Wisent, also called European bison, faced extinction in the early
20th century. The 360,000 animals living in
2000 are all descended from 12 individuals and only two distinct
Y chromosomes are left in the species. The population of
American Bison fell due to overhunting, nearly leading to extinction around the year 1890 and has since begun to recover.
A classic example of a population bottleneck is that of the
Northern Elephant Seals, whose population fell to about 30 in the 1890s although it now numbers in the tens of thousands. Another example are
Cheetahs, which are so closely related to each other that
skin grafts from one cheetah to another do not provoke
immune responses, thus suggesting an extreme population bottleneck in the past. Another largely bottlenecked species is the
Golden Hamster, of which the vast majority are descended from a single litter found in the
Syrian desert around
1930.
According to a paper published in 2002, the genome of the
Giant Panda shows evidence of a severe bottleneck that took place about 43,000 years ago
1. There is also evidence of at least one primate species that suffered from a bottleneck around this time scale.
Sometimes further deductions can be inferred from an observed population bottleneck. Among the
Galápagos Islands giant tortoises (themselves a prime example of a
founder effect), the comparatively large population on the slopes of Alcedo volcano is significantly less diverse than four other tortoise populations on the same island. Researchers' DNA analysis dates the bottleneck around 88,000 years before present (YBP), according to a notice in
Science, October 3,
2003. About 100,000 YBP the volcano erupted violently, burying much of the tortoise habitat deep in pumice and ash. The coincidence is suggestive.
Rather, I think it could be helpful to jointly think about what we would expect from such an event.
