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Differential Persistence (differential + persistence)
Selected AbstractsMicrobial community dynamics in a humic lake: differential persistence of common freshwater phylotypesENVIRONMENTAL MICROBIOLOGY, Issue 6 2006Ryan J. Newton Summary In an effort to better understand the factors contributing to patterns in freshwater bacterioplankton community composition and diversity, we coupled automated ribosomal intergenic spacer analysis (ARISA) to analysis of 16S ribosomal RNA (rRNA) gene sequences to follow the persistence patterns of 46 individual phylotypes over 3 years in Crystal Bog Lake. Additionally, we sought to identify linkages between the observed phylotype variations and known chemical and biological drivers. Sequencing of 16S rRNA genes obtained from the water column indicated the presence of phylotypes associated with the Actinobacteria, Bacteroidetes, Firmicutes, Proteobacteria, TM7 and Verrucomicrobia phyla, as well as phylotypes with unknown affiliation. Employment of the 16S rRNA gene/ARISA method revealed that specific phylotypes varied independently of the entire bacterial community dynamics. Actinobacteria, which were present on greater than 95% of sampling dates, did not share the large temporal variability of the other identified phyla. Examination of phylotype relative abundance patterns (inferred using ARISA fragment relative fluorescence) revealed a strong correlation between the dominant phytoplankton succession and the relative abundance patterns of the majority of individual phylotypes. Further analysis revealed covariation among unique phylotypes, which formed several distinct bacterial assemblages correlated with particular phytoplankton communities. These data indicate the existence of unique persistence patterns for different common freshwater phylotypes, which may be linked to the presence of dominant phytoplankton species. [source] The Persistence and Pricing of the Cash Component of EarningsJOURNAL OF ACCOUNTING RESEARCH, Issue 3 2008PATRICIA M. DECHOW ABSTRACT Prior research shows that the cash component of earnings is more persistent than the accrual component. We decompose the cash component into: (1) the change in the cash balance, (2) issuances/distributions to debt, and (3) issuances/distributions to equity. We find that the higher persistence of the cash component is entirely due to the subcomponent related to equity. The other subcomponents have persistence levels almost identical to accruals. We investigate whether investors understand the implications of the differential persistence of the three subcomponents. Our results suggest that investors correctly price debt and equity issuances/distributions but misprice the change in the cash balance in a similar manner to accruals. Our tests enable us to empirically distinguish the "accrual" and "external financing" anomalies with results implying that the accrual anomaly subsumes the external financing anomaly. Our results also suggest that naive fixation on earnings is unlikely to be a complete explanation for the accrual anomaly. Our findings are more consistent with investors misunderstanding diminishing returns to new investments. [source] A Reexamination of the Persistence of Accruals and Cash FlowsJOURNAL OF ACCOUNTING RESEARCH, Issue 3 2005JENNIFER FRANCIS ABSTRACT We reexamine prior studies' conclusion that accruals are less persistent than cash, focusing on two aspects of persistence that are crucial to determining its properties. The first (time specificity) refers to the fact that persistence describes how current-period shocks to income translate into next-period income. Traditional measures of accruals are, however, functions of current- and non-current-period transactions. We show that the inclusion of non-current-period transactions leads to a downward (upward) bias on the persistence of accruals (cash flows). We develop alternative measures of accruals and cash flows that are not misaligned and show that the differential persistence of cash flows over accruals is more than 70% smaller using these measures. The second aspect of persistence is firm-specificity. Specifically, we evaluate persistence using firm-specific estimations and find that more than 85% of firms show no evidence that accruals are less persistent than cash flows. [source] Genome scan in the mosquito Aedes rusticus: population structure and detection of positive selection after insecticide treatmentMOLECULAR ECOLOGY, Issue 2 2010MARGOT PARIS Abstract Identification of genes involved in local adaptation is particularly challenging for species functioning as a network of interconnected populations undergoing frequent extinctions,recolonizations, because populations are submitted to contrasted evolutionary pressures. Using amplified fragment length polymorphism markers, population genetic structure of the mosquito Aedes rusticus was analysed in five geographical areas of the French Rhône-Alpes region. We included a number of sites that were treated with the bio-insecticide Bacillus thuringiensis israelensis (Bti) for more than 15 years. Analysis of molecular variance revealed that most of the genetic variability was found within populations (96%), with no significant variation among geographical areas, although variation among populations within areas (4%) was significant. The global genetic differentiation index FST was low (0.0366 ± 0.167). However, pairwise FST values were significant and no isolation-by-distance at the regional level was observed, suggesting a metapopulation structure in this species. Bti -treatment had no effect on genetic structure and on within-population genetic diversity. Potential signatures of positive selection associated with Bti -treatment were detected for five loci, even though toxicological bioassays performed on field-collected larvae showed no significant difference in mortality between Bti -treated and nontreated sites. The difficulty of detecting moderate resistance in field-collected larvae together with possible differential persistence of toxins in the environment may explain our inability to detect a toxicological response to Bti in treated sites. The evidence for positive selection occurring at several genomic regions suggests a first step towards Bti resistance in natural mosquito populations treated with this bio-insecticide. Furthermore, this signal was detectable using genomic tools before any toxicological evidence for resistance could be identified. [source] | ||||||||||