Niche Properties and Construction by Fungi: Soilus Pungens

Introduction

• Topic of discussion: Niche properties and niche construction by fungi, particularly Soilus Pungens.
• Major gap in understanding fungal community ecology: Lack of detailed information on individual species.

High-Throughput Sequencing

• High-throughput sequencing has revolutionized understanding of fungal communities.
• Easier and cheaper over time.
• Knowledge gained on overall changes in community composition.

Community Structure vs. Individual Species

• Communities viewed as real entities (Clements' Superorganism vs. Gleason's Individualistic Species Responses).
• Species within the same habitat can respond to different environmental cues.
• Need for a bottom-up approach to fungal community ecology focusing on individual species.

Study Focus

• Three vignettes on:
  • Dispersal and recruitment of fungi.
  • Roles of critical soil macronutrients (nitrogen and phosphorus).
  • Overall community composition and chemistry in soils.
• Main organism: Soilus Pungens.

Dispersal

• Research conducted at Point Reyes National Seashore, a habitat for Soilus Pungens.
• Pine species (Pinus Muricata) as the host for Soilus Pungens.
• Study of dispersal limitations and colonization of pine seedlings.
  • Method: Collecting soil samples and measuring colonization of bait seedlings.
  • Findings: Evidence of dispersal limitation with rapid decrease in propagule availability.

Colonization Patterns

• From the community of 200 ectomycorrhizal species, only 20 colonize seedlings; only 7 show regular abundance.
• Different dispersal patterns observed in fungi.
  • Some fungi (e.g., Helbella vespertina) decrease quickly near forest edges.
  • Soilus Pungens can colonize seedlings far from forest edges.

Nutrient Dynamics

• Importance of nutrient availability for ectomycorrhizal fungi.
• Defining the niche, influenced by:
  • Host plants.
  • Key macronutrients (nitrogen and phosphorus).
• Experiment designed to measure the effects of nitrogen and phosphorus on seedling growth.

Mutualistic Niche Model

• Importance of both absolute nutrient concentrations and their ratios in fungal colonization.
• Soilus Pungens performs best in high phosphorus, low nitrogen conditions.
• Philopra Terrestris shows opposite preferences (high nitrogen, low phosphorus).

Competition and Complementarity

• Fungi interactions can affect plant growth outcomes negatively.
• Competition vs. mutualism in functional complementarity.
• Understanding these dynamics is essential for ecological predictions.

Niche Construction

• Process by which organisms change their local environment and selective pressures.
• Soilus Pungens plays a crucial role in aiding pine seedlings to establish and outcompete other plants.
• Influence of plant species on soil chemistry and microbial community dynamics.

Conclusions

• Emphasized the value of a bottom-up approach to fungal communities.
• Detailed species-level studies can improve understanding of community assembly.
• Open to questions from the audience.