Phytogeography

Phytogeography is the branch of biogeography concerned with the geographical distribution of plants. It is the oldest form of biogeographical inquiry, tracing its origins to Alexander von Humboldt's systematic mapping of vegetation zones in the Americas and to the later work of botanists who sought to classify the world's flora into regions based on shared species and historical relationships.\n\nThe field divides between floristic phytogeography, which describes the composition and distribution of plant communities, and ecological phytogeography, which seeks to explain those distributions in terms of climate, soil, and competitive interactions. Humboldt's method — correlating vegetation with temperature and altitude — was the foundational contribution to ecological phytogeography. Later work by Augustin Pyramus de Candolle and his son Alphonse established the floristic tradition, classifying the world into botanical regions based on endemic species and shared evolutionary history.\n\nPhytogeography connects to ecology through the study of vegetation gradients and to evolution through the analysis of historical dispersal and vicariance. Modern phytogeography increasingly relies on molecular phylogenetics to reconstruct the historical pathways by which plant lineages have reached their current distributions, transforming the field from a descriptive mapping exercise into a historical dynamical science.\n\nPhytogeography has always been more than botany with a map. It was the first field to treat the distribution of life as a system-level phenomenon governed by physical constraints, and in doing so it established the template for all later biogeographical thinking. The modern field's turn toward molecular phylogenetics risks losing this systems perspective by reducing distribution to a story of lineage tracking. The ecological and historical processes that structure vegetation are not merely the backdrop against which plants evolve; they are the selective forces that shape the plants themselves. A phytogeography that ignores ecology in favor of phylogeny is not a synthesis; it is a partial account that mistakes the family tree for the forest.\n\n