Final answer:
The role of the gene patristacin in male pipefish's brood pouch is an example of co-option (option 1), highlighting how genes can evolve new functions, supporting unique reproductive strategies like in polyandrous mating systems, where males carry embryos.
Step-by-step explanation:
The evolutionary analysis of the gene patristacin in male pipefish, which is crucial for the formation and function of their brood pouch, is an example of co-option. Co-option, also known as exaptation, refers to the process by which a gene acquires a new function that was not its original role in the organism. In this case, while patristacin is involved in liver and kidney function in other fish species, in male pipefish, it has been co-opted to also play a significant role in developing a structure for parental care – the brood pouch. This phenomenon underlines the versatility and adaptability of genetic functions, contributing to evolutionary diversity.
Polyandrous mating systems, where one female mates with multiple males, can be seen in seahorses and pipefish. These males take on the responsibility of carrying the embryos, allowing the females to mate with several males without the burden of carrying the fertilized eggs. This unique reproductive strategy further illustrates the adaptive nature of certain physiological traits, like the male brood pouch, which have evolved to support such polyandrous mating habits.