Host + parasites (DONE) Flashcards
What defines host-parasite interactions?
Host-parasite interactions involve one organism (the parasite) benefiting at the expense of the host, w long lasting coevolution
What is the key difference between host-parasite interaction & predator-prey interactions?
Host-parasite interactions are long-lasting & involve close coevolution
While predator prey interactions are short-term & often lethal for the prey
What is virulence (in the context of host-parasite relationships)?
Virulence refers to the damage caused by a parasite to its host
How do parasites evolve to optimise virulence?
Parasites balance exploiting the host w the need for transmission (not killing the host)
Often stabilising virulence over time
What happened w the Myxomatosis virus in Australian rabbits?
Over time, the Myxomatosis virus decreased in virulence, stabilising at an optimal level to ensure host survival for transmission
What is horizontal transmission in parasites?
Horizontal transmission occurs when parasites spread between individuals in the same generation
This is often associated w higher virulence
What is vertical transmission in parasites?
Vertical transmission occurs when parasites are passed from parent to offspring
Often associated w lower virulence
How does Wolbachia in woodlice affect virulence?
Wolbachia inc virulence when horizontal transmission in enforced in experimental settings
What are examples of diseases w lower virulence compared to vector-borne diseases?
Directly transmitted diseases typically have lower virulence compared to vector borne diseases (e.g. malaria)
What is the Red Queen Hypothesis?
The Red Queen Hypothesis suggests that both host & parasite are in a constant evolutionary race to adapt & counter-adapt
How do rare host genotypes relate to parasitism in the Red Queen Hypothesis?
Rare host genotypes initially escape parasitism
But as they become more common, parasites adapt to exploit them
This creates a continuous cycle
What is an example of the Red Queen Hypothesis in New Zealand snails?
Common clones of NZ snails show higher infection rate by lake-specific parasites
Supports the Red Queen Hypothesis
How does the Daphnia & Pasteuria experiment support the Red Queen Hypothesis?
Experiments w past & present pops of Daphnia & Pasteuria demonstrate temporal genotype cycling, consistent w the hypothesis
What is a host-trade off in the context of resistance?
Hosts face trade-offs between investing in resistance to parasites & other fitness traits like reproduction
How does resistance to parasites affect Drosophila’s reproduction?
Drosophila genotypes w higher resistance to parasites often show reduced fecundity
How does resistance to parasites affect fish?
In fish, resistance to parasites is often negatively correlated w tolerance, indicating a cost in dealing w infections
What is the geographic mosaic of coevolution?
Host-parasite interactions vary geographically due to local adaptations & environmental conditions
How do sticklebacks & parasites illustrate geographic mosaic coevolution?
In sticklebacks, parasite virulence & host resistance are influenced by water chemistry, w alkaline environments supporting higher parasite virulence
What defines a diffuse arms race in coevolution?
Diffuse arms races involve multiple host & parasite species interacting simultaneously
Leads to complex coevolutionary dynamics
What is an example of a diffuse arms race?
Cuckoo-host interactions, where cuckoo eggs mimic host eggs & hot birds evolve egg rejection behaviours
How do cuckoos adapt to host defences?
Cuckoos use egg mimicry, distract host parents w sparrow hawk-like cries & lay eggs rapidly to avoid detection
How do hosts counter cuckoo parasitism?
Hosts evolve egg rejection behaviours, identifying & removing foreign eggs
Why do Icelandic birds show lower rejection rates for cuckoo eggs?
Icelandic birds show lower rejection rates due to the lack of cuckoo parasitism in their environment
How does the size of host & cuckoo species correlate?
Larger hosts tend to support larger cuckoos, w adaptations aligning across species
What is egg ejection in cuckoo-host interactions?
Egg ejection occurs when cuckoos eject host eggs to monopolise parental care, typically in species w smaller hosts & cuckoos
What genetic factors are involved in cuckoo-host interactions?
Egg mimicry & host preference are likely linked to genes on the W chromosome –> allowing maternal inheritance of these traits
