The two phylogenetic trees given below represent evolutionary patterns in species or population.

The differently colored or dashed lines represent a single species or gene generalory.

Select the option that correctly identifies the type of evolutionary process that these two figures represents.

Correct option is A

Analyzing the diagrams:

Tree A:

• The blue lineage appears to transfer genetic material to another lineage (see red segment cutting across two lineages).

• This suggests gene flow between species, even after their divergence.

• This process is characteristic of hybridization, where two different species interbreed and genetic material is exchanged.

Tree B:

• Dashed black line shows a gene lineage that does not follow the species tree exactly.

• The gene tree deviates from the species tree, but no cross-species transfer is seen.

• This indicates incomplete lineage sorting (ILS): where ancestral genetic variation persists across speciation events, and gene trees do not match species trees due to ancestral polymorphisms.

Matching the descriptions to options:

Let’s evaluate the answer choices:

1. A – hybridization, B – incomplete lineage sorting 

   • A correctly shows cross-lineage gene flow = hybridization.

   • B shows discordance between gene and species trees without gene flow = ILS.
      This is the correct and most accurate match.

2. A – convergence, B – incomplete lineage sorting

   • Convergence refers to the independent evolution of similar traits, not gene tree structure.
      A does not represent convergence.

3. A – adaptive introgression, B – hybridization

   • Adaptive introgression is gene flow with selective advantage; Tree A does not give enough evidence for adaptiveness, just gene flow.

   • B does not show hybridization.
      Both mismatched.

4. A – hybridization, B – adaptive introgression

   • B shows ILS, not introgression or selection.

     B is incorrect.

Final Answer: Option 1 – A: hybridization, B: incomplete lineage sorting

 Information Booster:

• Hybridization: The interbreeding between two distinct species/populations that leads to gene flow. It often shows reticulate patterns (cross-connections) in phylogenies.

• Incomplete Lineage Sorting (ILS): When gene trees do not match the species tree due to retention of ancestral polymorphisms across speciation events. Common in rapidly radiating species.