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Abstract. The bark beetles Ips pini, I. perroti, and I. grandicollis are sympatric in pine forests of the north-central United States. They share the same limited phloem resource and often coexist within the same host trees. We tested whether phloem resources are partitioned in time and space by measuring spatial and seasonal colonization of logs. Differences among species in flight phenology, development...
The bark beetles Ips pini, I. perroti, and I. grandicollis are sympatric in pine forests of the north-central United States. They share the same limited phloem resource and often coexist within the same host trees. We tested whether phloem resources are partitioned in time and space by measuring spatial and seasonal colonization of logs. Differences among species in flight phenology, development time,...
Recent population-dynamic theory suggests that mechanisms of lethal interference competition can have profound effects on parasitoid coexistence and pest suppression in biological control systems. We investigated lethal intraspecific and interspecific interference competition in Eretmocerus eremicus and Encarsia sophia, parasitoids of the whitefly pest, Bemisia tabaci. Our first experiments evaluated...
Abstract. We investigated whether the food quality of tree foliage for African savanna browsers varies across the feeding height range of the guild. This was to address the question of why giraffes (Giraffa camelopardalis) generally feed at a higher level in the canopy than is accessible to all other browsers. We defined a giraffe browse unit (GBU) as the length of twig corresponding to the average...
Abstract. Guanacos (Lama guanicoe) are the only wild ungulate species widely distributed across the Patagonian steppe and have undergone a precipitous population decline since the introduction of domestic sheep (Ovis aries) 100years ago. There has been speculation that sheep ranching may have played a major role in guanaco population decline after monopolising the most productive land because of competition...
We investigated whether the food quality of tree foliage for African savanna browsers varies across the feeding height range of the guild. This was to address the question of why giraffes (Giraffa camelopardalis) generally feed at a higher level in the canopy than is accessible to all other browsers. We defined a giraffe browse unit (GBU) as the length of twig corresponding to the average "bite"...
Guanacos (Lama guanicoe) are the only wild ungulate species widely distributed across the Patagonian steppe and have undergone a precipitous population decline since the introduction of domestic sheep (Ovis aries) 100 years ago. There has been speculation that sheep ranching may have played a major role in guanaco population decline after monopolising the most productive land because of competition...
We tested the hypothesis that differences in temperature and desiccation tolerances of eggs of the container-dwelling mosquitoes Aedes albopictus and Aedes aegypti influence whether invading A. albopictus coexist with or exclude A. aegypti in Florida. In the laboratory, egg mortality through 30 days for A. albopictus was strongly temperature and humidity dependent, with low humidity and high temperature...
The success of some invasive species may depend on phenotypic changes that occur following introduction. In Argentine ants ( Linepithema humile) introduced populations typically lack intraspecific aggression, but native populations display such behavior commonly. We employ three approaches to examine how this behavioral shift might influence interspecific competitive ability. In a laboratory experiment,...
We tested whether interspecific competition from Aedes albopictus had measurable effects on A. aegypti at the typical numbers of larval mosquitoes found in cemetery vases in south Florida. We also tested whether the effect of interspecific competition from A. albopictus on A. aegypti differed between sites where A. aegypti either persists or went extinct following invasion by A. albopictus. Similar...
Spatial associations of seven herbivore species in the Kruger National Park, South Africa, are analyzed using a new technique, Correlative Coherence Analysis (CoCA). CoCA is a generalization of the concept of correlation to more than two sequences of numbers. Prior information on the feeding ecology and metabolic requirements of these species is used to contrast spatial scales at which hypothesized...
Many herbivores elicit biochemical, physiological, or morphological changes in their host plants that render them more resistant to co-occurring herbivores. Yet, despite the large number of studies that investigate how induced resistance affects herbivore preference and performance, very few have simultaneously explored the cascading effects of induction on higher trophic levels and consequences for...
Understanding the co-occurrence of ecologically similar species remains a puzzling issue in community ecology. The species-rich mouse lemurs (Microcebus spec.) are distributed over nearly all remaining forest areas of Madagascar with a high variability in species distribution patterns. Locally, many congeneric species pairs seem to co-occur, but only little detailed information on spatial patterns...
Recent evidence suggests that competitive interactions among herbivores are mostly indirect and mediated by plant responses to herbivory. Most studies, however, emphasize chewing insects and secondary chemistry, thus ignoring the diverse group of vascular-parasites that may be more likely to compete through induced changes in phytonutrients. Using an aboveground phloem-feeding aphid (Myzus persicae...
Nest-site selection involves tradeoffs between the risk of predation (on females and/or nests) and nest-site quality (microenvironment), and consequently suitable nesting sites are often in limited supply. Interactions with “classical” predators (e.g., those not competing for shared resources) can strongly influence nest-site selection, but whether intraguild predation also influences this behavior...
Assessing the importance of deterministic processes in structuring ecological communities is a central focus of community ecology. Typically, community ecologists study a single taxonomic group, which precludes detection of potentially important biotic interactions between distantly related species, and inherently assumes competition is strongest between closely related species. We examined distribution...
The rise of temperatures may enable species to increase their activities during winter periods and to occupy new areas. In winter, resource density is low for most species and an increased number of active consumers during this season may produce heightened competitive pressure. In Western France, the aphid parasitoid species Aphidiusavenae Haliday has been known to adopt a winter diapausing...
When specialists and generalists compete for a limited resource, specialists are more constrained because they are less likely to find an alternative resource. In parasitoids with overlapping host ranges, asymmetric competition should therefore exist where specialists are more likely to win the host in a contest. Competition between parasitoids has been studied mostly in hymenopterans. In hymenopteran...
Partitioning of the niche space is a mechanism used to explain the coexistence of similar species. Ectotherms have variable body temperatures and their body temperatures influence performance and, ultimately, fitness. Therefore, many ectotherms use behavioral thermoregulation to avoid reduced capacities associated with body temperatures far from the optimal temperature for performance. Several authors...
While interspecific competition is prevalent in natural systems, we do not yet understand how it can influence an individual’s phenotype within its lifetime and how this might affect performance. Morphology and swimming performance are two important fitness-related traits in fishes. Both traits are essential in acquiring and defending resources as well as avoiding predation. Here, we examined if interspecific...
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