Thursday, September 30, 2010

Discussion Question 3 (History and Biodiversity pattern and process) comments due Oct 5th

What are the factors promoting species richness? Why is biological diversity diminished in particular environments? Why aren't species able to overcome these limitations and undergo the process of speciation?

5 comments:

Vivian said...

Major factors that promote higher species richness include:
1. Greater access to solar energy.
The number of mammalian species decreases in areas farther away from the equator.

2. A longer evolutionary history.
Communities with no devastating environment impacts are allowed to diversify over time.

3. Availability of habitats with large area and wide roaming range.
In the island biogeography study by E. O. Wilson, insects were exterminated on multiple islands and the pattern of re-colonization was examined. One of the relationships found was called the Area Effect, which shows the correlation between increased area and greater number of inhabiting species.

4. An intermediate disturbance level.
J.H. Connell studied the mechanisms that allow the coexistence of different species due to disturbances that minimized competitive exclusion.

Among the many factors that impact biological diversity, the role of land use the main focus in a study by Maurus et al. (2012). Cultivation and other land use practices serve as some of the greatest and immediate threats to species richness. Habitats are often destroyed at a rapid rate, especially in developing areas. The experiment aimed to study mammalian species richness in areas with different levels of land use: a national park, a grazing area, and a cultivated area. The results showed little difference in species richness between the preserved area inside the park and the grazing area outside of the park. However, a decreased level of species richness was found in the cultivated area.

A similar level of species richness in a grazing area and a preserved area suggests that moderate level of disturbance maintains biodiversity. Also, a higher intensity of disturbance, such as cultivation, causes the number of species to decline. Many species are unable to overcome these impacts. This adversity is due to the rapid rate at which habitats are fragmented and resources are depleted.
Connell, J.H. (1978) Diversity in tropical rainforests and coral reefs. Science 199:1302–1310.
Maurus, J.M., Carbone, C., Pettorelli, N., and Durant, S. M. (2012). Conserving biodiversity in a changing world: land use change and species richness in northern Tanzania. Biodiversity Conservation 21: 2747-2759.

Jeffery Carter said...

1. Some factors promoting species richness are:
- Higher productivity (amount of carbon fixed by photosynthesis per unit area per time) Some examples of areas with high production are tropical rainforests and coral reefs. These areas have more resources, thus less competition and more niches to fill.

- Disturbances - species richness is higher in areas of intermediate disturbance.

Disturbances in Marine Intertidal Boulder fields: The Nonequilibrium Maitenance of Species Diversity
Wayne P. Sousa (1979)

This paper seeks to support the intermediate disturbance hypothesis.
Observations: Large boulders - 1 species of algae (superior competitor)
Medium boulders - 3 species of algae
Small boulders - 1 species of algae (primary successor)

When rocks of any size were glued down to prevent waves from moving them, the superior competitor dominated the rock.

2. Why is diversity diminished?

In areas with very low productivity or areas of high or low disturbance, species richness will be diminished.

3. Why can't species overcome all the limitations?

In order for sympatric speciation to occur multiple mutations must arise and be passed on to offspring, which is rare

Allopatric – requires some kind of geographic barrier
Natural event that creates a barrier – rare
Species has to leave the area ( go to an island for example)– this is difficult to do. Climate ranges are limited, a species cannot just move from where it lives and expect to do better where it moves to.

Peripatric (enters new isolated niche) and Parapatric (enters new adjacent niche) – there has to be a niche open

Speciation is rare – it is more likely that a struggling species will go extinct rather than undergo speciation, especially in an environment where species richness is not favored.

Kara Lai said...

1. Factors including species richness:

- sexual selection: may lead to reproductive isolation, thereby increasing speciation

-spatial separation: animals may favor living in a certain location in their environment, separating themselves from other types of animals

-competition: predation may open up space for other organisms and animals to colonize that would otherwise not be opened up if it weren't for competition

-geography: example: some animals may make it over a mountain while some animals of the same species will not. On one side of the mountain it rains a lot, while on the other side it is dry and hot. This physical barrier will force the species to adapt to the environment that they are in and over evolutionary time they will become different species. (Allopatric speciation)


2. Biological Diversity is diminished in particular environments and why are species able to overcome these limitations and undergo the process of speciation?

There may not be an adequate amount of food and other resources for a species to colonize and survive.

Space may be a problem as well, if there is not enough areas for a species to live it would be difficult for a new species to emerge.

The climate may be so extreme so that not many species can adapt to the environment. Also, there may be too much disturbance on the environment that wipes out everything, or there may be too little disturbance, so that the species composition is just fixed and the strongest competitor is never eliminated.

Michael Chang said...

Factors that affect species richness include:
Geographic Aspects
-Location: Species richness tends to be greater in spatial regions nearer to the equator. For example, species richness is greater in tropical areas than temperate areas.
-Island Biogeography: The larger the island, the greater its species richness since they allow for more opportunities and more habitats while reducing the chance of extinctions. Another factor is its distance to a colonizing source, such as a mainland. The closer the island is to the mainland, the greater its immigration rate.
Ecological Aspects
-Productivity: The higher the productivity of the region, the greater its species richness
-Disturbances: Intermediate Disturbance Hypothesis suggests that the highest species richness is found in regions of intermediate levels of disturbance (Sousa 1979). High disturbances will facilitate the growth of less competitive, but faster colonizing species while low disturbances will facilitate the growth of more competitive, but slower colonizing species. Intermediate disturbances allow the fast competitors to grow, but prevents the slow growing species from outcompeting them.
According to Angermeier and Karr, it is difficult to measure biodiversity of a region. Often, we think biodiversity at the species level; however the hierarchy of biodiversity extends beyond the taxonomic level to the genetic and ecological levels as well. As a result, to measure biodiversity, one must count all the taxonomic, genetic, and ecological elements present in the region of interest. However, even if all elements present were known, it is unfeasible to integrate all levels into a single value since the levels do not always correlate. Angermeier and Karr describe the concept of biological integrity which encompasses all elements of a region (biodiversity) as well as the occurrence of all processes that would transpire with little to no influence by humans. A high level of integrity reflects natural evolutionary and biogeographic processes and elements. High biological integrity occurs over many spatiotemporal scales including cellular processes that give genetic elements as well as energy flow at the ecological scale.

Sousa, Wayne P. Disturbance in Marine Intertidal Boulder Fields: The Nonequilibrium Maintenance of Species Diversity. Ecology , Vol. 60, No. 6 (Dec., 1979), pp. 1225-1239
Angermeier, Paul L. and Karr, James R.. Biological Integrity versus Biological Diversity as Policy Directives. BioScience , Vol. 44, No. 10 (Nov., 1994), pp. 690-697

Michael Chang said...

Factors that affect species richness include:
Geographic Aspects
-Location: Species richness tends to be greater in spatial regions nearer to the equator. For example, species richness is greater in tropical areas than temperate areas.
-Island Biogeography: The larger the island, the greater its species richness since they allow for more opportunities and more habitats while reducing the chance of extinctions. Another factor is its distance to a colonizing source, such as a mainland. The closer the island is to the mainland, the greater its immigration rate.
Ecological Aspects
-Productivity: The higher the productivity of the region, the greater its species richness
-Disturbances: Intermediate Disturbance Hypothesis suggests that the highest species richness is found in regions of intermediate levels of disturbance (Sousa 1979). High disturbances will facilitate the growth of less competitive, but faster colonizing species while low disturbances will facilitate the growth of more competitive, but slower colonizing species. Intermediate disturbances allow the fast competitors to grow, but prevents the slow growing species from outcompeting them.
According to Angermeier and Karr, it is difficult to measure biodiversity of a region. Often, we think biodiversity at the species level; however the hierarchy of biodiversity extends beyond the taxonomic level to the genetic and ecological levels as well. As a result, to measure biodiversity, one must count all the taxonomic, genetic, and ecological elements present in the region of interest. However, even if all elements present were known, it is unfeasible to integrate all levels into a single value since the levels do not always correlate. Angermeier and Karr describe the concept of biological integrity which encompasses all elements of a region (biodiversity) as well as the occurrence of all processes that would transpire with little to no influence by humans. A high level of integrity reflects natural evolutionary and biogeographic processes and elements. High biological integrity occurs over many spatiotemporal scales including cellular processes that give genetic elements as well as energy flow at the ecological scale.

Sousa, Wayne P. Disturbance in Marine Intertidal Boulder Fields: The Nonequilibrium Maintenance of Species Diversity. Ecology , Vol. 60, No. 6 (Dec., 1979), pp. 1225-1239
Angermeier, Paul L. and Karr, James R.. Biological Integrity versus Biological Diversity as Policy Directives. BioScience , Vol. 44, No. 10 (Nov., 1994), pp. 690-697