Introduction
The success of conservation of a species depends on the understanding of the ecological factors driving the continued survival of that population (Bonsall et al. 2014). This will aid in the understanding of the temporal dynamics of the population when looking at the relationship between per capita growth rate and the local density of that population (Bonsall et al. 2014). When populations are fragmented, they rely on dispersal through migration to prevent inbreeding, and run the risk of extinction if they can’t (Bicknell et al. 2014). Populations are classified as metapopulations if they are demographically or genetically isolated from one another (Hanski 1998).
The aim of this study was to 1) determine how the proportion of habitat patches occupied influenced the change in patch incidence and 2) investigate how the extinction and migration rates influence the amount of patches occupied.
Methods and materials
Deterministic equilibrium model
A vensim model was set up according to the following equation where dP is the change in patch incidence, m is the rate of successful migration, P is the proportion of patches and E is the extinction rate of occupied patches: dP/ dt = mP (1-P)-EP
As m and E are the parameters of the population, they are entered as: m= 0,2 and E=0,1 and assumed to remain the same throughout the simulation. The proportion of patches is varied, first assuming that most patches are empty (P= 0,1) and then most patches are occupied (P=1,0). Graphs were then constructed for dP and P.
Stochastic metapopulation extinction model
For this model, it was assumed that the metapopulation consisted of 6 populations with identical extinction probabilities i...
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Bonsall, M. B., Dooley, C. A., Kasparson, A., Brereton, T., Roy, D. B., & Thomas, J. A. 2014. Allee effects and the spatial dynamics of a locally endangered butterfly, the high brown fritillary (Argynnis adippe). Ecological Applications, 24(1), 108-120.
Fernández‐Chacón, A., Stefanescu, C., Genovart, M., Nichols, J. D., Hines, J. E., Páramo, F.,& Oro, D. 2014. Determinants of extinction‐colonization dynamics in Mediterranean butterflies: the role of landscape, climate and local habitat features. Journal of Animal Ecology, 83(1), 276-285.
Hanski, I.1998. Metapopulation dynamics. Nature, 396(6706), 41-49.
Hanski, I.1999. Habitat connectivity, habitat continuity, and metapopulations in dynamic landscapes. Oikos, 209-219.
Nee, S., & May, R. M.1992. Dynamics of metapopulations: habitat destruction and competitive coexistence. Journal of Animal Ecology, 37-40.
Reproduction and passing on genetic and behavioral traits to an offspring is a common fundamental to all the species on this planet. When studying forest ecology, it is crucial to study the proportion of individuals surviving at each stage of their growth as the lives and mortality experienced in a species population describes a characteristic of the species in question. In the case of American beech and sugar maple, their attempt to produce seeds is analogous to entering lottery, where every seedling has a potential chance of becoming a canopy but only some will survive and reach the canopy size; thus, becoming the fit ‘winners’. Our information shows that together, based on size class distribution, both the species display a ‘winner takes all’ pattern, which supports our hypothesis. The results showed a greater count for seedlings and short saplings than for tall saplings, sub-canopies and canopies. This is evident for a Type III survivorship curve. In Type III curve all individuals initially having a very low chance of survival. However, once the individuals pass their threshold age and survive, they live an advanced age. Only some individuals out the mast seeding production mature to become fully fit canopy trees. On the other hand, our hypothesis of canopy trees representing the bulk of the biomass was supported as the basal areas decreased going from growth stages of canopy to seedlings. This is evidence that once the individuals survive the bottleneck where there is high mortality of young individuals (seedlings), who are then considered as ‘losers’, will allow for the other larger size class individuals to flourish. Here, having considerable amount of dbh (diameter at breast height) accounts for greater surfac...
Soule, Michael E et al. “Ecological Effectiveness: Conservation Goals for Interactive Species.” Conservation Biology 17.5 (2003) : 1238-1250.
A different scenario takes place when an alien species is transported to a new area. Although direct competition with similar species is still a problem, the new kid in the block may have no natural pests and diseases. Thus, large stands of monocultures can occur. It is generally accepted that one plant species will support 10 species of animals. If one species takes over 99% of a given habitat dozens if not hundreds of species are lost from that area and some populations are stressed enough that extinction is possible.
Biodiversity is influenced by landscape fragmentation at various scales of space and time. The extinction of ecosystem types and component species may cause an increased patchiness of the landscape, resulting in lower population sizes and decreased connectivity. As a result, inhabitants may experience decreased dispersal abilities and lowered gene flows between populations.
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Long-term survival of a species depends on its ability to adapt to changing environmental conditions (Murphy, 1994). Genetic diversity within a species, which has taken 3.5 billion years to evolve, makes adaptations to these changing environments possible. Unfortunately, the rate of extinction of genetically diverse organisms is rapidly increasing, thus reducing this needed biodiversity, largely due to the human impacts of development and expansion. What was an average of one extinction per year before is now one extinction per hour and extinct species numbers are expected to reach approximately one million by the year 2000 (WWW site, Bio 65). As a result governmental and societal action must be taken immediately!
Gotelli, N. J., & Gillman, M.1996. A Primer of Ecology. Trends in Ecology and Evolution, 11(6), 265. Metapopulation Dynamics A Model of Metapopulation Dynamics pp 84
Willmer, P.. Ecology: Pollinator – Plant Synchrony Tested by Climate Change. Current Biology. Volume 22, Issue 4, 21 Feb 2012, Pages R131 – R132.
When environments are diversified and irregular, species can exhibit trade-offs in their ability to utilize local habitats and to exploit patches regionally. When the dispersal rates are low, each species persists only in the habitat type in which they are favored; local diversity is low. In contrary, at the highest rates of dispersal, species that are better at colonizing empty patches can dominate and drive other species extinct, even though those species ...
The question of the study is how is the northern brown bandicoot adjusting to habitat loss caused by human settlement in Brisbane? The hypothesis is large communities of bandicoots in small areas will observed and will not represent the population data from before the human expansion occurred.
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Sodhi, Navjot S., and Paul R. Ehrlich. 2010. Conservation Biology for All. Oxford: Oxford University Press.
The distance that an organism travels can tell us something about their preferred habitat, how they reproduce as well as being a primary determinant of their likelihood to survive. Dispersal between populations influences the likelihood of colonisation and extinction. If extinction occurs in one habitat patch populations may be rescued by individuals from a nearby population. A ...