Looks can be deceiving: speciation dynamics of co-distributed Angophora (Myrtaceae) species in a varying landscape

<p>Understanding the mechanisms underlying species divergence remains a central goal in evolutionary biology. Landscape genetics can be a powerful tool for examining evolutionary processes. We used genome-wide scans to genotype samples from populations of eight <i>Angophora</i> species. <i>Angophora</i> is a small genus within the eucalypts comprising common and rare species in a heterogeneous landscape, making it an appropriate group to study speciation. We found <i>A. hispida</i> was highly differentiated from the other species. Two subspecies of <i>A. costata</i> (subsp. <i>costata</i> and subsp. <i>euryphylla</i>) formed a group, while the third (subsp. <i>leiocarpa, </i>which is only distinguished by its smooth fruits and provenance) was supported as a distinct pseudocryptic species. Other species that are morphologically distinct could not be genetically differentiated (e.g., <em>A. floribunda </em>and <em>A. subvelutina</em>). Distribution and genetic differentiation within <i>Angophora</i> were strongly influenced by temperature and humidity, as well as biogeographic barriers, particularly rivers and higher elevation regions. While extensive introgression was found between many populations of some species (e.g., <i>A. bakeri</i> and <i>A. floribunda</i>), others only hybridized at certain locations. Overall, our findings suggest multiple mechanisms drove evolutionary diversification in <em>Angophora</em> and highlight how genome-wide analyses of related species in a diverse landscape can provide insights into speciation. </p>