05. ECOLOGICAL COMMUNITIES Flashcards
Define community
grp of potentially interacting spp that live together in space and time (Magurran 2004)
How do we often define communities
by vegetation of area e.g. melb’s 3 biomes = plains, coastal, hills - defined by landscape ft
Why do ecological communities exist?
eco comms arisen bc interactions bw spp over time in response to environ cond/demands.
history of geog land mass → shapes climate/resources → shapes div of eco comms
e.g. tundra ecosystem occurs in coldest regions of world vs desert ecosystems occur in hottest
→ landscape + spp that habitate it = reflections of e/o
What key processes influence ecological communities?
comms:
- selection
- drift
- diversification - X speciation
- dispersal
analogous to ft of pops: selection, genetic drift, mutation, gene flow
Define selection in relation to ecological communities
selection = changes in comm structure caused by deterministic fitness (non-random) diff bw taxa i.e. what taxa is most fit for temp/rainfall/soil/fire regime etc.
also note: selection pressure = varies over space/time; is ongoing; is density-dep
Define drift in relation to ecological communities
drift = random changes in comm structure/abundance of diff taxa
neutral process bc X features = favoured
Define diversification in relation to ecological communities
dinc in taxonomic div of comm over time due to evol i.e. evol of new lineages from existing lineages
outcome = new genotypes, forms, varieties, sub-spp + spp
ST or LT
Diversification can happen quite rapidly when…
selection pressure = sufficiently lg + generational length = sufficiently short
Define dispersal in relation to ecological communities
mvmt of indiv from one place to another
can occur at any stage of life cycle
involves immig/emig + impact varies dep on source/reciever, size of mig grp, dir of mig (one/both ways), and dist (long dist or link local comms = metacomm)
What is a metacommunity
grp of local comms occupying set of habitat patches + linked by disp of multi potentially interacting spp (Leibold et al. 2004)
What is a species pool?
grp of spp capable of persisting in an area
What does Keith 2017 conclude about the influence of history on Australian vegetation?
Aus veg comrpised of spp pools = reflections of evol filters (water + nutrient availability), abiotic factors (temp + fire regimes) + biotic factors (comp pred)
Name five of Australia’s biomes
- rainforest
- savannah
- heathlands/scrubs
- semi-arid eucalypt woodlands - mallee land
- freshwater wetlands
When was Australia’s warmest and wettest period?
late Palaeocene/early Eocene (50-60mya) - right before sep from Ant starts
When did the first arid climate arise in Australia?
late Miocene (7-12mya)
When did Australian contact with Asia start?
late Oligocene/early Miocene (18-25mya)
Since Australia’s seperation from Gondwana, what have been the overall climate trends?
cooler
drier → inc fire freq
When did major climate cycles (glaciation/inter-glaciation) start?
beginnign Pleistocene (2.58mya)
How has volcanism aided biological productivity in Australia
inc nutrient-density of soil → inc fertility
Outline the historical compositions of key Australian vegetation formations
Rainforest - G relic+ intrusive tropical
Heathlands - G autochthonus
Savannahs - G autochthonus + intrusive tropical
Tussock grasslands - intrusive cosmo
Alpine herbfields/shrubland - G autochthonus
What are dry-adapted traits called?
xeromorphic
What are fire-adapted traits called?
pyrophytic
What ecological processes have particularly influenced Australian plant communities?
- selection - temp, aridity, fire, nutrients etc
- diversification
- dispersal - from G or Asia
What is alpha diversity?
measure of a local eco comm according to its richness (# diff spp), evenness (relative abundnace of spp w/in comm) or both
What is beta diversity?
extant of change in comm composition/degree of diff across region
Name two indexes used for measuring the level of diversity of an ecological community?
Shannon + Simpson
What are two factors to consider when measuring the diversity of an ecolical community?
- detectability of spp - visibility can dep on life cycle stage/time of yr
- taxonomy
What is the difference between geographic and environmental space?
geog = 2D
environ = sum of all factors that influ environ e.g. roughness, southness, rainfall etc i.e. conditions + resources
Outline the difference between the fundamental and realised niche
fund = idealised multidim hyperspace that encompasses range of cond/resources that enable spp to survive
realised = space actually occ by spp - smler bc factor in: comp, disperal lims, disturbance events, stochasticity → can cause local extinct that mean spp X persist w/in fund niche
What are environmental gradients?
factors that influ environ cond → impact what spp can thrive/persist
e.g. eco niche of terr plants driven by cover, aspect, solar radiation, temp
What is competitive exclusion?
when one spp dominates over others in LT due to comp for sames resources
e.g. Elaeocarpus dentatus abundnace = lower when Nothofagus present (Leathwick & Austin 2001)
What is resource partitioning?
when spp changes morphology (size/shape - char displacement) OR behaviour (nocturnal/diurnal) → dec comp
e.g. alloptatric pops of Hydrobia (mud snails) = similar sizes vs sympatric pops H. ulvae is consistantly larger than H. ventrosa (Knox et al.)
How does spatial and temporal variability allow for co-existence of competing species/populations?
carves out space/time for spp/pop to have excl access to resources
e.g. Sedum smalii thrive in shallow soil vs Minuartia uniflora prefer deeper soil (Begon et al. 2006) → habitat w variable soil depth will enable co-existance
Name two subjective methods of classifying community patterns in space
- structure - according to height + density of veg
- what spp dominates/present
What are the limitations of classifying communities subjectively?
each comm = unique + rarely fulfills all char of formal def
Outline two objective methods of classifying community patterns in space
- data-based pattern analysis
- assoc (what spp commonly occur together)
- classif
- ordination (what specific environ cond are assoc w certain spp) OR cluster graph??
- mapping
- classify spp
- then model r/ship bw spp → predict across space (map)
Outline the different classifications of community interactions and give an example
- mutualism (+/+) - hummingbird/dianthus (nectar/pollination)
- comp for resources (-/-) - nothofagus/Elaeocarpus dentatus trees in nz (light)
- predation + parasitism (+/-) - ladybird eats aphids
- commensalism (+/0) - epiphytes
What is unique about parasites’ habitats?
host = alive → able to grow, respond + adapt
Example of protozoan parasite
malaria infects RBC
What form of organisms are most and least commonly parasitic?
most - opalinata, mesozoa, pentastomida
least - sarcodina, cnidaria, mollusca, chordata
Host species commonly…
have >1 parasite
mammals avg 8
birds avg 9
Even though parasites are commonly very small…
their totals abundance means they can have sig impact in eco comms
Draw the parasitic life cycle
v
Define predation through an ecological lense
consumer benefits at (mortal) cost to prey - e.g. incl herbivores/insectivorous plants
Direct impacts of predation on populations
- abundance of indiv
- evol of pred/prey spp - adaptations (e.g. camo) + gene pool - consider the impact of koalas choosing euc leaves w high N content + lower toxic chems
- distrib of spp
Indirect impacts of predation on population
- behaviour of prey
- e.g. hiding - Grasshopper in CT - hiding from spiders → dec daily activity 18% + dec grass content of diet 70% → 42% → pop decl (Schmitz 1998)
- spatial arrangement
- e.g. birds of preferred prey size stay away from Sparrowhawk nests (Forsman et al. 2001)
What is a keystone predator?
pred that plays such a sig role in eco comm that its absence would drastically change/end comm
Compare the impact of intimidation on prey with direct consumption
intimid has just as strong impact of prey demographics as direct consumption (Preisser et al. 2005)
poss bc behavioural changes → reduce fitness → pop decl
Consequences of introduced species herbivory on Australian vegetation
- change veg composition + structure - height/density
- inc cover
- inc exotic weeds
- dec plant spp richness
commonly bc grazing spp
Predation is an _ species interaction
exploitative
Describe the predator-prey cycle
Image 6
Food webs are reflections of…
trophic r/ships bw orgs
What are sub-webs?
food webs that incl difficult to detetect orgs i.e. parasites
What is the purpose of a topological food web?
quantify # + distrib of trophic conn using data
What are trophic cascades?
conseq of pred-prey rships that alter abundnace/biomass/prod of spp/functional gp/trophic lvl further down food chain
2 types:
- top-down control = pred have lg influ on comm i.e. keystone pred e.g. sea otters → sea urchins → kelp
- bottom-up control = prod/prey have lg influ on comm
can occur simul
What do food webs do?
summarise tropic r/ships
Across what scales can we study interspecific interactions?
- temporal
- geog
- morphometric (body size)
Outline two examples of interactions that differ on temporal scale
- tumbling flower beetle x eudicot flower = earliest known insect poll of flower - 99mya (Cretaceous)
- cane toad x sand goannas = novel pred-prey interactions → goannas harmed by bufotoxin → lower abundance in areas w CT (Feit et al. 2018) → trophic cascade bc inc abundnace goanna’s prey (Feit et al. 2018)
Outline one example of an interaction that occurs on a geographic scale
- bogong moth x mt pygmy possom
- BM larval stage in plains NSW/QLD → mig >1000km to cool caves of VIC alpine zone → poll plants along way + imp food source for MPP
- droughts in NSW/QLD → decl abundnace BM + light poll in VIC alpine zone = disrupting mig → trophic effect bc worsenign MPP endangerment
Outline two examples of an interaction that occurs on a morphometric scale
- humpback whale x antarctic krill (60mm/2g)
- fur seal x antarctic krill
Which scenario of climate change and chlorophyll concentration is best for krill habitat?
RCP2.6 (Hill et al. 2013)
Which scenario of climate change and chlorophyll concentration is worst for krill habitat?
RCP8.5 bc relative gross habitat growth potential is lowest at all lvls of chlorophyll concentration than RCP4.5 and RCP2.6 (Hill et al. 2013)
Antarctic krill is a _ species in the antarctic area
keystone
Why is chlorophyll important for krill?
krill feed on phytoplankton, which need chlorophyll to photosynthesise
Simple trophic web for antarctic community
sun → phytoplankton → krill → humpback whales + fur seals
Mutualistic relationships are the result of…
co-evolution
Define co-evolution
when unrelated orgs evolve in a co-ord manner
Types of mutualistic relationships
specific = bw 2 spp
diffuse = bw multi spp
Outline mycorrhizae
- fungi col roots of plants
- occurs in ~80% plant spp
- mutualistic r/ship bw plants + fungi
- F supply H20 + nutrients (e.g. N + P)
- P supply PT prods (e.g. sugars)
- results
- P inc resistance to pathogs
- creates mycorrhizal networks → transmit H20, nutrients + info (via biochem signals) bw plants → changes P behaviour/function = root/shoot growth/PT rate/foliar nutrition/defense response
What do mycorrhizal networks do?
transmit H20, nutrients + info (via biochem signals) bw plants
→ changes P behaviour/function = root/shoot growth/PT rate/foliar nutrition/defense response
e.g. aphid under attack from beetle sends signal to nearby P → release chem that repels beetles + attracts parasitic wasp to attack beetle
Outline an example of an animal-plant mutualistic relationship
- flying foxes x multi spp plants
- FF feed on nectar/blossoms/fruit of many spp plant → imp poll across Aus + Pac
- decl FF pop (driven into more uban environ) → neg impact on multi spp in non-urban plant comms
Outline an example of an animal-algal mutualistic relationship
- coral x zooxanthelle
- zooxanthelle live w/in coral pollups = dep on coral for habitat
- coral depend on zooxanthelle as nutrient source
Antagonistic coevolution can be compared to…
an evolutionary arms race
Outline an example of antagonistic coevolution
- toxic newts (prey) x garter snakes (pred)
- GS evolved inc resistance to newts’ tetrodotoxin → pressure on newts to inc toxin
- BUT res X geog uniform - variation in res = driven by selection (Brodie et al. 2002)
Outline two examples of how a disruptions to an interspecific interaction impacts the broader ecological community.
- potoroos x truffles x mycorrhizae
- sml mammals (e.g. long-nosed potoroo) feeds on truffles (subterr fruiting bodies of myc fungi) → disp spores → ‘ecosystem engineers’
- decl pop of sml native mammals since Eur col → dec truffle abundance → threatens multi plant spp bc X germinate/survive w/out mycorrhizal partner
- coral x zooxanthelle
- heat stress → coral expels zooxanthelle → ‘bleached appearance’
- w/out zooxanthelle coral starves + dies
- bleaching events corr w heat waves - CC
Explain how the disruption of the mutualistic relationship between coral and zooxanthelle impacts other components of reef communities.
inc ocean temps/freq of heat waves → inc coral heat stress → expel zooxanthelle → ‘bleached’ appearance + starve → die
→reef spp lose habitat
→ decl freq corallivore fish bc decl food source (living coral)
→ inc freq excavator fish bc inc food source (coral skeleton)
(Stuart-Smith et al. 2016)
What types of community change are important over short time scales (years-centuries)?
selection, disp, drift
(evol div req longer time)
Define and outline orderly succession and compare to stylised succession
nat changes to comp + structure of an eco comm over time
(implies replacement of one comm by another)
i.e. devt of one spp in area makes environ more suitable for diff spp to thrive → dominate
more realistic than total ‘replacement’ = ‘stylised succession’ = devt of diff veg comm in one space
Mountain ash is a _ species because…
keystone bc habitat for animals + responsible for storing lg amts C → imp for nutrient cycling
Decline in mountain ash
pop has 1/2 since 1997
Mechanisms to conserve mountain ash trees
maintain ~200m buffer zones of unlogged forest around trees → protect from:
- edge effects
- changes in microclimate
- impacts of nearby logging
- fire
- disease
How does disturbance impact ecological communities’ composition and structure?
influences selection, dispersal and drift.
over long time periods can even influence evol div bc spp emerge that are better adapted to specific disturbance regimes
Define and outline the significance of disturbance regime
dist reg = LT pattern of dist across geog area. measured by freq, size + intensity → determien prob/nature of next dist
est using historical data
Why are changes to disturbance regimes considered a threatening process?
changes to DR alter rate/nature of selection, dispersal and drift → rapidly change comp of eco comm - main concern = biodiv loss
e.g. too freq burning → decl mt ash + inc shrub forests = cascade bc habitat loss for animals → extinction/endangerment
Can a native species be considered invasive? If so, why?
e.g. COTS
Yes it is considered a pest because it is colonising regions beyond its natural habitat and abundance beyond its natural capacity as a direct result of human activity (agriculture fertilisers - floods - pollute ocean water - provide nutrients for COTS - inc COTS abundance - outbreak spreads bc currents carry larvae sth)
Cats and foxes are considered _ species in Australia
feral
(cats kill >1mil animals/day)
Factors that influence a species’ vulnerability to predation by feral species
- habitat
- birds in grasslands/shrubland/open forest/coastal habitats = more likely to be preyed upon by cats than in RF/freshwater areas (Woinarksi et al 2017)
- body size
- birds w body mass 1-3g = morely likely to be preyed upon by cats than 5g (Woinarksi et al 2017)
List feral herbivores in Australia and outline their impact on the landscape
- rabbits
- horses
- camel
- deer
- goats
→ change veg thru grazing + trampling → cause soil erosion + damage waterways
How can we manage the threat COTS pose to the GBR?
improve ag reg + water qual bc fertilisers polluting ocean -> stim COTS pop explosion -> devo impact on coral abundnace + ecosystem it supports bc keystone spp
Benefits and limitations of conservation of a single species
benefits:
- tangible target
- conceptually simple
- charismatic spp captures general pub’s attn → spark convos abt conserv
limitations:
- expensive e.g. captive breeding = $mils/yr
- risky
- futile if spp has X viable habitat
Benefits and limitations of conservation of ecological communities
benefits:
- target multi spp simult → more eff use of $/resources
- comprehensive/non-discrim - accounts for interspecfic interactions bc benefits all spp, X just cute/cuddly ones
limitations:
- req land/resource protection
- comm often subj to multi threat simult → more complex
Describe the Banksia Woodlands of the Swan Coastal Plain and outline the threats the community is facing
key ft:
- listed endang 2016
- SW WA biodiv hotspot - 600+ plant + animal spp incl 20+ threatened spp
threats
- habitat loss/frag bc ubant devt/ag
- mining
- dieback bc intro fungal pathog phytophthora
- invasive spp
- CC - inc temp + altered rain patterns
implications:
- honey possum = endemic to SW WA = threatened bc habitat loss
What threats does the Baw baw frog face and what actions have been taken to protect them?
CC + introduced pathogens
captive breeding program
What is the EPBC Act and what does it stand for?
‘environ protection and biodiv conserv’ act = Aus’ fed conserv legislation → framework to manage ‘matters of national environ sig’ (MNES)
1999
What are the different types of MNES?
- threatened spp
- mig spp
- threatened eco comms
Has the EPBC Act been effective?
widely regarded as ineff bc only intervened handful of times
overall environ = still in st of decl + spp = under inc threat
samuel review underway → recs intro new nat standards + intro ind environ regulating body
Describe the Australian Threatened Species Index (2019) trends for birds and mammals 1985-2016
- birds = steady decl 1985-2016
- mammals = stabilised 1985-96, improved 1996-98, declined again and stabilised 1999-2016
Describe two examples of threatened ecological communities threat posed
giant kelp forests of south-east Australia
- favours cold water
- endangered 2012
- vertical habitat for other spp (e.g. southern handfish = endangered spp)
- threats = CC (inc water temp + extreme storms) + inc nutrient availability
lowland RF of subtrop Aus
- critically endangered 2011
- tall closed forest
- biodiv hotspot
- prev one of Aus’ lgst RF but contracted sig bc clearing (timber, ag) + urban devt
- now highly fragmented
- grey headed flying fox pop decl dramatically
Urban development is creating…
ecological deserts
Tussock grass overgrowth and disturbance regimes
space bw tussock grass allows for other spp to grow
→ changing dist regs means tussock may overgrow → dec biodiv
solution = regular burning + targeted grazing
Example of why managing threats to ecological communities is difficult but important
Melb Strategic Assessment 2009 aimed to offset Vic Volcanic planis temp grasslands habitat loss but failed bc delays aquiring land
urgency = inc $ land + dec soil qual
Resource partitioning averts the problem of…
comp excl
Describe four types of resource partitioning
- habitat
- activity
- diet - diff dietary niches
- diet - gen vs spec
