Test 3 Flashcards
Disadvantages of wind pollination
Untargeted
Decreased likelihood of out-crossing
Much larger production of pollen needed
Plants don’t disperse well
Advantages of wind pollination
No dependence on a “third party”
No need to supply “reward”
Advantages of insect pollination
Facilitates out-crossing
Coupled with seed dispersal by birds and other factors, help plant colonize new habitats more rapidly
Reliable dispersal facilitated plant specialization
Disadvantages of insect pollination
Third party involved
Plant must produce reward
What is nectar?
Rich in sugars
Amino acids, proteins, and lipids
How do plants reward pollinators for services?
Plant gets its pollen transferred from anthers to stigmas
Pollen is a reward with lipid, starch, or protein
Nectar is an important food reward
Nectar from floral and extra-floral nectaries
Edible flower parts are another reward
Non edible pollinator rewards
Heat -usually involves beetles -flowers metabolize lipids and starches -includes water lilies -heat helps disperse scents -5 C temp. Diff. Insect mimics -orchids -wasp, ants deceived by plants -flower mimics female -scent and sight Other mimics -flowers mimic other flowers that offer rewards -smells like a dead animal and attracts flies
What are the costs of the pollinator?
Energy -thermoregulation -traveling -extraction of reward Risks -exposure to predators/parasites
What are the costs to the plant?
Pollination
Resources to produce reward
Risks of being robbed
Attraction of herbivores
Beetles pollination patterns
Clumsy flier
Hard exoskeleton
Usually associated with bowl plants like magnolias
Flies pollination patterns
Some have elongated mouthparts
Flowers are typically shallow with nectar exposed
Flowers are often drab or white with “bad” smell (dying animal, poop)
Lepidoptera pollination patterns
Have long tongue
Flowers erect with place to land
Sweet odors
Colorful-red is common
Moth flowers have less color but more odor
Bees pollination patterns
Bees are largest group of efficient pollinators
Both sexes take nectar
Bee adaptations for plant interactions
Plumose hairs Pollen transport structures Modifications of the tongue Diet of nectar and pollen Social behavior in some species
Plant adaptations for bees
Colors in bees range of vision
Uv reflectance common
Red uncommon for bee flowers
Separate petals
Odors
Open at certain times
Landing platformButterfly life cycle
Egg-few days
Larva-a few weeks
Wandering phase-looking for a place to pupate
Pupa-variable
Adult-a few weeksButterfly overwintering
Different types of Lepidoptera spend the winter in each life stage
Some do not overwinter;they spend the winter in warmer climates
Lepidoptera food principles
Larval food depends on species Adult food-continuous nectar sources Other adults need -water, minerals, resting places, sunbasking on stones Adults feed in sunshine Water/mineral sources must be shallow
Insecticide principles
Lepidoptera
Don’t use insecticide on larval or adult food sources
Most insecticides are broad spectrum
-kill many types of insects
Lepidoptera principles
Flower attraction
Adults are attracted to red, yellow, orange, pink, and purple blossoms that are flat-topped, clustered, and have short flower tubes
Good butterfly plants
Diversity is good
Native plants are important
-coevolution of plants and butterflies
-butterflies may be fooled but larvae don’t survive
Common GA butterflies
Monarch
Larval food-milkweed
Viceroy butterfly
Mimics poisonous monarch
Viceroys are also poisonous
Phytophagous insects
Approx. 50% of all insect species feed on plants
Insects are the dominant herbivores on the planet
Phytophagous feeding patterns
External feeders
- consume foliage, fruit, and roots directly
- suck plant juices
- examples:grasshoppers
Internal feeders
Only endopterygotes -complete metamorphosis Almost always larvae Borers -chew into stem
Gall insects
Galls-caused by abnormal growth of plant cells
Insect galls-wasps, aphids, thrips, moth caterpillars, beetles
Open galls-leaf grows around insect colony ex:aphids thrips
Closed galls-no opening
-typically larvae inside(endopterygotes)
Leaf miners
Larvae feed inside the lead
Only larvae
Diptera, Hymenoptera, Lepidoptera, Coleoptera
Categories of insect herbivores
Generalists feed on multiple species of plants
-most feed on less than 3 families of plants
Specialists may feed on a single species
-creosote bush grasshopper
-gulf fritillary and Passion flower
Antixenosis
Chemicals that deter feeding
Antibiosis
Have some kind of toxic effect on the insect when consumed
Allelochemical
Produced by one species, toxic to another
Plant chemical defenses-non protein amino acids
about 1000 known, hundreds from plants
Found abundantly in legumes, especially in seeds, where they can be found in quite high concentrations. One function is nitrogen storage in seeds.
Toxicity
- Direct toxicity from the amino acid or its breakdown products
- Some interfere with neurotransmitter molecules
- breakdown products of some may inhibit essential cellular process
- may interfere with absorption of water, leading to desiccation
Plant chemical defenses-cyanogenic glycosides
Store the cyanide molecule
Cyanide gas is released when the plant is damaged
-toxicity based upon the inhibition electron transport chain(energy)
Examples: wild cherry, almonds, Lima beans
Plant chemical defenses-alkaloids
More than 10,000 identified
1/3 of plants have them
Toxicity
- interference with DNA replication, transcription, translation
- enzyme inhibition
- receptor site blocking-the common mode of action in opiates
- often sugar mimics-may be inhibitors of glycosidase enzymes
Examples:morphine, caffeine, nicotine, cocaine, cocoa
Plant chemical defenses-proteinase inhibitors
Often inducible
Toxicity-interferences with protein digestion
Found in legumes, grasses, solanaceous plants(tomatoes, potatoes, tobacco)
Plant chemical defenses-terpenoids
Often repellent, bitter, toxic
Toxicity affect cell membranes and enzyme activity
Examples-catnip, cinnamon, cloves
Plant chemical defenses-insect hormone analogs
3 groups
- Ecdysis inhibitors interfere with the insect’s ability to molt (ferns and yews)
- Chiron synthetase inhibitors interfere with building a new exoskeleton (beans and many others)
- juvenile hormone analogs prevent the insect from receiving the proper hormonal signal for the final molt to adult
Plant chemical defenses- tannins and lignins
Tannins small and water soluble.
Lignins large insoluble polyphenol polymers associated with cell wall strengthening and protection from funghi
Toxicity
- astringency (withdraws water) may deter feeding
- may form complexes with dietary proteins and prevent assimilation
- may interfere with peroxidase activity and thus activate oxygen molecules, which are often very damaging cells
Plant defense-tolerance
Withstand damage without compromising fitness (reproductive success)
Many physiological processes involved
Soybean defoliation
Allelochemicals: how do insects cope?
Avoidance
Avoidance:just don’t eat them
-if an insect can recognize a toxin, it can avoid it
Feed on specific parts: proper “ratio” of nutrition to allelochemicals
Allelochemicals: how do insects cope?
Leaf trenching and petiole girdling
Leaf trenching and petiole girdling
- resins come out of leaf when they are damaged
- some insects girdle the petiole or cut trenches in the leaf to avoid when feeding l
Allelochemicals: how do insects cope?
Reduction of influence
Reduce influence of toxins after ingestion - alkaline midguts
Allelochemicals: how do insects cope?
Sequestration
Sequestration of toxic compounds
-sequestration:hold chemical in special tissues or structures where it cannot interfere with metabolism
Allelochemicals: how do insects cope?
Internal detoxification systems
Animals have water based excretory systems
Plant chemistry and the evolution of host specificity
Most insect specifies feed on a single plant family
-only 10% feed on more than 3 families
Plants call for help
When attacked, many plants release volatile organic compounds
Chemicals may repel pests
Chemicals may attract predators/parasitoids
Insects as disease vectors of plants
Insects transmit many disease organisms to plants and animals
Ways insects transmit disease
Mechanical-disease agent comes in contact with insect mouthparts, feet, etc. and is carried along
Circulatory-pathogen spends part of its life cycle in the insect
-ingested, circulates, ultimately ends up in salivary glands and transmits when feeds
Phytotoxemia plants show symptoms as a consequence of toxins injected by the insect
Important insect vectors
Hemiptera and Thysanoptera
Aphids, leafhoppers, whiteflies. And Thrips
Plant viral diseases
Tomato spot wilt virus
Plant viral diseases are transmitted by insects
Plant mechanical defense example
Tree hoppers looking like thorns
Chemical plant defense example
Caffeine
Tolerance plant defense example
Withstanding/outgrowing
