neotropical pharmacy very few leaves have insect damage. why? blackrivers are black. why? leaves are...

Neotropical Pharmacy

• Very few leaves have insect damage. Why?

• Blackrivers are black. Why? • Leaves are constantly exposed to

dangers, whatever the source


• In one study, it was estimated that the Amazon rainforest produced 900 metric tons per ha.

• The mass of all animals was estimated to be a mere 0.2 ha (0.02% of plant biomass)


• Very few secondary consumers (herbivores - 7%)

• Compare this to 19% eating living or dead wood (termites)

• 50% ate only dead vegetation• 24% some sort of carnivore• Why so few herbivores??

Neotropical Pharmacyplant defense compounds

• Drugs, drugs, drugs• Leaves of both tropical and

temperate zone plants are abundantly full of noxious chemicals

• “the world is not colored green to the herbivore’s eyes, but rather is painted morphine, L-DOPA, calcium oxalate, cannabinol, caffeine, mustard oil, strychnine, rotenone, etc” Janzen


• Most of these chemicals are termed ‘secondary compounds’ because most seem to lack a direct metabolic function, such as those in photosynthesis (also called allelochemics for defense at large)


• Their origin may have been by chance, with each combination potentially providing a little better defense

• As a result, most plants don’t just have a single compound…Why?

• Most have several, primarily to protect against herbivores, bacteria and/or fungi


• Alkaloids are among the most familiar and addictive drugs known

• Such drugs as cocaine (from coca), morphine (opium poppy), cannabidiol (hemp), caffeine (teas and coffees), and nicotine (tobacco) There are over 4,000 known alkaloids from >300 families and >7,500 sp

• About 20% of temperate sp contain them


• Alkaloids have a bitter taste (to mammals) and tend to disrupt liver and cell membrane function

• May also cause cessation of lactation, abortion, or birth defects

• Clearly many are addictive!!


• For example, caffeine has been shown to discourage insect feeding

• So is it a stimulant to us, an insecticide!


• Phenolic compounds are often abundant in plants

• One group adds the pungency to many of well-known spices and tannins provide the basic compounds used in tanning leather

• Particularly abundant in oaks and mangroves


• Work on Cecropia indicate young trees have high levels but older plants have less

• Plants in shade had less…so what?• In field experiments, plants with low

levels suffered 2x the herbivory• More leaves, less toxin per leaf…so

what


• Phenolics are small proteins stored in cell vacuoles that are broken when an insect or other herbivore bites the leaf

• Upon release, the phenols combine with various proteins, including those enzymes necessary for splitting polypeptides (parts of proteins) in digestion, perhaps making it more difficult for a herbivore to digest protein

Neotropical Pharmacy plant defense compounds

• It is thought leaf damage by insects or pathogens may stimulate production of phenolics

• However, not all insects are bothered by these compounds (e.g. leafcutting ants)

• They may be more valuable against microbes and/or pathogens


• Saponins are soaplike compounds that are relatively common in tropical plants and act to destroy the fatty component of the cell membrane. Some indigenous people utilize saponins to poison and capture fish, interfering with respiration


• Cyanogenic Glycosides (cyanide + sugar)

• When the sugar is digested, the sugar is released leaving the hydrogen cyanide

• Consequently, these plants are avoided by many species of herbivore


• Passionflowers, fed upon by caterpillars of Heliconius butterflies, have a relatively high load

• Each species can detoxify one or two cyanogenic glycosides, and thus specialize on these species

http://www.google.com/imgres?imgurl=http://bethshute.com/images/Heliconius-web.jpg&imgrefurl=http://bethshute.com/Butterfly%2520Prints%2520-%2520Semigloss%2520Finish.htm&h=399&w=513&sz=105&tbnid=fHufL_G1LvwJ::&tbnh=102&tbnw=131&prev=/images%3Fq%3Dheliconius%2Bpic&sa=X&oi=image_result&resnum=3&ct=image&cd=1


• Some strains of manioc have high concentrations of cyanogenic glycoside in the root

• To eat this, root must be washed thoroughly

http://www.bizarrebrazil.com/main/wp-content/uploads/2007/06/eckhout_manioc.jpg


• Cardiac Glycosides interfere with heart function. Digitalis, from the temperate zone plant foxglove and members of the milkweed family


• Terpenoids area a complex group of fat-soluble compounds that include monoterpenoids, diterpenoids, and sesquiterpenoids. Some are used in the synthesis of compounds that may mimic insect growth hormones or can be modified into cardiac glycosides

• Some discourage both insects and fungi (especially those that ants culture)


• Toxic Amino Acids are common in the bean and pea families and interfere with normal protein synthesis

• Some are strong hallucinogens (e.g. L_DOPA)


• Among the most familiar tropical plants are philodendrons in the arm family

• In the US, we have skunk cabbage, and these plants contain crystals of Calcium Oxalate, a caustic substance that makes the delicate tissues of the mouth burn

Neotropical Pharmacyother defenses

• Latex is another form of defense

• For those species who have developed chemical defense, adhesion to mouth parts is a strong defense


• Other species may be spiny or thorny or have leaves coated with diminutive ‘bed of nails’ called trichomes that sometimes impale caterpillars

• Even serrated leaves can be an effective deterrent for some predators


• Leaf toughness, nutrition value and fiber content also affect ability to resist herbivores

• In general, young leaves are eaten more than older leaves, even when phenols were present suggesting other factors could be quite influential

Neotropical PharmacyLatitudinal Trends

• Levin (1976) made a detailed study of the geographic distribution of alkaloid-containing plants

• Groups of herb, shrub, and tree species each contained a significantly greater percentage of tropical species with alkaloids (27%-45%)

Neotropical PharmacyEcological Trends

• Although defense compounds occur in species that occupy virtually all habitats, there are some trends

• Tropical lowland forests, mangrove swamps, deserts, and mountain rain and cloud forests are all habitats where defense compounds are abundant

• Alpine forests and grasslands, as well as disturbed areas have few such plants


• Defense compounds are abundant in lowland forest occurring on nutrient poor white, sandy soil forests, in the northern Amazon

• Replacing leaves are expensive and consequently, are long-lived and have extremely high concentrations of defense compounds


• Ultimately, leaves must be leached of compounds so they can be broken down

• What else do we find associated with this area?


• Areas undergoing ecological successin tend to have species that invest in defense compounds differently from those on poor soil

• Most successional species are racing to maximize their rates of growth

• They synthesize phenolics, cyanogenics and alkaloids, albeit in low concentrations, suggesting a low energy cost to do so


• Contrasting strategies may simply reflect the resource availability

• E.g. on sites where are poor, “expensive”, long lasting defense compounds are favored and on rich sites, “cheaper”, shorter-lived defense compounds are favored because the tree is able both to devote sufficient energy to rapid growth and replace defense compounds as needed


• As a result, many early-successional species are subject to herbivore damage.

• Janzen has estimated insect density may be 5-10x higher in successional areas

Neotropical PharmacyPlants vs. Monkeys

• Most monkeys are vegetarians• However, they are surrounded by

beautiful leaves, only of which a small subset are palatable


• The serendipitous adventure of Kenneth Glander

• He saw a mantled howler monkey fall 10m from a tree

• What would yourthoughts be?


• She was eating from the madera negra tree, which local use to obtain rotenone

• He spent 5,000 hrs watching howlers and maked 1,699 trees to see what they were eating


• Not surprisingly, monkeys are extremely selective in their feeding

• Of the 149 madera negra trees in the study area, the troop only fed on 3 trees!

• Not surprisingly, these three trees were found to have leaves free of alkaloids and cardiac glycosides, which are normally very high in this species


• Glander found that mantled howlers tended to favor young leaves that are relatively high in nutritional value but have not yet become loaded with defense compounds

• But when given little choice, they eat a few mature leaves and move to another tree. Why?


• Milton, studying on BCI, suggested that it was the relative amounts of protein ad fiber content, not secondary compounds

• These individuals tended to favor leaves that had a higher protein to fiber ratio

Neotropical PharmacyPlants vs. Insects

• How do those little herbivorous insects cope with all the compounds??

• One approach is to become highly specialized on just a few kinds of plants

• Being so small, most insects, including temperate species, can afford to become dietary specialists


• E.g. heliconius caterpillars feed exclusively on the vines of passionflowers

• The author discusses the complete defoliation of a single tree while all surrounding plants remained untouched


• Imagine if an insect were able to detoxify defense compounds (or sequester them), they could focus on that particular species and do quite well

• Also, if other species can’t detoxify the species in question, you may have a potential monopoly on this species


• Of course, there are generalists as well

• How do these guys get away with being generalists?


• Brachid Beetles provide examples of both feeding specialization and adaptation to host defenses

• Bruchids are seed predators, especially on legumes

• Females lay eggs on seed pods or directly in seeds and larvae enter pods upon hatching and feed on seeds before pupating


• In a survey of Bruchidae, Curclionidae, and Cerambycidae, about 75% of the species fed on a single plant species

• Only about 12% fed on 3 or more sp• Bruchids are widespread and

encounter a variety of potential hosts• However, there are local races

adapted to a particular species


• Consider the Arms race with Bruchids• Some hosts evolve toxic seeds, bruchids

either avoid them or become resistent• Some seed pods produce sticky gum

following penetration of bruchid larvae• Bruchids arrest development until seeds

mature and it is too late for pods to produce gum


• Some seed pods flake, removing eggs• Bruchids oviposit beneath the flaking• Some pods fragment or explode• Bruchids oviposit directly on the seed• Some seeds remain very small, then

grow quickly just prior to dispersal• Bruchids enter and eat immature

seeds or delay development, eating the bigger, mature seeds


• Both temperate and tropical butterflies are known for their affinities for feeding on specific plant families

• Caterpillars are usually much more selective than adults, who are feeding on nectar and aiding in pollen dispersal

• Furthermore, adults and juveniles have very different relationships with plants


• Heliconid Butterflies and Passionflowers

• A relatively exclusive relationship• Passionflowers contain various

cyanogenic glycosides and cyanohydrins, probably a response to strong herbivory by heliconids

• In addition, many species of passionflower have recruited ants


• Additional adaptations…


• One species of passionflower is winning as it is covered by minute hooked spines called trichomes

• As a result, caterpillars become impaled

• What should they do?• E.g. Mechantis isthmia and tomatoes

Neotropical PharmacyEthnobotany & Ethnozoology

• Native peoples (locals) in te tropics have much experience dealing with some of the toxins of the tropics

• Consider manioc; it grows well in poor soil, but also concentrates defenses like other plants growing in poor soils (specifically cyanogenic glycosides)

• Must grate it, soak it, and dry it


• What toxins are useful?• Chemicals have been extracted for

use in arrow (or dart) poisons, hallucinogens, fish poisons, drugs for medical and related use, stimulants and spices, oils and pigments

• Many plants we just don’t know about (e.g. in Brazil, <1% plants ever tested)


• Many of our good drugs come from this region

• E.g. quinine, from the alkaloid-laiden Cinchona bush, is reasonable against several malarias

• Resin extracts from Virola, a powerful hallucinogen, appears to be very effective in combating tropical fungal infections


• Ethnobotany has huge conservation potential

• Consider the formation of the Belize Association of Traditional Healers

• Have established a 2,400 reserve where cultivation and studying medicinal plants is the primary goal


• The Healing Forest (Schultes and Raffauf) discuss approximately 1,500 species and variants of plants

• 38 plants for diarrhea, 25 for headache, 18 for muscular aches, 38 for toothache, many for insect bites, 29 for snakebites, 26 for contraceptives


• In addition, others are alleged to aid in sinusitis, bleeding gums, stomach ulcers, cataracts, asthma, swollen breasts, epilepsy, testicular swelling, tumors, boils, blisters, mange, and baldness


• Curare, first ‘discovered’ by Charles Wateron in 1812, is used in hunting and is a powerful muscle relaxent

• There are a number of plants (lianas) in which this extract can be derived

• Still commonly used in surgeries


• Cocaine is a powerful and addictive narcotic (alkaloid)

• While a problem here, it is used abundantly in the tropics

http://cocaine.org/cokestrut.html


• E.g. ingestion of 100g of coca leaves is sufficient to supply one’s daily needs for calcium, iron, phosphorus, and vitamins A, B2, and E.

• It also suppresses fatigue and altitude sickness and is frequently used by Andean peoples


• Nutmegs are probably the best-known hallucinogens in the Neotropics

• Frequently used in spiritual divination to ritualistic diagnosis and treatment of disease

neotropical pharmacy very few leaves have insect damage. why? blackrivers are black. why? leaves are...

Documents

plant biomass slide

secondary compounds

basic compounds

etcjanzen slide

protein slide

source slide

little better defense

drugs leaves