Geographic isolation is a central mechanism of speciation, but perfect isolation of populations is rare. Although speciation can be hindered if gene flow is large, intermediate levels of migration can enhance speciation by introducing genetic novelty in the semi‐isolated populations or founding small communities of migrants. Here, we consider a two‐island neutral model of speciation with continuous migration and study diversity patterns as a function of the migration probability, population size, and number of genes involved in reproductive isolation (dubbed as genome size). For small genomes, low levels of migration induce speciation on the islands that otherwise would not occur. Diversity, however, drops sharply to a single species inhabiting both islands as the migration probability increases. For large genomes, sympatric speciation occurs even when the islands are strictly isolated. Then species richness per island increases with the probability of migration, but the total number of species decreases as they become cosmopolitan. For each genome size, there is an optimal migration intensity for each population size that maximizes the number of species. We discuss the observed modes of speciation induced by migration and how they increase species richness in the insular system while promoting asymmetry between the islands and hindering endemism.

Em fluidos com alta viscosidade, as forças inerciais são irrelevantes para a locomoção de organismos. No entanto, seu movimento se dá usando uma estratégia semelhante à um gato que se vira durante uma queda para cair em pé, uma vez que, ele não necessita de forças inerciais para se virar (seu momento angular é nulo em todo instante). Ambos são problemas de teoria de gauge e através de um modelo simples e com alto grau de simetria, podemos compreender a locomoção de corpos deformáveis em baixo número de Reynolds.