Lecture 12 & 13 Predation as disturbance Flashcards
what is predation?
The consumption of one organism (part or whole) by another and the first organism is alive after the attack (Begon et al., 1996)
4 types of predation
Carnivory - Lion
herbivory/grazors - cows on grasslands or even mosquitos on us
parasitism - isopod that eats a fish’s tongue & lives in its place & eats the food the fish eats
mutualism - corals and zooxanthellae (not bad though)
generalist predator
live in many different types of environments, and have a varied diet are considered generalists. Raccoon. or rabbit on grass.
what are the effects of a generalist predator?
Rabbits - eat lots of different species of plants. Stop competitive exclusion from happening & more species diversity.
what is exploiter-mediated coexistence?
where predation promotes the coexistence of species where there would otherwise be competitive exclusion.
In areas where the predator is fussy (thistle plants) they invest more energy in spikes and grow less / slower growth rates trade off. The plants that grow the fastest are best competitors but not defended so are eaten, if left would win. Things that grow fast are also more likely to be eaten more frequently by generalist predators.
What are the effects of Littorina (periwinkle) on algal diversity?
IN rock pools littorina increase diversity of green algae, IDH. On emergent subsrates Littorina decrease diversity as green algae are weaker competitors here and can’t grow as fast?
What is a keystone species?
Organisms that have an effect much bigger than you would expect because of how they interact in the food chain.
e.g. starfish Pisaster - when removed diversity in the organisms they predate decrease. (competitive exclusion).
what is Diet switching or ‘frequency dependent predation’ ?
where the predator preferentially consumes the most common type of prey. e.g. a butterfly will lay its eggs on different plant species but will end up laying more eggs on the most frequent plant. Eggs hatch a larvae will eat more of these plants.
case study for frequency dependent predation
guppies feeding on a mixture of naididae and fruit flies. The guppies ate more of whichever was more available (Murdoch et al., 1975) (generalists i suppose)
however, some species exhibit consistent preference such a study composed by Murdoch and Stewart-Oaten (1975) where a species of gastropod would consistently prefer Mytilus edulis over Mytilis californianilus no matter the abundance.
What is a specialist predator?
thrive only in a narrow range of environmental conditions or has a limited diet. A well-known example of a specialist animal is the Monophagous koala, which subsists almost entirely on eucalyptus leaves.
what are the effects of a specialist predator?
specialist pred will induce a frequency dependent response? predator-mediated coexistence as they decrease the abundunce of the prey they’re eating, their own species abundance will drop. There will be a lag phase. When the predator is at a low pop the prey will increase in numbers. a cycle.
What is a case study of specialist predator effects?
Disease & humans. Outbreak, resistance, some not resistant, this exploited then another outbreak.
A case study of specialist predator used as biological control:
A cactus (prickly pear) from south america and became hugely invasive in Australia. Found a predator from south America, moth (Cactoblastis). Just 3 years after introduction was pretty much all gone, but still a few that survived. Rare that species will ever wipe another species out, but hold back the pop size, therefore target species can’t competitively exclude other species as they won’t reach carrying capacity. (Dodd, 1936) However not always best solution cane toad introduced to eat beetles turned out to be a generalist predator and ate everything but (Phillips et al., 2007)
Case study of parasite predation:
current case study: Ash dieback, a fungus spread from europe that kills UK ash trees. it kills them by spreading a toxin from the leaves. Spores are released and spread to other trees through wind. it is thought 95% of ash will die in UK, affecting many patch communities.
Where does predation have the most and least significance on species diversity?
most - in stable environments
least - where environmental disturbance is more severe or un predictable
