Class Note for ECOL 182R at UA
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Date Created: 02/06/15
ECOL 182 Spring 2008 Lecture 2 Ecological communities amp conservation biology Dr Regis Ferriere Department of Ecology amp Evolutionary Biology University of Arizona What are the key terms Ecological communities xSloecies that live and interact in an area Species interactions Disturbances Species richness diversity Extinction Conservation biology Restoration reconciliation How do species interact with one another Predation Will the lynx eat the hare 39 Competition Mussels seaweed sea stars and barnacles compete for space in the intertidal zone 39 Mutualism These ant and acacia tree are help each other the ant gathers carrot like growths beltian bodies from the tree This is food In exchange the stinging ant protects the tree from many herbivores c y Parasitism This wasp is laying eggs inside aphids The wasp s larvae will exploit 7 the aphid s body content How can we describe the structure of a community Bytaxon W m community of the Sonoran desert By function Community of m of rattlesnakes x Community of plants pollinated by hummingbirds Measuring diversity Species richness Ecologists interested in how much it varies in space Measuring abundances and ranges Species population size and distribution xEcologists interested in how much they vary in time How does competition affect community structure Competition occurs when two organisms use the same resources and those resources are in limited supply xCompetition can be intraspecific or interspecific xlnterference competition means that organisms activities to access resources interfere Otherwise competition occurs by exploitation Competitive exclusion occurs when two competing species cannot survive competition one wins and takes over the habitat the other disappears Thus competition may restrict the abundances and ranges of species How does predation affect community structure The size of the populations of predators and prey typically undergo oscillations Locally predators can drive their prey to extinction Locus amencams Lynx ca naclcwsls Each pcpula1lon cycle consists of an Increase In a mak a decline and a N39urm r of low belore answer IDSI39BEI39EE lynx predator E o These pmdalorAprey cycles follow a regu ar osc atlng pattern Australasian birds megapodes lay their eggs in nest mound and do not incubate Eggs will be destroyed by eggeating mammals Thus megapodes are restricted to islands where the only mammalian C 1 Ch Cr 5 3 4 0 Number of pells l CJE JP m 4 D I I l l l l l l PMS 12155 miss mas mas 1935 1975 I935 predators are marSUpiaIS no eggeatingl How does mutualism affect community structure Mutualism exist between plants amp microorganisms between protists amp fungi among plants amp insects among animals among plants The mutualism between plants and nitrogenfixing bacteria Rhizobium is the basis of much life as we know it Mutualism sets the stage for parasitism A The bat feeds on the orchid s nectar Pollen sticks to mouthparts and is then spread to other orchid flowers B This orchid is cheating The odor shape and color mimic a bee mate Pollen sticks to the bee and will be carried to other flowers But the bee gets no mating no reward wasted energy How do disturbances affect communities Communities are constantly disturbed be their own members a tree falling on shrubs and grasses be natural external agents fires storms floods by human activities Ecological succession is the seguence of changes in community composition following a disturbance Even small disturbances can have dramatic effects when they hit a keystone species or an ecosystem engineer Disturbance of a particular trophic level can cause a trophic cascade of side effects Keystone species Ecosystem engineers A keystone species is a species that affects the entire community out of proportion to its own abundance Ecosystem engineers are organisms that build structures that create environments for other Species Sea star Pisaster ochraceus is a keystone species By consuming mussels it 39 creates open space taken over by many other species Sea star removal 39 experiment 28 species of animals and quot39 algae disappeared within 5 years Beavers are ecosystem engineers Preferentially cut down some tree species hence alter composition of vegetation Build dams create meadows and ponds that become habitats for other species How does a trophic cascade work A Al In Yellowstone High wolves initiated a x I e irpated restored trophic cascade Ta 15 Wolves prey on Low elks Without wolves elks Wolves Wolves Number of wolves A N o O 0 Wolfpopulation Culling I o p reve nted 5 susipgeanged o 0 390 39 on e 039 0 l f 39 Libelfula purbhola 5 i quot Elk B C aspens depleted streamsides of willows driving beavers to extinction Number of elk thousand 8 O l I l I l l 1900 1920 1940 1960 1980 2000 2020 Year I Figure 5513 Part 1 u Mimro momnrmmm vvruvuvltxm it NW v I lt gt ilt gtI Wolves present 1 Wolves absent 1 l I m or Number bl pollination visits per plant per 20 min N c Number or adult dragon ies seen per 5 min No sh Fish No sh 0 In Florida ponds absence of fish quot causes adult draqonflies to be more woo 1850 1ml 195 abundant which increases predation 1920 1999 0 Number of aspens recruited a Estab39ishmemda es on pollinating insects which causes plant populations to decline l u z I I I I I I I I HYPOTH ESIS Small boulders have fewer species growing on them than larger boulders because they are d a subjected to high levels of disturbance bad for species diversity Manon Sterilize a number of small boulders Secure some of them to the natural substratum with glue Leave other small boulders Intermediate Disturbance seeszeizasz sgf39eirse WW f Hypothesis Communities RESULTS Securedsmallbouldersaccumulated manymorespeciesthan unsecured small boulders disturbances often have more species than 5 communities with very low or very high levels of 4 disturbances 3 Low disturbance levels 32 favor a few superior 21 H competitors 0 6 Exp lmemmlim 2 26 CONCLUSIONSmallbouldershavefewerspecies because the higher rates at which they are moved by r g I O n waves prevent many species from surviving on them not because they are unsuitable habitat for local species What other processes determine species richness in mainland ecosystem More species found at low latitudes than at high latitudes Ecosvstem productivity and species richness influence each other But mechanisms remain poorly understood toward Spmres naiviess increases s Areas of high primey production are in wet tropical and subtropical regions and the wetter parts 01 temperate latitudes Mr qu turi Howeea ic fewer swatas Low primary production characterizes the not subtropical deserts where moisture is limiting and high laiitudes where cool temperatures lower phctosynthetic rates Tons of carbon fixed per hectare per year 20 40 GD 50 Number El lce uapsO El dzs CI 25 60 600 l 80109 El 100 300 I gt300 WU 120 140 l oi mammal spaces How do humans affect species diversity Indirectly by affecting ecosystem productivity and directly by accelerating the rates of extinction 40000 years g 3 Is the ivorybilled woodpecker 39 39 still alive Not seen for 60 years it might persist in the A Campephi39uspn mral39s wetland forest of Arkansas it Sophisticated camouflage A 7 regjuired for the track ago Australia had 13 genera of marsupials larger than 50 kg All species had gone extinct by 18000 years ago probably due to overhunting LIFE Be gure 571 in mtsciucfarmoul rubArum v LIFE Be Figure 572 m Mtwnaarnmaa wummv How do humans affect species diversity Indirectly by affecting ecosystem productivity and directly by accelerating the rates of extinction Conservation biology aims at understanding the factors and mechanisms of species extinction in order to keep extinction rates as close to natural as possible VWhat are the principles guiding conservation biology VWhat are the major factors of extinction How do they play out in ecological communities What are the principles of conservation biology Evolution is the process that unites all of bioloqv To be effective in preserving biodiversity we need to know how evolutionary processes generate and maintain that diversity The ecological world is dynamic There is no static balance of nature that can serve as a goal of conservation activities Humans are part of ecosvstems Human activities and needs must be incorporated into conservation goals and practices What are the major factors of extinction Habitat loss degradation and fragmentation Most important threat worldwide As habitats become more fragmented more species are lost from these habitats Small habitat patches can support only small populations and are adversely influenced by edge effects This area is not influenced by edge effects Isolated patches lose species than patches connected much more quickly main forest This area is in uenced by edge effects Because the width of the edge is relatively constant as the total area becomes Habitat patch smaller the edge becomes proportionately larger D a 3055 4375 64 888 Even larger patches lost gt some Spades 0f anima395 Low Percentage of patch influenced by edge effects High lae Figure 576 um Msmmu mmthgmznm 174 A r 7 a we LIFE Se Figure 575 m inmmmtolmmntpmmu v may it N Wary What are the major factors of extinction Habitat loss degradation and fragmentation Overexploitation Historically the most important cause of extinction Continues today Introduced predators competitors and pathogens xSpecies introduced to regions outside their original range often become invasive causing extinction of native species by competing with them eating them or transmitting diseases to them Rapid climate change VLikely to become an increasingly important cause of extinctions for those species that cannot adapt or shift their ranges as rapidly as climate warms Centers of bird species richness What can we do in practice Establishing protected areas is crucial to preserving biodiversity Protected areas selected by taking into account species richness endemism imminence of extinction and the need to protect representative ecosvstems 3 w V K H abitat type Tropical and subtropical moist broadleaved lorests Tropical and subtropical dry broadleaved forests Tropical and subtropical coniferous forests Temperate broadleaved and mixed forests Temperate conifer forests Borealforeststaiga savannas and shrublands Tropical and subtropical grasslands EDIE IIEI I Temperate grasslands savannas and shrublands Flooded grasslands and savannas Montane grasslands and shrublands Tundra Mediterranean forests woodlands and scrub Deserts and xeric shrublands Mangroves Marine ecoregions Freshwater ecoregions Centers of imminent extinctionquot are concentrated in tropical forests islands and mountainous regions Centers of endemic bird species tn mst ormom we Sam I r m 2 m 7n LIFE Be Figure 5711 What can we do in practice Establishing protected areas is crucial to preserving biodiversity Restoration ecology is an important conservation strategy because many degraded ecosystems will not recover or will do so only very slowly without human assistance Reconciliation ecology argues that to be successful conservation biologists must discover and use new ways to blend the rich natural world with the world of economic activity Suggested readings Thompson J N 1994 The Coevolutionary Process University of Chicago Press Chicago A thorough review of the processes by which coevolutionary relationships evolve Wardle D A 2002 Communities and Ecosystems Linking the Aboveground and Belowground Components Princeton University Press Princeton A comprehensive overview of the world39s terrestrial ecosystems that integrates aboveground and belowground structures and processes Lawton J H and R M May Eds 1995 Extinction Rates Oxford University Press London Provides coverage of the quantitative and qualitative methods of estimating extinction rates and their ecological and evolutionary causes Rosenzweig M L 2003 WinWin Ecology How the Earth39s Species can Survive in the Midst of Human Enterprise Oxford University Press London Argues that to be successful conservation biologists must discover and use new ways to blend the rich natural world with the world of economic activity Wilson E O 2002 The Future of Life Alfred A Knopf A graphic account ofthe diversity of life how little we know about it and the threats to its preservation
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