MECHANISMS OF LARGE-SCALE EVOLUTIONARY TRENDS.

Area of Science:

• Evolutionary biology
• Paleontology
• Biogeography

Background:

• Large-scale evolutionary trends, such as changes in size or complexity, can be driven by directional forces or occur passively in limited spaces.
• Distinguishing between driven and passive evolutionary trends is crucial for understanding macroevolutionary patterns.

Purpose of the Study:

• To introduce and validate a new statistical test (the subclade test) for distinguishing between driven and passive evolutionary trends.
• To compare the efficacy of the subclade test with existing methods (minimum behavior test, ancestor-descendant test).

Main Methods:

• Development of the subclade test, which analyzes the mean skewness of subclades from terminal distributions.
• Monte Carlo simulations to model clade diversification and assess the subclade test's performance.
• Application of the three tests to empirical data to evaluate their concordance.

Main Results:

• The subclade test, along with the minimum behavior and ancestor-descendant tests, can effectively differentiate between driven and passive evolutionary trends.
• The subclade test offers an advantage as it does not require detailed phylogenetic or time-series data, relying only on modern distributions.
• Empirical analyses showed concordant results across the three tests, supporting their validity.

Conclusions:

• The developed statistical tests provide robust tools for identifying the mechanisms underlying macroevolutionary trends.
• Passive and driven evolutionary mechanisms may represent distinct, natural categories of macroevolutionary causation.
• The subclade test is a valuable addition to the toolkit for studying evolutionary trends, particularly when historical data is limited.