Sonoran Desert Panorama Resources Examples of Sonoran Desert Interactions predator -­‐ prey interactions parasitism • chewed leaves -­‐ herbivory is considered predation on plants • mesquite branch with mistletoe attached • spider web insect parts (the rest may have been eaten by something) • prickly pear pad with cochineal • scat with obvious contents (fur, bones, etc.) • dog ticks (keep in a closed container) • mesquite or paloverde bean pods with symbiosis holes • any kind of flower (to discuss pollination = competition mutualism) • palo verde or mesquite bean pod (it • any kind of seed -­‐ all kinds of animals indicates that the flower was pollinated -­‐ likely compete for seeds to eat by an insect such as a bee = mutualism) • a saguaro " boot" -­‐ Gila woodpeckers, flickers, starlings, and house finches all compete • lichen (fungi and algae living together = mutualism) for nest space in saguaros • gall from oak, creosote, etc. (although sometimes considered parasitic, many galls formed by insects do not harm the host plant = commensalism) Energy Flow One way that organisms interact is through feeding relationships. When a cottontail rabbit eats grass, it is obtaining energy from the grass. The grass originally obtained that energy from the sun and through photosynthesis, converted it to carbohydrates which are a form of energy that animals can consume and use. Should a red-­‐tailed hawk come along and eat the cottontail, that hawk would gain energy from the rabbit, which had gained energy from the grass, which had gained energy from the sun. This feeding relationship is commonly called a food chain. Food chains describe the flow of energy through ecosystems. Food chains are typically more complex and involve numerous species eating and being eaten by other species. The term "food web" more accurately describes the complex feeding relationships in an ecosystem. Source: Unit 2 “A Dynamic Balance: Living in the Sonoran Desert” http://www.nature.nps.gov/views/KCs/SonoranDesert/Media/Documents/JUNTOS_EnglishPDFs/Juntosen
gunit2.pdf Accessed: Jan 24, 2013 Food Chains
The Sonoran Desert in the Southwestern United States may seem like a desolate place, but looks can
be deceiving, because a wide array of wildlife can be found in this very dry environment. You might
wonder how animals can make a living in the desert - after all, what is there for them to eat? Just like in
every other ecosystem, all animals must eat other organisms, or, at the very least, secretions of other
organisms, to acquire energy. We can follow a sequence of organisms that feed on each other to create
a food chain, or a sequence of organisms that feed on each other.
Since a food chain follows the sequence of organisms that feed on each other, it always starts with an
organism that gets its energy from an abiotic source, which is usually light from the sun. An organism
that gets its energy from an abiotic source is called a producer. Since plants get their energy from
sunlight, they are producers, and one of the common producers in the Sonoran Desert is the prickly pear
cactus. Many different animals eat the fruit of the prickly pear cactus, including Harris's antelope squirrel.
The squirrel is a consumer because it gets its energy from other organisms. In this case, the squirrel
gets its energy from the fruit of the prickly pear cactus.
In turn, the squirrel can be eaten by another consumer, the diamondback rattlesnake, and the
rattlesnake can then be eaten by a roadrunner… and no, that is not a mistake. In the Sonoran Desert,
roadrunners are deadly predators that will commonly pick up rattlesnakes by the tail and smash their
head repeatedly onto the ground in a whip-like fashion. Once the rattlesnake is dead, the roadrunner will
swallow it whole. In cases where the rattlesnake is too large to swallow all at once, the roadrunner will
partially swallow the snake, with its tail still hanging out of its beak. As the first parts of the snake are
digested, the roadrunner will then continue to swallow the rest of the snake.
The roadrunner itself can also be eaten by yet another predator: the Red-tailed hawk.
Source: http://education-portal.com/academy/lesson/food-chains-trophic-levels-and-energy-flow-in-an-ecosystem.html
Accessed: Jan 24, 2013
The Producers - the cacti, shrubs and plants.
The Primary Consumers – the kangaroo rat, cactus mouse, lizards, poorwill, and desert tortoise.
The Secondary Consumers – the kit fox, elf owl, redtailed hawk, scorpion, roadrunner, and
rattlesnake.
The Scavengers – the vulture and beetles.
The Decomposers or Detrivores – mushrooms, insects and microorganisms.
Source: Amsel, Sheri. “Food Webs.” Sonoran Desert Food Web. Exploring Nature Educational Resource. ©
2005 - 2013. January 23, 2013. <http://exploringnature.org/db/detail.php?dbID=2&detID=1222>
The Sonoran Desert is changed. We humans have been turning the land from the desert into
tourist attractions. These parks have spread for miles taking up the land that belongs to the
wild life. Then these creatures are pushed out of their natural habitat. Ranches have also been
taking up the desert land and with our livestock. People plant crops and some of the seeds
have been picked up by the wind or have been picked up by a bird and the seeds start to grow
were they land. This cycle begins again and after awhile the desert starts to have plants that do
not belong in the desert.
Source: http://www.blueplanetbiomes.org/sonoran_desert.htm
By Elora P. 2003
Accessed: Jan 24, 2013 Another example of commensalism is the relationship between the cactus wren and cholla cacti. Cactus wrens often build their nests in cholla cacti. The spines of the cactus help protect the nest from predators. In this symbiotic relationship, the cactus wren receives something it needs -­‐ nest protection. The cholla cactus does not benefit and it is not harmed by the nesting cactus wrens. Gila woodpeckers use their bills to make a hole in a saguaro cactus to use as a nest. The saguaro develops a hard “scab” around the nest to prevent further water loss. A new nest is built every year, but not always in the same saguaro. The old nest is then used by many other creatures including owls, woodrats, scorpions, snakes, and purple martins. Javelina are herbivores, meaning they eat plants. Some of the plants javelina eat include saguaro fruit, prickly pear fruit and pads, grasses, mesquite beans and palo verde pods. Sometimes seeds pass through the javelina unharmed. The seeds are then able to sprout. Young saguaros cannot grow in the open sun. They need what is commonly referred to as a ‘nurse’ plant. The nurse plant shades the young saguaro from the hot sun. It also prevents the young saguaro from freezing in the winter. Nurse plants are not harmed by the growing saguaro. Nurse plants include shrubs and trees such as palo verde, ironwood, acacia and mesquite. Source: AZ Game&Fish, Number 13, Education Branch and Heritage Fund “Wild Kids” http://www.azgfd.gov/i_e/ee/resources/wild_kids/relationships46.pdf Accessed: Jan 24. 2013 Without the keystone species, new plants or animals could also come into the habitat and push out
the native species. Some species of hummingbirds are keystone species in the Sonoran Desert of North
America. Hummingbirds pollinate many varieties of native cactus and other plants. In areas of the
Sonoran Desert with few hummingbirds, invasive species such as buffelgrass have taken over the
ecosystem.
Source: National Geographic. search: keystone species
Accessed: Jan 25, 2013 http://education.nationalgeographic.com/education/encyclopedia/keystone-­‐species/?ar_a=1 Ironwood as a Keystone Species and Nurse Plant Ironwood functions as a habitat modifying keystone species, that is, a species that exhibits strong influences on the distribution and abundance of associated species. Ironwood generates a chain of influences on associated understory plants, affecting their dispersal, germination, establishment, and rates of growth as well as reproduction. Scientists call these ecological dynamics "nurse plant ecology". Mesquites and palo verde also play this role, however, each tree caters to slightly different sets of plants in its "nursery". Ironwood is the dominant nurse plant in some subregions of the Sonoran Desert. As nurse plants, ironwoods provide safe sites for seed dispersal, seedling protection from extreme cold and freezes, and sapling protection from extreme heat and damaging radiation. They also function as prey refugia, providing herbs and cacti protection from herbivores preying on vulnerable plant seedlings. Finally, like other legumes, they alter the soil composition beneath their canopies, enriching the soil with nutrients such as nitrogen. Ironwood, often the tallest tree in its habitat, attracts birds and other seed dispersers who roost in its branches and generate a literal "rain" of seeds and whole fruit. The mere presence of ironwood and other legume trees can increase the number of bird species in desert scrub habitat by 63%. Germination rates are higher and seedling survival rates better due to the improved soil conditions. Plant health, survival and growth are also improved by the shade and protection from frost that ironwood's canopy offers. Thorny, low-­‐
sweeping branches keep out herbivores, promoting plant growth further. In turn, the greater diversity of plants growing in ironwood nurseries attracts a greater diversity of birds, both breeding and migratory. Source: Arizona Sonoran Desert Museum: Research “DESERT IRONWOOD PRIMER EXECUTIVE SUMMARY” http://www.desertmuseum.org/desert/ironwood_primer.htm Accessed: Jan 25, 2013