Why do plants and animals differ among biogeographic regions with similar climates?

The observation that plants and animals differ across biogeographic regions with similar climates is a fundamental concept in biogeography. While similar environmental conditions can support biomes with comparable life strategies and adaptations, the specific species inhabiting these regions are often distinct because their distributions are not determined by current climate alone.1

Several key factors explain these differences:

• Geologic History: Events such as continental drift have played a major role in shaping the distribution of life. The fragmentation and movement of continents over geologic time have separated species, encouraging independent evolution and speciation.12
• Geographic Barriers: Physical features such as mountains, oceans, and deserts act as barriers to dispersal, preventing species from moving between regions even if the climate is suitable.2
• Evolutionary Processes: When populations are isolated, they adapt to their unique environments, leading to genetic and phenotypic divergence.3
• Dispersal Capabilities: Differences in mobility—such as the ability of birds to cross barriers that terrestrial mammals cannot—influence which species populate specific areas.42

Ultimately, while climate influences the general type of community that can survive in a region, the specific composition of that community is a product of historical events, evolutionary adaptation, and the physical constraints on dispersal.41