44 Identifying Species Interactions in Ecosystems

Key Idea: Species interact in ways that are broadly similar regardless of the ecosystem in which they are found.

1. Complete the tables of relationships below for the examples illustrated, filling in the type of relationship, the effect (+, –, 0) and the species involved. The first one has been done for you. In the beech example, use the same answer format:

Species interactions on the African savannah

Zebras compete with other grazing mammals, such as wildebeest, for grazing space, forage, and water. This may be critical when resources are scarce, e.g. during a drought.

Interactions between zebras and other species

Interaction Zebra Species B

Competition –

Wildebeest

Ectoparasites, such as ticks (left) mites, and fleas, live attached to the skin or hair of the host, where they suck body fluids, cause irritation, and may act as vectors for disease-causing microorganisms. On the savannah, the zebra's main predators are lions (right) and hyaenas. Herbivory is a similar type of exploitation, except that the plant is usually not killed by the herbivore and may even benefit from regular cropping.

Species interactions in a Nothofagus (southern beech) forest

Rudolph89 CC3.0 The southern beech (Nothofagus), pictured left, has a competitive advantage over other New Zealand tree species, such as tawa, in areas of suboptimal soil or harsh climatic conditions. Many Nothofagus species are able to tolerate the low light of the subcanopy, and can grow rapidly.

Red mistletoe (left) is a hemiparasite of beech. It can photosynthesise, but it takes water and nutrients from the beech root system. The mistletoe is an important food source for bellbirds and tui who compete for nectar but also pollinate the mistletoe flowers.

J. Ladley UoC

Brushtail possums (left) are a major pest species in New Zealand, causing significant damage to native trees by eating their leaves, flowers, and fruit. When Nothofagus fruits heavily, more than 40% of a possum's diet can come from its flowers, fruit, and seeds.

Interactions between Nothofagus and other species

Interaction Nothofagus Species B

The association between the roots of Nothofagus and the fungus Amanita nothofagi (right) is a mutualism. These associations, or mycorrhizae, help the trees to absorb water and nutrients from the soil. In return, the fungi are provided with sugars from the tree.

Photo: Michael (inski) CC 3.0