San Francisco State University

About: San Francisco State University is a education organization based out in San Francisco, California, United States. It is known for research contribution in the topics: Population & Planet. The organization has 5669 authors who have published 11433 publications receiving 408075 citations. The organization is also known as: San Francisco State & San Francisco State Normal School.

Nonspecific patterns of vector, host and avian malaria parasite associations in a central African rainforest.

Abstract: Malaria parasites use vertebrate hosts for asexual multiplication and Culicidae mosquitoes for sexual and asexual development, yet the literature on avian malaria remains biased towards examining the asexual stages of the life cycle in birds. To fully understand parasite evolution and mechanism of malaria transmission, knowledge of all three components of the vector-host-parasite system is essential. Little is known about avian parasite-vector associations in African rainforests where numerous species of birds are infected with avian haemosporidians of the genera Plasmodium and Haemoproteus. Here we applied high resolution melt qPCR-based techniques and nested PCR to examine the occurrence and diversity of mitochondrial cytochrome b gene sequences of haemosporidian parasites in wild-caught mosquitoes sampled across 12 sites in Cameroon. In all, 3134 mosquitoes representing 27 species were screened. Mosquitoes belonging to four genera (Aedes, Coquillettidia, Culex and Mansonia) were infected with twenty-two parasite lineages (18 Plasmodium spp. and 4 Haemoproteus spp.). Presence of Plasmodium sporozoites in salivary glands of Coquillettidia aurites further established these mosquitoes as likely vectors. Occurrence of parasite lineages differed significantly among genera, as well as their probability of being infected with malaria across species and sites. Approximately one-third of these lineages were previously detected in other avian host species from the region, indicating that vertebrate host sharing is a common feature and that avian Plasmodium spp. vector breadth does not always accompany vertebrate-host breadth. This study suggests extensive invertebrate host shifts in mosquito-parasite interactions and that avian Plasmodium species are most likely not tightly coevolved with vector species.

Russia and the West from Alexander to Putin: Honor in International Relations

Abstract: 1. Introduction Part I. Theory: 2. Honor in international relations 3. The Russian state and its honor 4. Russia's relations with the West Part II. Honor and Cooperation: 5. The Holy Alliance, 1815-53 6. The Triple Entente, 1907-17 7. The collective security, 1933-9 8. The war with terrorism, 2001-5 Part III. Honor and Defensiveness: 9. The Recueillement, 1856-71 10. The peaceful coexistence, 1921-39 11. Containing NATO expansion, 1995-2000 Part IV. Honor and Assertiveness: 12. The Crimean War, 1853-6 13. The early Cold War, 1946-9 14. The Russia-Georgia War, August 2008 15. Conclusion Bibliography.

Host specificity and incidence of Trypanosoma in some African rainforest birds: a molecular approach

Abstract: Studies of host‐parasite interactions in birds have contributed greatly to our understanding of the evolution and ecology of disease. Here we employ molecular techniques to determine the incidence and study the host-specificity of parasitic trypanosomes in the African avifauna. We developed a polymerase chain reaction (PCR)-based diagnostic test that amplified the small subunit ribosomal RNA gene (SSU rRNA) of Trypanosoma from avian blood samples. This nested PCR assay complements and corroborates information obtained by the traditional method of blood smear analysis. The test was used to describe the incidence of trypanosomes in 479 host individuals representing 71 rainforest bird species from Cameroon, the Ivory Coast and Equatorial Guinea. Forty-two (59%) of these potential host species harboured trypanosomes and 189 individuals (35%) were infected. To examine host and geographical specificity, we examined the morphology and sequenced a portion of the SSU rRNA gene from representative trypanosomes drawn from different hosts and collecting locations. In traditional blood smear analyses we identified two trypanosome morphospecies, T. avium and T. everetti. Our molecular and morphological results were congruent in that these two morphospecies had highly divergent SSU rRNA sequences, but the molecular assay also identified cryptic variation in T. avium , in which we found seven closely allied haplotypes. The pattern of sequence diversity within T. avium provides evidence for widespread trypanosome mixing across avian host taxa and across geographical locations. For example, T. avium lineages with identical haplotypes infected birds from different families, whereas single host species were infected by T. avium lineages with different haplotypes. Furthermore, some conspecific hosts from geographically distant sampling locations were infected with the same trypanosome lineage, but other individuals from those locations harboured different trypanosome lineages. This apparent lack of host or geographical specificity may have important consequences for the evolutionary and ecological interactions between parasitic trypanosomes and their avian hosts.

The local–regional relationship: immigration, extinction, and scale

Abstract: While local processes (e.g., competition, predation, and disturbance) pre- sumably cause species exclusion and thus limit diversity in individual communities, regional processes (e.g., historical events, immigration, and speciation) are assumed to provide a source of species to colonize and thus enrich local communities. Ecologists have attempted to distinguish between these two sets of processes using graphical evidence for local as- semblage saturation. However, such efforts have been controversial and are antithetical to the fact that local diversity bears an imprint of both. We examine the local-regional species richness relationship from the perspective of the theory of island biogeography and develop a model that can produce the full range of observed local-regional richness relationships from linear to curvilinear. Importantly, unlike previous models, we do not require species interactions to produce the curvilinear pattern. Curvilinear relationships arise if per-species stochastic extinction rates are substantially higher than colonization rates, while linear relationships result if colonization rates are higher than extinction rates. Because we also show that merely changing the sampling scale can make local-regional relationships appear either saturated or unsaturated, an inference of ecological processes, derived solely from local-regional relationships, is unwarranted.

Translation and dispersion of sediment pulses in flume experiments simulating gravel augmentation below dams

Abstract: [1] The effectiveness of gravel augmentation as a river restoration strategy depends on the extent and duration of the topographic and bed texture changes created by the pulse of added sediment. Previous work has emphasized the strong tendency for natural sediment waves to propagate primarily by dispersion; however, pulse translation may occur for gravel additions to armored channels downstream of dams where added sediments are finer than the preexisting bed material. Here we report results of a laboratory investigation in which we created an immobile, armored bed and documented the spatial and temporal evolution of the bed topography and bed texture in response to gravel pulses of various volumes and grain sizes. The introduced sediment waves evolved by a combination of translation and dispersion, with a significant translational component. Pulse translation and dispersion can be readily discerned on a graph of the time evolution of the downstream cumulative distribution of elevation differences from the preexisting bed topography. Translation was most evident for smaller volumes of added sediment. Pulses of finer-grained gravel moved through the flume more rapidly, resulting in a larger magnitude but shorter duration of bed fining. More work is needed to understand the influence of bar-pool topography and flow magnitude and duration before the grain size and volume of gravel additions can be selected to achieve optimal patterns of pulse propagation.