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