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.

Evolution of multiple kinds of female sperm-storage organs in drosophila.

Abstract: Females of all species belonging to the family Drosophilidae have two kinds of sperm-storage organs: paired spherical spermathecae and a single elongate tubular seminal receptacle. We examined 113 species belonging to the genus Drosophila and closely allied genera and describe variation in female sperm-storage organ use and morphology. The macroevolutionary pattern of organ dysfunction and morphological divergence suggests that ancestrally both kinds of organs stored sperm. Loss of use of the spermathecae has evolved at least 13 times; evolutionary regain of spermathecal function has rarely if ever occurred. Loss of use of the seminal receptacle has likely occurred only once; in this case, all descendant species possess unusually elaborate spermathecae. Data further indicate that the seminal receptacle is the primary sperm-storage organ in Drosophila. This organ exhibits a pattern of strong correlated evolution with the length of sperm. The evolution of multiple kinds of female sperm-storage organs and the rapidly divergent and correlated evolution of sperm and female reproductive tract morphology are discussed.

Incomplete by Design and Designing for Incompleteness

Abstract: The traditional scientific approach to design extols the virtues of completeness. However, in environments characterized by continual change, there are challenges in adopting such an approach. We examine Linux and Wikipedia as two exemplary cases to explore the nature of design in such a protean world. Our observations highlight a pragmatic approach to design in which incompleteness is harnessed in a generative manner. This suggests a change in the meaning of the word “design” itself – from one that separates the process of design from its outcome, to one that considers design as both the medium and outcome of action.

Cosmic Star Formation History and its Dependence on Galaxy Stellar Mass

Abstract: We examine the cosmic star formation rate (SFR) and its dependence on galaxy stellar mass over the redshift range 0.8 10^{10.8} M_sun) was six times higher at z = 2 than it is today. It drops steeply from z = 2, reaching the present day value at z ~ 1. In contrast, the SFR density of intermediate mass galaxies (10^{10.2} < M < 10^{10.8} M_sun) declines more slowly and may peak or plateau at z ~ 1.5. We use the characteristic growth time t_SFR = rho_M / rho_SFR to provide evidence of an associated transition in massive galaxies from a burst to a quiescent star formation mode at z ~ 2. Intermediate mass systems transit from burst to quiescent mode at z ~ 1, while the lowest mass objects undergo bursts throughout our redshift range. Our results show unambiguously that the formation era for galaxies was extended and proceeded from high to low mass systems. The most massive galaxies formed most of their stars in the first ~3 Gyr of cosmic history. Intermediate mass objects continued to form their dominant stellar mass for an additional ~2 Gyr, while the lowest mass systems have been forming over the whole cosmic epoch spanned by the GDDS. This view of galaxy formation clearly supports `downsizing' in the SFR where the most massive galaxies form first and galaxy formation proceeds from larger to smaller mass scales.

Xa21D Encodes a Receptor-like Molecule with a Leucine-Rich Repeat Domain That Determines Race-Specific Recognition and Is Subject to Adaptive Evolution

Abstract: The rice Xa21 gene confers resistance to Xanthomonas oryzae pv oryzae in a race-specific manner. Analysis of the inheritance patterns and resistance spectra of transgenic plants carrying six Xa21 gene family members indicated that one member, designated Xa21D , displayed a resistance spectrum identical to that observed for Xa21 but conferred only partial resistance. Xa21D encodes a receptor-like protein carrying leucine-rich repeat (LRR) motifs in the presumed extracellular domain. The Xa21D transcript terminates shortly after the stop codon introduced by the retrotransposon Retrofit . Comparison of nucleotide substitutions in the LRR coding regions of Xa21 and Xa21D provided evidence of adaptive selection. Both functional and evolutionary evidence indicates that the Xa21D LRR domain controls race-specific pathogen recognition.

An unprecedented coastwide toxic algal bloom linked to anomalous ocean conditions

Abstract: A coastwide bloom of the toxigenic diatom Pseudo-nitzschia in spring 2015 resulted in the largest recorded outbreak of the neurotoxin, domoic acid, along the North American west coast. Elevated toxins were measured in numerous stranded marine mammals and resulted in geographically extensive and prolonged closures of razor clam, rock crab, and Dungeness crab fisheries. We demonstrate that this outbreak was initiated by anomalously warm ocean conditions. Pseudo-nitzschia australis thrived north of its typical range in the warm, nutrient-poor water that spanned the northeast Pacific in early 2015. The seasonal transition to upwelling provided the nutrients necessary for a large-scale bloom; a series of spring storms delivered the bloom to the coast. Laboratory and field experiments confirming maximum growth rates with elevated temperatures and enhanced toxin production with nutrient enrichment, together with a retrospective analysis of toxic events, demonstrate the potential for similarly devastating ecological and economic disruptions in the future.