Characteristics

I thought it would be important to provide a brief snippet of information on the traits and characteristics of both threatened and endangered species as well as those of invasive alien species. The characteristics of those species that are threatened by invasive alien species have relatively similar characteristics. According to the Florida Forest Stewardship, these are:

1. species with narrow habitat requirements and therefore unable to adapt to change

2. species of economic importance

3. species of large size

4. species having limited numbers of offspring per breeding period, long gestation periods or requiring extensive and intensive parental care

5. species with highly specialised adaptations

Typically, characteristics of invasive, alien species, as defined by the Pacific Northwest Research Station:

1. ability to tolerate a wide range of habitat conditions, i.e. they are less specific and more generalised individuals

2. the ability to grow and reproduce rapidly

3. Effectively and aggressively compete for resources

4. Lack of natural predators/pests/threat to growth in the new ecosystem

The combination of the characteristics of both the threatened species and the invasive species are what lead to the extinction and loss of of species in particular areas. It is therefore necessary to educate and understand the fragility of certain ecosystems and their interactions to prevent the loss of species.



http://www.fs.fed.us/pnw/invasives/index.shtml
http://www.sfrc.ufl.edu/Extension/florida_forestry_information/planning_and_assistance/threatened_and_endangered_species.html

Biocontrol Gone Wrong

Myxomatosis is a disease caused by the myxoma virus. The virus occurs naturally in certain rabbit species found in South America and in California and when present, only causes mild symptoms. It was first discovered in Uruguay in 1896 when the symptoms were first observed. These symptoms include bulging eyes, localised swelling around the head, face, ears, lips, anus and genitalia. The severe swelling can lead to blindness and facial distortion, leading to difficulties in drinking and eating. Myxomatosis is also associated with fatal pneumonia due to respiratory infection. There is no specific treatment for the virus and any treatment given is purely supportive, therefore the recommended way to deal with rabbits infected with the disease is to euthanise them to stop them suffering. It is therefore important to control the spread of the virus.

Myxomatosis is transmitted, particularly in Britain, via insect vectors (Ross and Tittensor, 1986). Insects that puncture the skin allow the bacteria to infect the host and therefore display the symptoms. It is therefore important to manage fleas when found on rabbits and to treat them immediately if there is an outbreak of the disease at the time.

The disease was imported into Australia in 1951 to control large rabbit populations with devastating effect. The disease was then illegally introduced to an estate in France in 1952 and spread naturally throughout wild rabbit and domestic rabbit populations across Westen Europe. The first case was reported in Kent in 1953 and was found across all of Britain by the end of 1855. The impact of the disease in Britain was devastating, it eradicated 99% of rabbit populations in an extremely inhumane way (Ross and Tittensor, 1986). The whole event taking place due to the introduction of a non-native pathogen for biological control of undesired species, highlighting mankind's inability to effectively control introductions and how our lack of knowledge of species interactions can lead to dramatic effects.

Myxomatosis, however, has been present in pulses. After the initial introduction in 1953 in Britain, the number of reports declined. This can be explained through the concept of critical community size (CCS), discussed by Fouchet et al (2008). Fouchet et al (2008) explain that the CCS of a host population infected by any parasite defines a point where the two time scales of extinction are very different between populations above or below the CCS. If above the CCS, extinction rates are much greater as the pathogen can maintain itself almost indefinitely and individuals within the population are regularly exposed to infection. Extinction rates below the CCS is much less and the parasite/infection will rapidly die out after it has been introduced into the population. However, a limiting factor of any parasite/virus/bacteria is its efficiency. What is often the case if the agent is particularly efficient at decimating host populations is the extinction of the agent itself as it manages to kill the host before transmission to another host (Fouchet et al, 2008). The CCS has been shown to significantly alter relationships between the host and the agent. The transmission of the bubonic plague from rats to humans has been found to take place when the rat populations are below the CCS and the agent moves to find the next available host. This happens, as stated before, because the agent is so efficient at killing the host, once an outbreak is present in a populations, the population numbers crash pushing the agent to find the next suitable host. This transmission, thankfully for human populations, has not taken place with myxomatosis, however the concept can be applied.

Presently, all domestic rabbits are immunised against the virus and an transmissible vaccine has been implemented for wild rabbit populations (Torres et al, 2001). However, this is another form of biocontrol and could potentially have similar undesired effects to that of myxomatosis, however tests with this vaccine have shown no undesired side effects (Torres, et al, 2001).

The case of myxomatosis show that bio control can be implemented and controlled effectively, however in this instance the process is incredibly inhumane. However, if the correct control measures and precautions are not put in implemented, the agent becomes an unwanted invasive alien species with, especially in this case, detrimental effects.

http://www.sciencedirect.com/science/article/pii/S0022519307005413
http://www.sciencedirect.com/science/article/pii/S0264410X01001840
http://www.jstor.org.libproxy.ucl.ac.uk/stable/pdfplus/2404476.pdf?acceptTC=true
http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2907.1986.tb00038.x/abstract