Campos et al., Steller’s sea cow uncertain history

Campos, A.A., C.D. Bullen, E.J. Gregr, I. McKechnie and K.M.A. Chan (2022). “Steller’s sea cow uncertain history illustrates importance of ecological context when interpreting demographic histories from genomes.” Nature Communications 13(1): 3674. Doi: 10.1038/s41467-022-31381-6

In their recent paper entitled “Steller’s sea cow genome suggests this species began going extinct before the arrival of Paleolithic humans”, Sharko et al.1 use novel genomic methods to infer the demographic history of this species. Based on a single specimen from the Commander Islands, the authors conclude that the species suffered a single catastrophic population decline approximately 400,000 years ago and was thus already on the verge of extinction well before human arrivals in the Late Pleistocene. Here we suggest their demographic assumptions warrant reinterpretation given the ecological barriers that likely structured sea cow populations along the North Pacific Rim. Our preliminary range simulations suggest that the Commander Is. population may have been physically isolated from others, making it unsuitable as a demographic inference for the entire sea cow North Pacific range. Under these assumptions, Sharko et al.’s findings are more likely indicative of the time since the isolation of this remnant population from the rest of the sea cow range, rather than representative of the population contraction of the species. This perspective highlights the importance of considering historical ecology and paleobiogeography when interpreting genomic data to infer past demographic histories….