Evolutionary biogeography and speciation: essay on a synthesis
Different continental and insular speciation processes are reviewed. The areal and clinal conceptions of speciation studies are discussed. I propose a revisited cline theory reconciling cline mechanics and allopatric speciation as cline analysis allows quantification in speciation description more easily and integrates polymorphism within speciation processes. In addition, insular speciation illustrates what could have been the first allopatric stages of many current continental speciations. Intrinsic correspondence is shown between areal and clinal conceptions, and between continental and insular speciation processes; this article is thus an essay towards a unified theory of speciation biogeography.