Ecological constraints on diversification in a model adaptive radiation.

Area of Science:

• Evolutionary Biology
• Microbial Ecology

Background:

• Adaptive radiation drives taxonomic diversification, but radiation size varies significantly across taxa and even within replicate radiations.
• Understanding the factors that regulate the extent of diversification is crucial for evolutionary biology.

Purpose of the Study:

• To investigate how environmental factors, specifically energy input (productivity) and disturbance, influence diversification within a single lineage of Pseudomonas fluorescens.
• To elucidate the mechanisms by which these factors constrain or promote the size of adaptive radiations.

Main Methods:

• A laboratory-based adaptive radiation experiment using Pseudomonas fluorescens.
• Systematic variation of productivity and disturbance rates to observe effects on diversification.
• Analysis of diversity patterns and underlying fitness costs associated with niche specialization.

Main Results:

• Diversification peaked at intermediate levels of both productivity and disturbance.
• Diversity declined at extreme levels of productivity and disturbance, following known ecological patterns.
• Pleiotropic fitness costs of niche specialization, modulated by productivity and disturbance, were identified as the mechanism reducing diversity.

Conclusions:

• Ecological gradients of productivity and disturbance can limit adaptive radiation size.
• These gradients decouple evolutionary diversification from ecological coexistence, even with strong diversifying selection.
• Findings provide insights into the regulation of evolutionary diversification in microbial systems.