Description
Reproductive barriers are anything that exists in nature and can reduce gene flow between species. It can be physical, such as a geographical constraint, or it can be due to genetic differences that prohibit species from producing viable offspring. These can be either a pre-zygotic or post-zygotic barrier. By studying the impacts of reproductive isolation on gene flow, scientists can grasp a better understanding of how species evolve. The objective of the study was to determine the seasonal reproductive cycles of two species of killifish in an area of overlap to determine it's effect on reproductive isolation. For a year, monthly samples of thirty individuals were sampled from Bing's Landing, which is one place in which these species overlap with very rare hybridization. With caudal fin clippings, genetic analysis were performed to genotype species and identify specific alleles. A histological analysis was also conducted using the Gonadosomatic Index along with Gamete Volume Fractions to estimate species reproductive timing. Each species' reproductive timing was used to clarify the strength of temporal isolation on reproductive isolation. The findings from the study showed that there were two major peaks in the reproductive cycles of the males for each species, one being around March and a second in late summer. These results suggested that both the male Fundulus grandis and F. heteroclitus species were relatively able to reproduce around the same time, indicating that temporal isolation was not a major factor for the male species. However, since the study did not have a huge representation of female F. grandis in the sample, it was not able to quantify the strength of temporal isolation on the reproductive cycles of the females for both species. With data collection now concluded, the study found that overall the spawning period of Fundulus grandis and F. heteroclitus were mostly similar between the male species. Future research should focus on increasing the representation of the female species of both Fundulus grandis and F. heteroclitus to help provide a complete picture on speciation, which would address a central concept of biological sciences.