RESUMEN
Social media has the potential to encourage prosocial behaviors at scale, yet very little causal evidence exists on the impact of related efforts. Blood donation is a particularly difficult, but essential prosocial behavior that is often critically undersupplied. We examine the effect of Facebook's blood donation tool on voluntary blood donation. We partnered with four major blood banks in the United States covering 363 collection facilities in 46 states and Washington, D.C. We tracked the tool's impact on blood donations during its staggered rollout on a sample of more than 47,000 facility-date observations from March 2019 to September 2019. The tool caused an increase of 0.55 total donations per facility per day (+4.0% [95% CI: 0.04%-8.0%]), and an increase of 0.15 donations from first-time donors per facility per day (+18.9% [95% CI: 4.7%-33.1%]). Longitudinal evidence from Brazil and India suggests the share of donors who both received a message from the tool and stated they were influenced by Facebook to donate increased from 0% to 14.1% [95% CI: 12.1%-16.2%] in the first year of the tool's deployment (i.e., September 2018 to August 2019). These meaningful increases, especially from first-time donors, demonstrate that social media platforms can play an important role in fostering offline prosocial behaviors that benefit the health and well-being of societies around the world.
Asunto(s)
Donantes de Sangre , Medios de Comunicación Sociales , Humanos , Brasil , Washingtón , IndiaRESUMEN
All organisms are faced with environmental uncertainty. Bet-hedging theory expects unpredictable selection to result in the evolution of traits that maximize the geometric-mean fitness even though such traits appear to be detrimental over the shorter term. Despite the centrality of fitness measures to evolutionary analysis, no direct test of the geometric-mean fitness principle exists. Here, we directly distinguish between predictions of competing fitness maximization principles by testing Cohen's 1966 classic bet-hedging model using the fungus Neurospora crassa. The simple prediction is that propagule dormancy will evolve in proportion to the frequency of 'bad' years, whereas the prediction of the alternative arithmetic-mean principle is the evolution of zero dormancy as long as the expectation of a bad year is less than 0.5. Ascospore dormancy fraction in N. crassa was allowed to evolve under five experimental selection regimes that differed in the frequency of unpredictable 'bad years'. Results were consistent with bet-hedging theory: final dormancy fraction in 12 genetic lineages across 88 independently evolving samples was proportional to the frequency of bad years, and evolved both upwards and downwards as predicted from a range of starting dormancy fractions. These findings suggest that selection results in adaptation to variable rather than to expected environments.
Asunto(s)
Evolución Biológica , Ambiente , Aptitud Genética , Neurospora crassa/fisiología , Adaptación Fisiológica , África , Haití , Neurospora crassa/genética , Estados UnidosRESUMEN
The gecko genus Phyllopezus occurs across South America's open biomes: Cerrado, Seasonally Dry Tropical Forests (SDTF, including Caatinga), and Chaco. We generated a multi-gene dataset and estimated phylogenetic relationships among described Phyllopezus taxa and related species. We included exemplars from both described Phyllopezus pollicaris subspecies, P. p. pollicaris and P. p.przewalskii. Phylogenies from the concatenated data as well as species trees constructed from individual gene trees were largely congruent. All phylogeny reconstruction methods showed Bogertia lutzae as the sister species of Phyllopezus maranjonensis, rendering Phyllopezus paraphyletic. We synonymized the monotypic genus Bogertia with Phyllopezus to maintain a taxonomy that is isomorphic with phylogenetic history. We recovered multiple, deeply divergent, cryptic lineages within P. pollicaris. These cryptic lineages possessed mtDNA distances equivalent to distances among other gekkotan sister taxa. Described P. pollicaris subspecies are not reciprocally monophyletic and current subspecific taxonomy does not accurately reflect evolutionary relationships among cryptic lineages. We highlight the conservation significance of these results in light of the ongoing habitat loss in South America's open biomes.
Asunto(s)
Biodiversidad , Lagartos/clasificación , Lagartos/genética , Filogenia , Animales , Evolución Biológica , ADN Mitocondrial , Ecosistema , Tipificación de Secuencias Multilocus , Proteínas Nucleares/genética , América del SurRESUMEN
The genus Gonatodes is a monophyletic group of small-bodied, diurnal geckos distributed across northern South America, Central America, and the Caribbean. We used fragments of three nuclear genes (RAG2, ACM4, and c-mos) and one mitochondrial gene (16S) to estimate phylogenetic relationships among Amazonian species of Gonatodes. We used Penalized Likelihood to estimate timing of diversification in the genus. Most cladogenesis occurred in the Oligocene and early Miocene and coincided with a burst of diversification in other South American animal groups including mollusks, birds, and mammals. The Oligocene and early Miocene were periods dominated by dramatic climate change and Andean orogeny and we suggest that these factors drove the burst of cladogenesis in Gonatodes geckos as well as other taxa. A common pattern in Amazonian taxa is a biogeographic split between the eastern and western Amazon basin. We observed two clades with this spatial distribution, although large differences in timing of divergence between the east-west taxon pairs indicate that these divergences were not the result of a common vicariant event.