Like a decent red wine, research requires expertise, collaboration and a lot of patience. And as in viticulture, the aroma of the final bouquet is often unpredictable. Our paper by Peart et al. started in 2012 as a back-up project: it survived two institutional moves, a temporary customs seizure, some challenging lab-work, and evolved as new members joined and provided fresh insight and novel expertise. The product that saw the light of day in 2020 truly speaks to the value of collaboration and perseverance.
Our initial idea was simple: use genomic data to retrace the demographic history of closely related species of pinnipeds (lat. penna=feather; pes=foot) and isolate the extrinsic and intrinsic factors driving it. We eventually achieved more than this. To get started, we collected samples from 17 species worldwide from the eternal frost of the Arctic, through the tropical Galápagos archipelago all the way to Antarctica. Some of the individuals were caught by us, but such an endeavour requires a huge collaborative effort, and we reached out to our colleagues in the seal community capitalizing on the effort of hundreds of cumulative years of field work. The herculean administrative task of shipping all of these samples of often endangered species across the globe took nearly as long. In the meantime, the Wolf lab relocated from Uppsala to Munich and Aaron started his own group in Canada. While samples were dropping in, we struggled with establishing a consistent genomic library protocol for the many species. And just when the project looked like a lost cause, it got reinvigorated by the creative, fresh energy of young post-docs and PhD students. With their creativity and bioinformatic skillset Claire, Sergio, Saurabh and Fidel gave proper wings to the feather-footed and lifted the project off the ground. Lesson learned: complex projects often have a winding history and rest on many shoulders. But they are worth every minute and simply much more rewarding than the smallest possible publishable unit.
But enough gossip about the history of the project - what did we actually find? Using the simple metrics of genetic diversity (π) and Tajima’s D, we were able to predict the effective size of each species (Ne) accounting for their basic biology and the oscillations populations experienced over time. We then related this genetic measure of long-term population size through time to estimates of current census population sizes (NC). The two showed a remarkably strong correlation and provided insight into central tenets of evolutionary theory, specifically the role of genetic drift versus linked selection. Perhaps our most novel insight, was that deviations from the predicted ratio of the two population size measures (Ne/NC) were telling about the species conservation status. There is certainly some nuance to interpreting these patterns, but the implications, we argue, could be quite far reaching. Because the data generated are relatively easy to come by, one could apply this to any group of other organisms to potentially predict the conservation status of less known or understudied species. But you be the judge!
Peart, C. R. et al. Determinants of genetic variation across eco-evolutionary scales in pinnipeds. Nature Ecology & Evolution 4, 1095–1104 (2020). doi: 10.1038/s41559-020-1215-5
Jochen Wolf and Aaron Shafer
Photo courtesy Simona Sanvito.