APS121 Evolution - Freckleton + papers & practicals Flashcards
What increased likelihood of making alarm calls in Belding’s ground squirrels?
More relatives in immediate vicinity
r x b >
c
kin selection is actually..
gene selection
A gene will spread in a population if it causes more copies of …
itself to be produced
- kin are more likely to share genes
r is…
the probability that a member of kin contains a gene for an altruistic act
b is…
the number of extra copies of the gene that the act yields
c is…
the cost to the giver in terms of the number of copies of the gene lost
what is the value of r between siblings?
cousins?
- 5
0. 125
Can unrelated individuals still behave altruistically towards each other?
Yes - for example if there is a way in which they can tell another individual shares a gene (e.g. hypothetical “green beard” gene)
- green beard gene confirms phenotype + linked nearby gene determines altruism
What do fire ants use to distinguish BB queens from Bb queens (bb die naturally)
Odours
workers kill BB phenotype
Why are green beards probably evolutionary unstable>
very easy to ‘cheat’ - possess green beard but do not reciprocate altruism
what does the segregation distorter gene do in drosophila?
Performs meiotic drive - ends up with 90% sd sperm and only 10% wildtype
selection acts on…
replicators - individual units that replicate themselves - those that leave the most copies are successful
- species are not replicators, nor are individuals
Rate of evolution varies through time. What are thought to be contributing factors?
- Climate and environmental change
- Competition
- Parasites
- Human exploitation
If 2 species have very similar requirements in the same environment they cannot co-exist. What must happen?
One species must either go extinct or evolve different requirements
- it is usually thought that the ecological process of extinction is faster than evolution and is therefore more likely (although cases such as Darwin’s finches show that this is not always the case - filled different niches in response to competition)
Give 2 examples of how human exploitation can drive the micro-evolution of a species
- Bighorn sheep - larger with bigger horns hunted for trophies, causing a reduction in animal size and horn length (as well as fluctuations in population size)
- fishing of cod led to maturation at a younger age and smaller fish
In British plant there is a negative relationship between flowering date and…
temperature (averaged across 250 years and 405 species)
What virus was introduced to australian rabbits in an attempt to control their population?
Myxoma virus (myxomatosis) - rapid generation time
1st epidemic 99% mortality
2nd 90%
3rd 40-60%
Death of hosts stops spread of parasites
- High virulence of parasite leads to a short period of spread - lower virulence leads to more secondary cases –> selection on parasites for less virulence and therefore higher exposure and spread
What is looking at the phylogenies of viruses and diseases in real time called?
Phylodynamics
What are a couple of situations where fast evolution can occur?
- superbugs
- pesticide resistance
What were the peaks in the measles case chart?
How about the influenza one?
Measles - consequence of school calendar
Influenza - selection, mutation and evolution + outbreaks every year due to lack of immunity
How do human activities change the environment?
What are the consequences?
- habitat loss
- climate change
- pollution
- reduced pop sizes
- extinction of pops and species
- loss of entire ecosystems
More recently what has been the main driver of human-caused extinctions?
Habitat loss (historically human exploitation and introduced species played a larger role)
What is phylogenetic niche conservatism?
Species inherit their niches from their ancestors - closely related species are ecologically similar - similar life histories - if change environment all will be affected (related species tend to all be threatened by the same processes)
In IUCN threat status what does EW indicate?
Extinct in the wild
What features correlate with extinction threat
- small geographic range
- large body size
- long gestation time
- high age at sexual maturity
- Low population density
- proximity to humans (+human density)
- High trophic level
- although different indicators more important for different species and groups of organisms
Is there a link between IUCN threat and phylogenetic conservatism?
Yes
- phylogeny is a moderately good predictor of extinction threat
What is phylogenetic diversity defined as?
The total amount of history shared by a group of species
- we can prioritise conservation efforts according to phylogenetic diversity
What are hotspots?
Areas of currently unusually high diversity - prioritising these will maximise conservation of phylogenetic diversity
What is Mullerian mimicry?
different to Batesian mimicry
When toxic species gain mutual protection from shared warning signals
- converge on the same aposematic (warning) pattern due to mutual protection from predators
Among snakes, what are warning signals and mimicry typically associated with?
Actively foraging, diurnal or crepuscular species
Are pitvipers diurnal, nocturnal or crepuscular?
nocturnal
- they are largely sedentary ambush predators
Where are pitvipers found?
Southeast Asia
In parts of Thailand and adjacent areas, several green species of pitviper overlap in range and display…
unusual conspicuous red colour pattern elements and striking phenotypic convergence - suggestive of mimicry
What DNA sequences were analysed to construct the pit viper phylogeny?
Four mitochondrial DNA sequences
In the pitviper paper what was the hypothesis?
No association between colour pattern and relative distribution
- Used Mantel matrix correlation test
- Rejected for all phenotypes except ‘no green’ and ‘green plus banding’
How many times did ‘green and red’ pit vipers evolve?
Green and banding?
Green only?
At least twice
At least three times
At least nine times
What is the ancestral pit viper colour?
‘not green’
- explains why no correlation between this colour pattern and relative distribution
What is suggested to be a reason for the correlation between ‘green only’ and ‘green plus other’ colour patterns and relative distribution?
Habitat-driven selection pressures involving camouflage and thermoregulation
How many genera showed the ‘green and red’ pattern
4
Why may male pit vipers gain more aposematism than females?
More active over a broader range of habitats while searching for mates during the breeding season - may increase risk of predation.
Females more sedentary lifestyle may make crypsis favourable over warning colouration
Many defended prey species occur in…
aggregations
What does the aggregation study want to find out?
Which order defence and gregariousness evolved in
Aggregated undefended prey are likely to be vulnerable to predation in the absence of…
satiation effects
In insects an association between aposematism (warning colouration) and…
gregarious has long been noted
What was Fisher’s contribution?
How could distastefulness evolve in an insect species?
- Distastefulness spread by saving of siblings who are likely to share many of the same attributes
- implied some form of gregariousness facilitates the evolution of distastefulness, which in turn generates selection for warning signals
What did Harvey et al. show?
How warning signals could evolve in defended prey that were clustered in family groupings
What dud Leimar et al. allow for?
Kin selection in their model of the evolution of warning signals.
What do most authors view aggregation as?
A group of prey that can be viewed simultaneously by a predator
How could distastefulness potentially evolve without aggregation?
If an insect also has a tough or flexible body it could survive a proportion of attacks by predators (and therefore pass on more genes)
- shown that aggregation is not an essential pre-requisite for distastefulness and aposematism
How could aggregation potentially evolve without defence? (considering will be more conspicuous and worthwhile feeding)
Perhaps satiation prevents all of a discovered group of prey from being consumed.
+ non-predatory benefits including modification of local microclimate for thermo- and hydro-regulatory reasons or overcoming host plant defences
Very large groups of defended organisms would provide…
the greatest protection from predation
What did Sillen-Tullberg conclude?
The evolution of warning colour (indicating investment in defence) is likely to evolve before gregariousness (in butterfly species) - and distastefulness/defences before aposematism
- however problem as gregariousness in butterfly larvae is uncommon anyway
What did Tullberg & hunter want to find out in their study?
whether gregariousness is likely to evolve in phylogenic branches:
- with warning coloration (compared to cryptic)
- > it was (in 10/12 cases)
- with repellant defence (compared to without defence)
- > it was (in all 9 cases)
What is it thought aposematic prey makes it easier for predators to do?
Remember distasteful experiences
What do the novel world papers involve?
wild passerine birds
It is thought that defence generally precedes…
Aggregation
- opposite to what fisher thought
