ESAIM: Control, Optimisation and Calculus of Variations (1)
Oryx (1)
Fauna & Flora International - Oryx (1)
Potential ecological and socio-economic effects of a novel megaherbivore introduction: the hippopotamus in Colombia
Amanda L. Subalusky, Elizabeth P. Anderson, Germán Jiménez, David M. Post, David Echeverri Lopez, Sebastián García-R., Laura J. Nova León, Juan F. Reátiga Parrish, Ana Rojas, Sergio Solari, Luz F. Jiménez-Segura
Journal: Oryx , First View
Published online by Cambridge University Press: 20 December 2019, pp. 1-9
Introduced species can have strong ecological, social and economic effects on their non-native environment. Introductions of megafaunal species are rare and may contribute to rewilding efforts, but they may also have pronounced socio-ecological effects because of their scale of influence. A recent introduction of the hippopotamus Hippopotamus amphibius into Colombia is a novel introduction of a megaherbivore onto a new continent, and raises questions about the future dynamics of the socio-ecological system into which it has been introduced. Here we synthesize current knowledge about the Colombian hippopotamus population, review the literature on the species to predict potential ecological and socio-economic effects of this introduction, and make recommendations for future study. Hippopotamuses can have high population growth rates (7–11%) and, on the current trajectory, we predict there could be 400–800 individuals in Colombia by 2050. The hippopotamus is an ecosystem engineer that can have profound effects on terrestrial and aquatic environments and could therefore affect the native biodiversity of the Magdalena River basin. Hippopotamuses are also aggressive and may pose a threat to the many inhabitants of the region who rely upon the Magdalena River for their livelihoods, although the species could provide economic benefits through tourism. Further research is needed to quantify the current and future size and distribution of this hippopotamus population and to predict the likely ecological, social and economic effects. This knowledge must be balanced with consideration of social and cultural concerns to develop appropriate management strategies for this novel introduction.
Identification of morphometric traits for screening of tejocote (Crateagus spp.) germplasm for better yield potential
Carlos A. Núñez-Colín, Jaime Sahagún-Castellanos, Fernando González-Andrés, Alejandro F. Barrientos-Priego, Sergio Segura, Raúl Nieto-Ángel
Journal: Fruits / Volume 64 / Issue 1 / January 2009
Introduction. Tejocote (Crataegus spp.) is an edible fruit species that some Mesoamerican cultures have cultivated since pre-Hispanic times in Mexico; however, this fruit crop has not undergone formal breeding. It is unknown whether morphological markers associated with fruit size exist to be used for indirect selection; this could be important, because this species has a large cycle. Our research aimed at studying phenotypic correlations between leaf and stomata characters with fruit weight; such correlations might be used as morphological markers for selection of superior germplasm for fruit weight. Materials and methods. Pearson's correlation coefficients of 36 leaf variables and three leaf stomata variables with fruit weight were calculated in 94 genotypes of four different species. Results. As expected, the correlations calculated for each species and for the species pool differed. However, the number of veins in leaves of reproductive shoots was positively correlated with fruit weight (P ≤ 0.05) in the two most important horticultural species. On the other hand, C. mexicana was the best option for selecting superior germplasm, and the most significant variables correlated with fruit weight in this species were leaf major axis length of large vegetative shoots, leaf elongation ratio and number of veins of reproductive shoot leaves. Discussion. These variables could be good selection indices or morphological markers that can be used for early screening of germplasm for yield potential.
Uniqueness of solutions for some elliptic equations with a quadratic gradient term
David Arcoya, Sergio Segura de León
Journal: ESAIM: Control, Optimisation and Calculus of Variations / Volume 16 / Issue 2 / April 2010
Published online by Cambridge University Press: 19 December 2008, pp. 327-336
We study a comparison principle and uniqueness of positive solutions for the homogeneous Dirichlet boundary value problem associated to quasi-linear elliptic equations with lower order terms. A model example is given by
$ -\Delta u+\lambda\frac{|\nabla u|^2}{u^r} = f(x), \qquad\lambda,r>0.$
The main feature of these equations consists in having a quadratic gradient term in which singularities are allowed. The arguments employed here also work to deal with equations having lack of ellipticity or some dependence on u in the right hand side. Furthermore, they could be applied to obtain uniqueness results for nonlinear equations having the p-Laplacian operator as the principal part. Our results improve those already known, even if the gradient term is not singular.