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Fundamental Unit of Biogeography Geographic Range Conveying Range – Outline Maps Range of Sooty Butterfly (Zegris eupheme) Conveying Range – Outline Maps Range of Racoon (Procyon lotor) Conveying Range – Outline Maps Range of Three-ridge Mussel (Amblema plicata) Conveying Range – Outline Maps Bird Map Conveying Range – Dot Maps Locations for emerald shiner (Notropis atherinoides) Conveying Range – Dot Maps Locations for brown trout (Salmo trutta) – dot and outline map Conveying Range – Dot Maps Blue jay distribution in 20th precentile contours Conveying Range – Contour Maps Blue jay distribution as relative abundance Limitations • Outline – not across entire range (clumped disperson) • Dots – inaccuracies of locale information • Contour – spotty data • BUT – Georeferencing – Geostatistics – GIS – integration of data Patchy Nature of Range - Spatially Patchy Nature of Range - Temporal Factors Affecting Distribution of Species • Limiting abiotic factors (range of tolerance) • Biotic interactions • Hutchisonian niche – n-dimensional hypervolume Niche Dimensions and Range • • • • Fundamental niche Realized niche Fundamental geographic range Realized geographic range Distribution of the barnacle Chthamalus stellatus (Connel 1961) Gaps in Distribution • Metapopulations – Sink and source subpopulations – Atlantic snail • Barriers Other Source and Sink Distributions • Migration – temporal and resourcedriven • Irruptions Red locust (Nomadacris septemfasciata) – source (black) and sink (gray) range Of Note • Any fluctuations of population size will influence the realized geographic range All winter at high latitude – will extend range with resource shortage Variation over Range Abiotic Limiting Factors • • • • Range of tolerance Fundamental niche Overlapping effects Trade-offs for tolerance of given factor Disturbance • • • • Limit/expand range of species Patch dynamics Intermediate disturbance hypothesis Bluff and Great Lakes Examples Pupfishes (Cyprinodon nevadensis) • Adults tolerate 0 – 42°C • Found in cold to hot springs across range • Eggs develop at 2036°C • Need access to a sink habitat to persist Biotic Factors - Competition • Exploitative • Interference • Ranges are often reflection of “ghosts of competition” past – example Connell’s barnacle study Kangaroo Rats (Didymops spp.) – was it competition? • Same niche • Two disjunct species • Realized niche of 3 species segregated by substrate • Competitive exclusion? • Resource partitioning? • Parapatric speciation? • No evidence of competition on edges Biotic Effects - Predation • Community regulator • Coevolutionary mechanism Loss of Barriers Keystone Predator Implications outside range of otter? Mutualism – Correlate to Distribution? Diffuse Competition • MacArthur (1972) – southern limits of many N. Amer. Birds not attributable to – Abiotic factors – Habitat limitation – Competition or Predation • 202 land birds in Texas, only 29 found in Panama; Panama 564 land bird species Yellow warbler (Dendroica petechia) – one of the 29 found in both. Insectivore, limited to mangrove swamps and islands in tropics