Bioe 147/247 Community Ecology Community Ecology & Space Landscape Ecology: Regions vs Local Effects The focus: Landscape ecology focuses on the distribution of communities in space, and the causes and consequences of this distribution. In landscape ecology, a community can be thought of as a ‘patch’ of habitat, and the different patches of habitats in a region are collectively called "a metacommunity". This concept allows ecologists to ask questions such as: How did the patterning of patches/communities develop over time? Does the arrangement of patches affect how different species use them? Do the dynamics/processes within a particular community result from influences (biotic or abiotic) inside or outside of that community? Do the dynamics/processes within a community result from the spatial patterning of that community in relation to other communities in the landscape? How it differs from what we’ve already covered: Most of this course has focused on structure and processes within communities. Landscape ecology considers the structure and processes that connect communities and how these may affect structure and processes within communities. Pickett and Cadenasso (assigned reading) refer to interactions among patches as “reciprocal effects of spatial pattern on ecological processes”. Landscape views are important not only to understand ecological processes more completely, but also because landscape-level considerations are at the heart of land management issues. Themes: 1. Metacommunities: ecological systems as a shifting mosaic of patches 2. Regional vs. local processes 3. Patches: ‘islands’ within a larger matrix. 4. Spatial arrangements (connectivity and corridors) of patches 5. Patch quality 6. Patch size 7. Ecologies of patches and matrix can affect each other 8. Linkages between vs processes within a patch 9. Landscapes and history 10. Putting it together: climate change, spatial ecology, species interactions and community stability The question of scale: The spatial scale for answering these questions depends on the particular system that is being studied. In some cases this can be very small scale (eg, log, tidepool, etc.); in others the study must consider processes over very large spatial scales (e.g., whole watersheds, mountain ranges, oceanic current systems, etc.), or some scale in between. 1 The Landscape View = Spatial Ecology metacommunities: a balance between local and regional processes 1. Shifting Mosaic: a region is a mosaic of patches – that change over time and space. a. patch = local community b. Patches across a landscape: A (shifting) mosaic 2 We can ask questions about the patches or the whole system. For instance: What is the stability of this system?? the answer depends on whether we refer to a local patch or to the larger region; often, each patch changes more often than the whole region: the region may be robustly stable even if each local community is fragile. 2. Regional processes influence local communities (and the reverse. Ex: The total number of species in a region affects S of local communities (even after accounting for differences in habitat area). Solid line = 1:1 relationship Each point = 1 Oak species Region = geographical range of each oak sp. Each point = local habitats with in an island Region = whole island 3 3. Patches & matrix Ex.: review example of Islands in Gulf of California in lecture and assigned reading for Climate Change. List the main pts. of this example re patch/matrix concepts. (From:Polis 1997) 4. Spatial arrangements (connectivity and corridors) of patches 4 5) Patch quality: source vs sink habitats High-Quality Low-Quality Paradox: Can only tell Source versus Sink habitats by detailed studies Ex.: Patch/matrix concepts can be applied to nature reserves and protected areas. Marine Protected Areas (MPAs) in Hawaii The densities of one species of fish (yellow tang) inside and outside of MPAs protected from fishing… but the same concept applies to communities. Reserv es support high densities of some species that can be sources of new recruits outside the reserve. 5 6. Patch sizes: review Species Area effects (and islands) from earlier in the course. A. Properties; core, edges and ecotones. B. Size Predators and prey experience that communities differently; because at this predators can influence their prey's species area relationships. 6 7. The ecologies of patches and matrix can affect each other. 8. Linkages between/among patches vs processes within a patch: closed vs open communities balance of internal vs external processes influencing a community. Marine? Freshwater? Terrestrial? 7 9. Landscape-level Changes: History is important patches, regions, long-term vs short-term effects The Matrix become the Patch Massachusetts – the Harvard Forest 8 10. Putting it together: climate change, spatial ecology, species interactions and community stability. (Ling et al. 2009. Proceedings of the National Academy of Sciences 52:22341-22345) Focus: southern expansion of sea urchin distribution to Tasmania i. Climate changes – sea surface temperatures ii. Species' interactions AND iii. Spatial ecology: MPA's 9 iv. Stability: resistance and resilience High urchin survival high herbivory on kelp urchin barrens Macroalgal cover (%) Sea Urchin Density 10 .