Synthesizing the phylogenetic evidence for mutualism-associated diversification

Area of Science:

• Evolutionary Biology
• Ecology
• Phylogenetics

Background:

• Mutualisms, interactions where species benefit each other, are hypothesized to promote species diversification.
• Existing empirical evidence supporting or refuting this hypothesis is conflicting due to diverse and potentially unreliable methodologies.
• Synthesizing data across different studies is challenging due to variations in data types and analytical approaches.

Purpose of the Study:

• To rigorously test the hypothesis that mutualisms spur species diversification using consistent phylogenetic comparative methods.
• To reconcile conflicting evidence by analyzing diverse datasets with standardized analytical techniques.
• To determine if observed variations in diversification rates are attributable to the nature of mutualisms or methodological differences.

Main Methods:

• Synthesized multiple phylogenetic comparative datasets.
• Applied sister-clade comparisons and hidden-state dependent speciation-extinction models for consistent analysis.
• Compared results across taxonomically overlapping datasets analyzed with different methods.

Main Results:

• The majority of datasets showed no significant effect of mutualism on diversification rates.
• Some datasets indicated a significant positive association, while a few suggested a significant negative association.
• Qualitative findings were consistent across different methods when analyzing overlapping datasets, irrespective of mixed quantitative results.

Conclusions:

• Mutualism does not universally drive species diversification across all studied taxa.
• The observed variation in diversification effects is likely due to the specific characteristics of the mutualistic interactions themselves.
• Methodological inconsistencies are less likely to be the primary cause of conflicting findings in previous studies.