https://repositorio.utem.cl/handle/30081993/1362 Sat, 04 Apr 2026 12:52:34 GMT 2026-04-04T12:52:34Z https://repositorio.utem.cl/handle/30081993/1376 Prey gathering may act as a counterattack measure against predators. Cossa, Martina; Cravero, Ester; Pugliese, Masaki; Venturino, Ezio Two generalist predators not interfering with each other and hunting the same single prey that gathers in a herd are here considered. The system allows only two possible final outcomes, the prey-free state in which both predators thrive at their own carrying capacities, an equilibrium that is always present, and coexistence, which is not guaranteed to exist. When it arises, it does it in pair, of which one point is a saddle. As a result, the phase space is partitioned into two domains of attraction corresponding to these two equilibria. If the prey represents a pest, this result would provide a theoretical tool for its eradication, provided that it is coupled with some human external action, such as insecticide spraying, which however can be administered just in a mild way, sufficient to push the system trajectories into the prey-free point domain of attraction. If it is a species to be preserved instead, corresponding measures for enhancing its survival should be taken, such as increasing its reproductivity or lowering the predators’ pressure, so that the state of the system would fall into the attraction domain of the coexistence equilibrium. Pág. 40 – 49, gráficos, fórmulas, tablas. Mon, 01 Aug 2022 00:00:00 GMT https://repositorio.utem.cl/handle/30081993/1376 2022-08-01T00:00:00Z https://repositorio.utem.cl/handle/30081993/1375 Temporal dynamics of alcohol consumption patterns: The peer pressure and binge drinkers’ role. Gutiérrez, Rodrigo; Vergaño-Salazar, J.G.; Rojas-Jara, Claudio; Martínez-Jeraldo, Nicole Alcohol consumption is a problem of both social and health interest since consumption at an early age increases the probability of developing alcohol dependence, along with a series of risks associated with diseases, violence, and injuries. In young people, the first episode and recurrence of alcohol consumption usually occur in the form of binge drinking, in which peers assume a protective or risky role. Mathematical modeling of binge drinking has frequently been performed based on interactions with other consumption patterns, defined in terms of quantity and frequency, without considering that the periodicity of excessive (or compulsive) alcohol consumption is associated with specific social contexts, such as parties, where mainly social drinkers adopt this pattern. Our objective is to analyze the influence exerted by social drinkers on their peers who adopt excessive alcohol consumption, as well as the recurrence and persistence of harmful consumption. We formulate a mathematical model described by a Filippov system, where the “contagion” dynamic is based on two transfer sequences according to the workweek and weekend. Our findings establish that depending on the parameter values of the model, four asymptotic periodic dynamics can arise. In addition to this, the existence of a trade-off between protective and risk factors is evidenced, allowing evaluation of the effect of social variables on binge drinking prevalence. Pág. 27 – 39, gráficos, fórmulas, imágenes Mon, 01 Aug 2022 00:00:00 GMT https://repositorio.utem.cl/handle/30081993/1375 2022-08-01T00:00:00Z https://repositorio.utem.cl/handle/30081993/1374 When shape matters: using a simple mathematical model to estimate critical area sizes in conservation. Abreu de Assis, Raul; Coronel Malavazi, Mazílio; Pazim, Rubens; Canale, Gustavo; Cecconello, Moiseis; Teixeira da Fonseca, Odair José In the analysis of anthropogenic impact on the environment arises the question of whether the shapes of preserved habitat fragments play an important role in the conservation of wild species. In this work we use a very simple mathematical model based on a reaction-diffusion equation to analyze the effects of geometric shape and area on the permanence of populations in habitat fragments. Our results indicate that a dimensionless quantity calculated from a combination of biological variables is the main component that determines if the species survives in the preserved fragment and whether its geometric shape is important. We provide a methodology to calculate critical area sizes for which population size is most affected by fragment shape. The methodology is illustrated in a preliminary study, in which the model is used to estimate threshold area sizes for habitat fragments of a threatened species Sapajus xanthosternos. Pág. 12 – 26, gráficos, tablas, fórmulas, imágenes. Mon, 01 Aug 2022 00:00:00 GMT https://repositorio.utem.cl/handle/30081993/1374 2022-08-01T00:00:00Z https://repositorio.utem.cl/handle/30081993/1373 An algorithm for the identification of indicator taxonomic units and their use in analyses of ecosystem state. Vega, Hernán de la; Falco, Liliana; Saravia, Leonardo; Sandler, Rosana; Duhour, Andrés; Velazco, Víctor N.; Coviella, Carlos Biological community structure can be used as an ecological state descriptor, and the sensitivity of some taxonomic groups or biological entities to environmental conditions allows for their use as ecological state indicators. This work describes an algorithm developed for the identification of such taxonomic units when comparing environments or ecosystems under different anthropic impacts. Based solely on presence or absence information in a database, the algorithm identifies indicator taxonomic units for each environment, estimates the belonging of any additional samples to a given environment, approximates the ecological niche of any taxonomic unit based on two or more selected environmental factors, and analyzes the frequency of any taxonomic unit in a selected combination of the environmental factors chosen. By using the approximation to the ecological niche of the taxonomic units present, given a new sample, the physicochemical parameters of the environment it was taken can be estimated by the units present in the sample. These analyses can be performed simultaneously for two or more taxonomic units. This work provides a description of how the mathematical method was developed. Based on this methodology, a freely downloadable R package for easy use was developed, (Ecoindicators, DOI: https://github.com/lsaravia/EcoIndicators). One of the advantages of this method, and the R-package mentioned is that it can be used for any ecosystem for which there is a suitable biological dataset associated with environmental factors. In addition, both this mathematical procedure and the package referred to, can be tailored by other researchers to fit their own needs. Pág. 1 – 11, gráficos, tablas, fórmulas. Mon, 01 Aug 2022 00:00:00 GMT https://repositorio.utem.cl/handle/30081993/1373 2022-08-01T00:00:00Z