Episode 64: What is a Common Mycorrhizal Network? – features Dr. Jason Hoeksema, a conversation that explores what common mycorrhizal networks are, how large they can grow, and whether they truly benefit the plants they connect.

Episode Summary: Dr. Jason Hoeksema is a plant ecologist and professor at the University of Mississippi who has studied mycorrhizal fungi and tree interactions since the early 1990s. He is co-author of a major 2023 review on mycorrhizal networks, has led international research collaborations in Europe, and has mentored graduate students while publishing findings on rare ectomycorrhizal plant discoveries. In this episode, he explains what common mycorrhizal networks actually are, how scientists study their size and structure, and why determining whether they benefit connected plants is far more complicated than it first appears.

Listen as Dr. Hoeksema distinguishes common mycorrhizal networks from general fungal networks, describes the confounding factors that complicate experiments testing whether these networks benefit plants, and shares the surprising discovery of an unexpected ectomycorrhizal relationship in a rare European wildflower.

In this episode we discuss:

• 01:36 – How Dr. Hoeksema first became fascinated with common mycorrhizal networks during graduate school
• 04:28 – His path into plant ecology, starting from an early interest in birds
• 06:38 – What distinguishes a "common mycorrhizal network" from general fungal networks or ecological interaction networks
• 09:08 – How large common mycorrhizal networks can grow, and the uncertainty around their continuity over space and time
• 11:25 – What resources and signals (phosphorus, nitrogen, carbon, water, and potential hormone signals) move through these networks
• 12:32 – Open questions about whether resource movement is meaningful or simply random diffusion
• 14:07 – Why testing whether common mycorrhizal networks benefit plants is experimentally difficult, including confounding effects from fungal community composition and soil volume restrictions
• 20:51 – Findings from the meta-analysis showing highly variable outcomes—from strongly positive to strongly negative effects on plants
• 22:22 – The personal and intellectual experience of re-examining his own past research for these confounding factors
• 25:34 – How common mycorrhizal networks may vary across different biomes, tree species, and mycorrhizal types (ectomycorrhizal vs. arbuscular)
• 25:41 – The research bias toward temperate Northern Hemisphere conifer forests and the need for more global studies
• 28:24 – A surprising discovery of ectomycorrhizal fungi on Pulsatilla patens (pasque flower), a plant not expected to form this type of symbiosis
• 32:30 – Advice for young researchers interested in mycorrhizal ecology and remaining open questions in the field
• 35:35 – Where listeners can learn more about Dr. Hoeksema's work

Resources:

• Dr. Jason Hoeksema's research website

This episode includes the track 'RSPN' by Blank & Kytt. The song is used under the Creative Commons Attribution 3.0 Unported License. You can find more of Blank & Kytt's music ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠here.⁠