Dipterans (two-winged insects) are thought to have evolved from a four-winged ancestor that had wings on both T2 and T3 thoracic segments, as in extant butterflies and dragonflies. Describe an evolutionary scenario for the evolution of dipterans from four-winged ancestors. What types of mutations could lead to a butterfly developing with only two wings?

Verified step by step guidance

1. Identify the ancestral state: Start by understanding that the ancestral state of dipterans likely had four wings, with wings on both the T2 and T3 thoracic segments.
2. Consider the role of homeotic genes: Homeotic genes, such as the Hox genes, are crucial in determining the identity of body segments. Mutations in these genes can lead to changes in segment identity, potentially transforming a winged segment into a non-winged segment.
3. Explore possible mutations: A mutation in a Hox gene, such as Ultrabithorax (Ubx), could suppress wing development in the T3 segment, leading to a two-winged phenotype. This mutation could result in the T3 segment developing as a haltere (a small balancing organ) instead of a wing.
4. Examine evolutionary advantages: Consider the evolutionary advantages of having only two wings. For instance, the development of halteres in place of hindwings in dipterans provides enhanced balance and maneuverability during flight, which could be advantageous for survival and reproduction.
5. Discuss natural selection: Natural selection would favor individuals with mutations that provide a survival advantage. Over time, the two-winged phenotype could become predominant in the population, leading to the evolution of dipterans from their four-winged ancestors.

Key Concepts

Evolutionary Adaptation

Evolutionary adaptation refers to the process by which species undergo changes over time to better fit their environment. In the context of dipterans, this could involve modifications in wing structure and function that enhance survival and reproductive success. For example, a reduction in wing size or number may allow for more efficient flight or energy conservation, leading to the eventual dominance of two-winged forms.

Genetic Mutations

Genetic mutations are changes in the DNA sequence that can lead to variations in physical traits. In butterflies, mutations affecting the development of wings could involve alterations in genes responsible for wing formation, such as those in the Hox gene cluster. These mutations can result in phenotypic changes, such as the loss of wings on one thoracic segment, which may be beneficial under certain environmental conditions.

Natural Selection

Natural selection is the mechanism by which individuals with advantageous traits are more likely to survive and reproduce. In the scenario of dipteran evolution, if two-winged individuals were better adapted to their environment than their four-winged counterparts, they would have a higher chance of passing on their genes. Over generations, this could lead to the prevalence of the two-winged phenotype in the population, illustrating the role of natural selection in evolutionary change.