Palaeogenomic analysis of black rat (Rattus rattus) reveals multiple European introductions associated with human economic history

The distribution of the black rat (Rattus rattus) has been heavily influenced by its association with humans. The dispersal history of this non-native commensal rodent across Europe, however, remains poorly understood, and different introductions may have occurred during the Roman and medieval periods. Here, in order to reconstruct the population history of European black rats, we generated a de novo genome assembly of the black rat, 67 ancient black rat mitogenomes and 36 ancient nuclear genomes from sites spanning the 1st-17th centuries CE in Europe and North Africa. Analyses of mitochondrial DNA confirm that black rats were introduced into the Mediterranean and Europe from Southwest Asia. Genomic analyses of the ancient rats reveal a population turnover in temperate Europe between the 6th and 10th centuries CE, coincident with an archaeologically attested decline in the black rat population. The near disappearance and re-emergence of black rats in Europe may have been the result of the breakdown of the Roman Empire, the First Plague Pandemic, and/or post-Roman climatic cooling.Competing Interest StatementThe authors have declared no competing interest.- Results and Discussion -- The demographic history of Rattus rattus and its closely related species -- A global phylogeography of the black rat based on mitochondrial DNA -- Ancient genomes reveal the relationships of European black rats over space and time - Discussion - Method

Effect of combining urea fertilizer with P and K fertilizers on the efficacy of urease inhibitors under different storage conditions.

Purpose Urease inhibitors provide a simple solution to mitigate ammonia loss from fertilized soil. Consumption of bulk blend fertilizers and compound fertilizers were increased in recent year and its enhanced efficiency and stabilized techniques were urgently required. However, it is essentially unknown if and how the efficacy of urease inhibitors is influenced by the inclusion of phosphorus (P) and potassium (K) fertilizers with urea. Materials and methods A laboratory study was therefore conducted to assess the impact of P and K (bulk blend scenario: combing urea with di-ammonium phosphate (DAP); compound fertilizer scenario: nitrogen (N)-P-K proportion as 16-16-16 (CN16) or 32-0-6 (CN32)) and additionally the impact of fertilizer storage duration and temperature on the efficacy of two different urease inhibitors NBPT and Limus® in reducing ammonia volatilization following application to soil. Results and discussion Both urease inhibitors significantly reduced ammonia loss from urea regardless of storage temperature and time. However, mixed storage of urea and DAP with urease inhibitors significantly decreased the efficacy of NBPT and Limus® in reducing ammonia loss. Ammonia loss increased exponentially with DAP addition rate and with storage time of the mixture. Storage at a higher temperature (30 °C compared with 20 °C) also reduced the efficacy of the inhibitors. Adding magnesium sulfate (MgSO4) to urea plus Limus® significantly mitigated the negative effect of DAP mixed storage on the efficacy of Limus® regardless of storage temperature and time. The urease inhibitors did not significantly reduce ammonia loss from CN16, but were effective for reducing ammonia loss from CN32. Conclusions The efficacy of urease inhibitors was compromised by P fertilizer. Urease inhibitor inclusion in the production of CN32, urea, and its blends (DAP + MgSO4) are recommended as an effective means of reducing the environmental cost causing by intensive agricultural production