scholarly journals Extinction probabilities, times to extinction, basic reproduction number and growth rates for tsetse (Glossina spp) populations as a function of temperature

2019 ◽  
Author(s):  
Elisha B. Are ◽  
John W. Hargrove
Keyword(s):  
High Temperatures ◽  
Female Offspring ◽  
Extinction Probability ◽  
Tsetse Flies ◽  
Linear Type ◽  
Escape Extinction ◽  
Tsetse Population ◽  
Time To Extinction ◽  
Extinction Probabilities ◽  
Different Levels

AbstractIncreases in temperature over recent decades have led to a significant reduction in the populations of tsetse flies (Glossina spp) in parts of the Zambezi Valley of Zimbabwe. If this is true for other parts of Africa, populations of tsetse may actually be going extinct in some parts of the continent. Extinction probabilities for tsetse populations have not so far been estimated as a function of temperature. We develop a time-homogeneous branching process model for situations where tsetse flies live at different levels of fixed temperatures. We derive a probability distribution pk(T) for the number of female offspring an adult female tsetse is expected to produce in her lifetime, as a function of the fixed temperature at which she is living. We show that pk(T) can be expressed as a geometric series: its generating function is therefore a fractional linear type. We obtain expressions for the extinction probability, expected number of female offspring per female tsetse, and time to extinction. No tsetse population can escape extinction if subjected, for extended periods, to temperatures outside the range 16 °C - 32°C. Extinction probability increases more rapidly as temperatures approach and exceed the upper and lower limits. If the number of females is large enough, the population can still survive even at high temperatures (28°C - 31°C). Small decreases or increases in constant temperature in the neighbourhoods of 16°C and 31°C, respectively, can drive tsetse populations to extinction. Further study is needed to estimate extinction probabilities for tsetse populations in field situations where temperatures vary continuously.Author summaryTsetse flies (Glossina spp) are the vectors of the African sleeping sickness. We derived an expression for the extinction probability, and mean time to extinction, of closed populations of the flies experiencing different levels of fixed temperatures. Temperatures play a key role in tsetse population dynamics: no tsetse populations can escape extinction at constant temperatures < 16°C > 32°C. The effect of temperature is more severe if tsetse populations are already depleted. Increasingly high temperatures due to climate change may alter the distribution of tsetse populations in Africa. The continent may witness local extinctions of tsetse populations in some places, and appearances in places hitherto too cold for them.

scholarly journals Improved estimates for extinction probabilities and times to extinction for populations of tsetse (Glossina spp)

2018 ◽  
Author(s):  
Damian Kajunguri ◽  
Elisha B. Are ◽  
John W. Hargrove
Keyword(s):  
Adult Female ◽  
Low Temperatures ◽  
Extinction Probability ◽  
Tsetse Flies ◽  
Female Mortality ◽  
Real Possibility ◽  
The Real ◽  
Time To Extinction ◽  
Mean And Variance ◽  
The Mean

AbstractA published study used a stochastic branching process to derive equations for the mean and variance of the probability of, and time to, extinction in population of tsetse flies (Glossina spp) as a function of adult and pupal mortality, and the probabilities that a female is inseminated by a fertile male. The original derivation was partially heuristic and provided no proofs for inductive results. We provide these proofs, together with a more compact way of reaching the same results. We also show that, while the published equations hold good for the case where tsetse produce male and female offspring in equal proportion, a different solution is required for the more general case where the probability (β) that an offspring is female lies anywhere in the interval (0, 1). We confirm previous results obtained for the special case where β = 0.5 and show that extinction probability is at a minimum for β > 0.5 by an amount that increases with increasing adult female mortality. Sensitivity analysis showed that the extinction probability was affected most by changes in adult female mortality, followed by the rate of production of pupae. Because females only produce a single offspring approximately every 10 days, imposing a death rate of greater then about 3.5% per day will ensure the eradication of any tsetse population. These mortality levels can be achieved for some species using insecticide-treated targets or cattle – providing thereby a simple, effective and cost-effective method of controlling and eradicating tsetse, and also human and animal trypanosomiasis. Our results are of further interest in the modern situation where increases in temperature are seeing the real possibility that tsetse will go extinct in some areas, without the need for intervention, but have an increased chance of surviving in other areas where they were previously unsustainable due to low temperatures.Author summaryWe derive equations for the mean and variance of the probability of, and time to, extinction in population of tsetse flies (Glossina spp), the vectors of trypanosomiasis in sub-Saharan Africa. In so doing we provide the complete proofs for all results, which were not provided in a previously published study. We also generalise the derivation to allow the probability that an offspring is female to lie anywhere in the interval (0, 1). The probability of extinction was most sensitive to changes in adult female mortality. The unusual tsetse life cycle, with very low reproductive rates means that populations can be eradicated as long as adult female mortality is raised to levels greater than about 3.5% per day. Simple bait methods of tsetse control, such as insecticide-treated targets and cattle, can therefore provide simple, affordable and effective means of eradicating tsetse populations. The results are of further interest in the modern situation where increases in temperature are seeing the real possibility that tsetse will go extinct in some areas, but have an increased chance of surviving in others where they were previously unsustainable due to low temperatures.

The dual role of hermaphrodite in the Drosophila sex determination regulatory hierarchy

Development ◽  
1995 ◽  
Vol 121 (1) ◽  
pp. 99-111 ◽  
Author(s):  
M.A. Pultz ◽  
B.S. Baker
Keyword(s):  
Sex Determination ◽  
Dosage Compensation ◽  
Regulatory Protein ◽  
Female Offspring ◽  
Normal Female ◽  
Female Development ◽  
Salivary Gland Cells ◽  
Maternal Function ◽  
Different Levels

The hermaphrodite (her) locus has both maternal and zygotic functions required for normal female development in Drosophila. Maternal her function is needed for the viability of female offspring, while zygotic her function is needed for female sexual differentiation. Here we focus on understanding how her fits into the sex determination regulatory hierarchy. Maternal her function is needed early in the hierarchy: genetic interactions of her with the sisterless genes (sis-a and sis-b), with function-specific Sex-lethal (Sxl) alleles and with the constitutive allele SxlM#1 suggest that maternal her function is needed for Sxl initiation. When mothers are defective for her function, their daughters fail to activate a reporter gene for the Sxl early promoter and are deficient in Sxl protein expression. Dosage compensation is misregulated in the moribund daughters: some salivary gland cells show binding of the maleless (mle) dosage compensation regulatory protein to the X chromosome, a binding pattern normally seen only in males. Thus maternal her function is needed early in the hierarchy as a positive regulator of Sxl, and the maternal effects of her on female viability probably reflect Sxl's role in regulating dosage compensation. In contrast to her's maternal function, her's zygotic function in sex determination acts at the end of the hierarchy. This zygotic effect is not rescued by constitutive Sxl expression, nor by constitutive transformer (tra) expression. Moreover, the expression of doublesex (dsx) transcripts appears normal in her mutant females. We conclude that the maternal and zygotic functions of her are needed at two distinctly different levels of the sex determination regulatory hierarchy.

scholarly journals Modelling the impact of climate change on the distribution and abundance of tsetse in Northern Zimbabwe

2020 ◽  
Vol 13 (1) ◽  
Author(s):  
Joshua Longbottom ◽  
Cyril Caminade ◽  
Harry S. Gibson ◽  
Daniel J. Weiss ◽  
Steve Torr ◽  
...  
Keyword(s):  
Climate Change ◽  
Population Dynamics ◽  
Spatial Resolution ◽  
Air Temperature ◽  
Mechanistic Model ◽  
Tsetse Flies ◽  
Weather Station ◽  
Catch Data ◽  
Tsetse Population ◽  
The Impact

Abstract Background Climate change is predicted to impact the transmission dynamics of vector-borne diseases. Tsetse flies (Glossina) transmit species of Trypanosoma that cause human and animal African trypanosomiasis. A previous modelling study showed that temperature increases between 1990 and 2017 can explain the observed decline in abundance of tsetse at a single site in the Mana Pools National Park of Zimbabwe. Here, we apply a mechanistic model of tsetse population dynamics to predict how increases in temperature may have changed the distribution and relative abundance of Glossina pallidipes across northern Zimbabwe. Methods Local weather station temperature measurements were previously used to fit the mechanistic model to longitudinal G. pallidipes catch data. To extend the use of the model, we converted MODIS land surface temperature to air temperature, compared the converted temperatures with available weather station data to confirm they aligned, and then re-fitted the mechanistic model using G. pallidipes catch data and air temperature estimates. We projected this fitted model across northern Zimbabwe, using simulations at a 1 km × 1 km spatial resolution, between 2000 to 2016. Results We produced estimates of relative changes in G. pallidipes mortality, larviposition, emergence rates and abundance, for northern Zimbabwe. Our model predicts decreasing tsetse populations within low elevation areas in response to increasing temperature trends during 2000–2016. Conversely, we show that high elevation areas (> 1000 m above sea level), previously considered too cold to sustain tsetse, may now be climatically suitable. Conclusions To our knowledge, the results of this research represent the first regional-scale assessment of temperature related tsetse population dynamics, and the first high spatial-resolution estimates of this metric for northern Zimbabwe. Our results suggest that tsetse abundance may have declined across much of the Zambezi Valley in response to changing climatic conditions during the study period. Future research including empirical studies is planned to improve model accuracy and validate predictions for other field sites in Zimbabwe.

scholarly journals Asymptotic Behaviour of Extinction Probability of Interacting Branching Collision Processes

2014 ◽  
Vol 51 (1) ◽  
pp. 219-234 ◽  
Author(s):  
Anyue Chen ◽  
Junping Li ◽  
Yiqing Chen ◽  
Dingxuan Zhou
Keyword(s):  
Asymptotic Behaviour ◽  
Generating Function ◽  
Power Law ◽  
Simple Form ◽  
Extinction Probability ◽  
Positive Zero ◽  
Extinction Probabilities ◽  
Collision Processes

Although the exact expressions for the extinction probabilities of the Interacting Branching Collision Processes (IBCP) were very recently given by Chen et al. [4], some of these expressions are very complicated; hence, useful information regarding asymptotic behaviour, for example, is harder to obtain. Also, these exact expressions take very different forms for different cases and thus seem lacking in homogeneity. In this paper, we show that the asymptotic behaviour of these extremely complicated and tangled expressions for extinction probabilities of IBCP follows an elegant and homogenous power law which takes a very simple form. In fact, we are able to show that if the extinction is not certain then the extinction probabilities {an} follow an harmonious and simple asymptotic law of an ∼ kn-αρcn as n → ∞, where k and α are two constants, ρc is the unique positive zero of the C(s), and C(s) is the generating function of the infinitesimal collision rates. Moreover, the interesting and important quantity α takes a very simple and uniform form which could be interpreted as the ‘spectrum’, ranging from -∞ to +∞, of the interaction between the two components of branching and collision of the IBCP.

scholarly journals A Review of Ecological Factors Associated with the Epidemiology of Wildlife Trypanosomiasis in the Luangwa and Zambezi Valley Ecosystems of Zambia

2012 ◽  
Vol 2012 ◽  
pp. 1-13 ◽  
Author(s):  
Hetron Mweemba Munang'andu ◽  
Victor Siamudaala ◽  
Musso Munyeme ◽  
King Shimumbo Nalubamba
Keyword(s):  
National Parks ◽  
Ecological Factors ◽  
Tsetse Fly ◽  
Wildlife Habitat ◽  
Conservation Strategies ◽  
Tsetse Flies ◽  
Tsetse Population ◽  
Wide Range ◽  
Reservoir Hosts ◽  
Zambezi Valley

Trypanosomiasis has been endemic in wildlife in Zambia for more than a century. The disease has been associated with neurological disorders in humans. Current conservation strategies by the Zambian government of turning all game reserves into state-protected National Parks (NPs) and game management areas (GMAs) have led to the expansion of the wildlife and tsetse population in the Luangwa and Zambezi valley ecosystem. This ecological niche lies in the common tsetse fly belt that harbors the highest tsetse population density in Southern Africa. Ecological factors such as climate, vegetation and rainfall found in this niche allow for a favorable interplay between wild reservoir hosts and vector tsetse flies. These ecological factors that influence the survival of a wide range of wildlife species provide adequate habitat for tsetse flies thereby supporting the coexistence of disease reservoir hosts and vector tsetse flies leading to prolonged persistence of trypanosomiasis in the area. On the other hand, increase in anthropogenic activities poses a significant threat of reducing the tsetse and wildlife habitat in the area. Herein, we demonstrate that while conservation of wildlife and biodiversity is an important preservation strategy of natural resources, it could serve as a long-term reservoir of wildlife trypanosomiasis.

scholarly journals Extinction Probability of Interacting Branching Collision Processes

2012 ◽  
Vol 44 (1) ◽  
pp. 226-259 ◽  
Author(s):  
Anyue Chen ◽  
Junping Li ◽  
Yiqing Chen ◽  
Dingxuan Zhou
Keyword(s):  
Branching Process ◽  
Sufficient Conditions ◽  
Necessary And Sufficient Conditions ◽  
Extinction Probability ◽  
Hitting Times ◽  
Collision Process ◽  
Markov Branching Process ◽  
Extinction Probabilities ◽  
Collision Processes ◽  
Necessary And Sufficient

We consider the uniqueness and extinction properties of the interacting branching collision process (IBCP), which consists of two strongly interacting components: an ordinary Markov branching process and a collision branching process. We establish that there is a unique IBCP, and derive necessary and sufficient conditions for it to be nonexplosive that are easily checked. Explicit expressions are obtained for the extinction probabilities for both regular and irregular cases. The associated expected hitting times are also considered. Examples are provided to illustrate our results.

scholarly journals Spatial eco-evolutionary feedbacks mediate coexistence in prey-predator systems

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Eduardo H. Colombo ◽  
Ricardo Martínez-García ◽  
Cristóbal López ◽  
Emilio Hernández-García
Keyword(s):  
Spatial Distribution ◽  
Natural Selection ◽  
Evolutionary Dynamics ◽  
Interspecific Interactions ◽  
Perceptual Range ◽  
Limited Mobility ◽  
Extinction Probabilities ◽  
Key Factor ◽  
Different Levels ◽  
Predator Community

AbstractEco-evolutionary frameworks can explain certain features of communities in which ecological and evolutionary processes occur over comparable timescales. Here, we investigate whether an evolutionary dynamics may interact with the spatial structure of a prey-predator community in which both species show limited mobility and predator perceptual ranges are subject to natural selection. In these conditions, our results unveil an eco-evolutionary feedback between species spatial mixing and predators perceptual range: different levels of mixing select for different perceptual ranges, which in turn reshape the spatial distribution of prey and its interaction with predators. This emergent pattern of interspecific interactions feeds back to the efficiency of the various perceptual ranges, thus selecting for new ones. Finally, since prey-predator mixing is the key factor that regulates the intensity of predation, we explore the community-level implications of such feedback and show that it controls both coexistence times and species extinction probabilities.

The Effect of Temperature Changes on the Thyroid-Pituitary Relationship in Teleosts

1958 ◽  
Vol 35 (4) ◽  
pp. 824-831
Author(s):  
P. Y. FORTUNE
Keyword(s):  
High Temperatures ◽  
Environmental Temperature ◽  
Marked Effect ◽  
Term Effect ◽  
Effect Of Temperature ◽  
Thyroid Activity ◽  
Temperature Changes ◽  
Long Term Effect ◽  
Different Levels

1. It is confirmed that TSH has a more marked effect on the teleost thyroid at high temperatures. 2. The secretion of TSH is increased at high temperatures. 3. The temperature to which the animal is subjected prior to the experiment has no long-term effect on thyroid activity. 4. The thyroid-pituitary relationship is affected by temperature changes, and it is suggested that the TH:TSH ratio may be set at different levels by altering the environmental temperature.

scholarly journals PSX-3 The impact of energy nutrition planes of ewes on the productive and reproductive performance of their offspring

2019 ◽  
Vol 97 (Supplement_3) ◽  
pp. 468-468
Author(s):  
Fernanda F Santos ◽  
Mariluce C Oliveira ◽  
Flávia M Moreira ◽  
Lucas Péricles A Buzzato ◽  
Tamires S Santos ◽  
...  
Keyword(s):  
Reproductive Performance ◽  
Maternal Diet ◽  
Female Offspring ◽  
Metabolizable Energy ◽  
Mating Season ◽  
Chi Square ◽  
Female Progeny ◽  
Chi Square Test ◽  
The Impact ◽  
Different Levels

Abstract The objective of this study was to evaluate different levels of metabolizable energy (ME) intake of late-gestating ewes on the productive and reproductive performance of their female offspring. Seventy-one crossbred ewes were distributed in three treatments: CTL = ME level according to recommendations of the NRC (2007); LESS = CTL less 10% ME per kilogram of dry matter (DM); and PLUS = CTRL plus 10% ME per kilogram of DM. Ewes were synchronized with hormonal protocol, controlled natural mating, and confirmed pregnancy using ultrasonographic imaging. The diets were given at the end of gestation (50 days) through weaning (60 days). The female progeny, from birth to the first mating season, received the same nutrition and sanitary management as their dams. They were weighed every 15 days from birth to the eighth month of age (first mating season), and the mortality rate was measured. The mating season lasted 34 days. The confirmation of pregnancy was performed with 30 and 60 days. The chi-square test was used to compare mortality and pregnancy rates, all with a 5% probability. Ewes in the LESS diet presented lower birth weight up to 8 months of age when compared to CTL and PLUS diets (P &lt; 0.005), which were not different from each other (P &gt; 0.005). Mortality was influenced by the maternal diet (P = 0.0017), with values of 57.1, 20, and 7.41% for the LESS, CTL, and PLUS groups, respectively. The pregnancy rate was 21.4, 70 and 55.6% for the LESS, CTL, and PLUS groups, respectively, with a difference between them (P = 0.0390). We concluded that the supply of low energy diets for dams caused losses in the performance and reproduction indexes of replacement ewes.

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