What is the value of derived traits for the reconstruction of phylogenies?

Derived traits are the characteristics that have evolved in a specific lineage and are not shared by the ancestor and all its descendants. These traits can be morphological, genetic, or physiological characteristics that distinguish one group of organisms from another.

A phylogeny represents the evolutionary relationships among a group of organisms, which are often represented as a branching tree diagram called a phylogenetic tree. In the tree, each branching point represents a common ancestor, and the length of branches reflects the degree of genetic change or the time since the divergence of two lineages.

Derived traits are crucial for reconstructing phylogenies because they provide evidence of shared evolutionary history among organisms. When two or more species share a derived trait, it suggests that they have a common ancestor that also possessed that trait. By identifying and comparing these derived traits across different organisms, scientists can infer the evolutionary relationships among them and reconstruct their phylogenetic history.

One main advantage of using derived traits in phylogenetic reconstruction is that these traits are more informative about the relationships among organisms compared to ancestral traits. Since ancestral traits are shared by all the descendants of a common ancestor, they are less useful in distinguishing closely related species. On the other hand, derived traits can help determine the order of branching events among lineages and identify unique evolutionary paths taken by different groups of organisms.

For instance, mammals are a group of vertebrates that possess several derived traits, such as hair, mammary glands, and three middle ear bones. By comparing these traits with those found in other vertebrate groups, scientists were able to determine that mammals share a more recent common ancestor with birds and reptiles, as opposed to amphibians and fishes. This information was valuable in reconstructing the phylogenetic relationships among vertebrates and understanding the evolutionary history of mammals. In conclusion, derived traits are valuable for the reconstruction of phylogenies as they provide insights into shared evolutionary history and help distinguish between closely related species. The identification and comparison of these traits across diverse organisms help scientists to better understand the evolutionary relationships and history of life on Earth.