Bifurcations in a discontinuous Leslie-Gower model with harvesting and alternative food for predators and constant prey refuge at low density.

Since environmental studies have shown that a constant quantity of prey become refuges from the predator at low densities and become accessible again for consumption when they reach a higher density, in this work we propose a discontinuous mathematical model, Lesli-Gower type, which describes the dynamics between prey and predators, interacting under the same environment, and whose predator functional response, of linear type, is altered by a refuge constant in the prey when below a critical value. Assuming that predators can be captured and have alternative food, the qualitative analysis of the proposed discontinuous model is performed by analyzing each of the vector fields that compose it, which serves as the basis for the calculation of the bifurcation curves of the discontinuous model, with respect to the threshold value of the prey and the harvest rate of predators. It is concluded that the perturbations of the parameters of the model leads either to the extinction of the predators or to a stabilization in the growth of both species, regardless of their initial conditions.

Bifurcations in discontinuous mathematical models with control strategy for a species.

In this paper a preliminary mathematical model is proposed, by means of a system of ordinary differential equations, for the growth of a species. In this case, the species does not interact with another species and is divided into two stages, those that have or have not reached reproductive maturity, with natural and control mortality for both stages. When performing a qualitative analysis to determine conditions in the parameters that allow the extinction or preservation of the species, a modification is made to the model when only control is assumed for each of the stages if the number of species in that stage is above a critical value.

Correlated Evolution of Acrobatic Display and Both Neural and Somatic Phenotypic Traits in Manakins (Pipridae).

Brightly colored manakin (Aves: Pipridae) males are known for performing acrobatic displays punctuated by non-vocal sounds (sonations) in order to attract dull colored females. The complexity of the display sequence and assortment of display elements involved (e.g.

Circulating adrenocorticotropic hormone levels, lactate levels, hematocrit and osmolality in relation to capture stress in Atlantic sharpnose sharks, Rhizoprionodon terraenovae.

Incidental capture of sharks during commercial and recreational fishing is of major conservation concern because of the potential effects it can have on physiological stress responses and survival. Endocrine aspects of the stress response are, however, poorly understood in elasmobranchs because of difficulties in measuring the primary glucocorticoid (1α-hydroxycorticosterone). Here, we combined measures of plasma adrenocorticotropic hormone (ACTH), the highly conserved pituitary hormone responsible for stimulating the release of adrenal/interrenal glucocorticoids, with measures of plasma lactate, osmolality, hematocrit, and behavior to gain a greater understanding of the capture stress response in Atlantic Sharpnose sharks, Rhizoprionodon terraenovae.

Nutrient foraging strategies are associated with productivity and population growth in forest shrubs.

Background And Aims: Temperate deciduous forest understoreys are experiencing widespread changes in community composition, concurrent with increases in rates of nitrogen supply. These shifts in plant abundance may be driven by interspecific differences in nutrient foraging (i.e.