mutualism/parasitism

why do we care about mutualism and parasitism?

crop and forest productivity, ecosystem functioning - mycorrhizae

crop pollination, honey production, and pollinator networks

parasites and diseases

symbiosis

intricate and long term living of two organisms

includes commensalism, mutualism and parasitism

often species specific

form may be contingent on environmental factors depending on context`

facultative symbiosis

occuring optionally

no dependence on specific partners, low risk of extinction if a partner goes extinct

obligate symbiosis

occuring by necessity

dependence on specific partners, high risk of extinction if a partner goes extinct

ex specialist pollinators

symbiosis gradient

gradients from mutualistic - commensal - parasitic

from facultative - obligate

commensalism

ecological interaction which is beneficial for one species but neutral for the other

ex barnacles benefit from whales, but whales are mostly neutral

commensalism - barnacles and whales

barnacles benefit from whales, substrate and dispersal

only found on whales - obligate, but some are facultative

whales experience no harm and no benefit usually, facultative

sometimes barnacles can be positive and act like armour on their fins, or too many can cause drag and spend more energy, or cause skin conditions

parasitism

ecological interaction that is beneficial for one organism but detrimental to the other

ex ticks obligate symbiosis on host animal

ex ticks and host - parasitism

ticks are obligate arachnoid ectoparasites, and feed externally on blood of other animals

host animal is harmed through blood removal and disease risk

other parasitism examples

mistletoes - hemiparasitic plants

tapeworms - in digestive tracts

tongue eating lice - crustaceans feed on blood and mucus in fish mouths

herbivores vs plant parasite?

parasite host interactions are similar to those seen in predator prey relationships or herbivore plant - exploitative

the difference is that a parasite forms a intricate and long term relationship with its host

parasites altering host behaviour

ex european starling, isopods and thorny parasitic worm

the worm lays eggs in the intestines of the bird, the eggs are then shed with feces, next a isopod eats the feces and the worm larvae will develop within it (intermediate host), the larvae alters the isopod behaviour to spend time in open areas where it is more likely to be eaten by the starling (primary host) and the cycle continuous

primary host vs intermediate host

parasite reaches adult stage and sexual maturity, vs parasite grows

red queen hypothesis

species must evolve to keep up with the evolution in their parasites and vice versa

perpetual co evolution between the two can be compared to an arms race

it takes all the running you can do to keep in the same place

mutualism

ecological interaction which is beneficial for both organisms

ex mychorrhizae

mycorrhizal fungi (MF)

plants benefit from increased nutrient uptake in the soil, while the fungi benefits from plants through the consumption of root exudates - carbs

can be parasitic, but environmentally dependent

arbuscular mycorrhizal fungi (AMF)

penetrate the cortical cells of plant roots

more mutualistic when grown in nutrient poor soil

occurs in 80% of plant species

Ectomycorrhizal fungi (EMF)

do not penetrate cortical cells

2% of plants species - conifers, blueberry - northern biome species

AMF and nutrient poor soil

predicted that in nutrient poor soil there is more carbohydrates exudate to the roots because more energy/allocation to the roots for the same growth

in nutrient rich soils, more energy is spent on the above ground foliage meaning less carbs in the roots

this means that MF colonizing in nutrient rich soil is going to be more aggressive in carb acquisition at the expense of host

experiement tested this with fertilized and unfertilized soil which was sterilized or not

MF and mutualism-parsitism continuum

plants were grown with and without MF and the change in biomass was compared

some plants increased growth with MF while others had no impact and others decreased

sometimes the fungus takes from the plant and does not give as much as it should

reciprocal parasitism

natural selection should favour a species own fitness rather than simply help organisms

in reference to the net effects of mutualism

mutualistic interactions

corals and zooxanthellae, lichens - fungi and algae, legumes and rhizobia bacteria - nitrogen fixation

corals and zooxanthellae

obligate interactions

coral and algae depend on each other for survival, when the coral becomes stressed - increased temp or pollution, the algae leaves the coral

this causes the coral to be bleached and vulnerable, the coral loses its main food source and is susceptible to disease

what can cause coral bleaching

increased ocean temps, runoff and pollution, overexposure to sunlight, and extreme low tides

lichens

symbiotic mutualism

a fungal biofilm and algae work together, the algae providing photosynthesis and the fungi providing structure and retaining moisture/protection

allows for the existence in tundra and other extreme climates

non-symbiotic mutualism

not all interactions are going to the intricate and constant body to body

ex pollinators, seed dispersers, cleaners like birds on cows or smaller fish and other fish

pollination

the transfer of pollen grains for reproduction by wind, water, animals or within the same flower

animals as pollen dispersal vectors

plant species which rely on pollinator usually have co evolved pollinators

there is a cost to the plant, such as energy expended for attraction rather than reproduction

the animal also has a cost, such as energy wasted searching for a specific plant → reciprocal parasitism but usually the benefits outweigh the plants

attracting pollinators adaptations

flower colour and scent

butterflies attracted to bright like yellow, orange, red, bees are red blind so prefer yellow or blue and nocturnal moths like scent released during the night

pollinators may be rewarded such as by pollen, nectar or the prospect of mating with a female

pollinators and ecosystem services

functions provided by nature which improve and sustain human wellbeing

bees as commercial pollinators

1/3 of global food production due to pollination

30$ bil USD per year

facilitated by managed honeybees maintained by humans

colony collapse disorder (CCD)

many colonies are lacking worker bees and cannot sustain themselves despite abundant honey

about 30% loss each winter since 2006, 3x higher than normal

possible reasons still investigated but thought to be due to parasites, pesticide poisoning, stress, inadequate forage

measures to protect pollinators

flower strips, landscape heterogeneity

in europe after have saw in 75% loss in insect biomass in 27 years