BIOL214 Ecology- Bilton Flashcards
What is a community?
A set of species co-occuring at a particular place and time
Assemblage
used interchanged with community
but applies to a taxanomic group (
community ecology
focuses on nature of predation, disturbance and consequences of competition
(small scale perspective)
How does the community assemble of a location build up over time?
.evolution of new species
.dispersal from other locations
Process that can lead to diversity
speciation
how one lineage becomes 2, responsible for diversity on earth
but diversity of lineages/ genetically divergence usually assosicated with ecological differntation- occupy different divergent niches.
immigration due to dispersal:
example:
beetle with active flight
consider how things move between localities
example: terrestrial insects- larval dispersal phase
Consider local communities and regional species pool
example: take a rocky shore
individual shores (rock) home to communites
but think of individual out cropping consider it as harbering local communityt that sit within a reginal species pool so all species that live within the overall area
(small in a big)
diagram shows individual localites in red and arrows show dispersal in regional pool of species
How does an individual patch effect a regional pool?
usually positively correlated local species richness and global species richness (more species in this the more potential)
alpha diversity and gama diversity
Why study islands?
hawaian arcapeligo-
why study islands?
easy to dictate where the edges are (boundaries)
result of isolation typically have fewer species then main land ( look at simialr island size, same latitude on mainland)
less species= easier to get everything (practical)
replicated natural communties
Rules to community assembly?
Islands and source pools
if dispersal range is shorter between source island- most things there will be able to get (ocean currents, active transport)
distance between island and source if its far away (example: )
so far away from source of coloists things will be isolated for a long time witout anything else will get there- therefore speciation will occur in situ.
Isolation is relative
ferns are common on even isolated islands and same species as other places, their dispersal phase means they can disperse huge distances (taxa dependant what= isolated)
endemics if old and isolated (not good at dispersing)
Theory (model) of island community assembly and dynamics
Mccarthur and wilson (1967)
Produces a simple model, dynamic balance between immigration/extinction or speciation and extinction
Point of crossing- equilibirum number of species on island (dynamic balance)
Why?
immigration seems curved as rate falls off when dispersal colonise-
good diperses come first- immegration falls once the amount of species in source pool runs out.
extinction increase? more compitiion for resources
interspecfic interactions drive extinction
Predicitions of the model (4)
Large islands have more species then small
(species are relationship)
Species richness declines with remoteness
(harder to reach lower immigration rates)
Number of species relatively constant through time
(unique prediction) Number of species composition will have a turnover through time. Actual species will change but the number will remain relatively constant.
Evidence of turnover is the key
Study example (Simberloff and wilson)
Mangrove islands
They defornated small mangrove islands using big canvas tents, lots of different sizes and fogged islands with insectise collected what was present.
look at fauna pre- releative number of species is about the same as what it had before for all sizes.
same amount but different species composition (sets of species change, as what arrives is by chance)
Why?
rapid immagration
relevant paper:
Adaptive radiation
Series of diversification events from a common ancester
long view: fossil record
dinosaurs- radiation in fossil record of body types, thus diversity in ecological roles.
regional and global diversification
mammal diversification
most dino death- molecular data can show mammal diversifcation (group timings etc)
Empty niches/ difficult to occupy
Adaptive radation my be causation in far off isalnds because they’re occupy and fitting the new niches through changing
example: gala finches- using resources that on the mainland others would be occupying- woodpecker and finch with a stick.
Example of adaptive radiation
Stickleback fish- found in coastal water and northern hem, rivers and lakes.
spines on back (3) anti predator device
an adnadromous fish- can live in various water like salmon, elaborate courthsip males build nest and care for eggs after getting the lady fish
Landlocked populations living in freshwater systems- show morpholigical mods compared to ancestrial ones
top fish has predators and the bottom doesnt- large difference in bony plates
Paxton lake (Stickle back)
2 ways of being a stickleback
Limnetic-feed largerly on plankon in open water, slim grassile fish, small mouth.
Benthic fish, fresh water isopods, insect larave in the sediment (grub around)
larger bodied bigger head, gap, body size. With signfigant morphological differences
radation in to 2 species (max of 12,000 to do so)
Are they 2 different species? They are behaving as so
Genetically very similar- no hybrids in nature- they nest and mate in the same place- but avoid mating with the other type (go for the specfic red colouration)
Can hybridze within the lab
Different lakes show the same thing has happened
How did now landlocked populations come to colonise?
canada- 12,000, created by land up lift at the end of glaciation
ice caps melt- sea levels rise- continents starts to rebound and raises up again from the new sea floor.
sea level rise and fall (scandanavia)
eustacy vs isoctacy
Eustatic sea level rise- melting of ice caps
Isostacy- reposition of land once its lost the weight of the ice.
Is radation adaptive? (experiment)
2 sickleback morphs set up in relevant aquaria- using growth rate as a surrogote of fitness
Results:
shows a trade of in environments, each fish does better in their own niche.
its innate not a learnt behaviour
hybrids come to be in the lab but dont work out better then their parents. (lower fitness)
Thus radation is adaptive
Has their been single or double invasion of lakes?
independent invasion and then evolution
Evolution in situ can be a great impact on diversification
East African Cichlids (example)
adaptive diversifcation
Why Ecologically diverse?
Cidclid females- females choosy for colour patterns in male (sexual selection)
mouth brooders, male has egg mimics that female touches when to release sperm
environmental change
pulses of diversification
alternating periods
blue lake and green lake conditions (shallow, termid, more algae, limited light)
driven by tectonics and climate cycling (glacial and interlglacial)
Hybridisaton in green lake conditions because females can see the colour
Mutations occuring at different events
Cyclid diversity paper
lake malwe
Ivory, S.J. et al. 2016. Environmental change explains cichlid adaptive radiation at Lake Malawi over the past 1.2 million years. Proccedings of the National Academy of Scicnes USA 113: 11895-11900.
Due to high genetic features in ecologically releavent genes
Adaptive radiation where there’s ecologically opportunity
pulsed enviormental change
sexual selection
hybridisation- for selection to act upon
Why are most species rare?
(globally rare)
individual communities (relative abundance)
communities are dominated by rare species- number of species occur relative occur at low abundance
long tail of things occuring in rare species
Wide spread species arent the norm
Are there different ways to be rare?
(Example Cypripedium slipper orchids)
Image shows distribution of genus
But most species are rare
Uk-Japan Cypripedium chalceolus
Wide spread but if you look at countries only found in a handful of places (yorkshire) and low density- specalised limestone soil.
Cypripedium subtropicum – (tibet)
Narrow range endemic
A raange of species in a genus thats considered rare but theres different aspects of rarity
Point endemics
Endemic to single localities
example: central portugal
e.g. Hydraena zezerensis (bug)
narrow range- one mountain, one stretch of stream and rocky cave area.
Different ways of being rare
population density
habitat range
geographic range
Rabinowitz’s types of rarity
only one way of being truly common
Common patterns in geographical range size (how widespread things are)
(gaston 2003)
abundance and occupancy tend to be related
Why are most species geographically restricted?
Possible mechanisms
Evolutionary age
Relative dispersal ability
Niche breadth
Biogeographic accident
evolutionary age
the longer a species has been around the more widespread we ecpect it to be.
Learnt to deal with things adaptive radiation(more time)
How to study this?
phylogenic tree- see a positive relationship branch length (how long ago split off) and geogrpahical range size
study- fish in north america (species life cycle)
pos at start, becomes negative because species start in single populaton which expands and gets geographically bigger range- isolation events- further speciation
likely hood overtime of single species becoming more restricted over time.
between range size and body size for a monophyletic group of 27 North American minnow species.
Relative dispersal ability
all else being equal
better at getting around should be more widespread- better at colonising and higher gene flow so no splitting (maintain this one species)
example- water beetle (damselfly)- wingloading capabillities
geographical range vs habitat type
enochrus (arribas etc al)
running water species- less geographical range size (ancestrial species decided to stay in salty moving water)
lentic- living in standing water- change in range size (different ancestrial standing water livers)
bigger wings compared to body size in standing water species compared- geological persistance of these types of habitats (puddles dry up etc)
paper for beetles- showing range size
Rundle, S.D., Bilton, D.T., Abbott, J.C. & Foggo, A. (2007a) Range size in North American Enallagma damselflies correlates with wing size. Freshwater Biology, 52, 471-477.
https://www.researchgate.net/publication/224264705_Range_size_in_North_American_Enallagma_damselflies_correlates_with_wing_size
Biogeographic accident
where they envovled and how easy it was to expand
island endemics- off the dataset their termpeature range would show that they’re fairly tolerant and therefore more widespread
consequence of developing in such as environment
example-
ice climate and communties
(What happens in the past effects the present)
Historical biogeography and present day ecology
image shows last few thousand years
example of ice cover
High latitudes were set in ice cap
dramatic changes in ecological changes- glacial-interglacial cycles
Trends in global temperature:
How do we know what happened before?
test shells of foramenifora- single cell eukarotes with a shell- coring the ocean sediment and looking at oxygen isotpes amount by 018 vs 016 shaped by the avalability of each and how its taken up by organsims
green line- overall trend in temperature
whats the pattern?
its got colder.
Present- 3 million years
much more variable in trend
overall trend is cooling, increase variabiltiy not due to more data-
018- heavy isotope of oxygen- relative amounts in benthic sediments in parts per thousand
Milankovitch cycles
orbital changes effecting global climate
eccentricity- how circular
(more even) vs ilpitical orbit (more summer less winter )around the sun shape of elipse changes every 100k years
Tilt- earths tilt releative to the sun, changes every 42k years. Greater the tilt greater seasonality
Precession (wobble around axis)-change 21k years effects seasons and how similar they are in both hemispheres.
Predicitng cooling and warming
earths orbit drives climate cycles
1.Role of antartica
(setting the stages for ice ages)
isolation and setting up of antartic current, leaves it free from heat transfer. Reflects solar radiation with the build up of ice.
2.The role of himalya and tibet
get paper
large area of upland above so more chance of build up of snow and ice- reflection-
disrupts global air circulation, warm air masses either side of plato
weathering of rocks like himalayan- deposition of carbonates takes co2 out of atmsohere and cools earth.
3.The role of the Isthmus of Panama
(closure)
gulf stream moves warm water north and thus more ice and snow in the arctic
How could plesiocene glaciations effect diversification?
driven evolution for a lot of narrow range species (narrow range endemic) in places
that experienced ice sheet expansion
wetter and drier periods in tropic areas isolated small forest habitats therefore things could diverge from each other.
Isolated by barrier (drier land etc) natural selection is different where these barriers are so things need to change
allopatric speciation (barrier)
example of species that survived- didnt go through intense perma frost-
Why is there an increase in diversity towards the tropics? (LDG)
12 different concept methods to why its occuring- Some pos
Local explanations:
coexistence without exclusion
Stucture of habitat in tropics (more canopy layers more species can fit- more species generally)
LDG was not always present in life history
tropical bands extends around the ecuator but this wasnt always the case when things were hotter
LDG occured in:
late permian
late ordivican
middle miocene
What is the relationship between ecosystem function and species richness?
graph-
green line: proportional loss each species contributes more or less equally (as species increases the rates of ecosystem fucntion increases. Same predictable loss with extinction.
High redundancy model- as the threshold is met then redundancy occurs. why? different niches are occupied but if you keep adding then niche overlap can occur.
functional redundacy
low redundacy- limited functunal redundacy, all species matter to lose species
purple: as long as somethings there should be fine
orange: more species lower the ecosystme function
black dots- idosyncracy
relative function doesnt fit a relationship is changing depending. Number of things doesnt matter but species identity is more important
idosyncracy and keystone species
keystone species- species which has disportunate impact on community, compared to their abundance or biomass (paine 1960’s)- bigger impact then you’d expect
removing one consumer:
dominants- big impact with habitat structure, but high biomass.
keystone species- bass, top down predation, starfish. Big impact on flow of chain.
(example leaf-litter breakdown study).
no single model can describe all results
depends on the taxa and system (idosyncracy)
biodiversity does impact ecosystem function tho
example study-
leaf litter breakdown from shredders
usually stuff that washes in
lab experiment of 1, 2, 3 of stone fly species in sweden.
12 indivduals and look at rate of litter loss.
across 3 species has a signifcant impact on how leaves break down. more of own species isnt as fast as different
issues? what if more species
would it still be the same? probelm of small scale study restricts to low biodiversity system. only one ecosystem process
thus meta
meta analysis
Van der Plas, F. 2019. Biodiversity and ecosystem functioning in naturally assembled communities. Biological Reviews 94: 1220–1245
try to summarise decades of work all together, see overall picture.
(duffy et al)
(van der plaas)
comparison of number of species vs functional compositon (groups) predator or consumer etc
In summary, a high biodiversity in naturally assembled communities positively drives various ecosystem functions. At the same time, the strength and direction of these effects vary highly among studies, and factors other than biodiversity can be even more important in driving ecosystem functioning. Thus, to promote those ecosystem functions that underpin human well-being, conservation should not only promote biodiversity per se, but also the abiotic conditions favouring species with suitable trait combinations.
