The Experts below are selected from a list of 309 Experts worldwide ranked by ideXlab platform
Carl F Friese - One of the best experts on this subject based on the ideXlab platform.
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the impact of fungi on soil seeds implications for plants and Granivores in a semiarid shrub steppe
Ecology, 1993Co-Authors: Thomas O. Crist, Carl F FrieseAbstract:Fungi are ubiquitous in soil and may affect seed survivorship directly by decomposition or pathogenesis, or indirectly through the effects of fungi on seed preference of Granivores. We studied the role of fungi in the persistence of soil seeds in a shrub-steppe ecosystem using two experimental approaches. In the first, we examined survivorship of 900 seeds of five shrub-steppe species in nylon bags over a 1 0-mo period and determined viable seed losses to germination, decomposition, and pathogens. The proportion of seeds representing a viable seed bank decreased from 84.4% in the May pre-experimental con- ditions to 4.4% in March. Decomposition and attack by fungi were responsible for the greatest decrease from fall to winter (0% in August, 32.0% in November, 35.2% in March) while germination accounted for the greatest decrease from winter to spring (18.5% in August, 21.9% in November, 55.0% in March). Small seeds were more likely to be lost to decomposition and pathogens, whereas larger seeds had greater losses to germination. A subset of 80 experimental seeds was cultured for seed-infecting fungi. We found fungi in virtually all seeds; the most common fungal isolates were cosmopolitan soil fungi, such as species of Penicillium and Mucor. These species are known producers of extracellular enzymes and mycotoxins. Two sterile (nonfruiting) forms of fungi were also frequently isolated, as were two pathogenic species of Fusarium. In a second experiment we placed seeds in fungal cultures obtained from soil seeds and presented moldy seeds along with control seeds to a shrub-steppe granivore, the western harvester ant (Pogonomyrmex oc- cidentalis). Ants harvested control seeds at nearly twice the rate of moldy seeds, suggesting that they avoided seeds infected with fungi. In this way, fungi may indirectly affect seed mortality due to predation by Granivores, in addition to the direct effects fungi can have on seed survivorship. We suggest that fungi may play an important role in soil seed dynamics, but one that is poorly understood.
Thomas O. Crist - One of the best experts on this subject based on the ideXlab platform.
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Harvester Ants (Pogonomyrmex spp.): Their Community and Ecosystem Influences
Annual Review of Ecology Evolution and Systematics, 2000Co-Authors: James A Macmahon, John F. Mull, Thomas O. CristAbstract:▪ Abstract We summarize the influences of harvester ants of the genus Pogonomyrmex on communities and ecosystems. Because of nest densities, the longevity of nests, and the amount of seed harvested and soil handled, harvester ants have significant direct and indirect effects on community structure and ecosystem functioning. Harvester ants change plant species composition and diversity near their nests. These changes result from differential seed predation by the ants, their actions as seed dispersers and competitors with other Granivores, and the favorable soil conditions they create through their digging. Their nest building creates islands of increased nutrient density. In some areas, the effects of their activities may be so pervasive that plant community structure is strongly influenced. Ant removal studies, which would reveal their total impact, have generally not been done. Granivore removals have been conducted in North America where ants are of lesser importance than small mammals, in contrast to ...
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the impact of fungi on soil seeds implications for plants and Granivores in a semiarid shrub steppe
Ecology, 1993Co-Authors: Thomas O. Crist, Carl F FrieseAbstract:Fungi are ubiquitous in soil and may affect seed survivorship directly by decomposition or pathogenesis, or indirectly through the effects of fungi on seed preference of Granivores. We studied the role of fungi in the persistence of soil seeds in a shrub-steppe ecosystem using two experimental approaches. In the first, we examined survivorship of 900 seeds of five shrub-steppe species in nylon bags over a 1 0-mo period and determined viable seed losses to germination, decomposition, and pathogens. The proportion of seeds representing a viable seed bank decreased from 84.4% in the May pre-experimental con- ditions to 4.4% in March. Decomposition and attack by fungi were responsible for the greatest decrease from fall to winter (0% in August, 32.0% in November, 35.2% in March) while germination accounted for the greatest decrease from winter to spring (18.5% in August, 21.9% in November, 55.0% in March). Small seeds were more likely to be lost to decomposition and pathogens, whereas larger seeds had greater losses to germination. A subset of 80 experimental seeds was cultured for seed-infecting fungi. We found fungi in virtually all seeds; the most common fungal isolates were cosmopolitan soil fungi, such as species of Penicillium and Mucor. These species are known producers of extracellular enzymes and mycotoxins. Two sterile (nonfruiting) forms of fungi were also frequently isolated, as were two pathogenic species of Fusarium. In a second experiment we placed seeds in fungal cultures obtained from soil seeds and presented moldy seeds along with control seeds to a shrub-steppe granivore, the western harvester ant (Pogonomyrmex oc- cidentalis). Ants harvested control seeds at nearly twice the rate of moldy seeds, suggesting that they avoided seeds infected with fungi. In this way, fungi may indirectly affect seed mortality due to predation by Granivores, in addition to the direct effects fungi can have on seed survivorship. We suggest that fungi may play an important role in soil seed dynamics, but one that is poorly understood.
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Harvester Ant Foraging and Shrub‐Steppe Seeds: Interactions of Seed Resources and Seed Use
Ecology, 1992Co-Authors: Thomas O. Crist, James A MacmahonAbstract:Granivore—seed interactions involve a feedback between granivore seed selectivity and seed availability. We examined this feedback to determine how seed preferences by the western harvester ant, Pogonomyrmex occidentalis, related to seed availability and, in turn, affected the soil seed pool. Preferences were estimated from natural diets as well as from experiments that controlled seed size, relative availability, and distance from ant nests. Seed availability to ants varied with season and over 2 yr. Colony activity and seed intake rates were correlated with seed availability. Seed preference by ants was correlated with the seasonal availability of preferred species, but not with unpreferred seeds. From the soil seed pool, ants preferentially harvested small, sound seeds. They removed 9—26% of the potentially viable seed pool each year, and as much as 100% of available preferred species. Seed densities were lower 2—7 m from nests, where foraging activity was concentrated, than 7—12 m from nests. In contr...
John R. Flowerdew - One of the best experts on this subject based on the ideXlab platform.
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Wood Mice — Small Granivores/Insectivores with Seasonally Variable Patterns
Activity Patterns in Small Mammals, 2020Co-Authors: John R. FlowerdewAbstract:The wood mouse (Apodemus sylvaticus) is found in a variety of habitats from woodland to ploughed fields and sand dunes to moorland (Flowerdew 1991). It has catholic feeding habits, taking fruits, seeds, shoots and invertebrates (Hansson 1985) and is thus broadly classed as a ‘granivore/insectivore’.
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wood mice small Granivores insectivores with seasonally variable patterns
2000Co-Authors: John R. FlowerdewAbstract:The wood mouse (Apodemus sylvaticus) is found in a variety of habitats from woodland to ploughed fields and sand dunes to moorland (Flowerdew 1991). It has catholic feeding habits, taking fruits, seeds, shoots and invertebrates (Hansson 1985) and is thus broadly classed as a ‘granivore/insectivore’.
Luc A Wauters - One of the best experts on this subject based on the ideXlab platform.
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Squirrels — Medium-Sized Granivores in Woodland Habitats
Activity Patterns in Small Mammals, 2020Co-Authors: Luc A WautersAbstract:A strictly diurnal activity pattern, with seasonal changes from a short unimodal pattern in winter, an intermediate one in spring and autumn, to a long, bimodal one in summer was consistent for all tree squirrel species. However, both interspecific and geographical variation occurred in the finestructure of the pattern. Moreover, tree squirrels adapted their activity to food availability and food quality by adjusting (1) the length of the active period, (2) the proportion of time spent foraging (autumn/winter) or spent feeding on primary food resources, and (3) the amount of time spent searching for food. Hence, differences in food availability (and rate of food intake) between woodland types caused habitat-related variation in the squirre’s activity pattern (Wauters et al. 1992). Little is yet known about how intraspecific competition affects the activity pattern of squirrels of different age and sex. It will need detailed studies of radio-tagged subadult and adult animals with overlapping home ranges to gain more insight into time-related home range use and behavioural mechanisms that might decrease the intensity of competition for space and food resources in non-territorial tree squirrels.
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squirrels medium sized Granivores in woodland habitats
2000Co-Authors: Luc A WautersAbstract:A strictly diurnal activity pattern, with seasonal changes from a short unimodal pattern in winter, an intermediate one in spring and autumn, to a long, bimodal one in summer was consistent for all tree squirrel species. However, both interspecific and geographical variation occurred in the finestructure of the pattern. Moreover, tree squirrels adapted their activity to food availability and food quality by adjusting (1) the length of the active period, (2) the proportion of time spent foraging (autumn/winter) or spent feeding on primary food resources, and (3) the amount of time spent searching for food. Hence, differences in food availability (and rate of food intake) between woodland types caused habitat-related variation in the squirre’s activity pattern (Wauters et al. 1992). Little is yet known about how intraspecific competition affects the activity pattern of squirrels of different age and sex. It will need detailed studies of radio-tagged subadult and adult animals with overlapping home ranges to gain more insight into time-related home range use and behavioural mechanisms that might decrease the intensity of competition for space and food resources in non-territorial tree squirrels.
Byron B Lamont - One of the best experts on this subject based on the ideXlab platform.
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bird pollinators seed storage and cockatoo Granivores explain large woody fruits as best seed defense in hakea
Perspectives in Plant Ecology Evolution and Systematics, 2016Co-Authors: Byron B Lamont, Mick E Hanley, Philip K Groom, Tianhua HeAbstract:Abstract Nutrient-impoverished soils with severe summer drought and frequent fire typify many Mediterranean-type regions of the world. Such conditions limit seed production and restrict opportunities for seedling recruitment making protection from Granivores paramount. Our focus was on Hakea, a genus of shrubs widespread in southwestern Australia, whose nutritious seeds are targeted by strong-billed cockatoos. We assessed 56 Hakea species for cockatoo damage in 150 populations spread over 900 km in relation to traits expected to deter avian granivory: dense spiny foliage; large, woody fruits; fruit crypsis via leaf mimicry and shielding; low seed stores; and fruit clustering. We tested hypothesises centred on optimal seed defenses in relation to (a) pollination syndrome (bird vs insect), (b) fire regeneration strategy (killed vs resprouting) and (c) on-plant seed storage (transient vs prolonged). Twenty species in 50 populations showed substantial seed loss from cockatoo granivory. No subregional trends in granivore damage or protective traits were detected, though species in drier, hotter areas were spinier. Species lacking spiny foliage around the fruits (usually bird-pollinated) had much larger (4–5 times) fruits than those with spiny leaves and cryptic fruits (insect-pollinated). Species with woody fruits weighing >1 g were rarely attacked, unlike those with spiny foliage and small cryptic fruits. Fire-killed species were just as resistant to Granivores as resprouters but with much greater seed stores. Strongly serotinous species with prolonged seed storage were rarely attacked, with an order of magnitude larger fruits but no difference in seed store compared with weakly/non-serotinous species. Overall, the five traits examined could be ranked in success at preventing seed loss from large woody fruits (most effective), fruit clustering, low seed stores, spinescence, to crypsis (least effective). We conclude that the evolution of large woody fruits is contingent on pollinator type (dictates flower/fruit location, thus apparency to Granivores), level of serotiny (response to poor soils and fire that requires prolonged seed defense) and presence of a formidable granivore (that promotes strong defense).
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Fruit-seed relations in Hakea: serotinous species invest more dry matter in predispersal seed protection
Austral Ecology, 1997Co-Authors: Philip K Groom, Byron B LamontAbstract:The ability to maintain a canopy stored seedbank (serotiny) is characteristic of many woody genera inhabiting fire-prone environments. The relationship between level of serotiny for 94 Hakea (Proteaceae) species in southwestern Australia and follicle mass, density, three wall thicknesses and seed mass was investigated. Two species were non-serotinous (fruits open at maturity), 12 were weakly serotinous (majority of fruits open at maturity), 9 were moderately serotinous (fruits open within five years of maturity) and 71 were strongly serotinous (fruits still closed at least five years after reaching maturity). A positive relationship existed between the level of serotiny and follicle morphology. Strongly serotinous species were more likely to have heavier, woodier and thicker-walled follicles than non- and weakly serotinous species. Moderately/strongly serotinous species invested more energy (six times higher follicle:seed mass ratio) than non weakly serotinous species, consistent with increased protection of the seeds from Granivores, pathogens, desiccation and/or heat. Recent work has shown that thicker fruit walls (strongly serotinous species) provide better insulation to seeds from heat, although the need to survive fire is just as critical for thin-walled, weakly serotinous species. Greater protection from Granivores may provide a better explanation for the adaptive significance of dense, thick-walled serotinous follicles, as the opportunities for predispersal granivore damage are low among weakly serotinous species.
