Colonization, evolutionary change, and speciation

Abstract ‘Colonization, evolutionary change, and speciation’ considers how founder populations may develop into island endemic forms. It briefly reviews the nature of the species unit, where species and subspecies fit into the taxonomic hierarchy, and the use of molecular methods, stem age, and crown age, in the depiction and dating of evolutionary relationships. It notes the distinctions between allopatry, sympatry, and parapatry in island evolution, and between novelty arising within islands and endemism through relictualism. It describes and evaluates, using case-study evidence, the phenomena of founder effects, genetic bottlenecks and genetic drift, natural selection and sexual selection, alongside processes of ecological release, density compensation, and character displacement. It describes general speciation models under the frameworks of allopatric/geographical speciation, competitive speciation, and hybridization, noting the imperfectly understood links between hybridization, polyploidy, and apomixis. It concludes with a brief evaluation of anagenesis and cladogenesis as frameworks for insular analysis.