Search results for " Ni"
showing 10 items of 3074 documents
Closely related crabs from opposite niches adopt different mechanisms to adjust oxygen transport
2008
The successful colonization of new environments is often achieved through adaptations or key innovations of existing physiological or biochemical mechanisms. The oxygen supply in marine invertebrates represent a complex and deeply integrated system which plays a fundamental role in animal adaptive plasticity. In particular, species which inhabit highly stochastic environments as shallow water or intertidal bands, have to cope with extremely different regimes of oxygen availability and effectively maintain a stable aerobic metabolism. Within this framework, we have focused on comparative physiology of Portunid Crabs hemocyanin, to evaluate the role molecular heterogeneity and functional plas…
Spatial structure and β-diversity of phytoplankton in Tibetan Plateau lakes: nestedness or replacement?
2017
Spatial patterns and β-diversity of phytoplankton assemblages depend on the relative importance of species dispersal capacity and species-sorting. Variability in species composition, composed by differences in species richness (nestedness) and/or species replacement, may be caused by niche availability and environmental selection. A field survey was carried out in Tibetan plateau on 38 lakes. Tibetan plateau lakes, located at high elevation, are harsh ecosystems characterized by low temperatures, low available nutrients, high UV amount, and strong salinity gradients. Only well-adapted species can survive in these environments. We therefore hypothesized that environmental filtering was the m…
Some like it deep : Intraspecific niche segregation in ruffe (Gymnocephalus cernua)
2017
Generalist fishes commonly show intraspecific niche segregation along the littoral–pelagic resource axis in lakes. Recent studies have shown that the deep, cold and seemingly unproductive profundal zone can also offer underutilised resources and facilitate specialised individuals, and can contribute to lake food webs via methane-derived carbon pathways. Despite numerous examples from salmonid fish species, such intraspecific niche segregation along a littoral–profundal resource axis has not been reported in percids or other predominantly littoral benthivorous fishes. Here, we describe a case of ruffe (Gymnocephalus cernua: Percidae) populations consisting of shallow- and deep-water dwelling…
Interactions between environmental variability and immigration rate control patterns of species diversity
2006
Abstract Theories focussing on local competition processes predict that species diversity is maximised with high-frequency environmental variability or alternatively with intermediate frequencies. The models coupling regional processes to local explanations of diversity patterns predict that the immigration rate from a regional species pool can strongly increase diversity. However, the interaction between local and regional processes in temporally fluctuating environment has received little attention. We explored in a simulation study how the patterns of species diversity are affected by the frequency spectrum of stochastic environmental variations and density independent immigration rate i…
2018
Marine life of the Southern Ocean has been facing environmental changes and the direct impact of human activities during the past decades. Benthic communities have particularly been affected by such changes although we only slowly understand the effect of environmental changes on species physiology, biogeography, and distribution. Species distribution models (SDM) can help explore species geographic responses to main environmental changes. In this work, we modeled the distribution of four echinoid species with contrasting ecological niches. Models developed for [2005-2012] were projected to different time periods, and the magnitude of distribution range shifts was assessed for recent-past c…
Stable isotopes reveal differences in diet among reed bunting subspecies that vary in bill size
2017
Reed bunting Emberiza schoeniclus subspecies vary considerably in bill size and shape and seem to be at an early stage of speciation, in which bill might be indirectly causing reproductive isolation. Hence, we evaluated whether bill size, as well as age and sex, are associated with foraging niche in three west European subspecies of reed bunting: the thin-billed schoeniclus, the intermediate-billed lusitanica and the thick-billed witherbyi. Blood sampling was undertaken at three sites in southwest Europe during the winter (when these subspecies co-occur), and stable isotope analyses (carbon and nitrogen) were performed to assess their foraging niches. Stable isotope analyses of potential fo…
2018
BackgroundThe 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 des…
Evolutionary ecology of fast seed germination—A case study in Amaranthaceae/Chenopodiaceae
2017
Abstract Germination is a vulnerable and risky step in a plant’s life cycle. Particularly under harsh environmental conditions, where time windows favourable for seedling establishment and survival are short or unpredictable, germination speed might play a highly adaptive role. We investigated the germination speed of 107 Amaranthaceae s.l. at two different temperatures and related the results to various plant and habitat traits taking into account the molecular phylogenetic relatedness of the species sampled. Germination speed is a fast evolving trait in Amaranthaceae s.l. It evolves towards significantly faster optima in C4 and halophyte lineages, albeit for different reasons. While C4 ph…
2018
Abstract Understanding the response of biodiversity to management, land use and climate change is a major challenge in farmland to halt the decline of biodiversity. Farmlands shelter a wide variety of taxa, which vary in their life cycle and habitat niches. Consequently, monitoring biodiversity from sessile annual plants to migratory birds requires dedicated protocols. In this article, we describe the protocols applied in a long-term research platform, the LTSER Zone Atelier “Plaine & Val de Sevre” (for a full description see Bretagnolle et al. (2018) [1] ). We present the data in the form of the description of monitoring protocols, which has evolved through time for arable weeds, grassland…