Redundancy and Resiliency Activity

Redundancy and Resiliency  

Biodiversity, or species diversity, is important for ecosystem integrity. Each species contributes something to the ecosystem; species influence pathways of energy and materials flow in an ecosystem. These actions or products can be called ecosystem functions. Since each species performs at least one ecological function (e.g., converts atmospheric N to biologically useful N compounds), biodiversity is synonymous with ecosystem functional diversity. A functional type is a set of species that have similar effects on an ecosystem process of similar response to ecosystem conditions. In ecosystems, particular ecological functions appear to show a lot of redundancy; for example, many kinds of critters eat caterpillars, and many kinds of herbs photosynthesize in a meadow. In ecology, we theorize this redundancy helps an ecosystem become more resilient. This means it can continue to provide pa particular set of ecosystem services after a disturbance that might have knocked out one or more species. Thus, having a large variety of species can provide a buffer for ecosystem fluctuations, changes and perturbations. However, even though species share MANY traits in common with MANY other species, the combination of features, (also known as functional traits) is generally thought to be unique for each species. Consider 2 species of native bees, each of which specializes in feeding only on Lupine. One species is an Andrena and nests in the ground; its populations are subject to periodic wipeouts in this environment by floods and heavy rains. The other is a species of Megachile that lives in dead twigs; it suffers wipeouts whenever there are forest fires (or even cool burning). The redundancy of these two species is in pollination of the same species of Lupine. It is unlikely that both a flood and a forest fire would occur in the same year, so the redundancy of the pollination function is likely to continue for a long time. The two bees are redundant in one pollination function, but they are not redundant in the other aspects to their lives in the ecosystem.

 

Human actions are increasing the rates of species extinctions and species invasions. These changes have a strong potential of changing ecosystems in indirect ways. How important is one species to overall ecosystem functioning? Relative abundance of a species is not by itself a good predictor of the importance of a species to the ecosystem. Redundancy of functions and compensations among species can stabilize an ecosystem and help an ecosystem recover more rapidly after a disturbance. As species within a particular functional group disappear, eventually, we expect their corresponding ecosystem functions to become less stable. However, loss of redundancy may not be apparent until an ecosystem is exposed to multiple types of stress.


In the diagram of the boreal forest food web, several diverse feeding relationships are shown.

 

 

1)How many different pathways can you find in the diagram that starts with a producer and ends with a secondary or tertiary consumer?

2)Rearrange the animals in the consumer groups(i.e., Primary Producers, Decomposers, etc.) into functional groups (i.e., how many leaf eaters, seed eaters, bird eaters, pine needle eaters are there?).

3)How would you find out whether or not any of the animals in each consumer group were redundant for one particular trait? What other aspects of their lives in the ecosystem might not be redundant?

4)What ecological purposes can you think of for this diversity of pathways of feeding relationships?

5)Under what circumstances do you think these different pathways between primary producers, secondary and tertiary consumers might have evolved?

6)Explain how you think this redundancy might benefit the arctic ecosystem under conditions of climate change.

 

Definitions:

Ecosystem Function: Traits that influence ecosystem properties or species responses to environmental conditions. Organisms' effects on ecosystems generally fall along a gradient; there are not really distinct groups.

Species Richness: the number of different species in an area

Resilience: Amount of disturbance a system can absorb and still remain within the same state, the ability to sustain ecosystem states under normal range of disturbances. Resistance of an ecosystem to perturbation and speed of recovery.

Redundancy: different animals living in the same ecosystem that perform the same ecosystem functions.

Functional Groups: Clusters of species that appear to provide the same ecological function. There will be variability of responses within each functional group.

 

Background information on consumers:

Red squirrel: seeds, nuts and cones of conifers; buds, flowers bark, berries,and mushrooms; also insects, eggs, mice

Ground Squirrel: fruit, seeds, leaves, occasionally newborn snowshoe hare

Snow Shoe Hare: clover, grasses and ferns in summer; buds, saplings and bark in winter.

Willow Ptarmigan: needles and buds of coniferous trees

Insects: herbaceous insects will eat aspen and poplar leaves and spruce buds, among other plants

Moose: twigs and shrubs, bark of saplings in the winter; Leaves, water plants, grass in the summer

Red Tailed Hawk: small rodents and birds, as well as larger insects

Goshawk: ptarmigan, grouse, rabbits, squirrels

Great Horned Owl: rabbits, mice, rats, grouse, ducks, crows

Red Fox: small rodents, birds, eggs, frogs and even insects. They will often scavenge leftover carcasses of larger game

Lynx: snowshoe hares, smaller rodents, ruffed grouse, reptiles and insects

Passerine birds: mainly insects

Northern Harrier Hawk: birds, mice, and voles

Wolf: moose, white-tailed deer and caribou. It will also hunt smaller game such as rabbits, ruffed grouse, beaver, muskrats and rodents even as small as mice, shrews and squirrels

Extension Activity:

Apply this activity to your study site. What major species of plants and consumers live at your site? Find out what the consumers feed on, and make a diagram of the probable feeding relationships by functional group. How might redundancy benefit the ecosystem?

Further Reading:

“Multiple functions increase the importance of biodiversity for overall ecosystem functioning.” Gamfeldt, L., Hillebrand, H., Jenssen, P.R.(2008) Ecology 89(5)1223-1231.

"Effects on biodiversity of ecosystem functioning; a consensus of current knowledge." Hooper, D.V. et al. (2005) Ecological Monographs 75: 3-35.