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Why do plant-based biogeographic regions often reflect older events in Earth’s history than animal-based regions?

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World map using color coding to show the distribution of major floral kingdoms, subkingdoms, and regions. Key floral kingdoms include Boreal (green), Neotropical (pink), Paleotropical (yellow), South African or Capensic (purple), Australian (orange), and Antarctic (blue). Boundaries for subkingdoms, regions, and divisions are marked with different colored lines, and major regions such as Indoafrican, North American, and Malesian are labeled across continents. — biogeographic region Floral kingdoms, subkingdoms, and major regions of the world.

Plant-based biogeographic regions often reflect older events in Earth’s history than animal-based regions primarily because plants are significantly less mobile than animals.1

Because plants lack the ability to disperse as easily as animals, their established associations and distributions have survived into the present relatively intact, preserving patterns that date back to more ancient phases of Earth's history. In contrast, the greater mobility of animals allows them to move more freely, often resulting in faunal distributions that have been altered or "swallowed up" by more recent ecological shifts and intermingling.1

Furthermore, land and freshwater plant groups are generally older than the animal groups with which they coexist. While biogeographic regions serve as useful tools for understanding evolutionary processes and geologic events, they are not absolute; they provide a sketch of organismal distributions that helps researchers identify past dispersal mechanisms and climatic corridors rather than explaining every specific case of distribution.1