Scirius Kittis meets Scirius Nevile: The Evolution of a New Species
Various experiments and measurements were performed in the field in order to compare the two types of rodents. The following is a list of the data collected through multiple observations over a span of two years. We captured 100 rats of each rodent population, and we found the average weight, length, hind limb, and forelimb measurements. In addition, we conducted experiments in regards to their top speed, average height that they could leap, gestation time, and average time spent in the courtship display.
St. Kitts Rodent
• Weight = 83g
• Length = 21.8cm
• Hind limb = 7.8cm
• Forelimb = 4.2cm
• Speed = 2.2m/s
• Average leap height = 1.4m
• Average gestation time = 29.3 days
• Average time spent in courtship display = 12.6 seconds
• Weight = 86g
• Length = 23.3cm
• Hind limb = 4.2cm
• Forelimb = 3.9cm
• Speed = 0.8m/s
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These rodents both started off as one common species classified under the common tree squirrel genus.
A bottleneck effect occurs when a population undergoes a dramatic decrease in size. This is often attributed to some type of natural disaster. Based on the case study, the species on St. Kitts most likely underwent a catastrophe. Since St. Kitts is an island, this it is very possible that this was caused by a hurricane or typhoon. Separation of the two islands is possible which contributed to the creation of two different species, and hurricanes are likely to hit and devastate populations on islands. The species on St. Kitts also have a speed and height advantage over the Nevis population, so the bottleneck effect is more likely to have wiped out their population since they have more favorable traits than their counterpart. If the island underwent a catastrophe, it is likely that the rodents were separated physically.
The second factor, allopatric speciation, occurred between the two rodents’ habitat. This is when a population is divided by a geographic barrier which prevents interbreeding between the two populations. These species are found on two different islands, so the water in between separates the two populations from interacting with one another. Due to this, both species could have developed changes in courtship rituals, developed new traits, and undergone changes to adapt to their environment.
The final factor, behavioral isolation, occurs when two species don’t recognize one another as mating partners due to incorrect courtship rituals. Since we tried to repopulate the St. Kitts by introducing the population from Nevis onto the island and no
success was found, behavioral isolation is very likely to have been the reason why. Our data supports this as well since the St. Kitts rodent spends 12.6 seconds during courtship display while the Nevis rodent spends 21.3 seconds, almost doubling the time that of the St. Kitts. We hope that these findings will allow ways for the population of these rodents to be able to reproduce and survive the ongoing developments on the island. With continued research and protection of these rodents they should be able to repopulate to a status where they will not be close to extinction.