This week I sent my last batch of worm DNA samples away for sequencing. Typically, we get our sequences back just two days later which is becoming more and more helpful as our time here draws to a close. We are now starting to compile our data into what is known as a phylogenetic tree. A phylogenetic tree is a way to visualize how different groups of organisms are related. In the case of my research project, I am making a phylogenetic tree with all the CO1 DNA barcoding sequences for specimens that I have been working with from Colon along with all the nemertean CO1 sequences that Dr. Maslakova has previously collected from the Caribbean. Including all the available nemertean DNA sequences from the Caribbean allows us to compare our samples to those that have already been found. The lines leading up to each specimen name represent the genetic difference between the CO1 genes of any two specimens. The longer the lines, the longer it has been since those two specimens or groups diverged from a common ancestor. The shorter the lines, the more closely related two samples are. In the tree above, there are 6 species. I knew that each of these groups were a distinct species because the lines that connect them are very short, but the lines between species (different color groups) are much longer. Specimens are considered separate species if there is more than a 4% (0.04) difference between their CO1 genes. This distance is represented by the scale bar at the bottom of the tree. The interesting part about this set of 6 species is that the 5 of the species that I have indicated with colored text all look almost exactly the same! They represent a “cryptic species complex” because the worms look the same, but are genetically 5 distinct species. You can see in their specimen names that they are all orange with a white tip. The 6th species at the bottom known as “candy cane” because it has not yet been officially described as a species has bright red and white stripes. Last weekend, about half of the REU interns had parents in town. We gave our parents a tour of the labs, campus, and the Charleston Marine Life Center. My parents and I also checked out a couple of the nearby state parks and went tide pooling!
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AuthorHi! I’m Megan Powers, a fourth year Biology and Environmental Sciences student at the University of Iowa. Throughout my summer at OIMB, I will be working with the Maslakova lab to assess Nemertean diversity in the Caribbean. Archives
August 2019
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