A dynamic model of nonviolent resistance strategy.

Why have some nonviolent revolutions succeeded even with modest participation numbers, while others have failed despite massive mobilization? We develop an agent-based model that predicts the outcomes of three well-known activism strategies. The first rapidly recruits a wide number of activists, which overwhelms the opponent's support network and encourages large-scale defections. In the second, activists who have already mobilized remain committed to success and inspire other civilians to protest even when they are unable to protest themselves. In the third strategy, campaigns focus their energy and influence directly on the regime's pillars of support. We find that this third strategy outperforms the others in generating defections, even when the size of the campaign is small. When activists have information about pillars' levels of loyalty to the regime, they can target persuasion on the pillars most likely to defect. Importantly, for small or medium-sized movements, the strategy of focusing on pillars-especially the least loyal pillars-is more likely to yield success than relying on rapid mobilization and numerical advantage alone.

Phylogeography of sugar kelp: Northern ice-age refugia in the Gulf of Alaska.

Many Northeast (NE) Pacific fishes and invertebrates survived Pleistocene glaciations in northern refugia, but the extent that kelps survived in northern areas is uncertain. Here, we test the hypothesis that populations of sugar kelp (Saccharina latissima) persisted in the Gulf of Alaska during ice-age maxima when the western margin of the Cordilleran ice sheet covered coastal areas around the NE Pacific Ocean. We estimated genetic diversities within and phylogeographical relationships among 14 populations along 2,800 km in the NE Pacific and Bering Sea with partial sequences of mitochondrial DNA 5'-cytochrome oxidase subunit I (COI, bp = 624, n = 543), chloroplast DNA ribulose-1,5-bisphosphate carboxylase large subunit-3' (rbcL, bp = 735, n = 514), and 11 microsatellite loci. Concatenated sequences of rbcL and COI showed moderate levels of within-population genetic diversity (mean h = 0.200) but substantial differences among populations (ΦST = 0.834, p < .0001). Microsatellites showed moderate levels of heterozygosity within populations (mean H E = 0.391). Kelps in the same organellar lineage tended to cluster together, regardless of geographic origins, as indicated in a principal coordinate analysis (PCoA) of microsatellite genotypes. The PCoA also showed evidence of nuclear hybridizations between co-occurring organellar lineages. Individual admixture plots with population clusters of K = 2, 6, and 9 showed increasing complexity with considerable historical admixture between some clusters. A time-calibrated phylogeny placed divergences between rbcL-COI lineages at 1.4 million years at most. The time frames of mutation in the rbcL-COI lineages and microsatellite population clusters differed among locations. The existence of ancient lineages in the Gulf of Alaska, moderate levels of genetic diversity, and the absence of departures from neutrality are consistent with northern refugia during multiple Croll-Milankovitch climate cycles in the Pleistocene Epoch.

The science of contemporary street protest: New efforts in the United States.

Since the inauguration of Donald Trump, there has been substantial and ongoing protest against the Administration. Street demonstrations are some of the most visible forms of opposition to the Administration and its policies. This article reviews the two most central methods for studying street protest on a large scale: building comprehensive event databases and conducting field surveys of participants at demonstrations. After discussing the broader development of these methods, this article provides a detailed assessment of recent and ongoing projects studying the current wave of contention. Recommendations are offered to meet major challenges, including making data publicly available in near real time, increasing the validity and reliability of event data, expanding the scope of crowd surveys, and integrating ongoing projects in a meaningful way by building new research infrastructure.

The physics of dissent and the effects of movement momentum.

How do 'people power' movements succeed when modest proportions of the population participate? Here we propose that the effects of social movements increase as they gain momentum. We approximate a simple law drawn from physics: momentum equals mass times velocity (p = mv). We propose that the momentum of dissent is a product of participation (mass) and the number of protest events in a week (velocity). We test this simple physical proposition against panel data on the potential effects of movement momentum on irregular leader exit in African countries between 1990 and 2014, using a variety of estimation techniques. Our findings show that social movements potentially compensate for relatively modest popular support by concentrating their activities in time, thus increasing their disruptive capacity. Notably, these findings also provide a straightforward way for dissidents to easily quantify their coercive potential by assessing their participation rates and increased concentration of their activities over time.

Population structure and genetic diversity of Sinibrama macrops from Ou River and Ling River based on mtDNA D-loop region analysis, China.

In order to understand the influence of human activities such as habitat fragmentation on freshwater fish population evolution, we investigated and compared the genetic diversity and phylogeography of Sinibrama macrops populations in the Oujiang River and Ling River. Mitochondrial control region sequences (D-loop region) of 131 specimens from six populations were obtained and analyzed. The diversity of main stream in the Ou River was lower than that in Ling River. Changtan population showed the lowest diversity (H = 0.646 ± 0.077; π = 0.00060 ± 0.00820). Pairwise FST, gene flow (Nm), and genetic distance (Da) indicated that Longquan and Changtan significantly differentiate from other populations. Nested clade phylogeographical analysis (NCPA) showed some clades and total cladogram experienced isolation by distance. In conclusion, the populations from severely fragmented Ou River have the lower diversity and more intense differentiation than that from the mainstream of Ling River, Changtan population present the lowest diversity and were isolated by the dam construction.