BIO 373 1st Edition Lecture 21 Outline of Last Lecture I Communities contd a Changes in communities i Agents of change 1 Abiotic 2 Biotic ii Succession 1 Primary and secondary succession 2 Early modes of succession 3 Connel and Slatyer s 3 modes of succession a Facilitation model b Tolerance model c Inhibition model Outline of Current Lecture II Communities contd a Changes in communities contd i Chapin experiment ii Mechanism of succession iii Alternative stable states These notes represent a detailed interpretation of the professor s lecture GradeBuddy is best used as a supplement to your own notes not as a substitute 1 Fouling communities 2 Stability change hysteresis III Species Diversity a Spatial scales i Global regional landscape local b Filters i Importance in invasive species c Models of coexistence i Resource portioning ii Intermediate disturbance hypothesis iii Lottery model Current Lecture Communities Contd Changes in communities contd o Succession Chapin Experiment Tested 3 models of succession at Glacier Bay Observed seedling survival and germination rate at succession stages o Pioneer Dryas Alder and Spruce o Determined dominate species and succession Mechanism of succession Facilitative interactions are often important drivers of early succession o Especially when physically conditions are stressful o Larger slower growing long lived species begin to dominate as succession progresses o Competition plays a larger role later in succession o Alternative stable states different communities develop in the same area under similar environmental conditions Stable when community returns to original state after perturbation Fouling communities and alternative states Agent of change was predation here Determined dominate species Stability community in original state Change community may enter another stable state Hysteresis reversal of change but no return to original conditions because original shift was large and reversal was not large enough Species Diversity Landscape patchwork of communities Interconnected spatial scales of species diversity o Global regional landscape local o Regional makes up global landscapes make up region local communities make up landscapes Series of filters that bring species into a communities o Filters determine community membership o Dispersal of immigration regional abiotic factors what can a species withstand species interaction local o Importance of filters in invasive species Dispersal who makes it down to next filter and who leaves Abiotic factors can other species withstand these conditions Important in removing invasive species who can withstand negative effects filters control if a species can become invasive or not will native species allow invasive species to become part of community models of coexistence o resource partitioning Intermediate disturbance hypothesis lottery model Resource partitioning theory by McArthur McArthur studied migratory birds during reproductive season and observed resource partitioning of nest size and feeding location To coexist must use resources in different ways Prevents dominance Species resource use falls on spectrum o Ex some eat larger size of prey some eat intermediate size some eat small o Species can specialize in resource use with character displacement evolution etc