Variation across Species and Levels: Implications for Model Species Research

Area of Science:

• Evolutionary Biology
• Comparative Genomics
• Molecular Biology

Background:

• Model species selection often assumes steady similarity decrease with phylogenetic distance and greater similarity at lower biological organization levels.
• Traditional comparative molecular research focused on similarities, while higher-level studies emphasized differences.
• Advances in comparative genomics reveal significant molecular differences, including gene regulation and protein-coding genes.

Purpose of the Study:

• To critically evaluate the assumptions underlying the use of model species in biological research.
• To investigate the relationship between species similarity, phylogenetic distance, and divergence time.
• To explore the extent and implications of molecular differences, including deep non-homology, across species.

Main Methods:

• Analysis of existing data on species similarity and phylogenetic distance.
• Review of comparative genomics findings regarding gene regulation and protein-coding genes.
• Examination of the phenomenon of non-orthologous gene displacement.

Main Results:

• Species similarity decreases with the square root of divergence time, not linearly, and can be non-monotonic.
• High-level homologous characters can be based on non-homologous genes (deep non-homology).
• Molecular differences between species can be substantial, challenging the generalizability of model species findings.

Conclusions:

• The assumptions about species similarity are not universally valid.
• Findings from model species may not generalize well to other species, even in molecular research.
• Deep non-homology highlights the complexity of molecular evolution and species divergence.