VL 3

Question 1

4 species interactions

Answer 1

Mutualism | obligate or facultative

Commensalism

Antagonism

Competition

Question 2

Three major categories of mutualism

Answer 2

Nutritional: Resources availability

Protective: Protection against enemies / abiotic factors

Dispersal: Movement

Question 3

Ants

Answer 3

Eusocial, colony building insects

Learnign and defensive traits

Long co-evolution with other species: mimetic, commensal, parasitic and mutualistic relationships

Question 4

Nutritional mutualism in ants - Mutualism between leafcutter ants and fungus

Answer 4

Obligate symbiosis:
- Ectosymbiont fungus digests biomass for ants
- Fungus cannot produce spores
- Ants farm the fungus

Additional mutualism in leafcutter ants: Pseudonocardia bacteria on ant surfaces secrete antibiotics to protect against pathogenic fungi

Question 5

Dispersal mutualism in ants - Seed dispersal by ants

Answer 5

Seeds have eliasomes: fruit bodies rich in sugars and lipids that attract ants

Ants transport seeds ~2 meters, but there are cases of 180 meters

Question 6

Protective mutualism in ants - Mutualism between ants and butterflies

Answer 6

Ants reduce need for parental investment

Larvae produce a sugary substance from their dorsal nectary organ in reward

Ants carry the larvae into their nests to pupate in safety

Almost all species of lycaenid butterflies have symbiotic relationships with ants

Range from facultative or obligative, mutualistic and parasitic

Question 7

Protective mutualism in ants - Mutualism between ants and aphids

Answer 7

Aphids tended by ants produce sweet honeydew

In exchange, ants protect aphids from predators and parasitic wasps

Question 8

How aphid’s enemies cope with ant protection?

Answer 8

Some parasitic wasps can use chemical mimicry so that they ‘taste/smell’ like aphids when the ant touches them with its antennae

Wasps with chemical mimicry are less recognized and attacked by ants than wasps without the mimicry

Question 9

Aphids

Answer 9

Aphids are small (~2mm) soft-bodied, sap-sucking and hemimetabolous insects

> 4000 species described
infest ~25% of all plant species

Question 10

Versatile life cycle of aphids

Answer 10

Sexual (autumn) and asexual reprofuction

Parthenogenesis: telescoping of generations

P.17

Autumn triggers production of male and female aphids
females of hatched eggs produce new females in spring / summer, pregnant with new aphids which are also pregnant with aphids

Question 11

Special polymorphism - Polyphenism

Answer 11

Two or more phenotypes in the same clone (genetically identical)

Example: Appereance of winged aphids in clonal population during stress - dispersal

Question 12

Importance of aphids

Answer 12

herbivores of ~100 cultivable plants

transmission of ~50% of vectored plant viruses

short generation time and migration

Example: migration from New Zealand to Tasmania

Question 13

Dispersal mutualism in aphids

Answer 13

Some plant virus “enhances” host plant traits and thereby attracting aphid vectors (persstent viruses)

Aphid vectors perform better on virus-infected plants

Aphids disperse the virus to novel host plants

Question 14

Nutritional mutualism in aphids - obligate

Answer 14

All aphids are associated with an obligate endosymbiotic bacterium

Endobacterium provides essential amino acids and vitamins missing in aphid’s diet

Aphid provides shelter and carbohydrates to endobacterium

Question 15

Nutritional mutualism in aphids - facultative

Answer 15

Expanding successful mutualisms

Aphids harbor facultative endobacteria that expand dietary options by:
- providing additional nutrients
- mediating suppression of plant defenses
- detoxifying harmful plant compounds

Acquisition facultative symbionts: Maternally inherited, sexual reproduction, environmentally (rare)

Question 16

Nutritional mutualisms with endobacteria - beyond aphids

Answer 16

Other sap-feeding insects (hemiptera= also rely on endosymbiotic bacteria to complement their nutrient-poor diet

Recently discovered example:
- Nymphs of squash bugs are born symbiont-free
- they acquire their symbionts by feeding on conspecific feces

Question 17

Protective mutualism in aphids - facultative

Answer 17

Defense against parasitism:
- few endobacteria species
- Not all bacteria strains are protective; for H. defensa it is necessary the presence of APSE phage

Protection against pathogenic fungus:
- Example: facultative endobacterium Regiella insecticola protect aphids against the fungus Pandora

Thermal tolerance:
- Aphids associated with certain facultative endosymbionts recover better from heat oor cold shocks

• Example: development of aphids combined with Serratia symbiotica is not affected by heat shock

Question 18

Cheating avoidance in aphid symbiosis

Answer 18

Regulating obligate endobacterium: microRNAs ceasing glutamate transport to bacteria

Regulating facultative endobacteria: vertical transmission not 100% efficient, regulation through obligate symbiont