Biogeographical Regions and Species Diversity

For almost two centuries, biologists have described large biogeographical regions, each hosting unique species shaped by history, climate, and geographical barriers. Traditionally, it was assumed that the internal organization of species differed significantly between regions like South America and Africa. However, global patterns, such as higher biodiversity in tropical zones compared to polar zones, suggest potential universal rules governing species distribution.

New Study Findings

A recent study published in Nature Ecology & Evolution, involving researchers from Spain, Sweden, and the UK, discovered a universal pattern in biogeographical regions across various species, including birds, mammals, and amphibians. They utilized global databases and network analysis tools to identify biogeographical regions and characteristic species.

• Species were categorized based on their presence in specific biogeographical clusters.
• Four diversity types were assessed: species richness, biota overlap, occupancy, and endemicity.
• The world was divided into seven repeating biogeographical sectors, consistently observed across regions and taxonomic groups.
• The study found a layered organization of biodiversity, resembling an onion: dense core hotspots with unique biodiversity, transitioning to species-poor outer layers.
• Temperature and rainfall were found to predict the biogeographical sector of species in 98% of cases, indicating environmental tolerance as a survival factor.

Implications for Conservation

• The study offers insights into broad ecological trends, highlighting how biodiversity spreads from regional hotspots, influenced by environmental filters like climate and elevation.
• This understanding is vital for conservation efforts, particularly in regions like the Indian Himalayas, which are affected by climate change.
• Smarter conservation strategies could focus on key habitats and natural corridors rather than traditional protected areas.
• Experimentation and observation of changes in rainfall and temperature can guide conservation priorities.
• Some geographical gaps were noted in the study, such as limited data for dragonflies in Eurasia and trees in North America. 
• Regions in the tropics and Global South, including parts of India, were also underrepresented, suggesting a need for further region-specific studies.

Overall, the newly discovered core-to-transition rule organizes species' distributions into layers, providing a clearer framework for conservationists to protect biodiversity.