Identifying Adaptation Origin: Gene vs. Species Phylogeny
The question asks for the best method to determine if the garter snakes' adaptation to newt toxin (tetrodotoxin or TTX) arose from a single evolutionary event or multiple independent events.
This requires comparing the evolutionary history of the specific gene involved (the sodium ion channel) with the evolutionary history of the species themselves (garter snakes).
Analyzing Evolutionary History Methods
- Gene Phylogeny: Tracks the evolutionary relationships between different versions (alleles or orthologs) of a specific gene.
- Species Phylogeny: Tracks the evolutionary relationships between different species based on overall genetic information or morphology.
By comparing these two phylogenies:
- If the gene tree topology closely matches the species tree topology, it suggests the trait (TTX resistance) evolved once in an ancestor and was inherited through speciation.
- If the gene tree topology differs significantly from the species tree topology, showing similar gene variants in distantly related species on the species tree, it suggests independent, multiple origins of the adaptation (convergent evolution).
Evaluating the Options
- Option 1 (Gene phylogeny of garter snakes only): Shows gene evolution but lacks the species context needed to infer origin timing across species.
- Option 2 (Species phylogeny of garter snakes only): Shows species relationships but not the specific genetic changes driving the adaptation.
- Option 3 (Newt phylogenies): Irrelevant for studying adaptation within garter snakes.
- Option 4 (Gene phylogeny of garter snake sodium ion channels AND species phylogeny of garter snakes): This is the correct approach. It provides both the evolutionary history of the target gene (sodium ion channel) and the evolutionary history of the species (garter snakes). Comparing them directly addresses whether the adaptation has a single or multiple origins.
Therefore, building and comparing these two specific phylogenies is the most suitable method.
Important Questions from Phylogenetic trees
A phylogenetic tree representing the evolutionary relationship between various vertebrates is shown below.
Given this tree topology, which one or more of the following statements is/are correct?A phylogenetic tree for the evolution of two pigmentation traits in species of fish is shown for clades X, Y and Z. Genes A and/or B, if mutated, can cause dark pigmentation in the body.
Which one or more of the following statements is/are correct?- Whales and dolphins are hypothesized to have evolved along the northern shore of the Tethys Sea, prior to the Indian plate's collision with the Eurasian plate. To which one of the following animals are these aquatic mammals most closely related?
In the phylogenetic trees shown, the tips represent different species of geckos(labeled A to E) and the areas to which they belong. Which one of these is most consistent with the hypothesis that the geckos colonized the Western Ghats from Northeast India through the Eastern Ghats?
The phylogenetic tree depicts the relationship between 5 species of snakes(labelled A to E) and provides information about their habitat specialization. Given the principle of parsimony (least number of evolutionary changes required)and that ancestor Y was terrestrial, which one of the options given is correct?
