Population bottlenecks at 4100-3800 BP and 1500-1300 BP (the latter assuming a second, less severe genetic bottleneck
in the Iron Age).
This may have resulted from the fact that selection induced another genetic bottleneck
or the fact that this colony resulted from newly collected field samples.
Large population declines, such as a fishery decline, can lead to a decrease in genetic diversity and potentially a genetic bottleneck
Rather than allowing them to move to a new evolutionary trajectory, the genetic bottleneck
they passed through constrained their future evolution.
After thriving during cooler times between 800,000 and 600,000 years ago, the bears seem to have suffered a genetic bottleneck
and crashed after a warmer period that started about 420,000 years ago.
A founder effect occurs when a new population emerges as a result of migration or some other cause; a genetic bottleneck
, on the other hand, occurs when an already-existing population shrinks due to a cataclysmic event, such as a famine or massacre.
If a harmful gene mutation is present at a higher frequency in a small group, because of segregation of a population or a genetic bottleneck
, and this small group tends to intermarry, then this harmful gene mutation may increase in frequency.
To examine the possibility of the occurrence of a recent population genetic bottleneck
, the distribution of allelic frequencies was analyzed following the Sign and Wilcoxon statistical tests, suggested by Luikart et al.
Together, these features indicate that the Peconic Bay aggregation from which we obtained our NY98 collection experienced a recent genetic bottleneck
or colonization from a few founders (Grant 2005), and an infusion of new genotypes from genetically differentiated individuals within the recent past.
We face a lot of challenges with the Spix's Macaw because of the very tight genetic bottleneck
the species is in," he explained, adding that the birds have a number of problems with embryo viability, infertility and disease.
commersonii from the Rio Grande, it is clear that the introduced population did not suffer a genetic bottleneck
during or immediately after introduction.
magnirostris occurred repeatedly, from several source islands as inferred from microsatellite markers, and these immigrations rescued the small first colonizing population from a genetic bottleneck