Meeting Abstract
Five broad regularities of biogeography and biodiversity are observed in many taxa with continental distributions: 1, power function-like species-area relationships; 2, log-normal distribution of species geographic range sizes; 3, mid-domain effects with more species towards the geographic center, and more early-branching, species-poor clades towards the geographic periphery; 4, exponential net diversification with log-linear accumulation of lineages through time; and 5, power function-like relationships between species-richness and cladal-diversity, where most clades are species-poor and few clades are species-rich. However, current theory does not provide a robust mechanistic framework to connect these seemingly disparate patterns. Here we present SEAMLESS – Spatially-Explicit Area Model of Landscape Evolution by SimulationS – that generates clade diversification by moving geographic barriers on a continuous, neutral landscape. SEAMLESS models the effects of barrier displacement on all three terms of macroevolutionary diversification: dispersal, speciation, and extinction. Barrier displacement merges adjacent areas allowing dispersal and larger geographic ranges, separates adjacent areas resulting in vicariant speciation and smaller geographic ranges, and subdivides areas resulting in extinction below a minimum species persistence threshold. SEAMLESS shows how dispersal is required to avoid clade-wide extinction, demonstrates that ancestral range size does not predict species richness, and provides a unified explanation for the five commonly observed biogeographic and phylogenetic patterns described above. SEAMLESS contributes to a theory of continental biogeography by modeling the macroevolutionary consequences of landscape evolution processes.
