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Population Ecology: Distribution & Abundance K. Harms photos from north of Manaus, Brazil.

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Presentation on theme: "Population Ecology: Distribution & Abundance K. Harms photos from north of Manaus, Brazil."— Presentation transcript:

1 Population Ecology: Distribution & Abundance K. Harms photos from north of Manaus, Brazil

2 A group of individuals of a species that occupy a given place at a given time Population Photo of members of a tadpole population from

3 Local distribution – generally patchy, not continuous (which reflects patchy character of habitat) Geographic distribution – the entire geographic range Distribution Hurlbert & White (2005) Ecology Letters, Fig. 1 Canyon wren (red) Cerulean warbler (blue) “X’s denote [Breeding Bird Surveys] on which the focal species were never detected over this period [ ], while filled circles indicate where the focal species were detected.”

4 Population size – the number of indivs. in the pop. Population density – no. indivs. per unit area Abundance Photo from

5 Human population density – 1994 Abundance Image from Wikimedia Commons

6 Abundance & Geographic Range Photo & geographic range map from Wikimedia Commons Puma (previously Felis) concolor

7 Abundance & Geographic Range Video & geographic range map from Wikimedia Commons Dionaea muscipula Endemic to Carolinas; native range is within 60-mile radius of Wilmington, N. C.

8 Most species are rare and geographically restricted Deborah Rabinowitz identified 7 forms of rarity Relative Abundance Image from Ricklefs (2000) TREE, based on original concept in Rabinowitz (1981) “Species in the upper left cube at the front exhibit no component of rarity. Those at the lower back right have all three components of rarity: small geographic range, narrow habitat breadth and low local density” Local abundance Geographic range Habitat breadth

9 Genets – single genetic indiv.; best focus for evolutionary questions Ramets – actually or potentially independent members of a genet; clones; best focus for how (semi-)independent physiological units compete What is an Invidividual? Photo of the many ramets of a single genet of a dune plant from Wikimedia Commons

10 Neither distributions nor abundances are static Dynamics Maps & photo of American alligator consuming a Burmese python from Wikimedia Commons Burmese python was introduced from Southeast Asia into South Florida; its range has been expanding ever since Native range Introduced range

11 Neither distributions nor abundances are static Dynamics Photo of Martha on display at Smithsonian Institution from Wikimedia Commons Passenger pigeons went extinct when Martha died on Sept. 1, 1914

12 Natal dispersal Other dispersal (among breeding sites, foraging patches, etc.) Migration Dispersal Links Populations Photo from Wikimedia Commons; Rubenstein et al. (2002) Science, Figs. 1 & 2 Migratory black-throated blue warbler

13 Why are there no camelids in the Rain Forest Biome? Distribution & Abundance are limited by Habitat Suitability, History & Dispersal Range map & photos of extant camelids from Wikimedia Commons

14 Why are there no camelids in North America? Distribution & Abundance are limited by Habitat Suitability, History & Dispersal Eocene Epoch – 56 to 33.9 mya Map from Wikimedia Commons; image from Examples of N. Am. Pleistocene Epoch megafauna (incl. Camelops) that went extinct ~ 10,000 yr ago

15 Clumped Dispersion Patterns What mechanisms could cause each of these patterns? Random Regular (over-dispersed)

16 Index of Dispersion (Variance-to-Mean Ratio) Dispersion Patterns D =  2 2  D > 1 D  1 D < 1

17 Scale of Focus Dispersion Patterns At larger scale D < 1 At smaller scale D > 1

18 Area-based counts – random or stratified random placement of many replicate plots, quadrats or transects; (average count/area) * total area = population estimate Methods Photo of random quadrat placement from

19 Distance methods – employ detection probability functions (one for each species or habitat) to weight observations & calculate population estimates Methods E.g., line transect of length, L E.g., point sampling for a period of time, t d1d1 d2d2 d3d3 d1d1 d2d2 d3d3

20 Mark-recapture studies Methods M 1 / N = R / M 2 N = (M 1  M 2 ) / R M1M1 = # of individuals caught & marked on 1 st occasion N = # of unknown individuals in the population R = # of marked individuals caught on 2 nd occasion M2M2 = # of individuals caught on 2 nd occasion Photo of wing-tagged frigatebird from Wikimedia Commons

21 Ecological niche-modeling Methods Lozier et al. (2009) J. Biogeogr.; Fig. 1 An analysis with a sense of humor: ENMs for Bigfoot / Sasquatch 551 reported sightings & auditory detections; 95 reported footprints Maximum entropy niche modeling approach implemented in software MAXENT Environmental data layers for 9 BIOCLIM variables in WORLDCLIM data set: annual mean temp.; mean diurnal range; isothermality (mean diurnal range / annual range); temp. annual range; mean temp. of wettest quarter; mean temp. of driest quarter; precip. seasonality; precip. of warmest quarter; precip. of coldest quarter

22 Ecological niche-modeling Methods Lozier et al. (2009) J. Biogeogr.; Fig. 2 Predicted range under current climate Predicted range under doubled [CO 2 ] “convincing environmentally predicted distributions… can be generated from questionable site-occurrence data” (Lozier et al. 2009)

23 Ecological niche-modeling Methods Lozier et al. (2009) J. Biogeogr.; Fig. 2 Predicted range under current climate “many [Bigfoot] sightings… may be cases of mistaken identity” (Lozier et al. 2009) Predicted range of American black bear using the same procedure


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