Gregarious Behaviour of Evasive Prey

Lecture on the first SFB/TR 15 meeting, Gummersbach, July, 18 - 20, 2004We model the formation of a herd as a game between a predator and a prey population. The predator receives some information about the composition of the herd when he chases it, but receives no information when he chases a solitary individual. We describe situations in which the herd and its leader are in conflict and in which the leader bows to the herd’s wish but where this is not to the benefit of the herd

Gregarious Behaviour of Evasive Prey

Lecture on the first SFB/TR 15 meeting, Gummersbach, July, 18 - 20, 2004We model the formation of a herd as a game between a predator and a prey population. The predator receives some information about the composition of the herd when he chases it, but receives no information when he chases a solitary individual. We describe situations in which the herd and its leader are in conflict and in which the leader bows to the herd’s wish but where this is not to the benefit of the herd.

Gregarious Behaviour of Evasive Prey

Gregarious behavior of potential prey was explained by Hamilton (1971) on the basis of risk-sharing: The probability of being picked up by a predator is small when one makes part of a large aggregate of prey. This argument holds only if the predator chooses its victims at random. It is not the case for herds of evasive prey in the open, where prey’s gregarious behavior, favorable for the fast group members, makes it easier for the predator to home in on the slowest ones. We show conditions under which, gregarious behavior of the relatively fast prey individuals leaves slowest prey with no other choice but to join the group.Failing to do so would signal their vulnerability, making them a preferred target for the predator. Analysis of an n + 1 player game of a predator and n unequal prey individuals clarifies conditions for fully gregarious, partially gregarious, or solitary behavior of the prey.

Clinical Features, Cardiovascular Risk Profile, and Therapeutic Trajectories of Patients with Type 2 Diabetes Candidate for Oral Semaglutide Therapy in the Italian Specialist Care

Introduction: This study aimed to address therapeutic inertia in the management of type 2 diabetes (T2D) by investigating the potential of early treatment with oral semaglutide. Methods: A cross-sectional survey was conducted between October 2021 and April 2022 among specialists treating individuals with T2D. A scientific committee designed a data collection form covering demographics, cardiovascular risk, glucose control metrics, ongoing therapies, and physician judgments on treatment appropriateness. Participants completed anonymous patient questionnaires reflecting routine clinical encounters. The preferred therapeutic regimen for each patient was also identified. Results: The analysis was conducted on 4449 patients initiating oral semaglutide. The population had a relatively short disease duration (42%  60% of patients, and more often than sitagliptin or empagliflozin. Conclusion: The study supports the potential of early implementation of oral semaglutide as a strategy to overcome therapeutic inertia and enhance T2D management

Acute Delta Hepatitis in Italy spanning three decades (1991–2019): Evidence for the effectiveness of the hepatitis B vaccination campaign

Updated incidence data of acute Delta virus hepatitis (HDV) are lacking worldwide. Our aim was to evaluate incidence of and risk factors for acute HDV in Italy after the introduction of the compulsory vaccination against hepatitis B virus (HBV) in 1991. Data were obtained from the National Surveillance System of acute viral hepatitis (SEIEVA). Independent predictors of HDV were assessed by logistic-regression analysis. The incidence of acute HDV per 1-million population declined from 3.2 cases in 1987 to 0.04 in 2019, parallel to that of acute HBV per 100,000 from 10.0 to 0.39 cases during the same period. The median age of cases increased from 27 years in the decade 1991-1999 to 44 years in the decade 2010-2019 (p < .001). Over the same period, the male/female ratio decreased from 3.8 to 2.1, the proportion of coinfections increased from 55% to 75% (p = .003) and that of HBsAg positive acute hepatitis tested for by IgM anti-HDV linearly decreased from 50.1% to 34.1% (p < .001). People born abroad accounted for 24.6% of cases in 2004-2010 and 32.1% in 2011-2019. In the period 2010-2019, risky sexual behaviour (O.R. 4.2; 95%CI: 1.4-12.8) was the sole independent predictor of acute HDV; conversely intravenous drug use was no longer associated (O.R. 1.25; 95%CI: 0.15-10.22) with this. In conclusion, HBV vaccination was an effective measure to control acute HDV. Intravenous drug use is no longer an efficient mode of HDV spread. Testing for IgM-anti HDV is a grey area requiring alert. Acute HDV in foreigners should be monitored in the years to come

Is the contribution of Mathematical Models to Biology limited to supply correct predictions?

Abstract: Two simple mathematical models of Population Genetics are introduced to master students in Biology. The first model shows that, in asexual populations, frequency independent selection alone cannot explain the maintenance of polymorphisms. In the second we see that, with the introduction of sexual reproduction, natural selection may allow a stable polymorphism, at least in large populations. A necessary and sufficient condition for it, in the case of two alleles on one locus, is heterozygote advantage. The result is applied to the case of sickle-cell anemia, where a polymorphism is apparently maintained without heterozygote advantage. This example underlines how the contribution of a mathematical model to Biology is not only in supplying correct quantitative predictions, but also in forcing to reconsider the assumptions, hence the entire view of a situation, when the predictions do not fit reality

Evolutionary stable strategies and short term selection in Mendelian populations re-visited

Abstract This note concerns a one locus, two allele, random mating diploid population, subject to frequency-dependent viability selection. It is already known that in such a population, any evolutionarily stable strategies (ESS), if only accessible by the genotype-to-phenotype mapping, is the phenotypic image of a stable genetic equilibrium (Eshel, I. 1982. Evolutionarily stable strategies and viability selection in Mendelian populations. Theor. Popul. Biol. 22(2), 204–217; Cressman et al. 1996. Evolutionary stability in strategic models of single locus frequency-dependent viability selection. J. Math. Biol. 34, 707–733). The opposite is not true. We find necessary and sufficient parametric conditions for global convergence to the ESS, but we also demonstrate conditions under which, although a unique, genetically accessible ESS exists, there is another, ‘‘non-phenotypic’’ genetically stable equilibrium