Overview of Lecture: 12/02 Ecology: Communities & Ecosystems Read: Text ch 54 & 55 Bullet Points: •! community ecology •! interspecific competition •! the Lotka-Volterra model •! competitive exclusion •! character displacement •! predators & parasites •! keystone species •! mutualisms •! gypsy moths •! Lyme disease •! invasive species •! global biodiversity •! That's all folks!http://www.youtube.com/watch?v=f99Y-tz9mHw&feature=relatedThen: consider existence & properties of multispecies communities w/ complex food webs and many indirect interactions.Suppose we can measure the impact of one individual of species 2 on the pop growth rate of species 1 relative to the impact of one additional individual of species 1?When grown in competition, P. aurelia drives P. caudatum out of the system When grown separately each species does fine (note: P. aurelia has smaller r but larger K) Note that P. aurelia has a bigger carrying capacity K than P. caudatum. This means that each P aurelia can survive & reproduce w/ less resources: ((1/KPa)th of the resource base) < ((1/KPc)th of the resource base). The growing pop of P.aurelia can drive resources below the minimum required for individual P. caudatum to reproduce.Chthamalus tolerates a broad range of exposure to air (broad fun. niche), but is a poor sumo wrestler. Balanus cannot tolerate long exposure to air (narrow fun. niche), but in lower inter-tidal, is very aggressive - pries off Chthamalus.Allopatric populations {in different places} of Geospiza fuliginosa and G. fortis have beaks of similar size, but on an island where both species occur {sympatric} a significant difference in beak depth has evolved.w/o starfish eating mussels, mussels displace everything elsehttp://www.stanford.edu/class/humbio103/ParaSites2001/trypanosomiasis/trypano.htmhttp://www.ars.usda.gov/is/graphics/photos/k7659-1.jpg Redman & Scriber - OECOLOGIA 125: (2) 218-228 OCT 2000("Resistant trees" were surrounded by defoliated trees … had no discernible gypsy moth damage) Redman & Scriber - OECOLOGIA 125: (2) 218-228 OCT 2000Redman & Scriber - OECOLOGIA 125: (2) 218-228 OCT 2000Redman & Scriber - OECOLOGIA 125: (2) 218-228 OCT 2000In ecology, as w/ gravity, ‘everything is connected to everything else’ - the trick is figuring out which interactions are ‘trivial’ & can be ignored. oak trees acorns mice deer ticks deer Borrelia burgdorferi http://www.ecostudies.org/research/reports/ostrept1.html + + + + + + + - - - Ostfeld et al. 2006. PLoS Biol. 4, e145 the acorn supply for mice & chipmunks 2 years back is a good predictor of Lyme disease risk.6.6 ha in Malaysia contained 711 tree species. 2 ha plots in Michigan forests contained 10-15 species. All of Europe north of the Alps has only 50 tree species. Geographic pattern of species richness in the land birds of North & Central America. Ongoing debate about: evolutionary age (time) – but tropics not so stable productivity (sunshine) – but max diversity at intermediate productivity predictability (seasonality) – so far so good predation – less competitive exclusion in tropics spatial heterogeneity – local adaptation & speciation etc. Global Biodiversity Conservation Priorities TM Brooks et al. Science 7 July 2006: 58-61. Full Text »| PDF »|Numbers of species affected by different threats believed to be responsible for causing population declinesa Wilcove et al. ([1], http://www.natureserve.org). Causes of decline All species [930] Plants [602] Birds [68] Direct human habitat destruction and fragmentation, including logging, road building and diversion of water 497 233 48 Exploitation (hunting, fishing and collecting) and poisoning and/or trapping 90 19 11 Fire and changes in fire regime 102 92 1 Pollution (herbicides, pesticides, oil spills, etc.) 32 4 5 Invasive alien predators and herbivores 131 73 39 Alien plants: competition & indirect habitat effects 431 410 19 Competition with exotic animals (excluding feral and domestic animals)b 67 0 14 Feral pigs (herbivory, predation, competition and/or habitat effects) 268 257 8 Grazing and/or trampling by domestic and feral cattle, goats, sheep, horses and burros 327 295 13 Hybridization with alien species 22 5 0 Diseases (including alien and native species) 33 3 23 Parasites (physiological and behavioral) 3 0 2 Other or unknown 169 134 8 Invasive exotic species are causing dramatic changes in ecological systems worldwide, and there is no question that invasive species are profoundly altering many communities and ecosystems. Zebra mussels are currently considered to be the major threat to North American freshwater unionid bivalves. Of a historic 281 species, 19 are known to be extinct, 21 are thought to be extinct, 77 are endangered, 43 are threatened, and 72 are of special
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