The following interferences were made by different researchers:
A. Eye spots were present in the ancestors and some species lost them.
B. Eye spots were not present in the ancestors.
C. Eye spots were lost more than once in evolution of the family.
D. Eye spots were gained only once while evolving from ancestors without them.
Which of the interferences are correct?
(1) A and B (2) C and D
(3) A and C (4) B and D

Tracing the Evolution of Eye Spots in Moths: Losses, Gains, and Ancestral States

The evolution of eye spots on moth wings is a classic example of how traits can appear, disappear, and reappear across evolutionary time. By mapping these traits onto a phylogenetic tree, scientists can infer whether eye spots were present in ancestral species and how often they were lost or gained during the diversification of a moth family.

Understanding the Scenario

In the given phylogenetic tree, some moth species have eye spots (marked by circles) while others do not. Researchers have made several inferences about the evolutionary history of this trait:

• A. Eye spots were present in the ancestors, and some species lost them.

• B. Eye spots were not present in the ancestors.

• C. Eye spots were lost more than once in the evolution of the family.

• D. Eye spots were gained only once while evolving from ancestors without them.

What Does Phylogenetic Evidence Suggest?

1. Ancestral Presence and Multiple Losses

Current research on eyespot evolution in Lepidoptera (the group that includes moths and butterflies) indicates that eyespot traits are evolutionarily labile—they can be gained and lost multiple times across different lineages. However, when a trait is present in multiple, distantly related branches of a phylogenetic tree, the most parsimonious explanation is that the trait was present in the common ancestor and was lost independently in multiple lineages, rather than being gained multiple times independently.

• Supporting A: If eye spots are scattered across the tree, it is likely they were present in the ancestor and lost in some descendant lines.

• Supporting C: The scattered absence of eye spots among species with close relatives that have them suggests multiple independent losses.

2. Single Gain Is Less Likely Than Multiple Losses

While eyespots can evolve independently, in the context of a single family tree where the trait is present in several branches, it is less parsimonious to assume multiple independent gains (especially if the trait is complex and developmentally regulated). Instead, it is more likely that the trait was lost multiple times.

• Against B and D: The idea that eye spots were not present in the ancestor (B) or were gained only once (D) does not fit the pattern if the trait is present in several non-adjacent branches.

Conclusion: Which Inferences Are Correct?

Based on phylogenetic principles and current evolutionary research:

• A. Eye spots were present in the ancestors and some species lost them.

• C. Eye spots were lost more than once in evolution of the family.

These explanations are most consistent with the observed distribution of eye spots and with established evolutionary models for complex traits in moths and butterflies.

Correct answer: (3) A and C

Further Reading

• Studies show that eyespots in Lepidoptera have evolved in complex ways, often involving multiple independent losses and occasional gains, but widespread presence across a family typically points to ancestral origin with subsequent losses.

• Understanding these patterns helps unravel the evolutionary pressures and developmental mechanisms shaping biodiversity in moths and butterflies.