BIO220 Events: Bird Watching, Finding Sources

• Optional events are offered to BIO220 students, for fun and information
• More information and a complete schedule is on Quercus under Modules → Beyond BIO

Upcoming Events

• A bird-watching tour of Humber Bay along the Lake Ontario shoreline on Saturday January 25th at 11:00 am
  • Sign up ahead of time using the link on Quercus
  • Observing songbirds and Arctic ducks that spend the winter in the bay
• How to Find Sources (with U of T Librarians) on Wednesday January 29th from 1:10 – 2:00 pm
  • On Zoom, linked on Quercus
  • Learning the best strategies for finding academic resources
  • Designed to support BIO220 students in their Sources Assignment & Climate Change Report

Persistent Fishing and Evolution of Harvested Species

• Size thresholds affect harvesting such as a net catching larger organisms but letting smaller ones swim through

Continuous Traits

• Phenotypes can vary continuously such as quantitative traits
• An example of quantitative traits includes size, mass, length, time to maturity, and behavior
• Traits with discrete qualitative categories contrasts those that vary continuously
• Mendelian traits like eye colour, tongue rolling, ear lobedness, and blood groups are discrete qualitative categories

Quantitative Traits

• Quantitative traits are determined by lots of genes that have a very small individual effect on the phenotype
• Environmental factors influence traits like nutritional status and body mass
• P = G + E + G×E is a simple rule of thumb where P is phenotype, G is genotype, E is environment
• The genotype of a given gene can be inferred from phenotype, unlike discrete Mendelian traits
• Examining the frequency of individual SNPs or alleles will not predict phenotypic values, therefore statistical descriptions must be used

Relevance of Quantitative Traits

• Health outcomes are quantitative traits, like heart disease risk, body mass index, or risk of schizophrenia
• These traits are classic quantitative traits as they stem from lots of genes with strong environmental influences
• It's "nature and nurture"

Truncation Selection

• Truncation selection is a strong form of directional selection
• Individuals with phenotypes above the threshold die while those below the threshold live
• The intensity of this selection can be measured by the difference in the mean of the population after selection compared to before selection; s = z* - z (where z is the population mean before selection)

Tracking Evolution

• Following the average phenotype in the population over time can track the evolution of quantitative traits
• Measuring, predicting, and following trends can track evolution
• Explicitly tracking genetic changes can also track evolution

Harvest-Induced Evolution

• The Atlantic cod evolved to be smaller, despite better growth conditions
  • Fish selected to be smaller, despite better growth conditions
• Tuskless-ness in elephants is another example of harvest-induced evolution
• In the Gulf of St. Lawrence Fishery, there was a declining abundance and size of fish

Declining Density and Increasing Temperature

• Low density promotes faster population growth and larger individual sizes
  • (K-N)/K values are at low values
• Warmer temperatures must promote faster growth, but observed data is not showing this
• Selection favored smaller size due to fishing
• Environmental forces and Evolutionary forces are at play in fish size
  • Environmental forces which are temperature and density push toward larger fish
  • Evolutionary forces push toward smaller fish through selection
• No net change in fish size despite fish density is implied

Continued Fishing

• Continued fishing can "trap" a population in this region, where smaller & less fecund fish dominate the population
• This will slow the recovery of population size

Elephant evolution in Mozambique

• The Mozambique Civil War from 1977-1992 de-wilded Gorongosa National Park
  • Involved land mines, child soldiers, and crimes against humanity
• In 1972, they lost 30,000 large herbivores, mainly due to 30 years of poaching
  • There were 3 elephants, 2 buffalo, 7 hippos, a few hundred antelopes
  • The Park started rewilding via translocation
  • What did 30 years of elephant poaching do?
• 20,000 elephants are poached per year globally
• Tusks are dimorphic in size, but female elephants have tusks
• 70% of females had 2 tusks before the war, 18.5% had none
• About 41% of immediate survivors had 2 tusks, and 51% no tusks
• 58% of offspring of survivors had 2 tusks, 33% had no tusks
• Tuskless may have a greater survival advantage.

Genetics

• A dominant X-linked locus can be lethal in males
  • Males are XY, females are XX
  • Let wt = x, alternative allele be X
• All males are tusked and therefore have xY

Cross with XX female

• XY males, with tusks

• XY males, lethal, not born

• XX females, heterozygotes

• xx females, with tusks

• X from a male is required, and those males die so XX females are never observed, and the location of where the said gene could be is located in a, b

Patterns of Campbell-Station case study from lecture

• Do they differ in force? genetic basis? demography

Differences between the cod case study and pike indicate

• What is the role of environmental conditions in masking evolutionary change?

Recap and Take-Aways

• Quantitative traits
• Selection differentials
• Tracking evolutionary change
• Human poaching as a selective force
• Genetics of sex-biased lethal mutations
• Conflicts between anthropogenic and natural selection
• Natural selection
• Visualizing natural selection