Assessing the origins of the European Plagues following the Black Death: A synthesis of genomic, historical, and ecological information.

The second plague pandemic started in Europe with the Black Death in 1346 and lasted until the 19th century. Based on ancient DNA studies, there is a scientific disagreement over whether the bacterium, Yersinia pestis, came into Europe once (Hypothesis 1) or repeatedly over the following four centuries (Hypothesis 2). Here, we synthesize the most updated phylogeny together with historical, archeological, evolutionary, and ecological information. On the basis of this holistic view, we conclude that Hypothesis 2 is the most plausible. We also suggest that Y. pestis lineages might have developed attenuated virulence during transmission, which can explain the convergent evolutionary signals, including pla decay, that appeared at the end of the pandemics.

Impact of past climate warming on genomic diversity and demographic history of collared lemmings across the Eurasian Arctic.

The Arctic climate was warmer than today at the last interglacial and the Holocene thermal optimum. To reveal the impact of past climate-warming events on the demographic history of an Arctic specialist, we examined both mitochondrial and nuclear genomic variation in the collared lemming (Dicrostonyx torquatus, Pallas), a keystone species in tundra communities, across its entire distribution in northern Eurasia. The ancestral phylogenetic position of the West Beringian group and divergence time estimates support the hypothesis of continental range contraction to a single refugial area located in West Beringia during high-magnitude warming of the last interglacial, followed by westward recolonization of northern Eurasia in the last glacial period. The West Beringian group harbors the highest mitogenome diversity and its inferred demography indicates a constantly large effective population size over the Late Pleistocene to Holocene. This suggests that northward forest expansion during recent warming of the Holocene thermal optimum did not affect the gene pool of the collared lemming in West Beringia but reduced genomic diversity and effective population size in all other regions of the Eurasian Arctic. Demographic inference from genomic diversity was corroborated by species distribution modeling showing reduction in species distribution during past climate warming. These conclusions are supported by recent paleoecological evidence suggesting smaller temperature increases and moderate northward forest advances in the extreme northeast of Eurasia during the Late Pleistocene-to-Holocene warming events. This study emphasizes the importance of West Beringia as a potential refugium for cold-adapted Arctic species under ongoing climate warming.

Conservation, spillover and gene flow within a network of Northern European marine protected areas.

To ensure that marine protected areas (MPAs) benefit conservation and fisheries, the effectiveness of MPA designs has to be evaluated in field studies. Using an interdisciplinary approach, we empirically assessed the design of a network of northern MPAs where fishing for European lobster (Homarusgammarus) is prohibited. First, we demonstrate a high level of residency and survival (50%) for almost a year (363 days) within MPAs, despite small MPA sizes (0.5-1 km(2)). Second, we demonstrate limited export (4.7%) of lobsters tagged within MPAs (N = 1810) to neighbouring fished areas, over a median distance of 1.6 km out to maximum 21 km away from MPA centres. In comparison, median movement distance of lobsters recaptured within MPAs was 164 m, and recapture rate was high (40%). Third, we demonstrate a high level of gene flow within the study region, with an estimated F ST of less than 0.0001 over a ≈ 400 km coastline. Thus, the restricted movement of older life stages, combined with a high level of gene flow suggests that connectivity is primarily driven by larval drift. Larval export from the MPAs can most likely affect areas far beyond their borders. Our findings are of high importance for the design of MPA networks for sedentary species with pelagic early life stages.

Environmental toxicology: population modeling of cod larvae shows high sensitivity to loss of zooplankton prey.

Two factors determine whether pollution is likely to affect a population indirectly through loss of prey: firstly, the sensitivity of the prey to the pollutants, and secondly, the sensitivity of the predator population to loss of prey at the given life stage. We here apply a statistical recruitment model for Northeast Arctic cod to evaluate the sensitivity of cod cohorts to loss of zooplankton prey, for example following an oil spill. The calculations show that cod cohorts are highly sensitive to possible zooplankton biomass reductions in the distribution area of the cod larvae, and point to a need for more knowledge about oil-effects on zooplankton. Our study illustrates how knowledge about population dynamics may guide which indirect effects to consider in environmental impact studies.

Periodic climate cooling enhanced natural disasters and wars in China during AD 10-1900.

Recent studies have linked climatic and social instabilities in ancient China; the underlying causal mechanisms have, however, often not been quantitatively assessed. Here, using historical records and palaeoclimatic reconstructions during AD 10-1900, we demonstrate that war frequency, price of rice, locust plague, drought frequency, flood frequency and temperature in China show two predominant periodic bands around 160 and 320 years where they interact significantly with each other. Temperature cooling shows direct positive association with the frequency of external aggression war to the Chinese dynasties mostly from the northern pastoral nomadic societies, and indirect positive association with the frequency of internal war within the Chinese dynasties through drought and locust plagues. The collapses of the agricultural dynasties of the Han, Tang, Song and Ming are more closely associated with low temperature. Our study suggests that food production during the last two millennia has been more unstable during cooler periods, resulting in more social conflicts owing to rebellions within the dynasties or/and southward aggressions from northern pastoral nomadic societies in ancient China.