关键词： Argentine ants   aphids   feeding guilds   herbivores   invasive ants   native ants   Salix   willow  

摘要： 1. We examined the relative effects of the invasive Argentine ant, Linepithema humile, and a common native ant, Prenolepis imparis, on the community of herbivorous insects occurring on willow trees, Salix lasiolepis in Northern California, U.S.A. 2. Using paired control and treatment branches from which we excluded ants and other non-volant predators, we found that effects of Argentine ants on the herbivore community were generally similar to those of P. imparis. Argentine ants and P. imparis suppressed the damage by skeletonising insects by 50%, but had little effect on most other external-feeding or internal-feeding guilds. 3. The abundance of aphids was 100% greater in the presence of Argentine ants, but there was no effect on aphid numbers in the presence of P. imparis. Late season aphid numbers were substantially higher in the presence of Argentine ants, but not P. imparis. 4. The effects of Argentine ants on skeletonising insects and aphids combined with the overwhelming abundance of Argentine ant workers, suggests that they may have substantial, but often overlooked, effects on the herbivore communities on other plant species in or near riparian habitats in which they invade.

关键词： Arachnida   delta C-13   delta N-15   food web   inquiline   Serengeti National Park   termites   trophic level  

摘要： 1. Termites (Isoptera) in tropical savannas are known as ecosystem engineers, affecting the spatial and temporal distribution of water, carbon, cations, and nutrients through their mound structures. Their mounds, however, also offer habitation to diverse taxa and feeding guilds of other invertebrates;a keystone role that has not been properly quantified. 2. The aim of this study was to explore the ecosystem role of termitaria in determining invertebrate diversity and their potential trophic interactions. We used stable isotopes to distinguish termite-feeding invertebrates from invertebrates merely living in termite mounds under field conditions. 3. The results suggest that inquiline spiders (Arachnida) do not feed on termites directly, but on other invertebrates within the termitaria that are termitophagous, elevating the spiders three trophic levels higher than the termites. 4. This study is the first to demonstrate food web interactions among inquiline invertebrates with a stable isotope approach. It provides evidence that termites play a keystone role in the system by providing habitat for various, trophically interacting invertebrates. These results illustrate a rather unexplored ecosystem property of savanna termites.

关键词： Birds   Endangered & extinct species   Trees   Wildlife conservation   Biological diversity   Native species   Wildlife observation   Grasses   Environmental education  

摘要： Secondary forest succession and tree planting are contributing to the recovery of the Cabo Rojo refuge (Headquarters and Salinas tracts) and Laguna Cartagena refuge (Lagoon and Tinaja tracts) of the Fish and Wildlife Service in southwestern Puerto Rico. About 80 species, mainly natives, have been planted on 44 ha during the past 25 y in an effort to reduce the threat of grass fires and to restore wildlife habitat. A 2007 survey of 9-y-old tree plantings on the Lagoon tract showed satisfactory growth rates for 16 native species. Multiple stems from individual trees at ground level were common. A sampling of secondary forest on the entire 109 ha Tinaja tract disclosed 141 native tree species, or 25% of Puerto Rico's native tree flora, along with 20 exotics. Five tree species made up about 58% of the total basal area, and seven species were island endemics. Between 1998 and 2003, tree numbers and basal area, as well as tree heights and diameter at breast height values (diameter at 1.4 m above the ground), increased on the lower 30 ha of the Tinaja tract. In this area, much of it subject to fires and grazing through 1996, exotic trees made up 25% of the species. Dry forest throughout the tropics is an endangered habitat, and its recovery (i.e., in biomass, structure, and species composition) at Tinaja may exceed 500 y. Future forests, however, will likely contain some exotics.

关键词： Atta laevigata   Atta sexdens   Biodiversity hotspot   Brazil   Cerrado   Herbivory  

摘要： Question: Plant communities in Paleotropical savannas are regulated by a combination of bottom-up and top-down effects. However, the paucity of ungulates and other large herbivores in Neotropical savannas has led to speculation that these communities are primarily structured by physical factors such as fire, precipitation and soil chemistry. We addressed the following question: How much plant biomass is consumed by leaf-cutter ants in Neotropical savannas, and is it comparable to the amount of biomass consumed by herbivores in Paleotropical savanna sites? Location: Our study was conducted at the Estacao Ecologica do Panga, located 30 km south of Uberlandia, Minas Gerais, Brazil. All field work was conducted in the vegetation type known as cerrado sensu stricto. Methods and Results: Using direct measurements of herbivory, coupled with estimates of plant productivity and ant colony density, we found that leaf-cutter ants (Atta spp.) consume 13-17% of the foliar biomass produced annually by woody plants in a Neotropical savanna (Brazilian cerrado). Although comparisons with other savanna systems are complicated by methodological differences among studies, the proportion of biomass consumed by Atta species is about 25% of that consumed by the entire ungulate community in some African savannas and greater than or comparable to the total herbivory observed in some terrestrial ecosystems. Conclusions: We hypothesize that this intense biomass consumption by Atta will have important ecological consequences for the cerrado ecosystem, because leaf-cutter abundance increases in fragmented or degraded habitats. These effects are likely to be exacerbated as anthropogenic pressure in this biodiversity hotspot increases.

关键词： choline   4-DAMP   M-3 receptor   aconitine   ouabain   arrhythmias   Ca2+  

摘要： It is well known that choline has protective effects on ischemic arrhythmias. We designed the present study to evaluate the antiarrhythmic effects of choline and to detect its related mechanisms in aconitine-induced rat and ouabain-induced guinea pig models of arrhythmia. Laser scanning confocal microscopy and patch-clamp technique were utilized to study the action of choline on intracellular calcium concentration and L-type calcium current (ICa-L) of cardiac myocytes. M-3 receptor antagonist 4-DAMP (4-diphenylacetoxy-N-methylpiperidine-methiodide) was applied preliminarily to evaluate the role of the M-3 receptor. Choline significantly increased the survival time of arrhythmic rats and guinea pigs, delayed the onset of arrhythmias and ventricular tachycardia, and decreased the arrhythmia score. The overload of intracellular Ca2+ induced by aconitine or ouabain was reduced in isolated myocytes pretreated with choline. Choline reduced the increased density of ICa-L induced by aconitine or ouabain. Moreover, the beneficial effects of choline were reversed by 4-DAMP. Choline produced antiarrhythmic actions on arrhythmia models by stimulating the cardiac M-3 receptor. The mechanism may be related to the improvement of Ca2+ handling.

关键词： Aceria parapopuli   cryptic speciation   foundation species   host race formation   hybridization   Populus  

摘要： Few studies have investigated the roles that plant hybridization and individual plant genotype play in promoting population divergence within arthropod species. Using nrDNA sequence information and reciprocal transfer experiments, we examined how tree cross type (i.e., pure Populus angustifolia and P. angustifolia x P. fremontii F-1 type hybrids) and individual tree genotype influence host race formation in the bud-galling mite Aceria parapopuli. Three main findings emerged: (1) Strong genetic differentiation of mite populations found on pure P. angustifolia and F-1 type hybrids indicates that these mites represent morphologically cryptic species. (2) Within the F-1 type hybrids, population genetic analyses indicate migration among individual trees;however, (3) transfer experiments show that the mites found on heavily infested F-1 type trees perform best on their natal host genotype, suggesting that genetic interactions between mites and their host trees drive population structure, local adaptation, and host race formation. These findings argue that hybridization and genotypic differences in foundation tree species may drive herbivore population structure, and have evolutionary consequences for dependent arthropod species.

关键词： Comparative biology   Evolution   Inquiry-based approach   Introductory biology   Phylogenetic analysis   Tree-thinking  

摘要： Biodiversity was originally taught in our Introductory Organismal Biology course at Michigan State University (LB144;freshman/sophomore majors) by rote memorization of isolated facts about organisms. When we moved to an inquiry-based laboratory framework to improve pedagogy, an unfortunate and unforeseen result was the loss of much of our study of biodiversity. In this paper, we describe the restructuring of LB144 to restore the study of biodiversity and organismal groups while retaining the benefits of an inquiry-based approach. The curricular intervention was accomplished through the creation and implementation of a four-week Comparative Biology laboratory stream. During this stream, student research teams recorded and organized observations that they made on a range of organisms and analyzed their data in a phylogenetic framework. During the stream, our students worked through a set of exercises designed to help them learn how to read, interpret, and manipulate phylogenetic trees. We placed particular emphasis on the concept that phylogenetic trees are hypotheses of relationship that can be tested with scientific data. This incorporation of phylogenies and phylogenetic analysis, or "tree-thinking," into our students' work provided an explicit synthetic evolutionary framework for their comparative biodiversity studies. End-of-stream products included a team phylogenetic analysis exercise and an individual comparative biology oral presentation. © 2009 Springer Science+Business Media, LLC.

关键词： EVOLUTION (Biology)   ANIMAL genetics   MARINE animals   BIOCOMPLEXITY   BIOLOGY -- Classification  

摘要： The genome sequence of Trichoplax adhaerens, the founding member of the enigmatic animal phylum Placozoa, has revealed that a surprising level of genetic complexity underlies its extremely simple body plan, indicating either that placozoans are secondarily simple or that there is an undiscovered morphologically complex life stage.

关键词： Glaucomys sabrinus   green-tree retention   mycophagy   Myodes californicus   Myodes gapperi   Tamias siskiyou   Tamias townsendii   truffle  

摘要： We studied the effects of 6 green-tree retention levels and patterns on the diets of northern flying squirrels Glaucomys sabrinus), Townsend's chipmunks (Tamias townsendii), Siskiyou chipmunks (T. siskiyou), western red-backed voles (Myodes californicus), and southern red-backed voles (Myodes gapperi) using fecal pellet analysis. These rodents are truffle spore dispersers and prey for forest predators such as the northern spotted owl Strix occidentalis caurina). Pretreatment diets showed differences in truffle and plant consumption among genera. Tree harvesting, especially in the 15% aggregated retention pattern, reduced frequency of Rhizopogon spores in the diet of voles, which may reflect a reduced ability of these animals to forage for Rhizopogon truffles, a decreased access to these truffles, or a reduction in Rhizopogon truffle abundance or frequency. Habitat island effects and edge effects provide conceptual frameworks for the reduction in consumption of Rhizopogon truffles by voles in green-tree aggregates. Overall, small mammal consumption of truffles showed little change in response to the treatments. Animals may be compensating for a locally declining food source by altering their foraging behavior. The long-term effect of this postulated behavioral compensation on small mammal energetics and population dynamics is unknown. Forest managers may reduce the impact of tree harvesting on these key forest ecosystem components by including green-tree aggregates within a dispersed retention matrix. JOURNAL OF WILDLIFE MANAGEMENT 72(8): 1747-1755;2008)

关键词： regional climate change   bioclimatic distribution   Savanna herbivory  

摘要： The future impacts of climate change are predicted to significantly affect the survival of many species. Recent studies indicate that even species that are relatively mobile and/or have large geographic ranges may be at risk of range contractions or extinction. An ecologically and evolutionary significant group of mammals that has been largely overlooked in this research is Australia's large marsupial herbivores, the macropodids (kangaroos). The aims of our investigation were to define and compare the climatic conditions that influence the current distributions of four sympatric large macropodids in northern Australia (Macropus antilopinus, Macropus robustus, Macropus giganteus, and Macropus rufus) and to predict the potential future impact of climate change on these species. Our results suggest that contemporary distributions of these large macropodids are associated with well-defined climatic gradients ( tropical and temperate conditions) and that climatic seasonality is also important. Bioclimatic modeling predicted an average reduction in northern Australian macropodid distributions of 48% +/- 16.4% in response to increases of 2.0 degrees C. At this temperature, the distribution of M. antilopinus was reduced by 89% +/- 0.4%. We predict that increases of 6.0 degrees C may cause severe range reductions for all four macropodids (96% +/- 2.1%) in northern Australia, and this range reduction may result 2.1% in the extinction of M. antilopinus.