Species B Species A Benefit (+)Not Affected (0)Harmed (-) Benefit (+)MutualismCommensalism Predation Herbivory Parasitism Not Affected (0)CommensalismNo Interaction?Amensalism Harmed (-) Predation Herbivory Parasitism AmensalismCompetition Symbiosis – an ecological coupling of two or more species in a coevolutionary relationship.
Plant-Animal Coevolution Plants have no opportunity to “flee” or to “hide”. Evolved defenses reflect that.
Many plants, particularly those in arid climates, produce sharp spines to protect themselves from herbivores. Herbivores that attempt to feed on them may be pierced by the spines, and perhaps even infected.
Other plants may produce chemical defenses. These are often referred to as secondary chemical compounds. Tobacco plants produce nicotine, which disrupts the metabolism of insects feeding on the leaves.
Seeds of some morning glories contain d-lysergic acid. It is believed that this leads to increased predation on insects that feed on the seeds.
Horseradish, and other members of the mustard family, produce mustard oil. This is a tissue toxin that provides protection from insects.
Milkweed and dogbane produce cardiac glycosides which are toxic to insects. Dogbane Milkweed
Leaf-cutter ants—mutualism Above ground, ants cut small pieces of leaves and carry them to their underground nests where the chewed leaves enrich soil. Into this soil, bits of fungi are planted that grow and provide food for the ants.
The ants carry on their bodies the bacterium Streptomyces which produces antibiotics to fight a fungal parasite.
Mutualism—fish The small Spanish hogfish dashes into the mouth of a willing barracuda where it feeds on debris and parasites. The hogfish gains a meal and the barracuda gains a cleaning.
Acacia is widely distributed in tropical regions. Ants and Acacias
In Mexico, Acacia cornigera has a close, mutualistic association with the ant Pseudomyrmex ferruginea.
FIGURE 10.3 Ants and Acacias-Mutualism (a) Ants feed off the Beltian bodies produced at the tips of leaves by the acacia tree and off nectaries along the stems. (b) Ants live in the hollow, swollen thorns of the acacia. The ants protect the acacia from phytophagous insects and from overgrowth of competing species of plants.
How could such a close relationship evolve? Perhaps….. 1.Acacias developed thorns for protection from herbivores. 2.Ants began to use acacias as nesting sites. 3.Ants that did not defoliate the host plant would be able to continue nesting there. In addition, if they attacked neighboring plants of other species, the host acacia would benefit and so would the ants. 4.Ants would be predisposed to definding their nest sites. This behavior could easily be extended to defending the host acacia. 5.Finally, any acacia that produced a food supplement (such as nectaries or Beltian bodies) would support more ants and thus be favored.
Honeybees and Flowers A major evolutionary advance of the Mesozoic Era was the appearance of the flowering plants, or angiosperms. While the gymnosperms that preceded them relied largely on the wind for pollination, many angiosperms use animal vectors to transfer pollen.
Among the best known flower pollinators are honeybees.
Honeybees are attracted to flowers for nectar and pollen. They have specialized “pollen baskets” on their legs which are filled with pollen during flower visits. In the visits, the honeybees transfer pollen from one flower to another.
Hummingbirds have a similar coevolved relationship with flowering plants.
Flower of an orchid Note the distinguishing nectar guides, the spots near the center of the flower.
Mutualism—birds and crocodiles This African crocodile relaxes and holds its mouth open. This signals Egyptian Plovers to enter and safely feed on fouling parasites and debris. The crocodiles gain a cleaning, and the plovers a meal.
Mutualism—oxpecker This red-billed oxpecker forages for parasites on the backs of African ungulates. Here the oxpecker is working around the neck of domestic cattle. Parasites tend to collect along the back of the neck where scratching cannot dislodge them. The oxpecker gains a meal, and its customers get rid of parasites.
Commensalism In some cases, interactions are not symmetric, i.e. one organisms benefits while the other is not impacted. Large African herbivores are often followed by insectivorous birds like the cattle egret.
Orchid flowers that mimics specific female wasps The flower’s mimicry attracts male wasps that arrive attempting to mate. Instead, the males only get doused with pollen, which they carry to the next expected amorous rendezvous.
Skunk cabbage Rolled within its large leaves are the reproductive parts of the plant. When these mature, a pungent odor is released, drawing in insects that naturally seek such odors. In searching within the flower for the odor, they become covered with pollen, which they carry to other plants as they continue their search.
Camouflage--stone plants These plants of dry and desert areas collect water within their tissues and occur in spare habitats where they could be easily spotted by grazing or browsing herbivores. However, their unusually rounded shape seems to make them appear like uninteresting stones, which are overlooked and these plants escape being eaten.
Camouflage—inedible The resemblance of these insects to inedible plant parts affords them some protection from prowling insect-eating predators, such as birds.
Camouflage—coloration and shape This dwarf seahorse (center) is camouflaged within the branches of this colonial sea fan. Reef, Solomon Islands.
Startle response, eyespots on butterfly Flashed suddenly when approached, the eyespots on the wings of some butterflies are thought to confuse the insect-eating bird with its own predator, such as an owl, causing the bird to pause and give the butterfly a chance to escape.
Startle Response - Eyespots When discovered in its cryptic disguise, some moths and butterflies can flash eyespots on their wings, startling the predator, and giving it an extra moment to make its escape. (b) The eyespots are thought to confuse the insect-eating bird with its own predators, such as an owl, causing the bird to pause.
Mimicry I Müllerian mimicry—Many bees, yellow jackets, and wasps have a common, bright yellow/black warning pattern, which they can all back up with an unpleasant sting. Batesian mimicry— Harmless syrphid flies evolved a similar color pattern, taking advantage of the avoidance of the yellow/black pattern.
Mimicry II a) Batesian mimicry between toxic monarch (model) and harmless viceroy (mimic), left and right, respectively. b) An example of Müllerian mimicry, where both ecologically sympatric pairs are distasteful, and both have warning coloration.
Adult monarch butterflies are protected from birds and other predators by the toxins in their tissues. These toxins are incorporated from the milkweeds they feed on as larvae (caterpillars). Life-cycle of monarch
FIGURE 10.11 Blue Jay Learning Aversion to Distasteful Monarch (a) This hand-reared blue jay, having never eaten a monarch, rips off the wings and gobbles down the body. (b) The toxins quickly make the blue jay sick, and it spits up the monarch. Thereafter, even if presented a monarch lacking such toxins, the blue jay refuses it.
Dodo bird (extinct) The flightless dodo lived on the island of Mauritus off the coast of Africa until the last bird was killed in 1681. It fed on plants and seeds, including the seeds of the Calavaria tree. These seeds had evolved thick coats to survive the passage through the grinding gizzard of the dodo. With the extinction of the dodo, these seeds no longer made such an abrading trip through the digestive tract, the coat remained thick, and the young tree embryo could not so easily germinate.
Flicker Frequency ? A newborn watersnake shown crawling (a, c) and motionless (b, d). In motion, the snake’s banding pattern looks evenly gray, as it would when exceeding the flicker frequency of a predator. (From Pough 1976.)