Nodes in phylogenetic trees are critical components that represent the common ancestors of the species that diverge from them. Each node marks a point in evolutionary time where a lineage splits into two or more descendant lineages. This splitting is indicative of speciation events, where one species evolves into multiple distinct species over time.
The arrangement of nodes helps visualize the relationships among various organisms, showing how they are related through common ancestry. The more closely related two species are, the more recent their common ancestor will be.
In summary, nodes in phylogenetic trees serve as important markers of evolutionary history, illustrating the connections between species and their ancestors, helping scientists and researchers understand the complex web of life on Earth.