The largest remaining migratory population of brindled wildebeest in southern Africa serves as a cornerstone prey species for large predators. Yet it has been understudied because of its remote location in the Greater Liuwa Ecosystem in western Zambia and Angola. Northern Michigan University alumna Steph Szarmach, along with Biology faculty members Alec Lindsay and Katherine Teeter, worked with collaborators in Zambia to explore the wildebeest's genetic diversity and demographic history. They are among the coauthors of a recently published paper on the study's findings.
“Very little is known about the Greater Liuwa Ecosystem, despite the size of its wildebeest population,” said Lindsay. “There had also been limited research on the population itself because it's not very close to the other wildebeest populations in Kenya and other areas, which are located in close proximity to people doing the research. There are no population centers near this habitat; a lot of Indigenous people are living there. But unfortunately, Angola had a long civil war from 1975 to 2002, and that had some pretty dramatic effects on the wildlife there. It's worth studying the wildebeest, even in this remote area, because the more we know about the prey population, the better informed we will be for all other species living there.”
Lindsay had previously completed a giraffe project with a collaborator in Zambia, and the two agreed to pursue a genetics project involving wildebeest. Szarmach became very interested in the project as a graduate student, and conducted work for the published study as part of her thesis project. Prior to participating in an NMU field studies course in Zambia, she said her only exposure to wildebeest came from reading research papers or working with their DNA in the lab.
“While most of my research was completed before the trip, traveling to Zambia offered me an amazing opportunity to view wildebeest in their natural habitat,” Szarmach said. “Analyzing genetic data through laboratory and computational work can become very abstract—it's valuable to also spend time observing your study species in the wild, because their natural history and ecology are important to consider when interpreting the genetic data. Through the ‘Zambassadors' trip, I was also able to meet Zambian biologists and conservationists and learn about all the great work going on to protect wildlife in Zambia.”
One of the challenges associated with researching a larger population of wildlife, according to Lindsay, is ensuring an adequate sample. The Zambian collaborators focus primarily on carnivores such as lions, hyenas and wild dogs. But they also have experience working in the Greater Liuwa Ecosystem, which few can claim.
“Over the years, they have both captured and radio-collared some of the wildebeest, and then they've also found recent kills from predators, and they would take tissue samples in all of those cases,” he said. “So it was a relatively random sample, because it happened over a number of years in a bunch of different locations. It wasn't like going out and just darting 75 individuals that might all be close relatives. It was a good, diverse sample.”
Szarmach's role was to sequence and analyze DNA from blue wildebeest tissues collected by Zambian Carnivore Programme biologists. An NMU research grant supported the genetic and computational work on campus. The late computer science professor Jeff Horn contributed to the interdisciplinary collaboration by creating a large computing cluster that his students trained Szarmach how to operate. She used this “massively parallel sequencing” method to sequence small regions of DNA from across the whole genome.
“That means she could get lots of sequence data through the genome for all 75 individuals at once, which can be used to characterize genetic diversity in a population,” said Teeter. “This technology generates huge data files, which is why we collaborated with Jeff Horn and his students. We needed much more computing power for the analysis than we could get from a laptop.”
“If everyone has either Type A or Type B fragments, there are maybe two distinct populations, if we can clearly define the differences,” Lindsay added. “But if everybody kind of has the same differences, then it looks like it's one population. And that's what we found. Personally, I thought we might see a little bit more inbreeding based on the history of that population. It definitely decreased in size, which can lead to more inbreeding. We suspect conservation measures were taken early enough that the population may have declined noticeably, but not for very long.”
Researchers estimated the wildebeest population size, then determined the effective population size from a genetic context. Not all of individuals counted are necessarily breeders contributing their genes to the next generation.
“If you think of the similar ungulate of white-tailed deer, we know that almost all of the female deer are going to mate, but maybe only a few of the males—the really big bucks,” Lindsay said. “It's kind of similar with wildebeest. So the genetic effective population size is oftentimes smaller. We think it's about one-tenth of the estimated population in southern Africa.
Other credited coauthors of the study were Jassiel M'soka, Egil Dröge, Hellen Ndakala, Clive Chifunte and Matthew S. Becker. Their paper, titled "Genetic diversity and demographic history of the largest remaining migratory population of brindled wildebeest (Connochaetes taurinus taurinus) in southern Africa," was published in the peer-reviewed journal PLoS One. Read it here.
“While completing my master's degree at NMU, I learned laboratory and computational skills that I carried with me into my doctoral program at Penn State,” said Szarmach, who earned her MS in biology from NMU in 2019. “Nearly every day I apply things I learned in classes at NMU, including biostatistics, phylogenetics and data visualization. I also gained a lot of teaching experience at NMU as a laboratory instructor for Introduction to Cell and Molecular Biology, which allowed for a smooth transition when I taught a similar lab at Penn State. I really enjoyed my NMU experience, and the Biology Department was a very warm and welcoming community.”
At Penn State, Szarmach continued to study migratory animals, but shifted her focus from mammals to birds. Her dissertation research integrated migration tracking and genomics to answer questions about the evolution of migration in the parulid wood-warblers. She successfully defended her dissertation at the end of May and will start a postdoctoral research fellowship at the Smithsonian Migratory Bird Center in September.