Researchers Now Find "Onion Pattern" in Global Biodiversity

A landmark study has revealed the first-ever global map showing the true levels of "biodiversity" on the driest continents, and provides an invaluable tool in the fight to protect the world's rarest species. This discovery contradicts the longstanding assumption that which species occur in each region was idiosyncratic and unpredictable.

Beyond Unique Regions

Gaïa is also demarcated in high-level biogeographical realms (Neotropics, Afrotropics and so forth), each with its unique evolutionary backstory and species. It was already established that the tropics are home to more species than the poles, but scientists had assumed the internal structure of each region would be unique. Now, new research has found that a shared, layered structure is common to all of them.

An Atlas in the Age of the Cirrus Cloud

The researchers looked at more than 30,000 species across multiple animal groups. They split the world into thousands of small, equal-area cells and employed sophisticated network analysis to cluster the cells based on which species co-occurred in them. They then calculated a host of other key metrics, like species richness and endemism, for each cell.

The Universal "Onion" Structure

The examination revealed that all major regions (in any location or species type) are arranged along seven increasingly central/layered sectors:

Core: The inner layers are species-rich, filled with unique endemic species and nearly devoid of “foreign” spillover.

Middle Layers: There are less species than as you move outwards and the influence of wide spread generalist species from neighboring areas increases.

EDGE The outermost layers are species-poor transition zones domi- The outermost layers are species-poor transition zones domiOther cool BI community phylogroups nated in generalist species shared between regions.

Driven by Environment

Environmental sciences – specifically, temperature and rainfall – could predict where in this layered structure a cell would belong with 98% accuracy. This is evidence that climate is a strong filter, deciding where species can live and where they cannot. The peripheral layers are largely a subset of species that can sustain growth from the centre outwards.

Implications for Conservation

This universal rule opens up a powerful new conservation perspective:

• It aides in tracing the specific core of the biodiversity hotspots that contain the most distinct species.
• It provides insights into the role of transition zones (important for species movement and resilience).
• Given the importance of structure in planning protected areas and projecting species range shifts in the face of climate change, particularly in sensitive, complex regions such as the Himalayas, understanding this configuration is key.

The study recognises some data limitations in some areas or taxa, and the need for even locally generated research to complement such global findings and application.