Comparing diversification rates in lakes, rivers, and the sea

Area of Science:

• Ecology
• Evolutionary Biology
• Ichthyology

Background:

• Freshwater habitats (<1% of Earth's water) host disproportionately high species diversity compared to marine environments.
• Habitat fragmentation is a common hypothesis for increased freshwater speciation, but sympatric speciation may also play a key role.
• Differences in speciation rates between rivers and lakes are crucial for understanding broad diversification patterns.

Purpose of the Study:

• To compare diversification rates of teleost fishes across marine, riverine, and lacustrine habitats.
• To investigate the drivers of the freshwater paradox, the high diversity of species in freshwater ecosystems.
• To evaluate the role of habitat type and speciation modes in shaping fish biodiversity.

Main Methods:

• Comparative analysis of diversification rates across different aquatic habitats.
• Application of biogeographic models to assess habitat evolutionary stability.
• Examination of speciation and net diversification rates in marine, riverine, and lacustrine fish species.

Main Results:

• Lakes exhibit the fastest speciation and net diversification rates among all aquatic habitats studied.
• Rivers are the primary source of freshwater fish diversity, despite lakes showing rapid diversification.
• Marine and riverine habitats show similar average net diversification rates; lacustrine habitats are evolutionarily unstable.
• The high diversity in freshwater is not solely explained by diversification rate differences.

Conclusions:

• Strong diversification rate differences alone do not explain the freshwater paradox.
• The evolutionary history and comparable time spent in riverine and marine habitats may account for the observed diversity patterns.
• Lacustrine radiations, while rapid, contribute less to overall diversity due to habitat instability.