Plant pathogens drive density-dependent seedling mortality in a tropical tree

Area of Science:

• Ecology
• Plant Pathology
• Tropical Biology

Background:

• Extraordinary tropical forest tree diversity is hypothesized to be maintained by density-dependent mortality, favoring rare species.
• Density-dependent mortality, particularly intense for seeds and small seedlings in tropical forests, has uncertain causes.
• Oomycota pathogens are investigated as a potential cause of this intense seedling mortality.

Discussion:

• Experimental fungicide application on Sebastiana longicuspis seedlings reduced mortality eightfold compared to untreated plots.
• Mortality exhibited strong density dependence: survival was unaffected by density in fungicide-treated plots but significantly higher at low densities in unsprayed plots.
• Transient density-dependent mortality observed in non-manipulative studies may underestimate pathogen impacts.

Key Insights:

• Pathogens from the Oomycota phylum are experimentally confirmed to cause intense mortality in neotropical tree seedlings.
• Fungicide treatment significantly increases seedling survival and eliminates density-dependent mortality.
• Plant pathogens play a crucial role in structuring tropical tree diversity through density-dependent mortality.

Outlook:

• Widespread pathogen-induced density-dependent mortality could be a key mechanism maintaining tropical biodiversity.
• Further research is needed to assess the prevalence and impact of plant pathogens across diverse tropical ecosystems.
• Understanding these dynamics is crucial for tropical forest conservation and management strategies.