Spotted habitat and feeding specialist old growth obligate vs Barred Owl generalist feeds in agricultural areas nests in forests outcompetes Spotted Owl when old growth is fragmented and surrounded by fields Spotted habitat and feeding specialist old growth obligate vs Barred Owl generalist feeds in agricultural areas nests in forests outcompetes Spotted Owl when old growth is fragmented and surrounded by fields SF Chronicle letter Nov 2005 another owl not land use 1 threatens spotted owl Refute this argument SF Chronicle letter Nov 2005 another owl not landuse 2 threatens spotted owl Refute this argument Forest fragmentation experiment in Brazil 100 ha fragment Rio Negro Alex Flecker Michael Goulding The Fishes and the Forest 1 hectare ha study plots forest interior 1 ha 1 ha 1 ha 10 ha 1 ha 100 ha fragment 10 ha 1 ha study plot forest edge 10 ha 3 4 Unfragmented Fragmented Freshly cut edges Years later 5 6 Amazon rainforest conversion Minimum critical size of ecosystem project Amazon northern Brazil Lovejoy Forest fragmentation experiment in Brazil Square reserves of jungle in sea of cleared land 100 ha fragment Small 1 ha 100 x 100 m patches blowdown edges topple interior understory vegetation shriveled Cow invasion 1 hectare ha study plots forest interior 1 ha 1 ha 1 ha 10 ha 1 ha 100 ha fragment 10 ha 1 ha study plot forest edge 10 ha Recovery dynamics change in edges 7 8 Unfragmented Species richness island biogeography and biodiversity reserves Fragmented MacArthur Wilson theory of Island Biogeography Space but no time assumes equilibrium S evaluated when E I and no biology All 2 species species have equivalent probabilities of dispersal extinction Dec 4 2006 energy time space Food chain Taxon or guild Strong interactions 9 10 Islands circumscribed hospitable habitats in a sea background matrix of less hospitable terrain e g ocean islands ponds mountain tops plant held waters phytotelmata boulders Attractive for study Can delimit populations communities with natural boundaries Provide replicates for comparative studies or manipulation Before 1963 1967 the field of island biogeography was important e g Galapagos for Darwin s and Indonesia for Wallace s theories of evolution but little touched by quantitative theory Historical idiosyncratic questions like How did the marsupials get to Australia Why have Hawaiian bees diversified from only one genus Then came MacArthur and Wilson 1967 The Equilibrium Theory of Island Biogeography 11 12 Island Size Well known log log species area relations for islands How far can we get in predicting diversity patterns on islands if we ignore biology and focus on island properties S c A z log S log C z log A Island properties z constant between 18 and 35 c taxon specific vagility constant Distance from mainland source Isolation difficulty of barrier stepping stones or lack thereof Area of island Habitat structural complexity Age time since creation disturbance Species properties Vagility dispersal ability Competitive ability Growth rate potential Vulnerability to pathogens predators Trophic position 13 14 Effect of distance from source on island species richness MacArthur Wilson Equilibrium Theory of Island Biogeography Immigration arrival of a new species Extinction loss of a species from island biota n tio ra ig m Im Nearer to New Guinea than 500 miles Farther than 500 miles Ex tin ct io n New Guinea Rate of immigration or extinction LE 53 27a Equilibrium number Number of species on island 15 16 MacArthur Wilson Equilibrium Theory of Island Biogeography Biogeography Predictions near small large far Mainland with P species in pool S should attain equilibrium value over time even with continual turnover of species dynamic equilibrium Large islands should have lower rates of extinction hence higher Sequil Near islands should have higher rates of immigration hence higher Sequil S p S S equilibrium number of spp S Equilibrium species number on island when gain rate loss rate S reached when Immigration Evolution Extinction Emigration or if Evolution and Emigration small when Immigration Extinction Effects of island size and distance only factors considered 17 Predict S far small S near small S far large S near large18 Assumptions Prediction number of species increases more rapidly with area on islands than in expanding sampled area of New Guinea land mass holds for Wilson s ants Islands have attained equilibrium No local evolution speciation 19 This graph shows that bird richness on some islands may not be in equilibrium but still recovering from historical disturbances 20 Rate Number of species 1883 eruption Krakatoa Rarata Landscape mosaics Shape Size Edge Area Corridors Most taxa not in equilibrium after 100 y 21 Use of Island Biogeography for reserve design Single Large or Several Small SLOSS Quinn and Harrison vs Terborgh S cAz If total area is limited several small reserves should protect more richness because z 1 0 22 Corridors Shape Edge Area Pros genetic interchange migration recolonization after disaster Cons more edge spread of disease aliens may act as sinks b d Cumulative species Design of reserves that anticipate global warming north south orientation May be why N Am has more species than Europe N S vs E W orientation of mountains Jim Brown Cumulative area 23 24 Edge effects Scott Robinson thrushes parasitic cowbirds and chain saws Source sink dynamics Krebs 299300 Southeast is source Midwest is sink for wood thrush 25
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