KEYSTONE SPECIES
Keystone species are those which have a too high impact on a particular ecosystem relative to its population. Keystone species are also critical for the overall structure and function of an ecosystem and influence which other types of plants and animals make up that ecosystem. Thus, in the absence of a keystone species, many ecosystems would fail to exist. A typical example of keystone species in the context of conservation biology is the predator-prey relationship. Small predators that consume herbivorous species prevent herbivores from decimating the plant species' ecosystem and are considered keystone species. In this scenario, despite the low number of predators required to maintain a low population of herbivorous species, without this keystone species, the herbivore population would continue to grow and thus consume all of the dominant plant species in the ecosystem.Since a keystone species is not a formal designation, scientists may debate which plants or animals in a particular ecosystem deserve the title. Some wildlife scientists say the concept oversimplifies one animal or plant’s role in complex food webs and habitats. On the other hand, calling a particular plant or animal in an ecosystem a keystone species helps the public understand just how important one species can be too many others' survival.
Many types of keystone species are cited by many scientists: predators, ecosystem engineers, and mutualists.
- The Predators
The Ecosystem Engineers
- The Mutualists
THE PREDATORS
Predators help control prey species populations, which affects the number of plants and animals further along the food web. Sharks, for example, often prey upon old or sick fish, leaving healthier animals to flourish. Only by their presence near seagrass beds can sharks keep smaller animals from overgrazing and wiping out the grass. In Australia, scientists observed that when tiger sharks were not near the grass beds, sea turtles—among tiger sharks’ favorite prey—tended to decimate them. But when tiger sharks patrolled the grass beds, the sea turtles were forced to graze across a much wider region.
SMALL MAMMAL PREDATORS:-
The sea otter (shown below) is considered a keystone species as its consumption of sea urchins, preventing the destruction of kelp forests caused by the sea urchin population. Kelp forests are critical habitat for many species in nearshore ecosystems. Sea urchins feed on the nearshore kelp forests in the absence of sea otters, thereby disrupting these nearshore ecosystems. However, when sea otters are present, sea urchins' consumption restricts the sea urchin population to smaller organisms confined to protective crevices. Thus, the sea otter protects the kelp forests by reducing the local sea urchin population.
LARGE MAMMAL PREDATORS
While small predators are important keystone species in many ecosystems, as mentioned above, large mammalian predators are also considered keystone species in larger ecosystems. For example, the lion, jaguar (shown below), and gray wolf have considered keystone species as they help balance large ecosystems (e.g., Central and South American rainforests) by consuming a wide variety of prey species.
Ecosystem Engineers
In many cases, a keystone species' vital role in an ecosystem is not fully appreciated until that species is gone. Ecologist Robert Paine, who coined the term “keystone species” in the 1960s, observed such species' importance in a study of starfish along the rocky Pacific coastline in Washington state. The starfish fed on mussels, which kept the mussel population in check and allowed many other species to thrive. When the starfish were removed from the area as part of an experiment, the mussel population swelled and crowded out other species. The biodiversity of the ecosystem was drastically reduced. Payne’s study showed that identifying and protecting keystone species can help preserve many other species' populations.
Informative ..well done
ReplyDelete