Urban animals 1&2 (adaptation among animals and birds) Flashcards
Studying Urban Evolution
- More than 55% of the human population lives in cities and urban landscapes cover 3% of the earths land surface - projected this will inc as population inc
- Urban landscapes cause habitat frgamentation, lowers species diveristy, more species invasion and a loss of native species
- Convergent evolution leads urban populations to look more similar to distant urban sites than the surrounding nonurban envirnments
○ There are always similar adaptations known as canalization - In urban areas there a lot of trash but etchncially food for animals - animals will reap the benefits - ex. Some use the sugar in all this trash as a better way to reproduce more often
- Early ecologists didn’t spend much effort on urban ecology as they felt that cities were anti life
- Pollution increases mutation rates which has been suggested will increase the rate of evolution within urban envrinments
○ Carcinogens also cause mutations and so does radiation
Fragmented ecosystems leads to lower population size reuslting in genetic drift
Genetic Drift and Population structure
- Reduced population diversitt
- Increased population divergence
- This has been demonstrated in both white footed mice and yellow toadflax
Genetic drift reduces within population diversity and increases between population divergence
Evolutionary Urban Innovation
- The urban envirnment introduces a unique set of envirnmental challenges which lead to unique evolutionayr adaptations
- Social learning is the process of learning through observing others behaviours
- Group dynamics and population structure will infleunce social transmission
- Ex. Birds found out how to open tinofiil and drink milk - they taught others - this was social leanring which is comon in urban areas
- Ex.
○ Several subpopulations of great tits were seeded with males traiend to open a puzzle box that rewarded mealworms
○ Subpopulations T1 and T2 seeded with male who used option A and T3-T5 where ones who opned using option B
○ Both options are the same thing
○ After 20 days, 75% of the subpopltins had learned and each would conform to their intial leanring behaviour
Social learning that everyone practcially learned how to open the specific door and those who learned that both work still continued with the door majority would use
Racoon Urban Evolution
- Procyon lotor (order: carnivora, suborder: Caniformia, family: procyonidae)
- In the same family as ringtails and olingos
- Name means washing predog
- Nocturnal and generalist (skillfull) omnivoruous
- Invasive species in Europe (introduced as a source of fur in the 1930s but then got released)
- Invsaive species in Japan (borught as pets and then reelased in the 1970s)
- Very few predators in colonized areas (especially urban or suburban envrinments)
- They like to live in decidious forest and have acceess to water
- They like to wash things and put hands in water bc it sensitizes their hands, helping them find food better
They do well in urban envrinments bc they are good at social learning - shy racoons learn better
Carnivora ORder
- Two super families: caniformia and feliformia
- Racoons are in canifmroia (dog side) - procyonidae is their group
Other aniamls include brears, panda, skunks etc (most things with fur like dogs)
- Racoons are in canifmroia (dog side) - procyonidae is their group
Racoon Urbvan Evolution CONTD
- Procyon lotor (order: Carnivora, family:Procyonidae)
- Racoons experince diff selective pressures in urban envrinments
- Higher reproducive rates and lower mortality
- Diff sources of mortality (threats by the urban ecosystem):
○ Vehicular collions
○ Higher rates of disease
○ Euthansia/animal control - Other mammals like cougars and foxes expeirence higher rates of mortality in urban envirnments (bc of same reasons)
- Racoons do better here bc trash helps them with reproduction and in rural envrinemnts they face more predators
- What makes them good
○ They are phenominal climbers
○ Social learners and nocturnal so they avoid humans
○ Can manipulate objects by washing items or food to get a beter sense of the item
○ Racoons prefer decidous forest over boreal forst espcially with along the riparian edges
○ Avoid the alpine habitats or areas with more than 30% snow coverage over the year
○ Store fat deposits in the tail and undergo torpor (hibernation) during the winter
○ Racooons in the wild live 2-5 years while those in captivity up to 18 years - Raccoon rabies viriant is the major rabies variant in the eastern US
○ Howevr dogs give us rabies more and rabies isnt curable if u get the symptoms - Between 8-10 mil rabies vaccine baits are deployed aerially across the US annuaully (given the raccooons)
- Canine distemper Virus (in raccoons): causes brain swelling and abnormal behaviours
○ Disoriented and lethargic leading to seizures
○ Aggressive if cornered (like to run away)
○ Disease is harmeless to humans but not to dogs - Urban raccoons have smaller home ranges than rural ones
Male ranges are bigger than remale both of which increase during breeding season bc they have multiple partners
Genetic Drift in Urban Envirnments
- Red fox (Vulpes vulpes)
- Red fox populations in Zurich switzerland have differences between urban and rural
- Urban populations have lower gentic diversity as a conseqeunce of smaller population size leading to genetic drift
- Similar trends seen in white footed mice and other rodent species
Leads to a decrease of within population diversity and an increase in between population divergence
Genetic Drift
- Genetic drift is random changes in allele frequencies as a result of randomly sampling gametes (eggs/sperm) each generation
- The smaller a sample is the less likely it is to reflect the alleles of the true population resulting in changes of allele frequnecies from generation to generation
- To form next population we only take out 10 – 50-50 chance of either – end up getting 6:4 ratio of the two alleles – now its 60 peach 40 green (allele frequeciy changed from gen to gen just bc u randomly sample, and allele frequency change on their own ) - now we end up pulling 7:3 (again allele changes) – simply by having limited population size from gen to gen, random sampling causes the allele frequencies to change
The genotype frequencies in random sample of partents are diff than the population (sampling error) so the allele fruencies in the population change over time
Genetic Drift imapcts
- Genetic drift is the random change in allele frequencies as a result of randomly sampling gametes (egg/sperm) each gen
- To understand drift, think of each geenration as a random sample of the gametes produced by the adults in the previous generation and drift as a sampling error spread across generations
- Genetic drift is an evolutioanry mechanism = change in allele frequency
- When a population is large, genetic drift is minimal:
○ Overtime genetic drift will randomly cause one of the allles to be lost or dissapear from the population and the other to go to a frequency of 1.0 (called fixation)
○ Which allele is lost isnt predictable
○ The smaller the population, the faster an allele will be lost
○ The larger the population, alleles will vary but never fixate quickly
○ Genetic drift is very strong when population size is small, weak when population size is large
○ Genetic drift will eventually cause one alleale to be lost and the other to inc to frequency of one (becomes fixed)
○ Genetic drift decreases gentic variation in populations
○ Genetic drift causes populations to become more idff (diverge from each other)
§ Natural selection is non random
§ Genetic drift is random
§ Natural selection is adaptive
§ Geentic drift is random, and can work against natural selection and be nonadaptive or work with natural selection and be adaptive - its not possible to predict what drift will do from one gen to the next
Ecological Traps: Coopers Hawks in Tucson Arizona
○ Coppers hawks (astur cooperii)
○ Coopers hawks are atrrcted to urban envirnments bc of the abudnace of nesting sites and prey
§ You would think they will thrive bc they can repropduce more often here but they end up having high death rates
○ Higher rates of mrotality for them
§ Window strikes (365-998 million deaths per year in us while 16-42 mil in canada)
□ Hunting birds will often die this way
§ Organophosphate poisoning (deliberate attempts to kill feral pigeon populations)
□ The pigeon traps don’t rlly end up killing pigeons just bc they reproduce sm
□ This ends up having a bigger impact on the coopers hawks bc they eat the traps or the poisoned pigeons and end up dying
§ Trichomoniasis paraiste infection from preying on Inca Doves
Doves are infected by this infection and coppers hawks die by eating them
Founders Efefcts: Common Blackbird
○ The common blackbird (turdus merula)
○ Relatively recent colonization of urban habitats, first observed in Germany in the 1820s
○ Studies of genetic variation and phylogentic relatedness indicate several independent colonizations of urban habitats as opposed to a leap frog model
○ Leap frog model would sugegst that urban sites were colonieed by other urban birds through migration
§ Hwoevrr it was found that this samping error happened bc black birds independtly invaded cities at separate times - it wasn’t just one urban hgroup in gemrnay moving out - parallel evolution bc they had the same derived state and ancestor state
○ These newly founded populations have lower dievrsity than rural populations bc of founders efefct
New population was founded by some membrers only of the orginal so many alleles are not actually moved out
Sampling Errors that arent genetic drift
○ Founder effect - when a small number of indoivduals found or start a new population, the allele frequencies in the new population can differ from the source population due to sampling error
○ Bottleneck - a sharp decline in population size bc of a bottleneck event that can change allele frequncies by samplong error
Founders efefct and bottle neck can happen at any stage like gemetic, zygotic, hjeuvaniles or adults but genetic drift can only occur during the gametic phase
Genetic Trends
○ Red backed salamander (plethodon cinereus, class amphibia)
○ Red backed salamdnder inhabits parks within urban areas including montreal
○ Populations are fragmented bc consrtrcution of roads
○ Species with poorer dispersal capabilities will exhibit greater population structure and lower genetic diveristy than larger mammals/birds
○ Small populations drive genetic loss via genetic drift
○ Habitat degradation and frgmentation causes the loss of species bc theres sm genetic drift occuring wherever there is frgamentation
○ Gene flow (dispersla) between populations increased divseirty within populations
§ When frgamentation occuring, this gene flow is stopped resulting in less diversity and leading more to genetic drift bc population is limited and random sampling erorrs occur
Life History Trends of Urban Aniamls
○ In a study of 3768 bird species across 137 cities
○ Ideniftied sevral trends regarding bird species in urbanized envrinments as compared to urban avoiders
○ Urban tolerance inc if:
§ Smaller body size - favoured in cities bc its cramped there
§ Generalism - generalist can survive in a wide range of niches including the nevrinment conditions and material avialbility - generalist do better in cities and those who are more specilized struggle
§ Bigger clutch size - fecundity selection - bigger families, hogher resources, more eggs being made
Greater longetivty and less tetroial with greater dispersal ability - you can seke out more resources, avoid predators and you are more used to other organisms being around you
Peregrine Falcons
○ Great at eating birds like pigeons, duck hawks and parakeets
○ Some cities keep these birds as a way of getting rid of pigeons rather than using the pigeon traps
○ Peregrine falcon or duck hawk (falco peregrinus; family falconidae)
○ Fastest animal on the planet
§ Can reach speeds in excess of 320 km/h when diving
○ Global distribution with a 19 distintc described subspecies
○ Peregrine falcons is an urban specilist, hunting rela pigeons, parakeets and ducks
○ Collisions remain the biggest threat to fledging urban falcons
§ Of the 160 reported fatalities, 27% were in the first weel
§ Mostly builidngs but also vehicles, aircraft and powerlines
○ Adult mortality is much much less and only for territorial combat
