11 Mutualism Chapter 15

22 Introduction ______________: Interactions between individuals of different species that benefit both partners. – _____________________ occurs when a species can live without its mutualistic partner. – _____________________ occurs when a species is dependent on a mutualistic relationship. Margulis and Fester amassed evidence eukaryotes originated as mutualistic associations.

33 Plant Performance and Mycorrhizal Fungi Two most common types of mycorrhizae: 1) (AMF) Produces arbuscules - site of exchange between plants and fungi, hyphae - fungal filaments, and vesicles - energy storage organs.

44 Plant Performance and Mycorrhizal Fungi Two most common types of mycorrhizae: 2) (ECM) Forms mantle around roots - important in increasing plant access to phosphorus and other immobile nutrients.

55 Mycorrhizae and Plant Water Balance Allen and Allen studied water relations of grass Agropyron smithii. – Plants with mycorrhizae maintained …

66 Mycorrhizae and Plant Water Balance Hardie suggested mycorrhizal fungi improve water relations by providing more extensive contact with moisture in rooting zone and providing extra …

77 Nutrient Availability and Mutualistic Balance Sheet Johnson investigated whether fertilization can select for less mutualistic mycorrhizal fungi. – Fungal partner received an equal or greater quantity of photosynthetic product in trade for low quantity of nutrients. In nutrient poor environments, many plants invest disproportionately in roots.

88 Nutrient Availability Results suggested mycorrhizal fungi from unfertilized soils supplied plants with … – Plants able to invest more energy in above-ground photosynthetic material… principle of ?

99 Ants and Bull’s horn Acacia Herbivores attempting to forage on accacia plants occupied by accacia ants are met by … Ant Benefits: – Thorns provide ___________________. – ____________________ provide sugar. – ____________________ are a source of oils and protein.

10 Ants and Bull’s horn Acacia

11 Experimental Evidence For Mutualism Janzen demonstrated ants significantly improve plant performance. – Acacias without ants had … – Suckers growing from accacia stumps occupied by ants lengthened … Suckers with ants survived _____________________ of suckers without ants.

12 Coral Mutualisms Zooxanthallae and Corals – Zooxzanthallae live …. Receive nutrients from coral. In return, coral receives organic compounds synthesized by zooxanthallae during photosynthesis. –

13 Coral Mutualisms Corals also control rate of zooxanthallae population growth and density by influencing... Main zooxanthallae benefit appears to be access to higher nutrient levels, especially … – Uptakes…

14 Coral Protection Mutualism Glynn found 13 coral species protected by crustacean mutualists. – Crustacean mutualists substantially improved chances coral will avoid attack by sea stars.

15 Coral Protection Mutualism Also found crab activity promotes coral health and integrity. – Pocillopora coral increases production of … Digestive tract of crabs inhabiting corals contained large quantities of __________.

16 Evolution of Mutualism Theory predicts mutualism will evolve where the benefits of mutualism exceed the costs. – Keeler developed models to represent relative costs and benefits of several types of mutualistic interactions. Successful mutualists – Unsuccessful mutualists –

17 Evolution of Mutualism Non-mutualists – For a population to be mutualistic, fitness of successful mutualists must be greater than unsuccessful or non-mutualists. – If not, natural selection will eventually eliminate the interaction.

18 Facultative Ant-Plant Mutualisms Keeler proposed for a facultative ant-plant mutualism to evolve and persist… proportion of plant’s energy budget ants save from ___________________________… must exceed proportion of the plant’s energy budget invested in …

19 Facultative Ant-Plant Mutualisms Conditions that may produce higher benefits than costs: – – – Low effectiveness of alternate defenses. –

20 Facultative Ant-Plant Mutualisms p [H ( 1 – D ) A ] > I A Plant’s energy budget devoted to “bribes” Probability of attracting mutualist Rate of herbivory Effectiveness of plant defenses Effectiveness of ant defenses

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22 Temperate Plant Protection Mutualism Ants are attracted to Aspen sunflowers because they produce nectar at extrafloral nectaries. – Rich in sucrose and amino acids. Inouye and Taylor never observed several species of ants collecting nectar from aspen sunflower blossoms nor tending aphids. – Extrafloral nectaries sufficient attractant.

23 Temperate Plant Protection Mutualism Proposed ants may protect sunflower’s developing seeds from seed predators. – Damaged over 90% of seeds produced by some flowers. Flowers without ants suffered 2-4 times more seed predation. Relationship remains facultative. – Every few years flower heads of aspen sunflowers are killed by late frost.

24 Temperate Plant Protection Mutualism