Search results for " niche"
showing 10 items of 252 documents
'Niche Selection' and the evolution of a complex behavior in a changing environment--a simulation.
2000
One of the key problems in theoretical biology is the identification of the mechanisms underlying the evolution of complexity. This paper suggests that some difficulties in current models could be avoided by taking account of “niche selection” as proposed by Waddington [21] and subsequent authors [2]. Computer simulations, in which an evolving population of artificial organisms “selects” the niche(s) that maximize their fitness, are compared with a Control Model in which “Niche Selection” is absent. In the simulations the Niche Selection Model consistently produced a greater number of “fit” organisms than the Control Model; although the Niche Selection Model tended, in general, to produce o…
Changes in feeding niche widths of perch and roach following biomanipulation, revealed by stable isotope analysis
2008
Summary 1. We made an empirical test of a recent proposal that feeding niche widths might be determined as variance of stable isotope values. We determined δ13C and δ15N values of perch (Perca fluviatilis), roach (Rutilus rutilus) and their prey from a biomanipulated lake, when the mass removal of fish led to reduced inter- and intra-specific competition and increases in zooplankton abundance and body size. 2. After the first fish removals, both perch and roach mean δ13C values decreased and mean δ15N values increased, indicating a greater diet contribution from pelagic sources. 3. Variances of both δ13C and δ15N values first increased in both fish populations, indicating a wider food spect…
Integrating species distribution models (SDMs) and phylogeography for two species of AlpinePrimula
2012
The major intention of the present study was to investigate whether an approach combining the use of niche-based palaeodistribution modeling and phylo-geography would support or modify hypotheses about the Quaternary distributional history derived from phylogeographic methods alone. Our study system comprised two closely related species of Alpine Primula. We used species distribution models based on the extant distribution of the species and last glacial maximum (LGM) climate models to predict the distribution of the two species during the LGM. Phylogeographic data were generated using amplified fragment length polymorphisms (AFLPs). In Primula hirsuta, models of past distribution and phylo…
Paleodiversity of the Superfamily Ursoidea (Carnivora, Mammalia) in the Spanish Neogene, related to environmental changes
2014
In the present study we analyse the diversity of the Superfamily Ursoidea during the Neogene of the Iberian Peninsula to further compare it with that of the Neogene of Western Europe to find the different associations of this group. The results indicate that both the diversity and the taxonomy amongst these two regions show important variations, thus letting their interpretation in terms of climatic differentiation. We might relate variations in the abundance of the Ursoidea to the environmental fluctuations taking place during the Miocene and Pliocene. Therefore, they could enable us to reach the assessment of these biogeographical distributions in order to deduce the preferential niches o…
Unveiling community patterns and trophic niches of tropical and temperate ants using an integrative framework of field data, stable isotopes and fatt…
2018
Background: The use and partitioning of trophic resources is a central aspect of community function. On the ground of tropical forests, dozens of ant species may be found together and ecological mechanisms should act to allow such coexistence. One hypothesis states that niche specialization is higher in the tropics, compared to temperate regions. However, trophic niches of most species are virtually unknown. Several techniques might be combined to study trophic niche, such as field observations, fatty acid analysis (FAA) and stable isotope analysis (SIA). In this work, we combine these three techniques to unveil partitioning of trophic resources in a tropical and a temperate community. We d…
Reversible neural stem cell niche dysfunction in a model of multiple sclerosis
2011
Objective The subventricular zone (SVZ) of the brain constitutes a niche for neural stem and progenitor cells that can initiate repair after central nervous system (CNS) injury. In a relapsing-remitting model of experimental autoimmune encephalomyelitis (EAE), the neural stem cells (NSCs) become activated and initiate regeneration during acute disease, but lose this ability during the chronic phases of disease. We hypothesized that chronic microglia activation contributes to the failure of the NSC repair potential in the SVZ. Methods Using bromodeoxyuridine injections at different time points during EAE, we quantified the number of proliferating and differentiating progenitors, and evaluate…
Transdisciplinary niches fostering Lifelong Learning
2011
Abstract The purpose of this paper is to outline a new approach of lifelong learning in the light of transdisciplinarity niches. Considering the issues education is currently confronting, a way to find solutions to these problems could be transdisciplinary research, consisting in transdisciplinary niches. The paper continues some previous research made in “Lucian Blaga” University of Sibiu in order to adapt engineering education to lifelong learning. It also provides two examples of transdiciplinary niches presented in two doctoral theses, which are now developed by “EU 2020 research cluster” in the aforesaid university. Both theses require a transdisciplinary approach and involve fields fr…
David against Goliath: Diagnosis and Strategies for a Niche Sport to Develop a Sustainable Fan Community
2021
Pilota, played using the hands, is a niche sport with origins dating back to Greco-Roman times. In the Valencian region of Spain, an indigenous version of the sport is played with healthy participation rates despite having to compete with the major global sports. This study is aimed at understanding the current situation of this sport in terms of knowledge, transmission channels, fan experience and media consumption, as well as the brand strategy challenges it faces for building a stable and sustainable fan community. The methodology consists of a combination of quantitative and qualitative techniques. Nearly 1500questionnaires completed across three study universes, four focus groups and 3…
Leaps and bounds: geographical and ecological distance constrained the colonisation of the Afrotemperate by Erica.
2018
Abstract Background The coincidence of long distance dispersal (LDD) and biome shift is assumed to be the result of a multifaceted interplay between geographical distance and ecological suitability of source and sink areas. Here, we test the influence of these factors on the dispersal history of the flowering plant genus Erica (Ericaceae) across the Afrotemperate. We quantify similarity of Erica climate niches per biogeographic area using direct observations of species, and test various colonisation scenarios while estimating ancestral areas for the Erica clade using parametric biogeographic model testing. Results We infer that the overall dispersal history of Erica across the Afrotemperate…
Past climate changes facilitated homoploid speciation in three mountain spiny fescues (Festuca, Poaceae)
2016
Apart from the overwhelming cases of allopolyploidization, the impact of speciation through homoploid hybridization is becoming more relevant than previously thought. Much less is known, however, about the impact of climate changes as a driven factor of speciation. To investigate these issues, we selected Festuca picoeuropeana, an hypothetical natural hybrid between the diploid species F. eskia and F. gautieri that occurs in two different mountain ranges (Cantabrian Mountains and Pyrenees) separated by more than 400 km. To unravel the outcomes of this mode of speciation and the impact of climate during speciation we used a multidisciplinary approach combining genome size and chromosome coun…