Biogeog, WIlsey et al 2023

What is the invasion-diversity-productivity paradox?

Species richness increases NPP in native communities but not in exotic-dominated communities.

What is the relationship between species richness and NPP in native ecosystems?

Positive; NPP increases with species richness.

What is the relationship between species richness and NPP in exotic ecosystems?

Weak, absent, or negative.

How do exotic species affect biodiversity and productivity?

Reduce species richness but often maintain or increase productivity.

Main study region?

Tallgrass prairies of the USA (Minnesota to Texas).

Key result for native sites?

NPP increased linearly with species richness.

Key result for exotic sites?

No significant richness-NPP relationship.

How much higher was NPP in exotic than native sites on average?

21.8 g m⁻².

What did the MEND experiment show?

Productivity was generally higher in exotic than native plots.

How did rooting patterns differ?

Exotics = shallow roots; natives = production throughout soil profile.

What happened to biomass with richness in native plots?

Increased with richness.

What happened to biomass with richness in exotic plots?

Unrelated or negatively related.

Did exotic species always have higher productivity?

No; only 2 of 3 datasets supported this.

How did latitude affect results?

Southern prairies: exotics more productive; northern prairies: natives more productive.

Why were southern exotics highly productive?

Many were productive C4 grasses.

Why were northern exotics less productive?

Many were less productive C3 grasses.

Did higher exotic productivity increase soil carbon storage?

No.

What happened to soil carbon stocks in exotic plots?

They were lower than in native plots.

What happened to CO₂ efflux in exotic soils?

It was higher, indicating greater carbon loss.

What is niche partitioning?

Species use resources differently, increasing total productivity.

How did niche partitioning differ between communities?

Greater in native than exotic communities.

Why does richness increase NPP in native communities?

More niche partitioning and facilitation.

What is facilitation?

Species helping each other grow or survive.

What is enemy release?

Exotics escape natural pathogens and enemies.

How does enemy release affect productivity?

Allows exotics to remain productive even at low diversity.

Were soil pathogens more abundant under native or exotic species?

Native species.

Main conclusion?

Biodiversity strongly supports productivity in native ecosystems, but invasive species can maintain high productivity despite low biodiversity.

Exam summary?

Native: more species = more productivity. Exotic: productivity often stays high regardless of diversity.