Download - Population Ecology: Distribution & Abundance K. Harms photos from north of Manaus, Brazil
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)
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 [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
Video & 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
Geographic
range
Hab
itat
bre
adth
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 range has been
expanding ever since
Native range
Introducedrange
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
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
Migratoryblack-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
Map 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?
RandomRegular
(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 scaleD < 1
At smaller scaleD > 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 transectof length, L
E.g., point samplingfor a period of time, t
d1
d2
d3
d1
d2d3
Mark-recapture studies
Methods
M1 / N = R / M2
N = (M1 M2) / R
M1 = # of individuals caught & marked on 1st occasion
N = # of unknown individuals in the population
R = # of marked individuals caught on 2nd occasion
M2 = # of individuals caught on 2nd 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:
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
Ecological niche-modeling
Methods
Lozier et al. (2009) J. Biogeogr.; Fig. 2
Predicted range under
current climate
Predicted range under doubled
[CO2] “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