Search results for "SPECIES RICHNESS"
showing 10 items of 427 documents
Inferring the Relative Resilience of Alternative States
2013
Ecological systems may occur in alternative states that differ in ecological structures, functions and processes. Resilience is the measure of disturbance an ecological system can absorb before changing states. However, how the intrinsic structures and processes of systems that characterize their states affects their resilience remains unclear. We analyzed time series of phytoplankton communities at three sites in a floodplain in central Spain to assess the dominant frequencies or "temporal scales" in community dynamics and compared the patterns between a wet and a dry alternative state. The identified frequencies and cross-scale structures are expected to arise from positive feedbacks that…
Biodiversidad en el Siglo XXI: más allá del conteo de especies
2018
In modern ecology, the traditional diversity indexes (usually of richness, abundance, and species evenness) have been highly revealing and useful for monitoring community and ecosystem processes. However, around two decades ago, a pioneering research team noticed that these indexes did not completely resolve their open questions. Thus, they suggested changing the way biodiversity was measured. At its base, this new methodology considers the distance between species (in phylogenetic or functional terms) before subsequently applying the appropriate biodiversity indexes. Including phylogenetic and functional elements in the evaluation of diversity allows us to approach the concept of biodivers…
The role of landscape, topography, and geodiversity in explaining vascular plant species richness in a fragmented landscape
2016
We explained vascular plant species richness patterns in a 286 km(2) fragmented landscape with a notable human influence. The objective of this study was two-fold: to test the relative importance of landscape, topography and geodiversity measures, and to compare three different landscape-type variables in species richness modeling. Moreover, we tested if results differ when only native species are considered. We used generalized linear modeling based variation partitioning and generalized additive models with different explanatory variable sets. Landscape and topography explained the majority of the variation but the relative importance of topography and geodiversity was higher in explainin…
Meiobenthic naidid and aeolosomatid oligochaetes from the profundal zone, and relations of species to eutrophication
1989
Oligochaetes were sampled using meiobenthos methods from depths of between 20 and 94 m in Lake Paijanne in 1986. Individuals belonging to several species of the Naididae and Aeolosomatidae, which are generally considered to include mainly littoral or lotic species, were found more or less regularly at these profundal depths. The naidid species Chaetogaster langi and Arnphichaeta leydigii were more abundant in the deepest areas than at 20 m. Species also appeared to react differently to water quality. The naidid species Chaetogaster langi and the aeolosomatid species Aeolosoma quaternarium, A. hernprichi and Rheomorpha neiswestnovae were most abundant on average at oligotrophic, unpolluted s…
Selecting networks of nature reserves: methods do affect the long-term outcome
1999
Data on vascular plants of boreal lakes in Finland were used to compare the efficiency of reserve selection methods in representing four aspects of biodiversity over a 63 year period. These aspects included species richness, phylogenetic diversity, restricted range diversity and threatened species. Our results show that the efficiency of reserve selection methods depends on the selection criteria used and on the aspect of biodiversity under consideration. Heuristic methods and optimizing algorithms were nearly equally efficient in selecting lake networks over a small geographical range. In addition, a scoring procedure was observed to be efficient in maintaining different aspects of biodive…
Food plant diversity as broad-scale determinant of avian frugivore richness.
2007
The causes of variation in animal species richness at large spatial scales are intensively debated. Here, we examine whether the diversity of food plants, contemporary climate and energy, or habitat heterogeneity determine species richness patterns of avian frugivores across sub-Saharan Africa. Path models indicate that species richness of Ficus (their fruits being one of the major food resources for frugivores in the tropics) has the strongest direct effect on richness of avian frugivores, whereas the influences of variables related to water–energy and habitat heterogeneity are mainly indirect. The importance of Ficus richness for richness of avian frugivores diminishes with decreasing sp…
Phytoplankton strategies and diversity under different nutrient levels and planktivorous fish densities in a shallow Mediterranean lake
2005
Two mesocosm experiments were carried out to investigate the dynamic effects of nutrients (nitrogen and phosphorus) and planktivorous fish additions on phytoplankton strategies and diversity. The phylogenetic and functional approaches were used to understand phytoplankton ecology in shallow Mediterranean lakes. The experimental approach is new for the study of algal functional groups. Nutrient loading and fish stocks enhanced biomass of small algae but decreased phytoplankton diversity and species richness. Faster species replacement and fluctuations in diversity occurred above loadings of 1 μM P and 21 μM N. Mesotrophic conditions favoured a diverse pool of species, including nostocales an…
Seawater carbonate chemistry and biogenic habitat shifts under long-term ocean acidification
2023
Experiments have shown that increasing dissolved CO2 concentrations (i.e. Ocean Acidification, OA) in marine ecosystems may act as nutrient for primary producers (e.g. fleshy algae) or a stressor for calcifying species (e.g., coralline algae, corals, molluscs). For the first time, rapid habitat dominance shifts and altered competitive replacement from a reef-forming to a non-reef-forming biogenic habitat were documented over one-year exposure to low pH/high CO2 through a transplant experiment off Vulcano Island CO2 seeps (NE Sicily, Italy). Ocean acidification decreased vermetid reefs complexity via a reduction in the reef-building species density, boosted canopy macroalgae and led to chang…
Seawater carbonate chemistry and fish communities properties off CO2 seeps in Japan
2020
Ocean acidification will likely change the structure and function of coastal marine ecosystems over coming decades. Volcanic carbon dioxide seeps generate dissolved CO2 and pH gradients that provide realistic insights into the direction and magnitude of these changes. Here, we used fish and benthic community surveys to assess the spatio-temporal dynamics of fish community properties off CO2 seeps in Japan. Adding to previous evidence from ocean acidification ecosystem studies conducted elsewhere, our findings documented shifts from calcified to non-calcified habitats with reduced benthic complexity. In addition, we found that such habitat transition led to decreased diversity of associated …
Seawater carbonate chemistry and coralline algal diversity
2021
Calcified coralline algae are ecologically important in rocky habitats in the marine photic zone worldwide and there is growing concern that ocean acidification will severely impact them. Laboratory studies of these algae in simulated ocean acidification conditions have revealed wide variability in growth, photosynthesis and calcification responses, making it difficult to assess their future biodiversity, abundance and contribution to ecosystem function. Here, we apply molecular systematic tools to assess the impact of natural gradients in seawater carbonate chemistry on the biodiversity of coralline algae in the Mediterranean and the NW Pacific, link this to their evolutionary history and …