Chapter 30.4, Problem 10SAQ

Summary Introduction

To draw:

A phylogenetic tree that illustrates an “escape and radiate” pattern of diversification for plants that evolve novel defenses.

Introduction:

The phylogenetic history involves the study of $\text{DNA}$ sequences of the different varieties of the milkweed plants. The significance includes the analysis of genes which provide the defense mechanisms to these plants. These plants secrete a secretion from the leaves which are eaten by the monarch butterflies leading to the development of the species with resistance to this plant. This leads to the development of more population of the species of insects like butterflies.

Explanation of Solution

Pictorial representation:

Fig.1: The diversification of different species of the milkweed species.

Explanation:

The development of species of the milkweeds has taken place in the evolutionary history. These plants have resin canals or ducts which secrete a chemical. The resin canal or duct is absent in many species of the milkweeds as revealed in the experimental study which indicated that the diversification of these plants have taken place as depicted in the phylogenetic classification.

The $\text{DNA}$ analysis of the genes revealed the significance and importance of these defense secretions in plants. The leaves of these plants are eaten by the larvae of monarch butterfly which explains the evolution of more varieties of milkweeds with fewer secretions of cardenolides and less number of latex or resin canals. This has explained the pattern of escape and adaptive radiation.

Conclusion

The phylogenetic tree that explains the “escape and radiate” pattern of the diversification of milkweed plants that evolve novel defenses includes the development of new varieties with less number of latex or resin canals and less number of cardenolides.