LATITUDINAL DIVERSITY GRADIENT (LDG)

Why in the News?
A 2024 study explored how two major types of mycorrhizal fungi—arbuscular mycorrhizal (AM) and ectomycorrhizal (EM)—shape the global pattern of biodiversity across latitudes. This research provides new insights into why tropical regions host more species than temperate or polar zones.

About LDG

Definition:
The Latitudinal Diversity Gradient (LDG) describes the global biodiversity pattern where species richness peaks near the equator and declines progressively toward the poles. This phenomenon is observed in plants, animals, and microorganisms.

Key Findings of the Study:

1. Role of Mycorrhizal Fungi:
   • Mycorrhizal fungi form symbiotic relationships with ~80% of plant roots, aiding in nutrient exchange (e.g., fungi supply phosphorus/nitrogen; plants provide carbohydrates).
   • Two dominant types were studied:
     • Arbuscular Mycorrhizal (AM) Fungi:
       • Dominant in tropical regions (near the equator).
       • Promote plant diversity by facilitating coexistence of multiple species through non-specific partnerships and efficient phosphorus uptake.
     • Ectomycorrhizal (EM) Fungi:
       • Common at higher latitudes (temperate/boreal zones).
       • Form exclusive relationships with specific tree families (e.g., pines, oaks), creating monodominant forests that suppress understory diversity.
2. Impact on Biodiversity:
   • In the tropics, AM fungi enhance soil resource-sharing, allowing diverse plant species to thrive.
   • At higher latitudes, EM fungi drive ecosystems dominated by single tree species (e.g., conifers), reducing overall biodiversity.

Mechanisms Behind LDG

• Tropical Hotspots:
  • High solar energy, stable climate, and AM fungi-driven nutrient cycling sustain hyper-diverse ecosystems like rainforests.
  • AM fungi minimize competition by distributing resources evenly among plants.
• Temperate/Polar Zones:
  • Harsher climates and EM fungi’s specialization favor few cold-adapted, fast-growing tree species.
  • EM fungi create dense root networks that monopolize soil nutrients, excluding other plants.

Significance of the Study

• Challenges traditional LDG explanations (e.g., climate stability, evolutionary time).
• Highlights soil microbial communities as critical drivers of global biodiversity patterns.
• Suggests conservation strategies must prioritize preserving soil fungi diversity, especially in threatened tropical ecosystems.

Broader Implications:

• Explains why deforestation and soil degradation disproportionately harm tropical biodiversity.
• Reinforces the role of microbial partnerships in ecosystem resilience amid climate change.

Conclusion:
The study bridges a key gap in ecology by linking below-ground microbial interactions to above-ground biodiversity trends. Understanding how fungi shape ecosystems could inform reforestation efforts and biodiversity conservation in a warming world.