Question

The Barton Springs salamander is an endangered species found only in a single spring in the city of Austin, Texas. There is growing concern that a chemical spill on a nearby freeway could pollute the spring and wipe out the species. To provide a source of salamanders to repopulate the spring in the event of such a catastrophe, a proposal has been made to establish a captive breeding population of the salamander in a local zoo. The zoo was asked to provide a plan for establishing this captive breeding population, with the goal of maintaining as much of the genetic variation of the species as possible in the captive population.

What factors are likely to lead to a loss of genetic variation in the captive population?
a. increased rate of mutation
b. a founder effect
c. reduced genetic drift over time
d. a lack of inbreeding
What strategy would likely be effective in mitigating the loss of genetic variation in the captive population?
a. keeping the sex ratio as close to 50:50 as possible
b. stopping gene flow to and from the captive population
c. regularly mating individuals that are related
d. keeping the captive population as small as possible

Answer 1

The factors that can lead to a loss of genetic variation in a captive population are the founder effect, a lack of inbreeding, and reduced genetic drift. To mitigate this loss, it is important to keep a balanced sex ratio to allow for natural mating and avoid regularly mating related individuals.

Step-by-step explanation:

The factors that are likely to lead to a loss of genetic variation in the captive population are a founder effect, a lack of inbreeding, and reduced genetic drift over time. The founder effect occurs when a small group of individuals becomes isolated and establishes a new population, leading to a reduced gene pool. A lack of inbreeding and reduced genetic drift can both result in a loss of genetic variation over time.

To mitigate the loss of genetic variation in the captive population, a strategy that would likely be effective is to keep the sex ratio as close to 50:50 as possible. This ensures a balanced representation of both males and females, increasing the potential for genetic diversity through natural mating. Regularly mating individuals that are related and keeping the captive population as small as possible can lead to a further loss of genetic variation and should be avoided.

Answer 2

1) Option b is correct. a founder effect

2) Option a is correct. keeping the sex ratio as close to 50:50 as possible

Step-by-step explanation:

The exposed situation is an example of an ex-situ conservation program. These programs are planned to keep and restore the population of species that are in danger of extinction. There are many challenges associated with captivity, and one of them is related to maintaining genetic diversity in the population.

1) Introducing a few animals of an endangered species into the zoo might be considered an example of the founder effect. Just a pregnant female is enough for it to occur. And the most significant problem associated with this event is the loss the genetic diversity or variability. When breeding animals in captivity there is a high risk of losing some genes and fixating others, due to inbreeding.

Genetic drift is the random change that occurs in the allelic frequency of a population through generations. The magnitude of this change is inversely related to the size of the original population. These changes produced by genetic drift accumulate in time. Eventually, some alleles get lost, while some others might set. Genetic drift affects a population and reduces its size dramatically due to a disaster or pressure-bottleneck effect- or because of a population split -founder effect-. In founder effect, a new population originates when a few individuals, coming from a bigger-sized population and carrying their genes, settle down in a new area and reproduce. This small population might or might not be genetically representative of the original one. Some rare alleles might be exceeded or might be lost by complete. Consequently, when the small population increases in size, it will have a genetically different composition from the original one. In these situations, genetic variability is reduced, and there exists the possibility of developing a peculiar allelic composition. When the number of individuals that originated the new population is low, the founder effect will be very extreme because the genetic drift effects are inversely proportional to the original number of individuals.

2) When selecting the animals that are being kept in captivity, it is significant to consider a few aspects concerning genetic diversity maintenance. The main objective is to prioritize the original genetic material.

• To get founder individuals that get to represent the maximum genetic variability of the population, or among population if possible.
• The sex proportion of the founder individuals should always be 1:1 or 50:50. This ratio is important to keep genetic variability, especially because many males in captivity might have reproductive problems. To keep diversity, females need to mate with different males, and not just a few of them.
• Animals should be subadults reaching their sexual maturity.
• When mating animals, they should be as different as possible to decrease the possibility of a common ancestor among the couple.