Serengeti Biodiversity

Biodiversity: Differentiation in the genotypology and

phenotypology of organisms as a function of evolution by natural selection

Natural Selection: Differential survivorship as a result of

adaptive characteristics of an organism with its environment,

resulting in greater reproductive success.

Driven by… mutation

Ecosystem: An bounded or unbounded

interconnected biosphere of mutually affected organisms within an

environment.

The Serengeti-Mara Ecosystem (SME) one of the oldest ecosystems on Earth

The Serengeti is the East African Acacia savanna – a Plains–Savanna biome. The majority is in Tanzania, but the northern part is in Kenya as the Masai Mara National Reserve.

World Heritage Site of UNESCO because of its large migratory ungulate populations, high diversity of large mammals and birds, prehistory sites (Olduvai).

25,000 km2

ShortgrassSoils are high in nutrients

Acacia woodlands in the west to Lake VictoriaFlood plains developed from ancient lakebeds near

Victoria

In the far northwest, broadleaved woodlands and the highest rainfall forms a refuge for the migrating ungulates

at the end of the dry season

1M wildebeest 200,000 zebraLionCheetahElephantsLeopardsHyenasGiraffeTopiBushbuck WarthogHippoRock hyraxGrants gazelleImpala 500 species of birds

1. The Great Migration: Herds of ungulates 25 miles long follow fresh grasses across the plains.

2. Fire: Anthrogenic and natural causes

Marked by shifts from grassland to woodland

Grasslands have naturally converted to woodland twice in the last one hundred years, once in 1900 and again in 1970. …many more impala in the park now because they are more adapted for the woodland environment.

Researchers believe that the emergence of the woodland environment was caused by a decline in the elephant population. Why?

Shaped by Two Powerful Forces

Elephants1960s: thought to cause decline of because often seen pushing over trees…

calls for culling of elephants.

Burning declined to a minimum in 1980 and has remained low because of heavy grazing by wildebeest – why does this matter?

Areas burned since 1980 have been between 5% and 25%, indicating that significant recruitment of trees should have occurred. But it didn’t’… why?

Elephants ate young tree recruits so extensively that no recruitment took place.

Demonstrates that there are multiple ecosystem states, in this case a woodland state and a grassland state both with elephants.

Implications for conservation vs protectionism and need for long-term research.

Role of Predators

Food supply limits population of wildebeests and large ungulates, but…Smaller smaller species are limited by mainly by predation. Why?

Higher exposure to carnivores (predators have harder time killing very large ungulates. Threshold of prey size where the main mode of limitation switches rapidly from food to predators as prey become smaller (about 150 kg, is approximately that of wildebeest). Migration allows populations to escape predator limitation to some extent.

Recent studies show that lions' hunting success is determined by the availability of dense cover for ambush rather than by the density of prey. These studies predict that the increase in dense cover due to the increase in young tree populations has benefited lions by enabling them to catch more prey; and greater hunting success should yield a decline in prey numbers. It has for small and medium sized prey.

The downward trend has been most pronounced since 1980, which covers the period when there was a substantial increase of young trees. Thus, plant structure indirectly affects predator functional responses and thereby herbivore numbers.

Wildebeest: Lynchpin Species

Wildebeest affect the populations of species far beyond their immediate food or predator species. They maintain diverse assemblage of small flowering plants on the plains. Removal of grazing for a decade changes the shortgrass plains into tallgrass.

With this change of grass structure there are changes in grasshopper diversity—some 49 species occur in tallgrass, whereas fewer than 13 species occur in shortgrass.

As the wildebeest population has increased, plant species diversity has declined.

Grassland structure also determines the types of bird species.

Wildebeest affect most components of an ecosystem. Loss of the wildebeest migration would radically alter the ecosystem.

Serengeti Research Institute: http://www.ntz.info/gen/

n00555.html

Serengeti Biodiversity Program: http://www.zgf.de/?

projectId=74&id=65&language=en

http://www.savetheserengeti.org/news/highway-news/report-serengeti-biodiversity-

centre/#axzz1usRLfxf5