Observe the map below and carefully read the study that foll…
Observe the map below and carefully read the study that follows. BACKGROUND As an expert in the field of mammalian reproductive strategies, you have been hired by the Caribbean Department of Nature and Island Resources. This organization is a cooperative of several Caribbean islands concerned with the loss of biological diversity on their island nations as tourism and development continue to grow. Scientists working on the island of St. Kitts and its sister island Nevis have uncovered what appears to be a previously undiscovered species of rodent. Based on the original description of this animal, it was placed in a genus within the squirrel family. What you have been hired to do is to help save the population on St. Kitts, which is small and threatened by development. The population is so small that individuals are having difficulty finding mates, with many members of the population failing to mate at all during the annual mating season. When you arrive in the region and begin your observations, you notice that the Nevis population is very healthy and could be used as stock for the recovery operation that you plan on the island of St. Kitts. In your recovery plan, you bring animals from Nevis into the population on St. Kitts to bolster the population numbers, ensure the availability of mates, and increase genetic diversity within the shrinking population. As a good scientist, you observe the reproductive behaviors of these animals in the field to ensure the success of your program. Within a very short time, you realize that your plan is failing. After the introduction of 240 Nevis rodents into the St. Kitts population, you are unable to observe a single successful reproductive event. Although these animals look very similar, you are concerned that they are two distinct species. Your focus now becomes identifying the differences between the two populations. What follows is a brief review of the data you collected from your study. ST. KITTS RODENT NEVIS RODENT Average weight: 83 g Average weight: 86 g Average length: 21.8 cm Average length: 23.3 cm Average hind limb: 4.2 cm Average hind limb: 8.8 cm Average forelimb: 3.9 cm Average forelimb: 6.1 cm Primary food source: Ground berries Primary food source: Tree nuts Average number of offspring per litter: 2 Average number of offspring per litter: 6 Average time spent in courtship display: 12.6 seconds Average time spent in courtship display: 41.3 seconds Mating season: July-August Mating season: July – August (a) (4 points) Based on the data above, describe 2 possible pre-zygotic barriers that might be preventing interbreeding between the St. Kitts rodents and those introduced from Nevis. (b) (4 points) Since the rodents do not seem to be mating in the wild, you decide to attempt artificial insemination. Sperm from 10 male St. Kitt’s rodents is collected and the 10 samples are combined into one. This mixed sperm sample is then used to inseminate 5 female St. Kitt’s rodents and 5 female Nevis rodents. If 4 of the five St. Kitt’s females, but none of the Nevis females become pregnant and deliver healthy offspring, is it more or less likely that the two populations have become separate species? What species concept is this experiment designed to test? Why are both St. Kitt’s and Nevis females inseminated in this experiment? (c) (4 points) Outline a scientifically plausible sequence of events that could have produced these two distinct rodent species from an original population located on St. Kitt’s. Be sure to include a description of the evolutionary forces (e.g., natural selection, genetic drift, gene flow, mutation, etc.) involved in speciation.