Population Ecology: Distribution & Abundance - PowerPoint Presentation

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

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 http://www.whateats.com/what-eats-a-tadpole-2

Local distribution – generally patchy , not continuous (which reflects patchy character of habitat, dispersal history, etc.) Geographic distribution – the entire geographic range Distribution Hurlbert & White (2005) Ecology Letters , Fig. 1 C anyon wren ( red) Cerulean warbler (blue) “ X’s denote [Breeding Bird Surveys] on which the focal species were never detected over this period [1993-2002], while filled circles indicate where the focal species were detected . ”

Population size – the number of indivs . in the pop.Population density – no. indivs. per unit area Abundance Photo from http://vitalsignsme.org/observation/species-comptonia-peregrina-was-found-flaming-toast-2010-10-06

Human population density – 1994 Abundance Image from Wikimedia Commons

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

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

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 (somewhere common or everywhere rare – within the native geographic range) Geographic range Habitat (niche) breadth

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

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 North American range (as an exotic , non-native , invasive species ) has been expanding ever since Native range Introduced range

Neither distributions nor abundances are static Dynamics K. Harms photos taken at Smithsonian National Museum of Natural History, Washington, D. C. Passenger pigeons went extinct when Martha (the very last individual) died on Sept. 1, 1914

Natal dispersalOther 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

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

Why are there no camelids in North America? Distribution & Abundance are limited by Habitat Suitability, History & Dispersal Eocene Epoch – 56 to 33.9 mya M ap from Wikimedia Commons ; image from http://www.jqjacobs.net/anthro/paleoamericans.html Examples of N. Am. Pleistocene Epoch megafauna (incl. Camelops ) that went extinct ~ 10,000 yr ago

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

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

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

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 http://midlandsconservanciesforum.wordpress.com/2013/01/10/gareths-news-on-bsp/

Distance methods – employ detection probability functions (one for each species or habitat) to weight observations & calculate population estimates Methods E.g., line transect o f length, L E.g., point sampling f or a period of time, t d 1 d 2 d 3 d 1 d 2 d 3

Mark-recapture studies Methods M 1 / N = R / M2 N = ( M 1  M 2 ) / R M 1 = # of individuals caught & marked on 1 st occasion N = # of unknown individuals in the population R = # of marked individuals caught on 2 nd occasion M 2 = # of individuals caught on 2 nd occasion Photo of wing-tagged frigatebird from Wikimedia Commons

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: a nnual 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

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)

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