DOI: 10.5061/dryad.8931zcrt8
title: Diversity patterns and speciation processes in a two-island system with continuous migration

description: 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.
description: <strong>supplementary.pdf</strong>
 contains the Supplementary Information to the manuscript. <strong>videos.zip</strong> contains
 three videos mentioned in the manuscript, showing the evolution of
 populations for specific values of genome size (<em>B</em>)
 and migration probability (<em>ε</em>): <em>B =
 1000</em> and <em>ε = 0.004</em>, <em>B =
 2000</em> and <em>ε = 0.004</em>, and <em>B =
 2000</em> and <em>ε = 0.02</em>. Frames show all
 individuals in each island in time steps of two generations, and the
 videos start at the onset of radiation. Individuals with the same color
 belong to the same species and they are connected by links when they
 belong to the same island. The bars on the right side indicate the
 distribution of abundances in each island over time. <strong>two-islands.zip</strong> is a
 package with the files to compile the simulation of the population
 evolution. Content: seed.in, infinite_model.f90, README.md, and
 Program_FiniteB_2islands.f90. We
 provide two codes, both written in FORTRAN: Program_FiniteB_2islands.f90 This program considers a finite genome, and the
 user can set the parameters in the code. The outputs are TemporalB.txt, NetworkB.txt,
 Ind_informatonB.txt. 1.1)
 Temporal.txt has 7 columns, the first 3 refers to the parameters:
 population size (pop), genome size (B) and migration rate (mig). The
 remaining columns refer to the time (generation), species code (esp), and
 its respective abundance in island 1 (abund1) and in island2
 (abund2). 1.2) Network.txt can be
 used to plot the network of genetic compatibility. It has four columns:
 the time (generation), codes of a pair of compatible individuals (ind1 and
 ind2), and the percentage of dissimilarity between the two individuals
 H/B*100 (H/B). 1.3)
 Ind_information.txt has five columns: it gives at each time (generation),
 the code of each individual (ind), its species (esp) under a global
 referential, the island that it is (island), and if it is a migrant
 (migrate_yes/no) For additional
 information, please, contact Sabrina Araujo (araujosbl@fisica.ufpr.br). infinite_model.f90 This program considers the infinite genome model, and the user can set the other parameters in the code. The outputs are: number.dat - time, sp.total, sp.island1, sp.island2 numbertot.dat - 3 lines for each time step: time, abundances of species in island1 time, abundances of species in island2 time, abundances of all species in the system