Increased spatial-genetic structure in a population of the clonal aquatic plant Sagittaria latifolia (Alismataceae) following disturbance.

The spatial genetic structure (SGS) of plant populations is determined by the outcome of key ecological processes, including pollen and seed dispersal, the intensity of local resource competition among newly recruited plants, and patterns of mortality among established plants. Changes in the magnitude of SGS over time can provide insights into the operation of these processes. We measured SGS in a population of the clonal aquatic plant, Sagittaria latifolia that had been disturbed by flooding, both before and after the flood. Over the four-year interval between measurements, we found substantial changes in the magnitude of SGS. In the first measurement (pre-flood), SGS was weak, even over short distances. By contrast, there was substantial SGS in the second measurement (post-flood), particularly over short distances. This change in SGS was accompanied by near complete turnover in the genotypic composition of the population. The genotypic richness of the population (the number of unique clones scaled by the sample size) was halved over the four-year interval. The clonal subrange-the distances between shoots within clones-also shrank considerably, with more than 5% of shoots having clone-mates at distances >10 m before the flood, but fewer than 5% of shoots having clone-mates at distances beyond 2 m afterwards. Clonal turnover and the re-establishment of SGS in clonal populations are both expected following local extirpation and recruitment. These data reveal the genetic signatures of disturbance and a subsequent flush of seedling recruitment and clonal expansion.

Preemptive dose reduction of warfarin in patients initiating metronidazole.

BACKGROUND: The goal of this study was to determine if preemptive dose reduction (PDR) of warfarin is effective in maintaining therapeutic anticoagulation in patients initiating metronidazole. METHODS: This is a retrospective, single-center, cohort study in a pharmacist-managed anticoagulation clinic of a university affiliated Veteran's Affairs (VA) Medical Center. Subjects were anticoagulation patients initiating metronidazole between 1 January 2002 and 30 March 2009. At the time of metronidazole initiation, patients were managed with PDR of warfarin or no dose reduction. The primary outcome was the average change in International Normalized Ratio (INR) between patients that received PDR vs. those that did not. RESULTS: In total, 20 patients met inclusion criteria with seven patients receiving PDR at the time of initiation of metronidazole, whereas 13 did not. Patients managed with PDR and those that were not were similar in age (mean±SD 69.4±12.9 years vs. 72.1±9.9 years, p=0.61), mean baseline INR before metronidazole (2.58±0.49 vs. 2.57±0.66, p=0.98), and mean time to follow-up after initiation of metronidazole (5.6±2.9 days vs. 7.0±3.7 days, p=0.40), respectively. The primary outcome was statistically significant with a mean difference in INR of 1.28 (p=0.01) between patients manag-ed with PDR vs. those that were not. The mean preemptive warfarin dose reduction was 34.6%±13.4% which resulted in no significant increase in INR (p=0.61). Secondary outcomes including INR values >4.0 (0% vs. 46%, p=0.05), the average number of warfarin doses omitted (0.43±0.79 vs. 1.15±1.27, p=0.17), use of phytonadione or fresh frozen plasma, and rates of bleeding events were not significantly different be-tween groups. No thromboembolic events occurred during the 30 days following metronidazole therapy. CONCLUSIONS: In patients determined to be appropriate candidates for PDR, a 30%-35% reduction in mean daily warfarin dose was effective in maintaining therapeutic anticoagulation in patients started on concomitant metronidazole.