Genetic Drift vs. Natural Selection
Name the 4 postulates of natural selection
1) variation
2) heritability
3) differential survival
4) adaptive traits persist
What two groups did the researchers divide their subjects into?
NYC and non-NYC
What is a name for the proportion of individuals in population that are heterozygous that the authors measure.
Observed heterozygosity
This was a measure of genetic diversity that was found to be similar between the NYC and non-NYC coyotes.
How does pathogenic diversity relate to decreased allelic richness in the NYC coyotes?
A decrease in this value in urban environments explains why decreased genetic variation may not necessarily have adverse effects on the NYC coyote population in the short term.
What is the name for a sudden, random reduction in population size that can drastically change allele frequencies regardless of fitness ?
bottleneck effect
What did researchers mainly use to differentiate between and identify species within the study (what were the DNA samples)?
Scat samples
What is allelic richness?
The average number of different alleles per locus within a population, and a measure of genetic diversity that differed between the NYC and non-NYC coyotes.
What is gene flow? (Alternatively, what is increased population size?)
One of the ways in which the initial population bottleneck that occurs during colonization of an urban environment can be counteracted to improve genetic diversity.
Did the paper conclude that NYC coyote genetic patterns were primarily driven by genetic drift or selection?
- not a lot of evidence for adaptation
What two types of genetic markers did the researchers compare between coyote population subgroups?
neutral genetic markers and immune-related markers (MHC-linked)
What causes balancing selection?
When selection favors diversity over selection of specific alleles, causing increased allelic variation within a population.
What is a potential consequence of limited gene flow in a small population that has undergone a population bottleneck?
inbreeding and/or increased vulnerability to novel environmental challenges (such as new diseases)
Name the phenomenon where multiple alleles are actively maintained in a population at frequencies larger than expected by genetic drift alone.
Balancing Selection
Greater variation between coyote populations in which type of microsatellite (neutral vs. MHC-linked) would be more indicative of natural selection occurring?
MHC - linked
(because these loci are tied to immune response: more variation can influence survival/reproduction more than variation in neutral traits would)
What similarities and differences in alleles between the non-NYC and NYC coyotes support the idea that they underwent a recent population bottleneck?
Similar heterozygosity but reduced allelic richness at neutral loci
What is one way to facilitate gene flow and increase genetic diversity in urban populations of animals?
Corridors which connect green spaces within urban environments with non-urban areas
- lots of other possibilities
According to the paper, what can we expect to see with heterozygosity frequencies within a population following a genetic bottleneck incident?
Heterozygosity within the population remains temporarily higher than expected
(allele loss happens faster than genotype reshuffling)
What is the name of the test the researchers used to determine whether selection is acting on MHC-linked loci?
Ewens-Watterson homozygosity test of neutrality
What is directional selection?
A type of selection that is supported by positive Fnd values at several loci
What evidence suggests that the NYC colonization occurred too recently to detect selection?
The authors obtained Fnd values at multiple loci that were positive, suggesting directional selection, but they were not statistically significant.