Question

Newts produce tetrodotoxin (TTX), a poison that targets sodium ion channels, for defense against their predators, garter snakes. Several species of garter snakes are resistant to newt TTX due to specific known amino acid substitutions in garter snake sodium channels. Which one of the following is best-suited to identify whether this adaptation in garter snakes has a single origin or multiple independent origins?

• A. Building a gene phylogeny of sodium ion channels in garter snakes
• B. Building a species phylogeny of garter snakes
• C. Building a gene phylogeny of newt sodium ion channels and species phylogeny of newts, and comparing them
• D. Building a gene phylogeny of garter snake sodium ion channels and a species phylogeny of garter snakes, and comparing them

Hint:

When studying evolutionary adaptations, comparing both gene and species phylogenies provides insight into whether an adaptation originated once (single origin) or multiple times (multiple origins).

Answer 1

The Correct Option is D

Step 1: Understand the purpose of building gene and species phylogenies.
To determine whether the adaptation to TTX in garter snakes is the result of a single origin or multiple independent origins, we need to compare the gene phylogeny of the sodium ion channels in garter snakes (which are involved in resistance) to the species phylogeny of garter snakes.

Step 2: Analyzing the options.
Option (A): Focuses only on the sodium ion channels in garter snakes, without considering their evolutionary history across species, making it less suitable for determining the origin of the adaptation.
Option (B): Builds only a species phylogeny of garter snakes but does not account for the genetic basis of the adaptation.
Option (C): Compares newt gene phylogeny with newt species phylogeny, which doesn’t help in identifying whether the adaptation in garter snakes has a single or multiple origins.
Option (D): Correctly suggests comparing the gene phylogeny of garter snake sodium ion channels to their species phylogeny, which helps identify whether the genetic adaptations occurred once or multiple times across species.

Final Answer: (D)