課件沉積學埋藏palaeoecology

1、Palaeosynecology(community ecology)communityassociation of populations which occur repeatedlyin space and timeinfluenced byphysico-chemical factorsbiological interactions (e.g., competition forfood, space, light) influences composition and structure structure of a community: of all interactions; asp

2、ects arediversity and trophic relationsin the fossil record: munity/associationDendrogramsQ-mode analysissamples compared on the basis of theirtaxonomic compositionR-mode analysisgrouping taxa based on their similaritiesof distribution amongsamplesCommunities contain species that arediagnosticcharac

3、teristicnon-diagnosticDifferent approachGradient analysis when smooth environmental gradientsexist and organisms replace each other graduallyTaxonomic uniformitarianism analysis Mioceneoverlapping rangeProblemsmany modern datanot availableassumptions ofthe same environ-mental parametersvery doubtful

4、Structural analysisanalysing diversity and trophic relationsindependant of age and compositionaspects of diversityspecies richness (number of species)species evenness (equitability)dominance diversity (combination of richness and evenness)Diversity indicesEvennessEvennessSimpsons indexShannon indexM

5、argaleffs index(dominance diversity)(minimum influence of sample size)(MacArthur)Upper Jurassic, Portugalspecies richness:rarefaction curvesThe diversity conceptenvironment: multidimensional volume (environmental hyperspace) containing the total set of habitable conditionsenvironmental parameters: a

6、xes of the hyperspaceenvironmental hyperspace: contains as many compartments as there are specieseach compartment: the niche of a species (including all biotic and abiotic aspectsthe shape of each compartment: determined by the environmental tolerances of the speciesrichness: corresponds to the numb

7、er of niches into which the hyperspace is dividedN niches determined bysize of the hyperspace (max. dimensions of all axes)size of each of the nichesthe extent to which the niches overlaprichness resource breadth and niche overlap,1average niche sizeDiversity varies in time and space- time-scale: ve

8、ry short to evolutionary- space: richness increases towards the equator richness increases from the shore to the open shelf richness increases from the outer shelf to the deep seaLatitudinal pattern of diversityDiversity in time and spaceDiversity patternresults from- historical- biological- physico

9、-chemical factorsmost important are- time- stability- resourceTimeeffect of evolution- biological interactions add axes to the hyperspace n niches increases- increasing specialisation smaller niches or subdivision of nichesStability is important, because- it determines the time available for evoluti

10、on- it determines the time available for succession during which diversity increases up to a point- stability is one of the dimensions of the hyperspaceResource= any axis of the hyperspace (e.g., space, salinity, food, T)- The narrow range of an environmental parameter little heterogeneity in the en

11、vironment low diversityVery important for diversity: interplay between resources andstabilityStability/resources-diversity relationshipLimitations of the diversity approachdiversity of fossil samples does not correspond to that oflive communities taphonomic biasmixing or selective transport may have

12、 distorted diversityvalues taphonomic biastime-averaging: telescoping two or more faunas into onestratigraphic horizon taphonomic biasTrophic structurepart of the structure of a communityillustrates the way in which energy flows through the communitydetermined by- physical parameters of the ecosyste

13、m (they control the relative abundances of organisms and the productivity)- biological parameters e.g., food requirements, type of feeding, trophic interactionstrophic structure can be described as- food pyramid with various trophic levels- energy flow (food web)food websunlight + dissolved nutrient

14、sprimary producers (plants)primary consumers (herbivores/detritus-f.)secondary consumers (carnivores)lowmiddle levelshighenergy loss from one level to the next: 80-90%food pyramidalgae100 200 300 400 gbiomasspolychaetesConusSimple examplein the fossil record: flow charts impossible to reconstruct!qu

15、antitative comprehensivefood webs very difficult toreconstruct!Energy flow in a seagrass community(Brasier 1975)trophic webDiagrammatic structure of a shallow water benthicecosystemTrophic structure of three associations from the Korytnica Clay (Miocene) of PolandRelationship between energy level/su

16、bstrate and trophiccomposition of benthic macrofaunas(Rhoads et al. 1972)Distribution of trophicgroups in differentenvironments differingin energy levelFox Hills Formation, Upper Cretaceous,Western Interior Seaway(Rhoads et al 1972)Benthic associations from the Fox Hills Fm, Western InteriorSeaway (

17、USA)(Rhoads et al 1972)(Scott)triangular plots to define certain environmentsOyster bankRelationship trophic structure-environmentsBiological interactionscompetition for space and foodstrategies- rapid growth- tiering- refuge in niches where little competition exists- use of chemical substances whic

18、h protect from overgrowthtiering: vertical subdivision of space by the organisms within acommunityTiering in eel grass community, NW Atlantic OceanTiering in Silurian nuculid community, Nova ScotiaEcological stratification on hardground surfacesTiering among Silurian suspension-feeders Predator-prey

19、 relationshipspredators reduce competition pressure mpre species canco-exist higher diversityhow can we document predation in the fossil record?contents of coprolitestraces of predationfragmentation of shells by crabsboreholes made by muricid and naticid gastropods andOctopusPlacenticeras with ?mosa

20、saur bite marksFossil evidence of predationShell fractures producedby crustaceansReaction of bivalvesto appearance ofmolluscivoresSymbiotic relationshiphermit crab - bryozoan(Palmer & Hancock 1973)Algal symbiosisno direct evidence!indirect evidence:- shell must be exposed to light- special light

21、-transmitting structures- high rate of calcification- isotope data (C and O isotopes are fractionated during photosynthesis and the fractionation may be preserved)- habitat (clear, shallow water)Amensalismpopulation 1 suffers, population 2 is not affectedpalaeontologically important: trophic amensal

22、ismBiological interactions through timesuccessionpredicatble temporal changes within a communitystages of succession: seresclassical studies distinguish: pioneer stage mature stage climax stageautogenic succession: driven by biological processesallogenic succession; driven by changes in the physical

23、 environmentprimary autogenic succession: organisms modify permanently their own physical environmentsecondary autogenic succession: organisms do notsteps in succession(1) unpopulated substrate(2) pioneer communitylow diversityr-strategists, opportunistschanges in micro-environment, formation of new

24、 niches(3) mature communitydiversity higheropportunists decreasespecialists increase(4) climax communitystablein the fossil record: succession usually not observable as time involved is too shorttimenspchanges in diversityChanges in community structure duringecological successionHypothetical stages

25、of thesuccession from Strophomena to Rostricellula community(Ordovician, USA)not directly observable!Mechanismsof secondaryautogenicsuccessionoutcrop scaleecologicalsuccessionwithin anestablishedcommunitysmall-scalechanges at the specimen levelSuccession in reefsReef successionDominationDiversificat

26、ionStabilizationColonizationSiluro-Devonian pioneeer reefSiluro-Devonian climax reefsuccession in reefs often multifactorial(environmentally in-duced and biologicallyinduced).Often, both processescannot be kept apart.Time-averagingchanges species diversity drasticallymay alter species compositionpre

27、vents recognition of short-term fluctuationsreflects long-term trends(Frsich 1978)taphonomic feedbackProcesses causing time-averaging(Frsich 1978)Time averaging.influences relative abundanceand diversityTime 1Time 2Time 3Environmentaldistribution oftime-averaging(Frsich & Aberhan 1990)Criteria f

28、or recognising time-averagingbiostratigraphicecologicaltaphonomicsedimentologicalTime-averaged shell bedBear River Fm (Albian) of southern Wyoming, Western Interior Seaway(Frsich & Kauffman 1983)Bear River Fm (Albian) of southern Wyoming, Western Interior SeawayExamples of time-averagingVolgianM

29、ilne Land, East GreenlandhardgroundformationExamples of time-averagingtime-averaged tracefossil assemblagesThe guild concept in palaeoecologygroup of species that exploit the same class of environmentalresources in the same waygrouping of species with similar niche requirementstaxonomy only of minor

30、 importanceThe members of a guild occupy a cube of the hyperspace defined bythe following three axes:food source (feeding habit)bauplan (reproduction, growth, physiology)space utilisation (mode of life)Guild (ecotype)Community replacement/community evolutionParallel andalternatingassociations in tim

31、efeatures:analogous morphotypeand guild compositiontimeshort-termalternationslong-termsubstitutionTiering history of Phanerozoic colonial suspension-feedersEvolution of tieringTiering in suspension-feeding echinodermsEvolutionary changes within environmentsin the early Palaeozoic in the MesozoicThe

32、holistic community approach(Kauffman & Scott)Case history: Environmental distribution of Siluriancommunity relicts in the Welsh BasinWalesThe Iapetus OceanThe Iapetus Ocean in the SilurianPalaeogeography of the Welsh Basin in the Silurianand sea floor topography based on brachiopod communitiesSi

33、lurian brachiopod communities in WalesLingula communityEocoelia communitySilurian brachiopod communities in WalesClorinda communityStricklandia communitySilurian graptoliteassemblage in the basin centerCase historyPalaeoecology of macrobenthic faunas from the Lower Jurassic of ChileM. AberhanThe Chi

34、lean back-arc basinin the JurassicThe Chilean back-arc basinin the JurassicCluster diagrams of benthicassociations in the LowerJurassic of ChileExamples of benthic associationsfrom the Lower Jurassic ofChileExamples of benthic associations from the Lower Jurassic of ChileRarefactioncurves of benthic

35、associationsfrom the LowerJurassic of ChileFauna-substrate relationsin the Jurassic of ChileLife habit-substraterelationships in theLower Jurassic ofChileSubstrate relation-ships of brachiopodsin the Lower Jurassicof ChileLife habit-substraterelationships in theLower Jurassic of ChileReplacement of

36、associations in the Lower Jurassic of ChileReplacement of benthicassociations as a resultof changes in oxygen level(Lower Jurassic, Chile)Changes of benthicassociations through time(Lower Jurassic ofChile)Faunal distribution alongan onshore-offshoretransect in the LowerJurassic of ChileDistribution of guildsalong an onshore-offshoretransect in the JurassicCase HistoryPalaeoecology of benthic macrofaunasfrom the Lower Jurassic of SW EuropeSchistes cartonsToarcianTruc de