The Effects Of Habitat Fragmentation And Rodent Diversity Biology Essay


The study compared communities of small mammals in differing habitats with varying degrees of fragmentation. This included forests, forest edges and disturbed pasture areas across 6 Panamanian national parks and surrounding areas. At each park 3 types of habitats were chosen, pristine forest, edge areas where there was distinct transition between forest and disturbed habitat and anthropogenically disturbed areas. For each of the habitat types they compared small mammal communities, species composition, richness, eveness and relative abundance.

For each area a 10m x 10m grid was sampled with 100 live traps (8 x 8 x 2cm), with each trap baited with peanut butter and oats

Generalist species are often associated with the transmission of pathogens to humans, such as the parvovirus, rabies and this case hantavirus. Hantaviruses are transmitted to humans by inhalation of the virus from rodent urine, faeces, saliva or by direct contact such at bites (Tsai, 1987). Hantaviruses cause hemorrhagic fever with renal syndrome in Asia and Europe and hantavirus pulmonary syndrome in the America’s, whilst the number of cases reported is relatively low mortality is considered quite high.

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Landscape fragmentation and habitat loss has been recognised as one of the most important threats to global biodiversity (Cox et al, 2002). This essay will provide an insight into a study conducted by Suzan et al in 2006 that highlights one of the many problems that poses a threat to biodiversity with habitat fragmentation.

It is suggested that habitat fragmentation and destruction is responsible for the creation of simplified communities that are dominated by generalist species. Generalist species have a high adaptability to a range of habitats, whereas the specialist species are adapted to a narrowly defined habitat and are prone to become endangered or extinct due to destruction and fragmentation of their habitats (Suzan et al, 2008). Prior to undertaking the study Suzan hypothesized that habitat fragmentation and loss of diversity due to human activities such as human

This study compared communities of small mammals in different habitats with varying degrees of fragmentation. The study was undertaken at 6 national parks and surroundings areas in Panama and included 3 habitat types for each location, these being pristine forest, anthropogenically disturbed areas, and edge areas where there was a transition between forest and disturbed habitat.

The species compositions form each of the habitat types clearly showed differences in mammal composition and abundances in each of the habitat areas. The forest habitats hosted higher species diversity and several specialist forest species. Generalist species were common throughout the edges and disturbed areas, although the overall abundance of species was greatest in the forest areas, with the edge areas having the greatest species diversity. The results showed that the edge and disturbed areas had significantly higher abundances of the Hantavirus hosts, Oligoryzomys flavescens (Choclo virus) and Zygodontomys brevicauda. Species richness and diversity was lowest in the disturbed areas, than in the forest and edge areas.

The study showed that fragmented habitats are associated with lower diversity of small forest mammals and higher densities of rodent populations that are host to potentially fatal Hantaviruses. It also highlighted that specialist forest species that survive in a narrowly defined habitat are prone to endangerment or extinction due to continual habitat destruction from agricultural or urban spread. The study also showed that the generalist species are able to survive in small forest areas and in the human dominated environments. It is possible that with the increased abundances of generalist species there can be other ecological consequences such as the endangerment of endemic fauna and the alteration of food chains.

Some questions come to mind after reviewing the study that are left unanswered these being: Should the Hantavirus host species invade the pristine forest areas what will be the effect on the forest species? Would this lead to further declines or even extinction of the species found in the forest areas? Given that the study focuses mainly on the increasing distribution of the hantavirus hosting species it is thought that the theory on metapopulation dynamics would be most appropriately applied to study. It is thought that it would benefit the study if it was applied to the populations of the hantavirus species to model the potential expansion of the species. This would help in determining the overall effect on the species that inhabit the edge and forest areas. One such model was devised by Hess (1996) with his model generally built on the metapopulation model devised by Levin (1969). His model synthesized his mathematical epidemiology model with a metapopulation model and showed that highly contagious diseases of moderate severity can spread widely and in turn increasing the probability of metapopulation extinction. Another study using a metapopulation model was undertaken in Kanagawa Prefecture, Japan to predict the range and expansions of the feral raccoon (Procyon lotor).

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Metapopulation dynamics and landscape connectivity are important for species abundance and diversity in fragmented habitats (Gonzalez et al, 1998).