlantic Cod ◽  
Adult Mortality ◽  
Natural Mortality ◽  
Density Dependent

Negative density-dependent regulation of population dynamics promotes population growth at low abundance and is therefore vital for recovery following depletion. Inversely, any process that reduces the compensatory density-dependence of population growth can negatively affect recovery. Here, we show that increased adult mortality at low abundance can reverse compensatory population dynamics into its opposite—a demographic Allee effect. Northwest Atlantic cod ( Gadus morhua ) stocks collapsed dramatically in the early 1990s and have since shown little sign of recovery. Many experienced dramatic increases in natural mortality, ostensibly attributable in some populations to increased predation by seals. Our findings show that increased natural mortality of a magnitude observed for overfished cod stocks has been more than sufficient to fundamentally alter the dynamics of density-dependent population regulation. The demographic Allee effect generated by these changes can slow down or even impede the recovery of depleted populations even in the absence of fishing.

scholarly journals Contrasting effects of the alkaloid ricinine on the capacity of Anopheles gambiae s.l. to transmit Plasmodium falciparum

2021 ◽  
Author(s):  
Domonbabele François de Sales Hien ◽  
Prisca S. L. Paré ◽  
Amanda Cooper ◽  
Benjamin K. Koama ◽  
Edwige Guissou ◽  
...  
Keyword(s):  
Growth Rate ◽  
Plasmodium Falciparum ◽  
Anopheles Gambiae ◽  
Ricinus Communis ◽  
Control Agent ◽  
Phenotypic Traits ◽  
Anopheles Coluzzii ◽  
Vector Borne Diseases ◽  
Anopheles Gambiae S.L ◽  
The Impact

Abstract Background: Besides feeding on blood, females of the malaria vector Anopheles gambiae s.l. readily feed on natural sources of plant sugars. The impact of toxic secondary phytochemicals contained in plant-derived sugars on mosquito physiology and on the development of Plasmodium parasites remains elusive. The focus of this study was to explore the influence of the alkaloid ricinine, found in the nectar of the castorbean Ricinus communis, on the mosquito ability to transmit Plasmodium falciparum. Methods: Females of Anopheles gambiae and its sibling species Anopheles coluzzii were exposed to ricinine through sugar feeding assays to assess the effect of this phytochemical on mosquito survival, the level of P. falciparum infection, and the growth rate of the parasite. Results: Ricinine induced a significant reduction in the longevity of both Anopheles species. Ricinine caused acceleration in the parasite growth rate with an earlier invasion of the salivary glands in both species. At a concentration of 0.04 g l-1 in An. coluzzii, ricinine had no effect on mosquito infection, while 0.08 g l-1 ricinine-5% glucose solution induced a 14% increase in An. gambiae infection rate. Conclusions: Overall, our findings reveal that consumption of certain nectar phytochemicals can have unsuspected and contrasting effects on key phenotypic traits that govern the intensity of malaria transmission. Further studies will be required before concluding on the putative role of ricinine as a novel control agent, including the development of ricinine-based toxic and transmission-blocking sugar baits. Testing other secondary phytochemicals in plant nectar will provide a broader understanding of the impact, which plants can have on the transmission of vector-borne diseases.

scholarly journals Reduced human-biting preferences of the African malaria vectors Anopheles arabiensis and Anopheles gambiae in an urban context: controlled, competitive host-preference experiments in Tanzania

2020 ◽  
Author(s):  
Yeromin P Mlacha ◽  
Prosper P. Chaki ◽  
Athuman Muhili ◽  
Dennis J. Massue ◽  
Marcel Tanner ◽  
...  
Keyword(s):  
Vector Control ◽  
Anopheles Gambiae ◽  
Anopheles Arabiensis ◽  
Host Preference ◽  
Urban Setting ◽  
Sub Saharan Africa ◽  
Rural Setting ◽  
Malaria Vectors ◽  
Baited Traps ◽  
The Impact

Abstract BackgroundHost preference is a critical determinant of human exposure to vector-borne infections and the impact of vector control interventions. Widespread use of long-lasting insecticide-treated nets (LLINs) and indoor residual spraying (IRS) across sub-Saharan Africa, which protect humans against mosquitoes, may select for altered host preference traits of malaria vectors over the long term. Here, the host preferences of Anopheles arabiensis and Anopheles gambiae sensu stricto (s.s.) were experimentally assessed in the field, using direct host-preference assays in two distinct ecological settings in Tanzania.MethodsEight Ifakara Tent Trap (ITT), four baited with humans and four with bovine calves, were simultaneously used to catch malaria vectors in open field sites in urban and rural Tanzania. The numbers of mosquitoes collected in human-baited traps versus calf-baited traps were used to estimate human feeding preference for each site's vector species. ResultsThe estimated proportion [95% confidence interval (CI)] of mosquitoes attacking humans rather than cattle was 0.60 [0.40, 0.77] for An. arabiensis in the rural setting and 0.61 [0.32, 0.85] for An. gambiae s.s. in the urban setting, indicating no preference for either host in both cases (P=0.32 and 0.46, respectively) and no difference in preference between the two (Odds Ratio (OR) [95%] = 0.95 [0.30, 3.01], P=0.924). However, only a quarter of An. arabiensis in the urban setting attacked humans (0.25 [0.09, 0.53]), indicating a preference for cattle that approached significance (P=0.08). Indeed, urban An. arabiensis were less likely to attack humans rather than cattle when compared to the same species in the rural setting (OR [95%] = 0.21 [0.05, 0.91], P =0.037). ConclusionUrban An. arabiensis had a stronger preference for cattle than the rural population and urban An. gambiae s.s. showed no clear preference for either humans or cattle. In the urban setting, both species exhibited stronger tendencies to attack cattle than previous studies of the same species in rural contexts. Cattle keeping may, therefore, particularly limit the impact of human-targeted vector control interventions in Dar es Salaam and perhaps in other African towns and cities.

Temporal change in body mass of two sympatric hamster species and implications for population dynamics

2014 ◽  
Vol 92 (5) ◽  
pp. 389-395 ◽  
Author(s):  
Chuan Yan ◽  
Tongqin Xu ◽  
Xiaoping Cao ◽  
Fusheng Wang ◽  
Shuqing Wang ◽  
...  
Keyword(s):  
Population Dynamics ◽  
Body Size ◽  
Body Mass ◽  
Northern China ◽  
Underlying Mechanism ◽  
Growth Data ◽  
Extrinsic Factors ◽  
Factors Affecting ◽  
Density Dependent ◽  
Maximum Body

Shifting of body size distributions of animals has been a long-time focus in population ecology, but the underlying mechanism of density-dependent changes in body size and its implications for population dynamics of animals are largely unknown. In this 26-year study, we investigated intrinsic and extrinsic factors affecting body mass of the Chinese striped hamster (Cricetulus barabensis Pallas, 1773) and the greater long-tailed hamster (Tscherskia triton de Winton, 1899) in the Northern China Plain. We proposed three hypotheses to explain body mass shifts in the two hamster species: growth, survival, and reproduction hypotheses. Our results showed that mean and maximum body masses of both hamster species were positively correlated with population density, and that this density-dependent change in body mass is more likely to be caused by a change in mortality rates, not by a change in growth rates or reproduction rates. The sustained decline of body mass during the study period was probably caused by increased mortality owing to an increase in the area of agricultural irrigation. Our results suggest that, under the condition of lacking survival and growth data, the maximum body mass (which represents survival rate), minimum body mass (which represents growth rate), and mean body mass are very useful criteria in revealing intrinsic and extrinsic effects on population dynamics and the underlying mechanisms.

GENETIC FEEDBACK AND SIMULATED ENVIRONMENTAL CATASTROPHES

1975 ◽  
Vol 107 (12) ◽  
pp. 1343-1348 ◽  
Author(s):  
William J. Sydor ◽  
David Pimentel
Keyword(s):  
Population Dynamics ◽  
Control System ◽  
Population Regulation ◽  
Feedback System ◽  
Plant Population ◽  
Common Occurrence ◽  
Feedback Systems ◽  
Population Mean ◽  
Density Dependent ◽  
The Impact

AbstractAn investigation was made of the impact of a series of environmental catastrophes upon herbivore population regulation through density-dependent genetic feedback interactions with simulated plants. Mean density and amplitude of fluctuation of the herbivore in the control system (only susceptible alleles in the plant population) were higher than in the genetic feedback system (3 resistant alleles and 3 susceptible alleles in the plant population). Mean density and amplitude of fluctuation of the herbivores in the catastrophic system (only susceptible alleles in the plant population and the herbivore population subject to a series of environmental catastrophes) were lower than in the control and genetic feedback systems, but both mean density and amplitude of fluctuation were higher than in the genetic feedback and catastrophic system (3 resistant and 3 susceptible alleles in the plant population and the herbivore population subject to a series of environmental catastrophes). The results of this experiment suggest that genetic feedback can exert a controlling influence in population dynamics even in systems where environmental catastrophes are a common occurrence.

scholarly journals Reduced human-biting preferences of the African malaria vectors Anopheles arabiensis and Anopheles gambiae in an urban context: controlled, competitive host-preference experiments in Tanzania

2020 ◽  
Vol 19 (1) ◽  
Author(s):  
Yeromin P. Mlacha ◽  
Prosper P. Chaki ◽  
Athuman Muhili ◽  
Dennis J. Massue ◽  
Marcel Tanner ◽  
...  
Keyword(s):  
Vector Control ◽  
Anopheles Gambiae ◽  
Anopheles Arabiensis ◽  
Host Preference ◽  
Urban Setting ◽  
Sub Saharan Africa ◽  
Rural Setting ◽  
Malaria Vectors ◽  
Baited Traps ◽  
The Impact

Abstract Background Host preference is a critical determinant of human exposure to vector-borne infections and the impact of vector control interventions. Widespread use of long-lasting insecticide-treated nets (LLINs) and indoor residual spraying (IRS) across sub-Saharan Africa, which protect humans against mosquitoes, may select for altered host preference traits of malaria vectors over the long term. Here, the host preferences of Anopheles arabiensis and Anopheles gambiae sensu stricto (s.s.) were experimentally assessed in the field, using direct host-preference assays in two distinct ecological settings in Tanzania. Methods Eight Ifakara Tent Trap (ITT), four baited with humans and four with bovine calves, were simultaneously used to catch malaria vectors in open field sites in urban and rural Tanzania. The numbers of mosquitoes collected in human-baited traps versus calf-baited traps were used to estimate human feeding preference for each site's vector species. Results The estimated proportion [95% confidence interval (CI)] of mosquitoes attacking humans rather than cattle was 0.60 [0.40, 0.77] for An. arabiensis in the rural setting and 0.61 [0.32, 0.85] for An. gambiae s.s. in the urban setting, indicating no preference for either host in both cases (P = 0.32 and 0.46, respectively) and no difference in preference between the two (Odds Ratio (OR) [95%] = 0.95 [0.30, 3.01], P = 0.924). However, only a quarter of An. arabiensis in the urban setting attacked humans (0.25 [0.09, 0.53]), indicating a preference for cattle that approached significance (P = 0.08). Indeed, urban An. arabiensis were less likely to attack humans rather than cattle when compared to the same species in the rural setting (OR [95%] = 0.21 [0.05, 0.91], P = 0.037). Conclusion Urban An. arabiensis had a stronger preference for cattle than the rural population and urban An. gambiae s.s. showed no clear preference for either humans or cattle. In the urban setting, both species exhibited stronger tendencies to attack cattle than previous studies of the same species in rural contexts. Cattle keeping may, therefore, particularly limit the impact of human-targeted vector control interventions in Dar es Salaam and perhaps in other African towns and cities.

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