Plant defenses against herbivores Plants can’t run away from herbivores Plants can’t hide –...
-
Upload
pauline-floyd -
Category
Documents
-
view
217 -
download
0
Transcript of Plant defenses against herbivores Plants can’t run away from herbivores Plants can’t hide –...
![Page 1: Plant defenses against herbivores Plants can’t run away from herbivores Plants can’t hide – leaves must be exposed too catch light for photosynthesis.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649ced5503460f949b9c59/html5/thumbnails/1.jpg)
Plant defenses against herbivores
• Plants can’t run away from herbivores
• Plants can’t hide – leaves must be exposed too catch light for photosynthesis.
• Plants are usually too abundant to be cryptically colored!
• Therefore, plant defenses operate
in situ, either directly or indirectly
![Page 2: Plant defenses against herbivores Plants can’t run away from herbivores Plants can’t hide – leaves must be exposed too catch light for photosynthesis.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649ced5503460f949b9c59/html5/thumbnails/2.jpg)
Types of defense
• Mechanical
• Chemical
• Biotic
• Phenological
A species may use more than one of these lines of defense, and may use different ones at different stages of its life
![Page 3: Plant defenses against herbivores Plants can’t run away from herbivores Plants can’t hide – leaves must be exposed too catch light for photosynthesis.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649ced5503460f949b9c59/html5/thumbnails/3.jpg)
Mechanical defenses
• Hairs on leaf surface
• Spines – modified leaves
• Thorns – modified shoots
• Toughness
Other modifications – e.g. fake eggs on Passiflora tendrils fool ovipositing Heliconius butterflies
![Page 4: Plant defenses against herbivores Plants can’t run away from herbivores Plants can’t hide – leaves must be exposed too catch light for photosynthesis.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649ced5503460f949b9c59/html5/thumbnails/4.jpg)
Hairiness - multipurpose
![Page 5: Plant defenses against herbivores Plants can’t run away from herbivores Plants can’t hide – leaves must be exposed too catch light for photosynthesis.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649ced5503460f949b9c59/html5/thumbnails/5.jpg)
spiny thistles and Eeyore
![Page 6: Plant defenses against herbivores Plants can’t run away from herbivores Plants can’t hide – leaves must be exposed too catch light for photosynthesis.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649ced5503460f949b9c59/html5/thumbnails/6.jpg)
Thorns to prevent biting, climbing
![Page 7: Plant defenses against herbivores Plants can’t run away from herbivores Plants can’t hide – leaves must be exposed too catch light for photosynthesis.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649ced5503460f949b9c59/html5/thumbnails/7.jpg)
Chemical defenses
1. Palatability/acceptability influencers: feeding inhibitors
2. Digestibility reducing compounds
3. Toxins
![Page 8: Plant defenses against herbivores Plants can’t run away from herbivores Plants can’t hide – leaves must be exposed too catch light for photosynthesis.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649ced5503460f949b9c59/html5/thumbnails/8.jpg)
Palatability influencers
Pre-chomping: volatile compounds, may repel herbivores, but specialized herbivores may use them as a cue
Post-chomping:
Tannins (astringency) – oaks; Oxalic acid – sorrels; Calcium oxalate – Araceae; photosensitization; cyanogenic glycosides
![Page 9: Plant defenses against herbivores Plants can’t run away from herbivores Plants can’t hide – leaves must be exposed too catch light for photosynthesis.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649ced5503460f949b9c59/html5/thumbnails/9.jpg)
Digestibility reducers
e.g. Tannins – reduce assimilation of plant proteins by herbivores by interfering with proteolytic enzymes
Herbivores eat a lot, assimilate little
Grow more slowly, may fail to develop in suitable season
Longer in larval stage, vulnerable to enemies
![Page 10: Plant defenses against herbivores Plants can’t run away from herbivores Plants can’t hide – leaves must be exposed too catch light for photosynthesis.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649ced5503460f949b9c59/html5/thumbnails/10.jpg)
Toxins – Cabbages and glucosinolates
Peter J. Bryant
Common green-eyed white
Cabbage white
![Page 11: Plant defenses against herbivores Plants can’t run away from herbivores Plants can’t hide – leaves must be exposed too catch light for photosynthesis.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649ced5503460f949b9c59/html5/thumbnails/11.jpg)
Giant swallowtail and
Rutaceae hostplants
Fireflyforest.net
![Page 12: Plant defenses against herbivores Plants can’t run away from herbivores Plants can’t hide – leaves must be exposed too catch light for photosynthesis.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649ced5503460f949b9c59/html5/thumbnails/12.jpg)
Toxins
e.g. cardiac glycosides in Asclepias Cows and sheep eating plants get sick, have
abortions, etc…Most insects avoid foliage except monarch
butterflies. Their caterpillars are toxic due to sequestration of the milkweed toxins!
Certain specialists are adapted to feed despite toxins.
![Page 13: Plant defenses against herbivores Plants can’t run away from herbivores Plants can’t hide – leaves must be exposed too catch light for photosynthesis.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649ced5503460f949b9c59/html5/thumbnails/13.jpg)
Milkweed and monarch caterpillar
![Page 14: Plant defenses against herbivores Plants can’t run away from herbivores Plants can’t hide – leaves must be exposed too catch light for photosynthesis.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649ced5503460f949b9c59/html5/thumbnails/14.jpg)
Monarch butterfly life cycle
Adults benefit from sequestered cardenolides too!
![Page 15: Plant defenses against herbivores Plants can’t run away from herbivores Plants can’t hide – leaves must be exposed too catch light for photosynthesis.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649ced5503460f949b9c59/html5/thumbnails/15.jpg)
Naïve birds will remember…
![Page 16: Plant defenses against herbivores Plants can’t run away from herbivores Plants can’t hide – leaves must be exposed too catch light for photosynthesis.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649ced5503460f949b9c59/html5/thumbnails/16.jpg)
Idea leuconoe (Lepidoptera subfamily Danainae)on Parsonsia alboflavescens (Apocynaceae)
c/o
Tat
yana
Liv
shul
zF
ield
wor
k in
Tai
wan
![Page 17: Plant defenses against herbivores Plants can’t run away from herbivores Plants can’t hide – leaves must be exposed too catch light for photosynthesis.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649ced5503460f949b9c59/html5/thumbnails/17.jpg)
Tithorea pinthias Nymphalidaeon Prestonia portobellensis
Dan Janzen – Santa Rosa National Park
![Page 18: Plant defenses against herbivores Plants can’t run away from herbivores Plants can’t hide – leaves must be exposed too catch light for photosynthesis.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649ced5503460f949b9c59/html5/thumbnails/18.jpg)
Plumeria and Pseudosphinx tetrio
http://biological-diversity.info Belize wildlife site
Squirrel cuckoos whack and snack
![Page 19: Plant defenses against herbivores Plants can’t run away from herbivores Plants can’t hide – leaves must be exposed too catch light for photosynthesis.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649ced5503460f949b9c59/html5/thumbnails/19.jpg)
Biotic protection
• Ants tending extrafloral nectaries and/or residing in plant body protect plants
• Parasitoids visiting nectaries may also provide plant protection
• Plants can benefit from ants tending certain herbivores as well, but not always
• Beneficial mites can eat herbivorous mites – plants may have domatia to house them
![Page 20: Plant defenses against herbivores Plants can’t run away from herbivores Plants can’t hide – leaves must be exposed too catch light for photosynthesis.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649ced5503460f949b9c59/html5/thumbnails/20.jpg)
Senna mexicana foliar nectaries and ant
![Page 21: Plant defenses against herbivores Plants can’t run away from herbivores Plants can’t hide – leaves must be exposed too catch light for photosynthesis.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649ced5503460f949b9c59/html5/thumbnails/21.jpg)
Turnera ulmifolia in greenhouse
![Page 22: Plant defenses against herbivores Plants can’t run away from herbivores Plants can’t hide – leaves must be exposed too catch light for photosynthesis.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649ced5503460f949b9c59/html5/thumbnails/22.jpg)
Vicia sativa with stipular nectaries
![Page 23: Plant defenses against herbivores Plants can’t run away from herbivores Plants can’t hide – leaves must be exposed too catch light for photosynthesis.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649ced5503460f949b9c59/html5/thumbnails/23.jpg)
Phenological defense
• Timing of production of parts susceptible to herbivory
• Leaf flushing
• Masting – flowering/fruiting every 2-5 years synchronously with others (predator satiation)
![Page 24: Plant defenses against herbivores Plants can’t run away from herbivores Plants can’t hide – leaves must be exposed too catch light for photosynthesis.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649ced5503460f949b9c59/html5/thumbnails/24.jpg)
New leaf flushing – phenological defense?
![Page 25: Plant defenses against herbivores Plants can’t run away from herbivores Plants can’t hide – leaves must be exposed too catch light for photosynthesis.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649ced5503460f949b9c59/html5/thumbnails/25.jpg)
Mast fruitingmast = beech
A “mast year” occurs when the number of acorns or other nuts (like Beech nuts Hickory nuts or Hazel nuts) produced by a tree or shrub in a single season is much higher than usual.
![Page 26: Plant defenses against herbivores Plants can’t run away from herbivores Plants can’t hide – leaves must be exposed too catch light for photosynthesis.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649ced5503460f949b9c59/html5/thumbnails/26.jpg)
Jargon of antiherbivore defense
Plant types Feeny Rhoades & Cates
Short-lived (rare &/or ephemeral)
“hard to find”
Qualitative defenses
“Unapparent”
Long-lived (abundant &/or persistent)
“bound to be found” Quantitative
“Apparent”
![Page 27: Plant defenses against herbivores Plants can’t run away from herbivores Plants can’t hide – leaves must be exposed too catch light for photosynthesis.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649ced5503460f949b9c59/html5/thumbnails/27.jpg)
Qualitative vs. Quantitative
Qualitative defenses (e.g. toxins) – very effective against non-adapted species, effective in small amounts on all but specialist herbivores
Quantitative defenses – more effective in larger doses, general-purpose, e.g. toughness, low nutrients, digestibility-reducers
![Page 28: Plant defenses against herbivores Plants can’t run away from herbivores Plants can’t hide – leaves must be exposed too catch light for photosynthesis.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649ced5503460f949b9c59/html5/thumbnails/28.jpg)
Plants and their parts
Unapparent Apparent
Annual species Woody perennial spp
Early successional spp Climax spp
Rare spp Common spp
Young leaves Mature leaves
Leaves Bark, stem
Deciduous leaves Evergreen leaves
![Page 29: Plant defenses against herbivores Plants can’t run away from herbivores Plants can’t hide – leaves must be exposed too catch light for photosynthesis.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649ced5503460f949b9c59/html5/thumbnails/29.jpg)
Optimal defense theory
• Considers costs to plants of antiherbivore defenses
• Qualitative defenses cheaper than quantitative defenses?
• Maybe just more appropriate – act quickly against specific herbivores
• Lots of debate over the years…
![Page 30: Plant defenses against herbivores Plants can’t run away from herbivores Plants can’t hide – leaves must be exposed too catch light for photosynthesis.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649ced5503460f949b9c59/html5/thumbnails/30.jpg)
Physiological ecologists to the rescue…
• The cost of defense are one of the constraints on leaf form and function
• Photosynthetic capacity, nitrogen, longevity, and susceptibility to herbivores are all related
• Quantify these things for a cost-benefit analysis
![Page 31: Plant defenses against herbivores Plants can’t run away from herbivores Plants can’t hide – leaves must be exposed too catch light for photosynthesis.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649ced5503460f949b9c59/html5/thumbnails/31.jpg)
Benefit from a leaf =[rate of carbon gain * carbon gain period]
minus[carbon cost of growth and maintenance +
losses to herbivory]
• CO2 exchange can take care of all except herbivory losses
• Amount of nitrogen in leaf correlates with photosynthetic capacity
![Page 32: Plant defenses against herbivores Plants can’t run away from herbivores Plants can’t hide – leaves must be exposed too catch light for photosynthesis.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649ced5503460f949b9c59/html5/thumbnails/32.jpg)
Effects of herbivores can be dramatic!
Hawaiian landscapeprotected from cattlegrazing on Mauna Loa
![Page 33: Plant defenses against herbivores Plants can’t run away from herbivores Plants can’t hide – leaves must be exposed too catch light for photosynthesis.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649ced5503460f949b9c59/html5/thumbnails/33.jpg)
Odocoileusvirginianusssp. clavium
![Page 34: Plant defenses against herbivores Plants can’t run away from herbivores Plants can’t hide – leaves must be exposed too catch light for photosynthesis.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649ced5503460f949b9c59/html5/thumbnails/34.jpg)
Earlier deer exclosures on Key Deer Refuge –at least 25 years old.
No fire in that time (note wooden posts).
Woody plant coversubstantially greater inside fenced areas
Long term protection fromdeer browsing?
![Page 35: Plant defenses against herbivores Plants can’t run away from herbivores Plants can’t hide – leaves must be exposed too catch light for photosynthesis.](https://reader036.fdocuments.in/reader036/viewer/2022062421/56649ced5503460f949b9c59/html5/thumbnails/35.jpg)
Fire and Key Deer Herbivory• Fire clears dense understory• Promotes resprouting and seed
germination• New foliage more palatable to
deer• Preferential grazing may affect
understory plants:– Growth– Reproduction– Recruitment and/or persistence