BIOL 140 Exam 1
animal ingredients for ant-acacia mutualism
1. herbivores 2. Pseudomyrmex ants (Formicidae) living in hollow twigs (in the neotropics - in Africa, they are ants of the genus Crematogaster)
four ant-acacia traits (of the acacia) of great importance to the obligatory mutualism
1. thorns 2. nectaries 3. Beltian body 4. in full leaf in dry season
ants in acacia-ant mutualism
In the neotropics, all obligate (and protective) acacia-ants are in the genus Pseudomyrmex just one species, and one colony, occupies each tree in addition to mutualists, some act as parasites to the system
spines as a defense
spines in general are a quite passive defense, unless accompanied by barbs, covered with venoms (sting rays, sea urchins), or possessed of a hollow center and a gland turning it into a syringe (bees, wasps, ants, scorpions, snakes, cone snails).
What happened 65 million years ago? What survived?
A 25 km wide asteroid hit the earth off the tip of what is today of the Yucatan Peninsula The impact crater is huge and molten materials splashed as far north as Pennsylvania. It created a tidal wave several kilometers high that probably went around the earth several times before it subsided. The equivalent to a "nuclear winter" created by the dust and debris cloud probably lasted three or more years. Photosynthesis basically turned off. Not a good time to be here. Led to the extinction of massive numbers of all the species in major taxa, with dinosaurs being the one you know best. However, some "microdinosaurs" did survive the event - what you know today as birds. Some small mammals survived as well. North and South America were not yet joined when meteor hit so flora/fauna had not mixed yet and were recovered separately
"plant ingredients" for ant-acacia mutualism
1. acacias with thorns coevolved with browsing mammals 2. acacias with foliar nectaries (or extra-floral nectaries as they are also called) 3. acacia tree leaves that evolved as food bodies (Beltian bodies) 4. and leaves may be retained even in dry weather
parataxonomist
A locally-based employee who collects samples and records their natural history online
Why does the size of elephant-like megafauna (gomphotheres, mastodons, mammoths) matter?
A single animal of this size can eat a huge portion of a tree's fruit crop, may allow very large seeds to pass through the molar mill unharmed (and without spitting them out), and may carry a large number of seeds many kilometers in its foraging range.
How did the big herbivores survive in Africa, if they could not survive hunters in the new world?
African hunters evolved with their prey, who presumably evolved their escape behaviors as well (were there for several thousands of years) Africa has indeed lost a number of large herbivores during the past 150,000 years - these were probably the animals that could not or did not evolve either the behaviors or morphologies to withstand Homo sapiens as predator. Herbivores now only notice and are bothered by your presence in African wild where they haven't been hunted in many generations if you are as close to them as is the range in which you can accurately throw a hunting spear
locations of independent coevolution of ants and acacias
African tropics and New World tropics
Guacimo fruit
Another megafauna dry forest fruit eaten by horses Hard and dry, and covered with a thin layer of molassus, the mature fruits taste and smell quite similar to rock-hard raisins. A horse may eat 2000+ in a single meal Expand to full-size at the beginning of the dry season, to be shed to earth-bound dispersal agents in the last two months of the dry season
Who used to disperse seeds of megafauna fruits?
Large mammals that went extinct in Pleistocene megafauna extinction 11,500 years ago that you can see in LaBrea tar pit now Ground sloths, glyptodonts (like 2 meter long armadillos), 7 species of new world camels (only 2 of which survived), gomphotheres (elephant sized animals)
Along with big herbivores of Pleistocene?
Big carnivores--> sabertooth tiger, lions larger than today's African lion, large packs of dire wolves (each one of which was larger than the timber wolf), leopards, several species of large fast bears, and undoubtedly a host of smaller carnivores Probably preyed on juvenile animals and went extinct along with the big herbivores
difference between herbivore and carnivore digestion
Carnivores-- once the food is in its gut, the digestion process for any one of hundreds of species vertebrates is about the same The herbivore head is a marvel of distinctive processing to deal with the secondary compounds and other indigestibles, and that is just the beginning of the process (the gut later on)
allochemicals
Change in terminology from secondary compounds with recognition that they're not secondary, they're just different- they leave out of a plant and are toxic to other plants
insects and chemical dfenses
there are some insects that can eat plants like milkweed once in their life and acquire their chemical defenses
Mammoths
Heavily grass eaters, would undoubtedly have dispersed massive amounts of small seeds of the small plants that they swallowed (the foliage was the fruit) BUT did not live in forests of the kinds rich in the megafauna fruits being discussed in this lecture ---> the extinction of the mammoths probably had little impact on neotropical vegetation and population dynamics
Art of herbivory with latex
Herbivores can cut off new supply of latex by biting leaf in half of making ring of tiny bites before eating it so they deal with the amount of latex currently in it but not more as it is produced
Does the ant-acacia "need" the acacia-ant?
His thesis settled this- walked out into an open pasture and cut down two ant-acacias, dragged one home to dissect and left the other in place came back to two stumps later and from one stretched a single perfect green sucker shoot covered with leaves, ants and young thorns, perhaps 50 cm tall, while from the other were a few ratty defoliated strands of branchlets with a few thorns and leaf fragments
Humans and secondary compounds
Humans have been harvesting and trading/selling/bartering secondary compounds from plants as long as there have been human societies, and probably longer - given that various species of primates have been shown to choose plant parts to eat (and even rub on their bodies in mosquito-ridden rainforest) according to their medicinal/drug properties rather than nutrient traits. Some obvious medicinal uses, also likely that essential parts of achieving close-contact civil sociality among highly aggressive, physically dangerous, long-lived large mammals is achieved via the behavior-modifying effects of secondary compounds such as nicotine, morphine (the active ingredient in opiates) and ethanol
Humans and rubber trees
Humans like parasite feeding on secondary compound the tree produced for its defense The gooey polymers in the latex from rubber trees is "cured" (really, precipitated) by heat and acid into the stretchy stuff we call natural rubber. Almost all commercial rubber you encounter today is, however, synthetic rubber made from polymers extracted or synthesized from oil. The trick to commercial plantation production of rubber was how to non-lethally wound the tree in such a manner that it would continue to produce latex. They developed a small curved knife that cut deep enough to cut latex vessels but not too deep that it would get to the part below that would kill the tree Made cuts going down tree every few days so bark would regrow by the time they got to the bottom and started from the top again The drain on the tree's energy budget is sufficiently great that trees from which latex is being regularly harvested make almost no seeds and produce almost no new wood
Bird nesting and acacia
In short there has been selection for the evolution of the trait or the ability of the bird to chose an occupied ant-acacia or proximity to a wasp nest as a nest site, but this implies or suggests no evolutionary change on the part of either the ant colony or the ant acacia. No coevolution here.
Impact of removal of ants
Increased herbivory When it begins to suffer herbivore damage, it also, then, begins to put on vertical height less rapidly, and when overtopped by the adjacent foliage of other species, declines in health and vigor extremely rapidly just from shading Also leaves them vulnerable to vine growth- The early successional stages occupied by ant-acacias are very rich in individuals and species of fast-growing vines. The ant-acacia is a natural trellis, with the thorns and various short branches making excellent anchoring points for many kinds of climbing.
Crescentia alata
Intro story to Plesitocene megafauna extinction because it was a mystery to scientists for a while what dispersed their seeds (can't be water dispersed, too present in places that do not flood) Lots of large (orange/grapefruit sized) fruit would fall to ground seemingly to rot (inside just has a mildly bitter pulp and the fruits never ripen, just fall off the tree) If you step on one of the fallen fruits it crumbles into black rotting goo-- Crescentia is horse-dispersed. Makes sense-- Growing in the open. The empty shells below the trees. Fruits dropped to the ground. Fruits ripening on the ground. Fruits hard to exclude other organisms from the molassus.
Gomphotheres
Like elephants, they would have been major dispersers of seeds of all sizes (elephants let seeds as large as tennis balls get past the molar mill) as well as major creators of disturbance in the forest, disturbance that would have in turn influenced seedling survival and generally increased forest diversity Has two sets of tusks (lower set presumably for digging out roots and tubers, and uprooting trees)
In a 2-3 year old succession field after a fire many still living acacia root stock had sprouted many sucker shoots, each to be quickly eaten off by insect herbivores while there were some dead (above ground) ant-acacias that had a single (or two) large healthy stump sprouts with beautiful large perfect leaves, large thorns, and were adding 1-2 cm of height every 1-2 days. A small amount of search revealed that the fire had been hot enough to kill many ant colonies (or at least their queens) but not all and in these cases the colony had moved back to the dead stump. Does this show that they need each other?
Not necessarily-- correlation versus causation Possible that in this particular case the few surviving ant colonies simply moved around the site until they found the few ant-acacias that were growing exceptionally well (for whatever soil, moisture and sun reasons) and moved into them. Need a more manipulative experiment
Idiosyncratic preferences
Pleistocene megafauna would have had them for certain fruits and not others like cattle having no interest today in the guazuma fruits that horses eat
rubber tree
Rubber tree latex apparently works as a defensive secondary compound primarily through physically gooing up whatever insect is boring into the tree trunk, rather than carrying another very noxious toxic molecule such as a cardiac glycoside. The gooey polymers in the latex are then "cured" (really, precipitated) by heat and acid into the stretchy stuff we call natural rubber. Almost all commercial rubber you encounter today is, however, synthetic rubber made from polymers extracted or synthesized from oil.
Human hunters and megafaunal extinction
The speed and intensity varies on different continents/locations, but the bottom line is that primitive humans had a major impact long before we became concerned about deforestation, contamination, modern overfishing, etc. Since those Pleistocene hunters swept through the new world, it is nonsense to talk of "virgin forest", "pristine forest", unsullied wilderness, etc. since the removal of our megafauna and its resultant ripple effects took place long, long before anyone began to think about conservation. That it was done with Clovis spear points instead of machine guns and DDT is irrelevant with respect to its impact.
herbivores do not eat Latin binomials
The statement that herbivores eat this or that species of plant is only half true All species of herbivores have the trait that they eat some specific part of whatever plant species they feed on.the defenses of a plant - chemical and physical - are not spread uniformly (in quantity or kind) through the parts of a plant. Roots are very different from leaves, seeds are very different from wood, flowers are very different from pollen, etc. So, when an herbivore breaches the defenses of a plant, normally this means that it has breached the defenses, those particular defenses, of some particular plant part.
aposematic colors
Very bright colors with high contrast (red, orange, yellow) to warn predators that they are poisonous
Not quite anachronisms from Australia Queensland forest
Very large brightly colored fruits of tree found on forest floor the clearly had a not color blind seed disperser-- Cassowary is only disperser left, if they were gone these brightly colored fruits would be an anachranism Were all of Australias large vertebrates to be eliminated, how many generations would it be before these colors would be gone, before selection generated wind-dispersal (if it could), before the fruits had evolutionarily shrunk to a size suitable for pigeons and other small frugivores?
Humans coming to North America in 9000 BC
Wave of specialized hunters- clearly swept the new world of its large NAIVE herbivores in a very thorough manner. They were probably specialist hunters, simply killing, eating and moving on (stone tipped impressive weapons) If specialist human hunters took out some large fraction of the adults and juveniles of a prey species in a given area, the (then) starving carnivores would have conducted the clean up.
how do insects get preserved in amber?
get stuck in hardened resin that was a trees defense against herbivores humans use resin for slides in lab since it does not biodegrade under lab conditions
Why is best pot grown in sunlight?
When the plant has a lot of nutrients, it turns into a female (costs more to make seeds than pollen) and the tetrahydracannabinol is almost entirely produced on the surfaces of the ovaries (fruits, in jargon). When it is starved, most plants are male. --> the plant only invests in defense of tetrahydracannabinol for the ovaries (and this is used as the primary active ingredient for marijuana cigarettes)
Wasp nests and acacia
When the wasp colony begins its nest of paper mache (bits of cellulose stripped off of wood and bark, mixed with saliva), it also covers the point of attachment with a dark resin (origin unclear) that clearly contains chemicals that are repellant to the acacia-ants Also if a single acacia-ant were to wander out onto the nest, the many wasps patrolling its surface would immediately attack and dismember or drop it from the nest no indication of any evolutionary response of the acacia-ant or the ant-acacia to wasp nests. The wasps are proper commensals to the acacia-ants
Acacia-ant/ant-acacia examples of NOT coevolution
While the acacia-ant and the ant-acacia are clearly coevolved (that is to say, neither acquired its relevant traits in the absence of the selective effects of their impact on the other), there are a variety of other obligatory or facultative interactants with the ant-acacia that do not display coevolution with the ant-acacia or the acacia-ant. Some caterpillars eat the ant-acacia (the caterpillar has the odor of the colony on it and marches around eating leaves as though it were simply part of the ant colony) A type of furry moth lays her eggs on the leaves (curved and slippery, and of such large diameter that the ants cannot open their mandibles wide enough to get around them) --> Syssphinx mexicana has evolved a number of traits as part of its obligatory use of ant-acacias (its larvae develop poorly or not at all on other species of Fabaceae, presumably because of the defensive chemicals in the foliage of these other plants), but there is no indication that the ants have evolved any trait (either repulsive or facilitatory) in response to the presence and activities of Syssphinx mexicana eggs, caterpillars and adults. Caterpillar, beetle, moth, wasps--> all have different ways they use/exploit the trees as a resource and different defenses against the ant and the point is that even if they evolved traits in response to the ants, the ants evolves nothing in response/defense to these interactions
What animal today can swallow golf-ball sized seeds whole and have them pass all the way through the digestive tract intact?
Wild cassowary- flightless bird The one large vertebrate that escaped the aboriginal hunters of 50,000 years ago
Why is wood woody?
Wood is a complex structure of cellulose (a sugar) with various kinds of lignins (alcohol polymers) attached that is essentially indigestible to all but bacteria and protists - they are the only organisms that make the enzymes needed to break it down Very first growing upright plants would have been super vulnerable a really easy immobile food source for all the animals around at the time- must have been very intense selection right then for a structural compound that was indigestible
benefits to acacia
giving the acacia a competitive edge over other successional plants by both 1. reducing herbivory and 2. reducing shading by neighboring upright plants and vines
alkaloids
a class of naturally occurring organic nitrogen-containing bases. Alkaloids have diverse and important physiological effects on humans and other animals. Well-known alkaloids include morphine, strychnine, quinine, ephedrine, and nicotine.
likely evolutionary initiation of ant-acacia coevolution
a non-acacia-ant colony takes up residence in hollow thorns (essentially, very thin twigs) that have been hollowed out by boring beetle larvae (as occurs today in some species of non-ant-acacia thorns). There is immediately the opportunity, then, for selection to favor better (for the ants) thorns, more nectar from the acacia's nectaries, and more intense territorial behavior and foraging by the ants on the foliage of the acacia it is occupying
Batesian mimics
a species that is not poisonous that has evolved to resemble a poisonous model species
Beltian body
a structure on the ant-acacia that did not have a morphological or physiological forerunner before the obligatory mutualism evolved at tip of each leaf, pinna, and leaflet morphologically part of the leaf but instead of putting normal leaf tissue inside, the plant puts vitamins (note the carotenoid color), lipids and proteins in large quantities in the Beltian body which are then snipped off by worker ants, cut into pieces, and fed to the larvae
obligatory mutualism
a type of mutualistic relationship whereby one species cannot survive without the other species ants and acacia are an example of this but it is more complex than just this simple statement
acacia-ant mating
after calling, The male climbs on and mates for almost exactly ten seconds, during which time he transfers all the sperm that she will use during her (up to) 20-year lifespan. Then she lets go of the substrate and falls to the ground, and by the time she gets there, he has disengaged and (we think) gone off in search of other virgin females. She immediately reaches up with her legs and breaks off her wings, and starts out in search of small unoccupied ant-acacias to start a new colony. She can search for at least 30 days without food or water, living off of her reserves (this can be shown by confining her in a glass tube in the laboratory - it is not known how long she lives in nature, nor whether she would feed on anything). Since she has no wings, her search is by walking through the foliage and across the ground - a behavior that makes her potential prey for a very large number of small predators.
how is animal defense different from plants?
animal defense is mostly behavioral or physical, plant is chemical (and some physical)
tannins and leather
animal skin "rots" because bacterial enzymes are able to bind onto the collagen proteins in skin and begin to break them down when exposed to water tannins block these enzymes by binding onto digestive enzymes in the mouth (astringency) and gut (stomach ache from green apples)
starch
another sugar that is very difficult to digest is starch, an energy storage compound for plants
acacia nectaries
ants visit the nectaries for the sugary liquid produced (exuded) and in the process forage (for prey) more on the foliage of the plant than they otherwise would and territorily protect the nectaries from other intruders between foraging and protecting, this reduces the threat of herbivory nectaries are genus wide trait, not just in acacias with ants, and all also have thorns but not all thorns have stipules nectaries in neotropical ant-acacias are, however, particularly developed in size and production ants obtain all of their sugars from this nectar, and do not go off the ant-acacia to collect nectar from other species of plants in the vicinity
role of large herbivorous mammals in ant-acacia system (deer example)
are ant-acacias edible? thorns do not stop deer (it was aware of the thorns and avoided them to some degree, but that the thorns were only a partial protection against such a tender-faced browser (an elephant or camel would have simply eaten the entire branch, thorns and all)) --> relevant to the earlier controversy in that it was commonplace to argue that "the ant-acacias do not "need" their ants because they are protected by the thorns" with ants on tree stinging deer's face? The outcome was that it took five minutes to eat a single leaf, a leaf that would have been eaten in 15-20 seconds when ant-free, deer eventually lost interest and wandered off
resins and gums
as a generality are produced by nearly all gymnosperm trees (the characteristic odor of a pine, balsam, fir, etc. tree). Additionally as a generality, resins are common defenses in wet (e.g., rain forest) habitats, while both resins and gums (water soluble) are found as defenses in arid areas Upon exposure to air, most resins harden into a seal for a wound in tree bark, but the resins themselves are generally very toxic to animals as well. Resins are not for drinking (non-water soluble compounds), gums are usually water rich carbohydrate polymers
coffee
caffeine is an alkaloid in the seed to protect it from seed-eating rodents (and probably insects and seed-eating birds as well) In the seed, a sugar molecule is bound to the caffeine - the roasting of the seed disassociates the two (and the hot water probably does it some more), for a direct movement of the caffeine into the blood stream through the walls of the intestine This is a dose makes the poison example that varies for animals of different sizes- we can handle some caffeine but small rodents cannot
secondary compounds
called this because they play no visible role in the plant's physiology (not part of the composition of the plant) but important-- a vast arsenal of compounds made explicitly by the plant, moved by the plant, stored by the plant, converted by the plant, etc. as part of its daily interactions with the great zoo of fungi, animals and microbes that wanted the goodies in the plant examples: lectins, alkaloids, cyanogenic, uncommon amino acids, terpenes, flavonoids, phenolics, protease inhibitors, saponins,
lectins
carbohydrate binding protein, appear in bean seeds just before they are mature so other animals can eat the bean seeds but we have to cook beans to denature the lectins before we can eat the mature ones Different lectins coagulate the blood of different vertebrates If you eat non denatured lectins it binds on the proteins on the wall of your gut (intestines) and stop/blocks whatever the protein was gonna do
tea
contains teine (another alkaloid like caffeine and nicotine) and tannin (comes off as flavor, but in fact it is actually tanning our gut and interfering with digestion by binding to the gut wall (the astringent taste in your mouth) and to enzymes in the gut)-- proteins from milk can bind to tannins and render them non-noxious
behaviors of twig-inhabiting ants
diurnal foragers large eyes with which they see prey forage singly (running across the foliage, grabbing a prey item, and bring it back to the nest for the larvae) sting to protect themselves and kill prey "vacuum clean" the foliage surface for very small food items that are then brought back as a compact pellet and fed to the larvae
impact of shade/sun on acacias
even if both shade and sun acacias have large ant colonies present, the shade ones will grow very poorly
attack by herbivores
every plant is under constant assault by an enormous array of many species of herbivores - fungi, viruses, bacteria, archaea, insects, mites, vertebrates cannot run or hide as a result plants have not just one defense, but many defenses
anacardic acid convergence
evolved as secondary compound defense in both poison ivy and gingko tree fruit independently why put chemical defense in fruit? fruits are evolutionarily designed to be eaten but just those that will put the seeds in the "right" place, and certainly not before their time ("ripe"). It may well be that the anacardic acid is part of the protection of the developing fruit and seed.
acacia-ant calling
female flies to the top of the tallest object in the area (telephone pole, tall tree, short tree on the top of a high hill, etc.), lands on the substrate, and stands still with her genital cavity open and sting extended upward She is releasing a pheromone that goes down wind. The males from all colonies in the area smell this pheromone and fly upwind to where she is At this time, both males and females are subject to strong predation by wasps and other ants (and probably bats and other predators).
3 big misuses of coevolution
generally it is equated to interaction, mutualism, symbiosis, or animal-plant interaction and this is wrong 1. A pair of species whose traits are mutually congruent must have coevolved 2. A herbivore parasite on a plant coevolved with the defense timing, chemistry, morphology, etc. when in reality the parasite will feed on whichever plants it can circumvent the defenses of in the new place it arrives in with the abilities it has at the time 3. When other evidence shows a parasite evolved traits to circumvent the defense of its host people assume coevolution but it is likely that the defense traits were coevolved with animals no longer present or parasitizing them in their habitat-- so the defense trait circumvented was probably not evolved in response to the parasite in question
scarification
generally taken to mean the cutting or rupture or abrasion of the seed coat, allowing water to enter and the germination process to begin not good for dispersal if it happens in digestive track of disperser- they will die in anaerobic gut
green acacia thorn interior
has soft white pulp that is excavated out by the acacia-ants in rendering the thorn suitable as yet one more living space among the many on the tree entire ant colony lives in these thorns, and does not (any longer, evolutionarily) live in hollow twigs or on the ground (or on other species of plants) One acacia-ant colony may, however, occupy several individual ant-acacias (even two of two species) not produced in larger size and numbers in response to browsing of the acacia-- same amount produced with or without ant colony present
Why might a young tree not put a lot of effort into making secondary compounds to protect core?
in anticipation of the time decades in the future when it can "afford" to have a hollow core the hollow core is a nitrogen harvesting device (because water and fungi break into core then animals roost in it), and like any behavior, the tree "pays" something for it. And probably not as much as would appear. The hollow core to a steel bar does not weaken it nearly as much as it would appear to, and when large trees die, they generally do not shatter around the hollow core, but rather uproot or gradually fall apart
dry season ant-acacias
in full leaf in the full dry season, when all the other foliage in its vicinity (easily 20 other species of plants) is essentially leafless (deciduous). By retaining its leaves throughout the dry season (which presumably has its cost in deeper roots, more waxy leaf cuticles, greater resistance to herbivory, and ??), the ant-acacia maintains a full and healthy acacia-ant colony
ant-acacia seed dispersal
insect-pollinated (as are other species of Acacia) by insects that basically can and do move in and out of the tree crown with relative impunity (in contrast to insects intent on feeding on foliage) inflorescences produce pollen
likely location of ant-acacia coevolution
intergrade between desert and tropical dry forest, allowed the neotropical Acacia to move into areas traditionally occupied by desert Acacias because of their new competitive advantage
Beetle and acacia
its distribution in nature covers a large part of the distribution of ant-acacias (from tropical Mexico to Costa Rica). The adult beetle is found in nature only in the crowns of occupied ant-acacias, eating the foliage Deals with ant colony because it is like an armored car and this ant species cannot kill or maim it
hemlock
leaves and seeds are rich in the alkaloid coniine, which is extremely toxic to vertebrates and presumably has kept this plant from being grazed to the ground by big herbivores The seeds fall to the ground, and are eaten by quail in the late summer with no visible effect. The quail then migrate south and fly across the Mediterranean to overwinter in North Africa (or at least they did in the "old days" before too much hunting nearly extinguished them) After this very long flight they are so exhausted that they can barely fly and the hungry people in North Africa eat them but then die because the quail do not actually detox the conine in the hemlock seeds, but rather (somehow) they store it (sequester it) in the breast muscle
phenolics
like tannins, stick together in a chain and the whole chain is very reactive in terms of sticking onto other things, specifically proteins, which blocks fungi/bacteria/proteins from getting to proteins and breaking them down I think
Mullerian mimics
look dangerous and are dangerous; convergence on similar appearance reinforces protection example we talked about: extremely complex topic to try to tease out whether we should view this red and black ladybird beetle as a coevolved member of the Mullerian mimicry ring associated with milkweeds, or simply the result of convergence on a red and black aposematic flag because this is a particularly effective signal for small foraging birds to recognize, or the combination of both
anachronistic
many of the things that made the world what it is today (selective pressures) are not there anymore (i.e. leftover thing in ecology that was selected for due to a relationship or environmental factor that is no longer present) the ant and acacia, although both still exist, have an interaction that is built upon fragments of previous coevolutionary partners that are no longer around or relevant
are secondary compounds static defense systems?
no, they can have passive and inducible components example is beetle mining through leaf tissue and plant then reacting to it by depositing massive amounts of tannins in the walls of the cells bordering the tunnel---> plant can "notices" the damage and hormonally signals other parts of the plant to produce more (and sometimes even more kinds) of secondary compound defenses
Pleistocene megafauna extinction
occurred at the end of the Pleistocene, about 11,500 years ago (9,500 BC)
Diffuse coevolution
occurs when one or both populations in coevolution are represented by an array of populations that generate selective pressure as a group
terpenes
odiferous chemicals (chemicals that give off or have a specific smell) - strongly scented
Why did ALL the species of ant-acacias either retain or evolve their small-animal-dispersed seeds?
partly that the large mammals want nothing to do with ant-acacias moving into wetter (more dense vegetation) habitats, the best chance for survival of juvenile acacias is through being dispersed into tree falls or other natural breaks in the canopy. This is generally "best" done via small vertebrate dispersal rather than wind, especially if the optimal sites are few and far between.
worker ants
patrol the surface of their ant-acacia night and day, though the intensity of patrolling varies in the 24-hour cycle, and some parts of the tree are patrolling more densely than are other parts move rapidly over the surface, and seem to find intruders as much by bumping into them as by vision
evolution of Beltian body
probably started with a starving ant colony (during the dry season) chewing on leaflet ends to get moisture and liquid food, with subsequent selection favoring the plant individuals that had slightly more nutrient- or water-rich leaflet tips
purposes of resin
protects from herbivory and protects against desiccation during the long dry winter when not only does not much rain fall (leading to dry soil), but water transport to replace lost water in the plant is slowed because of the low temperatures
protease inhibitors
secondary compound, do same thing as lectins but bind to your own digestive enzymes instead of gut wall
Mastodons
should be thought of as North American forest elephants - smaller, more versatile, and feeding on shrubs, tree foliage, fruits, seeds and tubers - almost a gigantic pig herding animal a grass diet is lethal for them because the silicon in the grass grinds off the molars at an unacceptably high rate
Acacia thorns
stipular thorns- they are evolutionarily modified stipules long, thin, needle-tipped evolved as defense against herbivore browsing in arid/semi-arid environments paired- two per node degree of expression influenced by how much of a threat browsing is (lower down thornier for example) structures that evolved into "domatia" or "homes" of ants in this coevolutionary story
trichromes
structures that act in thorn-like manner but are too small for human eye to see really just modified hairs act as defense to "tender tongued" herbivores don't need to be functional as spines/spears/needles- if they are hooked it is really hard for small herbivorous insects to walk along their food
cyanogenic
sugar that produces cyanide
Marijuana chemical defense
tetrahydracannabinol When an insect is deceived into eating tetrahydracannabinol (it has to be hidden in its regular food), its ovaries and testes shrivel up to nothing. A fairly effective defense against herbivores
ants influence on nectaries' production
the ants neither stimulate the production of the nectar nor have to remove it before more is produced The foliar nectaries of ant-acacias produce far more sugar (nectar) than do the foliar nectaries of more "ordinary" plants with a diffuse mutualism with many species of ants (and perhaps, parastitic wasps) that generally do not nest in the plant
coevolution
the evolutionary change of a "first" species in response to a change in a "second" species, followed by a further evolutionary change in the second species in response to this evolutionary change by the first In nature it is generally behind predator-prey relationships, as well as a variety of mutualisms such as flowers-pollinators, fruits-seed dispersers, and ants that protect plants (or aphids)--- but it is common for one of the partners to drop out of the "race" leaving the other with the traits as just anachronistic history or to be used against other species
humans and jicaro
the horse that disperses the seeds is again going extinct as it is replaced with motorbikes, jeeps and intensive cattle ranching (which is itself going extinct in many areas). And, quite predictably, the jicaro is also disappearing from the landscape.
horses and camels circumventing plant defenses
they are particularly good at this, in the case of tannins they can eat green bananas that are bitter and not edible to humans before they are ripe because of tannins, but the horses and camels salivate a ton and the fresh tannins in the green bananas bind to the mucopolysaccharides in the saliva, and down it goes the microbial community in the horse's/camel's intestine, fueled by the other goodies in the bananas, degrades the tannin-protein complex The protein peptides and amino acids are recovered by the horse and recycled back into saliva. The tannins are eventually defecated out, probably bound to other less useful compounds. tannins are still there when you eat ripe bananas but they bind to themselves, rendering them ineffective
leaves and thorns on ant and non-ant acacias
thorns in non-ant acacias are usually longer than leaves for protection against herbivores ant-acacias have swollen thorns that are large but much shorter than the leaves- clearly not much protection against large herbivores and no protection at all against small herbivores
all plants have defenses against herbivores
true At the extreme, even cellulose - not digestible by any animal or even a plant - undoubtedly has its unique indigestible structure (after all, it just a mere sugar) owing to selection to protect against herbivores. Direct personal defenses are to be expected in plants - they are not good at running away.
each defense is breached by some herbivore; no herbivore can breach all
true In other words, no plant has hit on the trick of producing non-biodegradable parts, and there are no total generalists among the herbivores.
one beast's poison is another's drink
true any given chemical defense of a plant has a very high chance of being precisely why some other species of herbivore feeds on it - either because it actually uses the defensive molecules or because it has an unusual ability to detox or otherwise evade the defensive molecule. And if not (very rare cases), then that defense compound will still have some microbe(s) that will degrade it further down the food chain (therwise, the world would be ankle deep in that compound).
saponins
type of secondary compound, Molecules formed from a sugar reacting with an alcohol, can cause GI irritation etc.
flavonoids
type of secondary compound, in acacias
queen thorns
very large, twisted, and inflated thorns that could be home to the colony's queen stronger, and harder to rip/break open evolved to protect queen because if she dies the colony dies (she is not replaced)
acacia-ant fruits
yellow inflorescences (very short branches with hundreds of tiny flowers) green immature inflorescences full-sized but immature dark green fruits (pods) opened mature fruit (with the yellow fruit pulp with seeds inside that, and one seed hanging on a pulp fiber)
Every acceptable food kind has satiation levels
yes a herbivore can feed on this or that plant part, but almost invariably there are limits on the amounts and rate at which it can be eaten - and much of the pace of that rate is set by the speed with which the herbivore can detoxify or neutralize the plant part's defenses rather than how fast it can assimilate nutrients. like drinking one cup of coffee versus 5 we have a certain amount of every food that we can consume (like coffee) and it's more for humans because we're big than it would be say for a mouse- dosages