With reference to Figure 2 briefly explain in your own words why the combination

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With reference to Figure 2 briefly explain in your own words why the combination of experimental and phylogenetic data is necessary to make a convincing argument that the striped/stripeless phenotype is likely an adaptation to predation rates

40 Striped 24 Stripeless 8 environment TRENDS in Ecology & Evolution Figure 2. Dorsal stripe morphology as an adaptation to predation in Timema walking sticks. (a) Two morphs of T. cristinae on their respective host plants: striped (blue outline) and stripeless (red outline) (photographs by Aaron Comeault). (b) A manipulative ecological experiment measuring selection on individuals with and without stripes in both habitats (16]. In the presence of bird predators, the striped morph has higher fitness on plants with needle-like leaves, whereas the stripeless morph has higher fitness on broad leaves. Fitness of the morphs is equivalent on the two plant types in the absence of predators [93]. (c) To test for the broad-scale consequences of such divergent selection, a phylogenetic study of all 21 species of Timema was conducted. Timema walking sticks evolved a dorsal stripe five or six times independently, each time associated with a shift to needle-like leaves. Species with dorsal stripes are marked with a blue dot; those without stripes are marked in red. Use of broadleaf host plants is ancestral, with repeated host shifts to plants with needle-like leaves associated with the evolution of a dorsal stripe. Species with members that shifted to needle-like leaves are marked with grey plants above tips (bottom panel redrawn from [15])

Explanation / Answer

While phylogenetic studies are aimed at deciphering the evolutionary relationships among a group of organisms, experimental studies allow for study of mechanistic hypothesis that drove these evolutionary traits to be fixed. Since both of these methods individually suffer from certain drawbacks, a combined study using both the approaches complement for each other and can address interpretational drawbacks that are inherent with each of the methods. While phylogenetic studies can generate useful data, manipulative experiments can be used on populations to test the data. Phylogenetic data helps the researchers with data that can be used to design an experiment and verify the hypotheses.

The same way, experimental results can provide data that can be used to test the phylogenetic relationship between the populations. Without experimental evidence, cause and effect cannot be determined only from the phylogenetic studies.

Experimental studies on extant walking sticks to evaluate if crypsis is the driving force for the trait-environment association. The results given confirm that dorsal stripes allow crypsis and protection from predators.

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