Lecture 9: Mutualism & symbiosis Flashcards
what does symbiosis mean?
living together
what is mutualism?
beneficial interaction between both species
what is not mutualism?
symbiosis
what does mutualism involve?
reciprocal exchange of goods between two species
what is nutritional mutualism?
providing limiting nutrients (resources) from one species to another
what is defensive mutualism?
when one species receives protection against predators or parasites in exchange for offering shelter or food to its partner species
what is dispersal mutualism?
one partner receives food as a thank you for helping flowers transfer their pollen
what is the honey bee example of mutualism?
Yao people in Mozambique harvest wild honey, but can’t find bees’ nests easily. Honeyguides (Indicator indicator) eat beeswax and know where nests are, but can’t access them easily. Honeyguides recognize the specific sound that Yao honey-hunters make to attract them
how do you change the Lokta Volterra model to model mutualism?
add a plus sign instead of a minus sign in the bracket of the interspecific Lokta Volterra model
what is the outcome of Lokta Volterra’s model of mutualism?
they lead to silly outcomes where both populations undergo unbounded exponential growth, in an orgy of mutual benefaction
What limits the population growth of
mutualists? ITD
-Strong intra-specific competition
-A third species such as a predator or a competitor
-Diminishing returns to mutualism as the population grows
what is the outcome of positive feedback between mutualists?
generating runaway population growth
how did Simberloff define invasive meltdown?
when two native species facilitate one another’s spread
what are Spring ephemerals?
herbs that flower right after the snow melts producing a short-lived carpet of flowers
what is the native seed-dispersing ant?
Aphaenogaster rudis
what is the Invasive seed-dispersing ant?
Myrmica rubra
what type of plant do native ants like?
native plants
what type of plant do invasive ants like?
invasive plants
what is the job of cleaner fish? what is the mutualism aspect of this?
feed on ectoparasites on the
bodies of client fish
cleaners get food, clients benefit from fewer parasites
where do the clients of the cleaner fish visit?
cleaning stations or territories of cleaner fish
what is the outcome of removing cleaner fish experimentally?
increase the number of parasites in clients
what does the presence of cleaner fish on reefs affect?
species diversity reefs
what did redouan bshary study?how did he study?
natural variation of cleaner fish
studies their effects by adding and removing them
what did Darwin predict about orchids?
these flowers must be pollinated by insects with very long proboscis
what does the relationship between flowers and insects represent?
they represent reciprocal adaptation
what do aphids feed on? what is the benefit and downside to this?
phloem sap
rich in sugar
poor in essential amino acids
how do aphids provide their host with essential amino acids?
with their intracellular bacteria
how do aphids reproduce?
mothers vertically transmit their eggs to their offspring
what are the genomes like of vertically transmitted endosymbionts?
small
how many base pairs is the mitochondrial genome in humans? how many genes do they encode?
17000 and encode just 37 genes
which genes do Endosymbiotic bacteria lose?
the ones they do not need
Are mutualisms often highly
specialized?
But most mutualisms are NOT tightly coevolved species-specific interactions
why do Endosymbiotic bacteria lose genes that they no longer need? (2)
Some functions are unnecessary because bacteria are no longer free-living (protected inside host cells)
Other functions ‘outsourced’ to host genome
how do most species in mutualism interactions reproduce? what does this mean?
horizontally
partners are acquired anew each generation
are mutualism one-to-one interactions?
usually many to many interactions
what are Current ‘hot’ areas of mutualism research? (2)
Understanding networks of interactions among large numbers of species
Microbiomes
what are microbiomes?
all the microbes living together in a community
how many pollinator species do plants have? how many plant species do pollinators have?
Most plants have many pollinators species; most pollinators visit many plant species
what are sequencing-based methods to characterize microbial diversity in a host?
conserve genes, DNA sequencing, culture microbes
Sequence a highly conserved gene, usually the bacterial 16S rRNA gene
Use DNA sequence data to identify microbes
Frees us from having to culture microbes in order to
study them
what do Mammal gut microbiomes reflect? (3)
DPM
diet, phylogeny(history of evolution) and morphology (the structural features of organisms)
what does accumulating evidence about microbiomes suggest? MIT
suggests a host’s microbiome affects its metabolism, immune system, and other traits
what have Researchers compared microbiomes among? (3) CBM
human cultures, body parts, and medical conditions
Microbiome researchers often ask the same questions ecologists ask of any community. (4)
which and how many, space or time or environmental gradients, simpler systems, adapt
What determines which and how many species live together in a community?
How do communities change across space or time or along environmental gradients?
Can we predict complex community dynamics by knowing what happens in simpler systems involving only one or a few species?
How do species adapt to their (host) environment and each other?
