Interactions between species

Question 1

What is biodiversity?

Answer 1

species richness + genetic variability of species + habitat richness + diversity of species interactions

Question 2

Types of ecological interactions (Name, effect on A, effect on B)

Answer 2

Neutralism: 0/0
Amensalism: -/0
Commensalism: +/0
Competition: -/-
Mutualism: +/+
Predation, parasitism: +/-

Question 3

Name possible interactions between plants and other species

Answer 3

plants: competition, allelopathy
animals: pollination, seed dispersal, herbivory
fungi: plant pathogens, mycorrhizae
microorganisms: plant pathogens, nitrogen fixation

Question 4

Name indirect plant-plant interactions

Answer 4

Competition for light, nutrients, water availability, pollinator abundance, herbivores, micorrhizae

Question 5

Name two types of competition

Answer 5

Intraspecific: between individuals of the same species
Interspecific: between individuals of different species

Question 6

How can we measure competition?

Answer 6

Field manipulations:
Planting additional individuals, increasing density („additive experiments“)
Removing individuals („removal experiments“)
Measuring directly the amount of available resources and translocation of them
Common garden experiments:
Controlled conditions, keep some factors constant and vary others (density, spacing, size)

Question 7

What is a fundamental and a realised niche?

Answer 7

Fundamental niche
Range of abiotic conditions, under which a species can thrive and
reproduce, without being outcompeted by other species
Realized niche
Range of abiotic conditions, under which a species is found in nature

Question 8

What is Allelopathy?

Answer 8

• Some plant species release organic compounds that inhibit germination and growth of other plants (allelochemicals)
• Allelopathy reduces competition
• Allelopathy may occur interspecific (between different species) or intraspecific (between individuals of the same species)
• Allelopathy plays an important role in shaping the species composition of plant communities
• Allelochemicals are mostly small molecules and secondary metabolites (alkaloids, phenol derivates, terpenes)

Question 9

Example chamise (Adenostoma fasciculatum), a shrub of the Californian Chaparral
Observation:
There are no plants between the shrubs (even no annuals).
There are plenty of annual plants outside chamise
Question:
What inhibits the establishment of other plants?

Name possible causes and how to check them.

Answer 9

Competition for nutrients: Experiments with fertilization excludes competition for nutrients.
Competition for water: Unlikely, as Adenostoma is deep-rooted and annuals germinate in winter (rainy season).
Allelopathy: Removing Adenostoma shrubs promotes the establishment of annuals.

Question 10

Name allelopathic responses

Answer 10

suppression of seed germination, inhibition of root and shoot growth and other meristems

Question 11

What are the interactions between plants and mycorrhizae?

Answer 11

• relationship between certain fungi (mycorrhizae) and plants
• Mykorrhizae connect plants in the soil and form an extensive network of hyphae („wood wide web“)
• The fungus receives organic compounds from the plant’s photosynthesis The plant receives water and nutrients (i.e. phosphorus)
• Many plant species depend on mycorrhizae
• > 80% of all angiosperm species and all gymnosperm species have mycorrhizae

Question 12

What are the two types of mycorrhizae?

Answer 12

Endomycorrhizae: hyphae penetrate into the cells of the root epidermis
Ectomycorrhizae: the fungus envelopes small roots

Question 13

Def: Co-evolution

Answer 13

co-evolution, the evolution of traits as a function of interrelationships between unrelated taxa, e.g. by the properties of one species evolving together with those of another species. Adaptations, which are caused by interactions, are called co-adaptations. These interrelationships include, among others, the dependence between hosts and their parasites, between partners in symbiosis or between predators and their prey, as well as relationships between animals and their food plants or between plants and their animal pollinators.

Question 14

What is Co-evolution?

Answer 14

Directed selection on certain traits of both partners in an interacting relationship.

Question 15

Name species interactions and possible adaptations of each partner (in regards to co-evolution).

Answer 15

Predator - Prey: Pred: velocity, behaviour. Prey: velocity, behaviour.
Flower - pollinator: Flower: form, size, scent, colour. Pollinator: form, behaviour.
Plants - seed dispersers. Fruits/seeds: form, colour, scent, secundary metabolites. Seed dispersers: form of beak, behaviour.
Plants - herbivores: Plants: mechanical and chemical defenses- Herbivores: form, behaviour, physiology.
Plants - plants: strong growth, vegetative reproduction, allelopathy

Question 16

Summary species interactions

Answer 16

• hold species together in an ecosystem
• form stable communities
• keep balance between species
• can be very complex
• are a significant part of biodiversity
• lead to the high number of species