That means; the number of species corresponds with the biodiversity of a certain place or an ecosystem. However, the variations within a particular species could also be considered as the index of biodiversity, which means the number of subspecies or individual variations accounts for biodiversity. When considering a large region such as country or an island, the number of different ecosystems is a great index of biodiversity of that region.
However, biodiversity is not related to the land area of the place; it is the number of ecosystems or the number of species that are important in biodiversity. For example, Greenland is a large island, but its biodiversity is much lower compared to Sri Lanka, which is a tiny island. Thus, this example indicates another important aspect of biodiversity — biodiversity of tropical regions is higher compared to that of temperate regions.
It is because most of the solar energy is trapped at the tropics by green plants via photosynthesis , and there are organisms to consume that as food. Rainforests and coral reefs are amongst ecosystems with the greatest biodiversity.
Species richness refers to the number of different species present in a certain place of interest. Since species richness indicates a number, the value could be similar in two places with similar environmental conditions. However, species richness does not account the importance of charismatic or endemic species.
It only indicates the number of species present, but it does not specify which species are present. Therefore, the application of species richness in the conservation of biodiversity is not a key component. In fact, species richness does not consider the variation of the density of certain species.
One main feature of species richness is that it treats all the species in equal respect, and it implies that all the species are common and widespread. Hence, species richness only provides an idea of taxonomical diversity. Studies of niche overlap can be for resources of food, habitats, or timing for use of habitats.
An example of two species with similar niches, and that do not occur together are the redfin shiner and the Ouachita Mountain shiner in the Little River watershed of Oklahoma and Arkansas. Both species are small minnows that inhabit rocky pools in small to medium streams, and consume aquatic macroinvertebrates. Food webs describe the trophic, or feeding relationships among the members of a community.
Trophic relationships refer to where and how organisms obtain their energy. For example, primary producers are organisms that convert energy from light or heat into organic tissue. Plants are an example of a primary producer. Consumers are organisms that get their energy from eating primary producers. A rabbit is a consumer that eats grasses. Predators are organisms that eat consumers. A wolf is a predator that eats rabbits.
Food webs can be simple or they can be complex, depending upon the number of species in a community. Food webs can vary in complexity by the number of connections between member species. Spatial and temporal comparisons of communities provide information about the things that cause differences in species occurrence and abundance patterns. A spatial comparison refers to comparing similar communities that occur in different locations.
This allows an ecologist to test if there are differences in climate, landscape features, geology, or habitats that occur with different species assemblages. For example, in small streams, the fish species that occur in a riffle habitat stream location with change in height of the stream bottom tend to be different than the fish species that occur in pool habitats stream location with constant stream bottom height.
In other words the fish assemblages of riffles differ from the fish assemblages of pools. The assemblage differences are largely due to the fact that the habitats are so different. Riffles have higher gradients, increased flows, and larger substrates than the pool habitats of streams. At a larger scale, fish assemblages in larger rivers differ from fish assemblages in small streams. A temporal comparison refers to comparing the same community at different times.
The species composition of communities and assemblages changes with time. Change may occur following disturbance events, or change may occur due to stochasticity in assemblages. The predictable change that occurs to assemblages in the context of a natural disturbance regimen, is frequently interpreted as succession. Communities can be characterized by natural disturbance regimes. Disturbance events are characterized by their frequency and impact.
Disturbances can include variation in climate, variation in flooding frequency or drought frequency, or frequencies of storm events. Species have adaptations that were shaped by exposure to natural disturbance regimes during their evolutionary history. For example, insects that occur in temperate headwater streams frequently have life history adaptations that result in larval stages being present during the season when leaf inputs from terrestrial plants are high.
Insects that occur in desert streams might have adaptations for surviving unpredictable flood events. The life histories of organisms are a product of their local environment, including the predictability of disturbance regimes.
Organisms can be classified in three general life history modes. An interesting product of this classification exercise was that species in these three groups differ in their ability to survive disturbances. For example, fish species with low juvenile survivorship, low number of offspring, and with early maturity tend to be successful in habitats with unpredictable droughts or floods. Species with a different suite of life history traits such as low juvenile survivorship, high number of offspring, and late maturity cannot survive unpredictable flood or drought disturbances.
Gotelli, N. Quantifying biodiversity: procedures and pitfalls in the measurement and comparison of species richness. Ecology Letters 4 , Pyron, M. Stability of the fish assemblages of the Wabash River from Freshwater Biology 51 , Taylor, C. Regional parapatry of the congeneric cyprinids Lythrurus snelsoni and L. Copeia , Winemiller, K.
Patterns of life history diversification in North American fishes: implications for population regulation. Canadian Journal of Fisheries and Aquatic Sciences 49 , Predation, Herbivory, and Parasitism. Characterizing Communities. Species with a Large Impact on Community Structure. Successional Changes in Communities. Effects of Biogeography on Community Diversity. Community Ecology Introduction. Avian Egg Coloration and Visual Ecology. Causes and Consequences of Biodiversity Declines.
Disease Ecology. The Ecology of Avian Brood Parasitism. Elemental Defenses of Plants by Metals. The Maintenance of Species Diversity. Neutral Theory of Species Diversity. Abiotically-Mediated Direct and Indirect Effects. For example, if two communities both have five species, species richness would be five for both communities.
If the first community had individuals and 80 of them were all one species, this would not be a community with a very even distribution. If the second community had individuals, with 20 individuals belonging to each of the five species, this community would be more evenly distributed.
Because it was more evenly distributed, community two would have a greater species diversity. In the image below, community one would have a greater species diversity because the spread of species is more even. What is the difference between species diversity and species richness?
Kate M. Dec 28,
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