The Experts below are selected from a list of 2835 Experts worldwide ranked by ideXlab platform
John K. B. Ford - One of the best experts on this subject based on the ideXlab platform.
-
Dietary Overlap and niche partitioning of sympatric harbour porpoises and Dall’s porpoises in the Salish Sea
Progress in Oceanography, 2013Co-Authors: Linda M. Nichol, Anna M. Hall, Graeme M. Ellis, Eva Stredulinsky, Melissa Boogaards, John K. B. FordAbstract:Abstract Ecological theory regarding the coexistence of similar species predicts resource partitioning will arise through competition and lead to different ecological niches. The diets of harbour porpoises (Phocoena phocoena) and Dall’s porpoises (Phocoenoides dalli) in the Salish Sea were investigated for evidence of resource partitioning between these ecologically similar species. Stomach contents of 36 harbour porpoises and 11 Dall’s porpoises were analysed and ten and six fish taxa were identified in each, respectively. Pacific herring (Clupea pallasi) was important in the diet of both porpoise species and walleye pollock (Theragra chalcogramma) was second in importance in the Dall’s porpoises. Pacific herring was estimated to contribute 60% to the total caloric intake of harbour porpoises. In addition to herring, Pacific hake (Merluccius productus), walleye pollock and a species of Pyschrolutidae were present in the diet of both porpoise species. Pianka’s Index of niche Overlap indicated substantial Dietary Overlap between the porpoise species based on measures of prey frequency of occurrence and prey percent numerical abundance. These results seem contrary to predictions from ecological theory. However, habitat and activity pattern differences between the two porpoise species exist and represent other dimensions of niche that likely contribute to resource partitioning in ways that were not strongly evident in stomach contents. Dall’s porpoises, which prefer deeper water habitat in the Salish Sea than harbour porpoises, may feed more on walleye pollock which spawn in deep water. Dall’s porpoises are also known to feed at night when lipid-rich mesopelagic prey such as Myctophidae and Bathylagidae, both present in the Dall’s porpoise samples, migrate upwards from depths in excess of 200 m. In contrast shiner perch, present only in harbour porpoise samples, is a species associated with shallow nearshore habitats. Resource partitioning is also likely to occur in accordance with seasonal prey availability.
-
Dietary Overlap and niche partitioning of sympatric harbour porpoises and dall s porpoises in the salish sea
Progress in Oceanography, 2013Co-Authors: Linda M. Nichol, Anna M. Hall, Graeme M. Ellis, Eva Stredulinsky, Melissa Boogaards, John K. B. FordAbstract:Abstract Ecological theory regarding the coexistence of similar species predicts resource partitioning will arise through competition and lead to different ecological niches. The diets of harbour porpoises (Phocoena phocoena) and Dall’s porpoises (Phocoenoides dalli) in the Salish Sea were investigated for evidence of resource partitioning between these ecologically similar species. Stomach contents of 36 harbour porpoises and 11 Dall’s porpoises were analysed and ten and six fish taxa were identified in each, respectively. Pacific herring (Clupea pallasi) was important in the diet of both porpoise species and walleye pollock (Theragra chalcogramma) was second in importance in the Dall’s porpoises. Pacific herring was estimated to contribute 60% to the total caloric intake of harbour porpoises. In addition to herring, Pacific hake (Merluccius productus), walleye pollock and a species of Pyschrolutidae were present in the diet of both porpoise species. Pianka’s Index of niche Overlap indicated substantial Dietary Overlap between the porpoise species based on measures of prey frequency of occurrence and prey percent numerical abundance. These results seem contrary to predictions from ecological theory. However, habitat and activity pattern differences between the two porpoise species exist and represent other dimensions of niche that likely contribute to resource partitioning in ways that were not strongly evident in stomach contents. Dall’s porpoises, which prefer deeper water habitat in the Salish Sea than harbour porpoises, may feed more on walleye pollock which spawn in deep water. Dall’s porpoises are also known to feed at night when lipid-rich mesopelagic prey such as Myctophidae and Bathylagidae, both present in the Dall’s porpoise samples, migrate upwards from depths in excess of 200 m. In contrast shiner perch, present only in harbour porpoise samples, is a species associated with shallow nearshore habitats. Resource partitioning is also likely to occur in accordance with seasonal prey availability.
Jesper Madsen - One of the best experts on this subject based on the ideXlab platform.
-
Resource partitioning in sympatric arctic‐breeding geese: summer habitat use, spatial and Dietary Overlap of Barnacle and Pink‐footed Geese in Svalbard
Ibis, 2020Co-Authors: Nina E Eide, Espen Bergersen, Jesper MadsenAbstract:The spatial, habitat and Dietary Overlap of two breeding goose species was studied in Sassendalen, Svalbard, in summer 2003 based on abundance within 500 × 500-m grid squares and faecal diet analyses during pre-breeding, nesting and post-hatching periods. More than half of all Pink-footed Geese Anser brachyrhynchus occurred in the absence of Barnacle Geese Branta leucopsis during nesting and post-hatching periods compared to c. 20% when concentrated by pre-breeding snow cover. In contrast, only 5% of Barnacle Geese were observed in the absence of Pink-footed Geese pre-breeding, 15% during nesting, and 35% post-hatching. Among six defined habitat types, Barnacle Geese resorted more to ‘upland’ habitats during pre-breeding and nesting and to lowland lakes post-hatching when compared to Pink-footed Geese. Although Pink-footed Geese showed less change in seasonal habitat preference, many shifted to the river valley bottom post-hatching, giving access to open water (predator avoidance) and lush green vegetation (foraging for goslings). The smallest extent of distributional Overlap between the two species occurred post-hatching, but each species was also highly restricted by snow cover during pre-nesting. The greatest extent of Overlap in distribution and diet occurred during incubation, when large Dietary variation between different breeding valleys reflected local food availability around nests (probably a result of nest-site preference rather than food selection per se ). Whether this means that increased interactions within and between the two goose species with future increases in local density are most likely to be manifest at this stage of the summer is impossible to determine without knowledge of available food resources and manipulative experiments. More detailed investigations of the effects of foraging by both species on plant structure, quality and community composition are necessary to predict likely outcomes of future changes in population densities of both species.
-
resource partitioning in sympatric arctic breeding geese summer habitat use spatial and Dietary Overlap of barnacle and pink footed geese in svalbard
Ibis, 2009Co-Authors: Nina E Eide, Espen Bergersen, Jesper MadsenAbstract:The spatial, habitat and Dietary Overlap of two breeding goose species was studied in Sassendalen, Svalbard, in summer 2003 based on abundance within 500 × 500-m grid squares and faecal diet analyses during pre-breeding, nesting and post-hatching periods. More than half of all Pink-footed Geese Anser brachyrhynchus occurred in the absence of Barnacle Geese Branta leucopsis during nesting and post-hatching periods compared to c. 20% when concentrated by pre-breeding snow cover. In contrast, only 5% of Barnacle Geese were observed in the absence of Pink-footed Geese pre-breeding, 15% during nesting, and 35% post-hatching. Among six defined habitat types, Barnacle Geese resorted more to ‘upland’ habitats during pre-breeding and nesting and to lowland lakes post-hatching when compared to Pink-footed Geese. Although Pink-footed Geese showed less change in seasonal habitat preference, many shifted to the river valley bottom post-hatching, giving access to open water (predator avoidance) and lush green vegetation (foraging for goslings). The smallest extent of distributional Overlap between the two species occurred post-hatching, but each species was also highly restricted by snow cover during pre-nesting. The greatest extent of Overlap in distribution and diet occurred during incubation, when large Dietary variation between different breeding valleys reflected local food availability around nests (probably a result of nest-site preference rather than food selection per se ). Whether this means that increased interactions within and between the two goose species with future increases in local density are most likely to be manifest at this stage of the summer is impossible to determine without knowledge of available food resources and manipulative experiments. More detailed investigations of the effects of foraging by both species on plant structure, quality and community composition are necessary to predict likely outcomes of future changes in population densities of both species.
-
minimal intra seasonal Dietary Overlap of barnacle and pink footed geese on their breeding grounds in svalbard
Polar Biology, 2007Co-Authors: Espen Bergersen, Ingunn M Tombre, Jesper MadsenAbstract:We analysed barnacle Branta leucopsis and pink-footed goose Anser brachyrhynchus summer diets (May–July 2003) based on the proportions of different plant constituents in the faecal material of adult breeding birds in Sassendalen, Svalbard to assess potential inter-specific competition. Diets were highly restricted and Overlapped little during pre-nesting and post hatch. During incubation both species showed greatest variety in their diet, reflecting site-specific differences in local food abundance. However, locally the diets of pink-footed and barnacle geese resembled each other most at this time (although still differing significantly). The conflicting needs of nest defence and maintenance of body condition constrains the extent of the feeding resource utilised by nesting pairs and explains slightly greater Dietary Overlap at this time. Hence, there is little evidence of inter-specific competition (interference or depletion) at present, but this is most likely to be manifest during the incubation period in the future if goose numbers continue to increase. More detailed investigations of the degree of spatial Overlap of the two species and their effects on plant structure, quality and community composition are necessary to predict likely outcomes of expected increases in numbers of both goose species.
Renzo Perissinotto - One of the best experts on this subject based on the ideXlab platform.
-
coexistence of habitat specialists under environmental change investigating Dietary Overlap in two brachyuran species at peritidal stromatolite ecosystems
Estuaries and Coasts, 2019Co-Authors: Nasreen Peer, Gavin M Rishworth, Renzo PerissinottoAbstract:The extant stromatolite pools in Port Elizabeth, South Africa, provide a unique ecotone habitat at the interface of fresh groundwater seepage and the marine intertidal zone. Within this transition environment, we investigated the coexistence of two brachyuran species with different habitat preferences, i.e. marine and freshwater by quantifying niche Overlap. The aim was to determine whether shifting environmental pressures or variability within the stromatolite pools (i.e. regular state shifts between marine and freshwater conditions) would invoke a Dietary response or competitive interaction between these two species that are usually separated by their habitat tolerances. It was hypothesised that there would be little Overlap between the two species but that this Overlap would be greater in winter compared to summer due to reduced ectothermic activity. Stable isotope niche analysis revealed no Dietary Overlap between the two species at any site or in either season (summer or winter). Furthermore, isotope signatures suggest that both species feed on resources from their respective microhabitats. Despite the usual tendency of ecotone or edge populations to adopt a generalist diet, both species were able to remain habitat specialists, likely due to their highly mobile nature and access to suitable microhabitats within this dynamic freshwater/marine ecotone. This study is important from an environmental change perspective as it supports the hypothesis that populations occupying transitional environments such as these might be more tolerant of habitat shifts than their counterparts dwelling in more stable localities, and thus these populations are more likely to coexist.
-
stable isotope evidence for Dietary Overlap between alien and native gastropods in coastal lakes of northern kwazulu natal south africa
PLOS ONE, 2012Co-Authors: Nelson A F Miranda, Renzo PerissinottoAbstract:Background Tarebia granifera (Lamarck, 1822) is originally from South-East Asia, but has been introduced and become invasive in many tropical and subtropical parts of the world. In South Africa, T. granifera is rapidly invading an increasing number of coastal lakes and estuaries, often reaching very high population densities and dominating shallow water benthic invertebrate assemblages. An assessment of the feeding dynamics of T. granifera has raised questions about potential ecological impacts, specifically in terms of its Dietary Overlap with native gastropods. Methodology/Principal Findings A stable isotope mixing model was used together with gut content analysis to estimate the diet of T. granifera and native gastropod populations in three different coastal lakes. Population density, available biomass of food and salinity were measured along transects placed over T. granifera patches. An index of isotopic (stable isotopes) Dietary Overlap (IDO, %) aided in interpreting interactions between gastropods. The diet of T. granifera was variable, including contributions from microphytobenthos, filamentous algae (Cladophora sp.), detritus and sedimentary organic matter. IDO was significant (>60%) between T. granifera and each of the following gastropods: Haminoea natalensis (Krauss, 1848), Bulinus natalensis (Kuster, 1841) and Melanoides tuberculata (Muller, 1774). However, food did not appear to be limiting. Salinity influenced gastropod spatial Overlap. Tarebia granifera may only displace native gastropods, such as Assiminea cf. ovata (Krauss, 1848), under salinity conditions below 20. Ecosystem-level impacts are also discussed. Conclusion/Significance The generalist diet of T. granifera may certainly contribute to its successful establishment. However, although competition for resources may take place under certain salinity conditions and if food is limiting, there appear to be other mechanisms at work, through which T. granifera displaces native gastropods. Complementary stable isotope and gut content analysis can provide helpful ecological insights, contributing to monitoring efforts and guiding further invasive species research.
Linda M. Nichol - One of the best experts on this subject based on the ideXlab platform.
-
Dietary Overlap and niche partitioning of sympatric harbour porpoises and Dall’s porpoises in the Salish Sea
Progress in Oceanography, 2013Co-Authors: Linda M. Nichol, Anna M. Hall, Graeme M. Ellis, Eva Stredulinsky, Melissa Boogaards, John K. B. FordAbstract:Abstract Ecological theory regarding the coexistence of similar species predicts resource partitioning will arise through competition and lead to different ecological niches. The diets of harbour porpoises (Phocoena phocoena) and Dall’s porpoises (Phocoenoides dalli) in the Salish Sea were investigated for evidence of resource partitioning between these ecologically similar species. Stomach contents of 36 harbour porpoises and 11 Dall’s porpoises were analysed and ten and six fish taxa were identified in each, respectively. Pacific herring (Clupea pallasi) was important in the diet of both porpoise species and walleye pollock (Theragra chalcogramma) was second in importance in the Dall’s porpoises. Pacific herring was estimated to contribute 60% to the total caloric intake of harbour porpoises. In addition to herring, Pacific hake (Merluccius productus), walleye pollock and a species of Pyschrolutidae were present in the diet of both porpoise species. Pianka’s Index of niche Overlap indicated substantial Dietary Overlap between the porpoise species based on measures of prey frequency of occurrence and prey percent numerical abundance. These results seem contrary to predictions from ecological theory. However, habitat and activity pattern differences between the two porpoise species exist and represent other dimensions of niche that likely contribute to resource partitioning in ways that were not strongly evident in stomach contents. Dall’s porpoises, which prefer deeper water habitat in the Salish Sea than harbour porpoises, may feed more on walleye pollock which spawn in deep water. Dall’s porpoises are also known to feed at night when lipid-rich mesopelagic prey such as Myctophidae and Bathylagidae, both present in the Dall’s porpoise samples, migrate upwards from depths in excess of 200 m. In contrast shiner perch, present only in harbour porpoise samples, is a species associated with shallow nearshore habitats. Resource partitioning is also likely to occur in accordance with seasonal prey availability.
-
Dietary Overlap and niche partitioning of sympatric harbour porpoises and dall s porpoises in the salish sea
Progress in Oceanography, 2013Co-Authors: Linda M. Nichol, Anna M. Hall, Graeme M. Ellis, Eva Stredulinsky, Melissa Boogaards, John K. B. FordAbstract:Abstract Ecological theory regarding the coexistence of similar species predicts resource partitioning will arise through competition and lead to different ecological niches. The diets of harbour porpoises (Phocoena phocoena) and Dall’s porpoises (Phocoenoides dalli) in the Salish Sea were investigated for evidence of resource partitioning between these ecologically similar species. Stomach contents of 36 harbour porpoises and 11 Dall’s porpoises were analysed and ten and six fish taxa were identified in each, respectively. Pacific herring (Clupea pallasi) was important in the diet of both porpoise species and walleye pollock (Theragra chalcogramma) was second in importance in the Dall’s porpoises. Pacific herring was estimated to contribute 60% to the total caloric intake of harbour porpoises. In addition to herring, Pacific hake (Merluccius productus), walleye pollock and a species of Pyschrolutidae were present in the diet of both porpoise species. Pianka’s Index of niche Overlap indicated substantial Dietary Overlap between the porpoise species based on measures of prey frequency of occurrence and prey percent numerical abundance. These results seem contrary to predictions from ecological theory. However, habitat and activity pattern differences between the two porpoise species exist and represent other dimensions of niche that likely contribute to resource partitioning in ways that were not strongly evident in stomach contents. Dall’s porpoises, which prefer deeper water habitat in the Salish Sea than harbour porpoises, may feed more on walleye pollock which spawn in deep water. Dall’s porpoises are also known to feed at night when lipid-rich mesopelagic prey such as Myctophidae and Bathylagidae, both present in the Dall’s porpoise samples, migrate upwards from depths in excess of 200 m. In contrast shiner perch, present only in harbour porpoise samples, is a species associated with shallow nearshore habitats. Resource partitioning is also likely to occur in accordance with seasonal prey availability.
Nina E Eide - One of the best experts on this subject based on the ideXlab platform.
-
Resource partitioning in sympatric arctic‐breeding geese: summer habitat use, spatial and Dietary Overlap of Barnacle and Pink‐footed Geese in Svalbard
Ibis, 2020Co-Authors: Nina E Eide, Espen Bergersen, Jesper MadsenAbstract:The spatial, habitat and Dietary Overlap of two breeding goose species was studied in Sassendalen, Svalbard, in summer 2003 based on abundance within 500 × 500-m grid squares and faecal diet analyses during pre-breeding, nesting and post-hatching periods. More than half of all Pink-footed Geese Anser brachyrhynchus occurred in the absence of Barnacle Geese Branta leucopsis during nesting and post-hatching periods compared to c. 20% when concentrated by pre-breeding snow cover. In contrast, only 5% of Barnacle Geese were observed in the absence of Pink-footed Geese pre-breeding, 15% during nesting, and 35% post-hatching. Among six defined habitat types, Barnacle Geese resorted more to ‘upland’ habitats during pre-breeding and nesting and to lowland lakes post-hatching when compared to Pink-footed Geese. Although Pink-footed Geese showed less change in seasonal habitat preference, many shifted to the river valley bottom post-hatching, giving access to open water (predator avoidance) and lush green vegetation (foraging for goslings). The smallest extent of distributional Overlap between the two species occurred post-hatching, but each species was also highly restricted by snow cover during pre-nesting. The greatest extent of Overlap in distribution and diet occurred during incubation, when large Dietary variation between different breeding valleys reflected local food availability around nests (probably a result of nest-site preference rather than food selection per se ). Whether this means that increased interactions within and between the two goose species with future increases in local density are most likely to be manifest at this stage of the summer is impossible to determine without knowledge of available food resources and manipulative experiments. More detailed investigations of the effects of foraging by both species on plant structure, quality and community composition are necessary to predict likely outcomes of future changes in population densities of both species.
-
resource partitioning in sympatric arctic breeding geese summer habitat use spatial and Dietary Overlap of barnacle and pink footed geese in svalbard
Ibis, 2009Co-Authors: Nina E Eide, Espen Bergersen, Jesper MadsenAbstract:The spatial, habitat and Dietary Overlap of two breeding goose species was studied in Sassendalen, Svalbard, in summer 2003 based on abundance within 500 × 500-m grid squares and faecal diet analyses during pre-breeding, nesting and post-hatching periods. More than half of all Pink-footed Geese Anser brachyrhynchus occurred in the absence of Barnacle Geese Branta leucopsis during nesting and post-hatching periods compared to c. 20% when concentrated by pre-breeding snow cover. In contrast, only 5% of Barnacle Geese were observed in the absence of Pink-footed Geese pre-breeding, 15% during nesting, and 35% post-hatching. Among six defined habitat types, Barnacle Geese resorted more to ‘upland’ habitats during pre-breeding and nesting and to lowland lakes post-hatching when compared to Pink-footed Geese. Although Pink-footed Geese showed less change in seasonal habitat preference, many shifted to the river valley bottom post-hatching, giving access to open water (predator avoidance) and lush green vegetation (foraging for goslings). The smallest extent of distributional Overlap between the two species occurred post-hatching, but each species was also highly restricted by snow cover during pre-nesting. The greatest extent of Overlap in distribution and diet occurred during incubation, when large Dietary variation between different breeding valleys reflected local food availability around nests (probably a result of nest-site preference rather than food selection per se ). Whether this means that increased interactions within and between the two goose species with future increases in local density are most likely to be manifest at this stage of the summer is impossible to determine without knowledge of available food resources and manipulative experiments. More detailed investigations of the effects of foraging by both species on plant structure, quality and community composition are necessary to predict likely outcomes of future changes in population densities of both species.