The Experts below are selected from a list of 318 Experts worldwide ranked by ideXlab platform
Richard D Norris - One of the best experts on this subject based on the ideXlab platform.
-
Pelagic Species diversity, biogeography, and evolution
Paleobiology, 2020Co-Authors: Richard D NorrisAbstract:Pelagic (open-ocean) Species have enormous population sizes and broad, even global, distributions. These characteristics should damp rates of speciation in allopatric and vicariant evolutionary models since dispersal should swamp diverging populations and prevent divergence. Yet the fossil record suggests that rates of evolutionary turnover in Pelagic organisms are often quite rapid, comparable to rates observed in much more highly fragmented terrestrial and shallow-marine environments. Furthermore, genetic and ecological studies increasingly suggest that Species diversity is considerably higher in the Pelagic realm than inferred from many morphological taxonomies.Zoogeographic evidence suggests that ranges of many Pelagic groups are much more limited by their ability to maintain viable populations than by any inability to disperse past tectonic and hydrographic barriers to population exchange. Freely dispersing Pelagic taxa resemble airborne spores or wind-dispersed seeds that can drift almost anywhere but complete the entire life cycle only in favorable habitats. It seems likely that vicariant and allopatric models for speciation are far less important in Pelagic evolution than sympatric or parapatric speciation in which dispersal is not limiting. Nevertheless, speciation can be quite rapid and involve cladogenesis even in cases where morphological data suggest gradual Species transitions. Indeed, recent paleoecological and molecular studies increasingly suggest that classic examples of “phyletic gradualism” involve multiple, cryptic speciation events.Paleoceanographic and climatic change seem to influence rates of turnover by modifying surface water masses and environmental gradients between them to create new habitats rather than by preventing dispersal. Changes in the vertical structure and seasonality of water masses may be particularly important since these can lead to changes in the depth and timing of reproduction. Long-distance dispersal may actually promote evolution by regularly carrying variants of a Species across major oceanic fronts and exposing them to very different selection pressures than occur in their home range. High dispersal in Pelagic taxa also implies that extinction should be difficult to achieve except though global perturbations that prevent populations from reestablishing themselves following local extinction. High rates of extinction in some Pelagic groups suggests either that global perturbations are common, or that the Species are much more narrowly adapted than we would infer from current taxonomies.
-
Pelagic Species diversity biogeography and evolution
Paleobiology, 2000Co-Authors: Richard D NorrisAbstract:Abstract Pelagic (open-ocean) Species have enormous population sizes and broad, even global, distributions. These characteristics should damp rates of speciation in allopatric and vicariant evolutionary models since dispersal should swamp diverging populations and prevent divergence. Yet the fossil record suggests that rates of evolutionary turnover in Pelagic organisms are often quite rapid, comparable to rates observed in much more highly fragmented terrestrial and shallow-marine environments. Furthermore, genetic and ecological studies increasingly suggest that Species diversity is considerably higher in the Pelagic realm than inferred from many morphological taxonomies. Zoogeographic evidence suggests that ranges of many Pelagic groups are much more limited by their ability to maintain viable populations than by any inability to disperse past tectonic and hydrographic barriers to population exchange. Freely dispersing Pelagic taxa resemble airborne spores or wind-dispersed seeds that can drift almost ...
Isabel Palomera - One of the best experts on this subject based on the ideXlab platform.
-
trophic structure of Pelagic Species in the northwestern mediterranean sea
Journal of Sea Research, 2016Co-Authors: Marta Albopuigserver, Joan Navarro, Marta Coll, Craig A Layman, Isabel PalomeraAbstract:Ecological knowledge of food web interactions within Pelagic marine communities is often limited, impairing our capabilities to manage these ecologically and economically important marine fish Species. Here we used stable isotope analyses to investigate trophic interactions in the Pelagic ecosystem of the northwestern Mediterranean Sea during 2012 and 2013. Our results suggest that European sardine, Sardina pilchardus, and anchovy, Engraulis encrasicolus, are consumers located at relatively low levels of the Pelagic food web. Unexpectedly, the round sardinella, Sardinella aurita, appeared to be located at a higher trophic level than the other small Pelagic fish Species, although previous studies found similarity in their diets. Isotope data suggested that trophic niches of Species within the genera Trachurus spp. and Scomber spp., were distinct. Atlantic bonito Sarda sarda, European hake Merluccius merluccius and European squid Loligo vulgaris, appeared to feed at higher trophic levels than other Species. Despite some intraspecific seasonal variability for some Species, community trophic structure appeared relatively stable through the year. These data provide an important step for developing models of food web dynamics in the northwestern Mediterranean Sea.
S. R. Carpenter - One of the best experts on this subject based on the ideXlab platform.
-
Pelagic Species size distributions in lakes: Are they discontinuous?
Limnology and Oceanography, 2001Co-Authors: T. D. Havlicek, S. R. CarpenterAbstract:Aquatic ecologists have many models for size distributions of Pelagic communities. However, few studies have looked for discontinuities (clumps of similarly sized Species or gaps of sizes that contain no or relatively few Species) in Pelagic community size structure. We investigated size distribution characteristics in aquatic communities by calculating kernel density functions for plankton and fish in 11 lakes in Wisconsin. Size distributions in aquatic communities of these lakes were not smooth. Rather, multiple lump and gap regions were found within each functional group of phytoplankton, zooplankton, and fish. Simulations showed the gaps could not be explained by incomplete censuses of Species or by systematic underestimation of intraspecific size variation. In an experimentally enriched lake, before and after comparisons showed lumps were not affected by large additions of P and N, even though biomass and production changed substantially. Lump regions in the two lakes with both food web manipulations and nutrient enrichment were substantially less similar pre- versus postenrichment than the reference lake and the lake with only nutrients added, but lump number remained relatively unchanged. Lakes that differed widely in nutrient status, trophic structure, Species diversity, and area had similar size distributions. Comparisons of functional groups showed that phytoplankton had more lumps than zooplankton. In these north temperate lakes, size distribution characteristics seem to be conservative properties shaped by common regional ecosystem processes and organism patterns and not by lake-specific factors.
Joan Navarro - One of the best experts on this subject based on the ideXlab platform.
-
trophic structure of Pelagic Species in the northwestern mediterranean sea
Journal of Sea Research, 2016Co-Authors: Marta Albopuigserver, Joan Navarro, Marta Coll, Craig A Layman, Isabel PalomeraAbstract:Ecological knowledge of food web interactions within Pelagic marine communities is often limited, impairing our capabilities to manage these ecologically and economically important marine fish Species. Here we used stable isotope analyses to investigate trophic interactions in the Pelagic ecosystem of the northwestern Mediterranean Sea during 2012 and 2013. Our results suggest that European sardine, Sardina pilchardus, and anchovy, Engraulis encrasicolus, are consumers located at relatively low levels of the Pelagic food web. Unexpectedly, the round sardinella, Sardinella aurita, appeared to be located at a higher trophic level than the other small Pelagic fish Species, although previous studies found similarity in their diets. Isotope data suggested that trophic niches of Species within the genera Trachurus spp. and Scomber spp., were distinct. Atlantic bonito Sarda sarda, European hake Merluccius merluccius and European squid Loligo vulgaris, appeared to feed at higher trophic levels than other Species. Despite some intraspecific seasonal variability for some Species, community trophic structure appeared relatively stable through the year. These data provide an important step for developing models of food web dynamics in the northwestern Mediterranean Sea.
Marta Coll - One of the best experts on this subject based on the ideXlab platform.
-
trophic structure of Pelagic Species in the northwestern mediterranean sea
Journal of Sea Research, 2016Co-Authors: Marta Albopuigserver, Joan Navarro, Marta Coll, Craig A Layman, Isabel PalomeraAbstract:Ecological knowledge of food web interactions within Pelagic marine communities is often limited, impairing our capabilities to manage these ecologically and economically important marine fish Species. Here we used stable isotope analyses to investigate trophic interactions in the Pelagic ecosystem of the northwestern Mediterranean Sea during 2012 and 2013. Our results suggest that European sardine, Sardina pilchardus, and anchovy, Engraulis encrasicolus, are consumers located at relatively low levels of the Pelagic food web. Unexpectedly, the round sardinella, Sardinella aurita, appeared to be located at a higher trophic level than the other small Pelagic fish Species, although previous studies found similarity in their diets. Isotope data suggested that trophic niches of Species within the genera Trachurus spp. and Scomber spp., were distinct. Atlantic bonito Sarda sarda, European hake Merluccius merluccius and European squid Loligo vulgaris, appeared to feed at higher trophic levels than other Species. Despite some intraspecific seasonal variability for some Species, community trophic structure appeared relatively stable through the year. These data provide an important step for developing models of food web dynamics in the northwestern Mediterranean Sea.
