Ants of the rainforests of South America. Why are some species only found in some places?

2009 REU Intern Elizabeth Loehrer


Senior Molecular Biology major at Loyola University

REU Mentor: Dr. Corrie Moreau (Assistant Curator, Zoology/Insects)

Symposium Presentation Title: Patterns of Diversification in South American Pheidole:  A Molecular Approach (Arthropoda: Hexapoda: Insecta: Hymenoptera: Formicidae)

Symposium Presentation Abstract: Though the Amazon is known to be a rich and diverse ecosystem, much of the origin and evolution of the Amazonian biota is still unclear.  Using the most speciose ant genus, Pheidole, as my study system, I tested two of the Amazonian origin of species hypotheses, specifically I examined the river barrier hypothesis and the uprising of the Andes hypothesis.  The two hypotheses suggest that speciation events occur in accordance to the formation of natural barriers (e.g. a major river or mountain range respectively) that would prevent two populations from mating and thus lead to diversification (Haffer 2008, Cracraft & Prum 1988). My supervisor, Dr. Corrie Moreau collected Pheidole specimens from various locations in Ecuador, Peru, and Venezuela prior to the commencement of my project. I extracted the DNA from ninety-five specimens and amplified two different genes, EF-1α-F2 and COI.  I used the bioinformatics program, Sequencher® to perform a multiple sequence alignment of my data and TNT® and DNApars® to construct molecular phylogenetic trees of Pheidole.  I then examined the correlation between branching patterns on the tree and the geographic collection site of each specimen to determine the validity of the river barrier hypothesis and the uprising of the Andes hypothesis.  Initial findings with the EF-1α-F2 data did not reveal definitive patterns between geographic location and speciation events, particularly due to multiple polytomies within the tree. Finishing the data set for COI as well as amplifying additional genes may improve tree resolution, which would allow for a better analysis of the connection between diversification and geographic barriers.

Original Project Description: The rainforests of South America are home to thousands of ant species, but what are the historical reasons why some species are found in some places and not others? Several hypotheses have been suggested to explain speciation in the Neotropical rainforests. Using DNA and ants collected from Ecuador and Peru we will be able to test some of these ideas.

Research methods and techniques: Interns will receive training in DNA extraction, PCR, and sequencing in the Museum's core genetics facility, the Pritzker Laboratory and the DNA Discovery Center. They will participate in data collection, assembly and phylogenetic analysis, and be introduced to concepts surrounding the estimation of phylogeny and its uses in studying systematics, evolution, and biogeography.