Eco - Populations 1

population

a group of individuals of the same species inhabiting a given area

equation for number of individuals in the future

number of individuals now

+ births

- deaths

+ immigration

- emigration

= number of individuals in the future

distribution

geographic area where individuals of a species occur

abundance

number of individuals in a given area

what does it mean that populations are dynamic?

means that distribution and abundance can change over time and space

unitary organisms

form and tining of development of that form is highly determined

modular organisms

form and timing of development is not so predictable; individuals are composed of a number of modules

how do ecologists define populations?

all individuals of the same species within a given area; close enough for occasional mating

dispersion

the spatial distribution of organisms

• random

• regular, uniform, even, or overdispersion

• aggregated, contagious, clumped, or underdispersion

what are the two ways in which abundance can be reported as?

1. population size (# of individuals)

2. density (# of individuals per unit area)

quadrants

sampling areas of specific size, such as 1 m²

mark-recapture studies

used for mobile organisms

• a subset of individuals is captured and marked or tagged, then released

• at a later date, individuals are captured again, and the ratio of marked to unmarked individuals is used to estimate population size

formula for mark-recapture studies

N = (M x C)/R

• N - total population size

• M - captured and marked (1st time)

• C - captured (2nd time)

• R - recaptured organisms

relative population size

number of individuals in one time period or place relative to the number in another

• estimates are based on data presumed to be related to absolute population size

metapopulation

a collection of local subpopulations connected by dispersal; group of geographically isolated populations linked by dispersal

dispersal

movement of individuals into (immigration) or out of (emigration) an existing population

sources vs sinks

sources - populations that have individuals that disperse to other populations (emigration)

sinks - populations that receive more immigrants than the number of emigrants they produce

dispersion: regular vs random vs clumped

• regular dispersion - individuals are evenly spaced throughout their habitat

• random dispersion - individuals are randomly spaced

• clumped dispersion - more common in natural populations

abiotic features that determine habitat suitability

moisture, temperature, pH, sunlight, nutrients, etc.

species distribution models

models that can predict the geographic range of a species

• species can tolerate broad rangers of physical conditions, while others have narrow ranges

fundamental niche

range of conditions and resources that allows a species to maintain a viable population (grow, survive, reproduce)

realized niche

niche occupied in the presence of biological interactions

• fundamental niche + effects of competition and predation

conditions vs resources

conditions: not depleted or consumes (pH, salinity)

resources: depleted or consumed (food, N, P)

what factors impact a species’ range?

• habitat suitability

  • abiotic - fundamental niche

  • biotic interactions - realized niche

• disturbance

• geological history and evolution

• dispersal limitation

  • human introductions

• migrations

migration

type of dispersal in response to seasonal variation in resources

• can involve round trip movement of the whole population

Hierarchical framework for the concept of a population

• local population

• metapopulation

• subspecies (ecotype)

• species

molecular ecology

the use of genetic markers to track individuals (or genotypes) among populations

• proteins (allozymes)

• DNA sequences

• microsatellite loci

• single nucleotide polymorphisms (SNPs)

what do molecular genetic markers tell ecologists about populations?

the markers allow ecologists to determine which populations of organisms are exchanging genes and to understand population structure