Chapter 54 Part 1: Community Structure: Interspecific Interactions and Species Diversity

Temporal Partitioning

Partitioning of Time

Example of temporal partitioning

2 mouse species naturally nocturnal but coexist by one being nocturnal

Nocturnal

Active during the night

Diurnal

Active during the day

Character Displacement

tendency for characteristics to be more divergent in sympatric populations than in allopatric populations of same species

Sympatric Populations

populations occupying the same geographic area and capable of encountering one another

Allopatric Populations

populations that are geographically separated from each other

Predation

a (+/-) interaction where one species kills (predator) and eats the other species (prey)

What are some feeding adaptations of predators

claws, fangs, poison

Examples of behavioral adaptations of prey

hiding, fleeing, forming herds/schools, self-defense, alarm calls

Besides behavioral, what other defense adaptations can animals have

morphological and physiological

What are some defenses porcupines and skunks have?

mechanical and chemical defenses

Aposematic coloration

bright warning colors

Cryptic coloration

camouflage, makes prey hard to see

Batesian mimicry

A type of mimicry in which a harmless species looks like a species that is poisonous or otherwise harmful to predators.

Mullerian mimicry

two or more unpalatable species resemble each other

How can predators use mimicry?

to approach prey ex: mimic octopus - take on appearance/movement of more than dozen marine animals

Herbivory

a (+/-) interaction where herbivore eats part of plant/algae

What has herbivory led to for plants?

plant mechanical and chemical defenses and adaptations

Symbiosis

Relationship where 2 or more species live in direct and intimate contact w one another

Parasitism

(+/-) interaction; one organism (parasite) gets nourishment from another (host), host is harmed

Endoparasites

Parasites that live within body of host

Ectoparasites

Parasites live on external surface of host

Can parasites have multiple hosts?

Many have a complex life cycle with a number of hosts

How can some hosts change the behavior of the host?

In a way that increases the likelihood that parasite will be transmitted to next host

How do parasites affect host population?

Affect the survival, reproduction, and density of host pop.

Mutualism

(+/+) interaction, interspecific; benefits both species

Obligate mutualism

one species cannot survive without the other

Facultative mutualism

both species can survive alone

Commensalism

(+/0) interaction; one species benefits, other is neither harmed nor helped

Why are commensalism interactions hard to document in nature?

Any close association likely affects both species

3 types of symbiosis

mutualism, commensalism, parasitism; facilitation

Facilitation

(+/+) or (0/+) interaction; one species has positive effects on another without direct and intimate contact

Concept 54.2

Diversity and trophic structure characterize biological communities

In general, do species in a community exert strong control on community structure?

No, few species do

What are 2 fundamental features of community structure?

1. Species diversity

2. Feeding relationships

Species diversity

of a community > the variety of organisms that make up the community

2 components of species diversity

species richness, relative abundance

Species richness

number of different species in community

Relative abundance

proportion each species represents of all individuals in the community

What can diversity be compared by using?

Diversity index

Shannon diversity index (H)

H = -[(pA ln pA) + (pB ln pB) + (pC ln pC) + ...]

Meanings of

A, B, C, ...

p

ln

A, B, C, ... = species

p = relative abundance of each species

ln = natural logarithm

Is determining the number and abundance of species in a community hard?

Yes, especially for small organisms

What can help determine microbial diversity

Molecular tools

Why do ecologists manipulate diversity in experimental communities?

To study the potential benefits of diversity

What are benefits of communities with higher diversity?

More productive, more stable, better withstand and recover from stresses, more resistant to invasive species

What does it mean to be more productive

Produce more biomass (total mass of all organisms)

Invasive species

organisms that become established outside their native range